3164 lines
170 KiB
XML
3164 lines
170 KiB
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<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
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"http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"
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[<!ENTITY % poky SYSTEM "../poky.ent"> %poky; ] >
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<chapter id='profile-manual-usage'>
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<title>Basic Usage (with examples) for each of the Yocto Tracing Tools</title>
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<para>
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This chapter presents basic usage examples for each of the tracing
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tools.
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</para>
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<section id='profile-manual-perf'>
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<title>perf</title>
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<para>
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The 'perf' tool is the profiling and tracing tool that comes
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bundled with the Linux kernel.
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</para>
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<para>
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Don't let the fact that it's part of the kernel fool you into thinking
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that it's only for tracing and profiling the kernel - you can indeed
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use it to trace and profile just the kernel, but you can also use it
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to profile specific applications separately (with or without kernel
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context), and you can also use it to trace and profile the kernel
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and all applications on the system simultaneously to gain a system-wide
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view of what's going on.
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</para>
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<para>
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In many ways, perf aims to be a superset of all the tracing and profiling
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tools available in Linux today, including all the other tools covered
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in this HOWTO. The past couple of years have seen perf subsume a lot
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of the functionality of those other tools and, at the same time, those
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other tools have removed large portions of their previous functionality
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and replaced it with calls to the equivalent functionality now
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implemented by the perf subsystem. Extrapolation suggests that at
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some point those other tools will simply become completely redundant
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and go away; until then, we'll cover those other tools in these pages
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and in many cases show how the same things can be accomplished in
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perf and the other tools when it seems useful to do so.
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</para>
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<para>
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The coverage below details some of the most common ways you'll likely
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want to apply the tool; full documentation can be found either within
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the tool itself or in the man pages at
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<ulink url='http://linux.die.net/man/1/perf'>perf(1)</ulink>.
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</para>
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<section id='perf-setup'>
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<title>Setup</title>
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<para>
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For this section, we'll assume you've already performed the basic
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setup outlined in the General Setup section.
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</para>
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<para>
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In particular, you'll get the most mileage out of perf if you
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profile an image built with the following in your
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<filename>local.conf</filename> file:
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<literallayout class='monospaced'>
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<ulink url='&YOCTO_DOCS_REF_URL;#var-INHIBIT_PACKAGE_STRIP'>INHIBIT_PACKAGE_STRIP</ulink> = "1"
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</literallayout>
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</para>
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<para>
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perf runs on the target system for the most part. You can archive
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profile data and copy it to the host for analysis, but for the
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rest of this document we assume you've ssh'ed to the host and
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will be running the perf commands on the target.
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</para>
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</section>
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<section id='perf-basic-usage'>
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<title>Basic Usage</title>
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<para>
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The perf tool is pretty much self-documenting. To remind yourself
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of the available commands, simply type 'perf', which will show you
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basic usage along with the available perf subcommands:
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<literallayout class='monospaced'>
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root@crownbay:~# perf
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usage: perf [--version] [--help] COMMAND [ARGS]
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The most commonly used perf commands are:
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annotate Read perf.data (created by perf record) and display annotated code
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archive Create archive with object files with build-ids found in perf.data file
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bench General framework for benchmark suites
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buildid-cache Manage build-id cache.
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buildid-list List the buildids in a perf.data file
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diff Read two perf.data files and display the differential profile
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evlist List the event names in a perf.data file
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inject Filter to augment the events stream with additional information
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kmem Tool to trace/measure kernel memory(slab) properties
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kvm Tool to trace/measure kvm guest os
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list List all symbolic event types
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lock Analyze lock events
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probe Define new dynamic tracepoints
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record Run a command and record its profile into perf.data
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report Read perf.data (created by perf record) and display the profile
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sched Tool to trace/measure scheduler properties (latencies)
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script Read perf.data (created by perf record) and display trace output
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stat Run a command and gather performance counter statistics
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test Runs sanity tests.
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timechart Tool to visualize total system behavior during a workload
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top System profiling tool.
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See 'perf help COMMAND' for more information on a specific command.
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</literallayout>
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</para>
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<section id='using-perf-to-do-basic-profiling'>
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<title>Using perf to do Basic Profiling</title>
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<para>
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As a simple test case, we'll profile the 'wget' of a fairly large
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file, which is a minimally interesting case because it has both
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file and network I/O aspects, and at least in the case of standard
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Yocto images, it's implemented as part of busybox, so the methods
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we use to analyze it can be used in a very similar way to the whole
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host of supported busybox applets in Yocto.
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<literallayout class='monospaced'>
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root@crownbay:~# rm linux-2.6.19.2.tar.bz2; \
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wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>
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</literallayout>
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The quickest and easiest way to get some basic overall data about
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what's going on for a particular workload is to profile it using
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'perf stat'. 'perf stat' basically profiles using a few default
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counters and displays the summed counts at the end of the run:
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<literallayout class='monospaced'>
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root@crownbay:~# perf stat wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>
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Connecting to downloads.yoctoproject.org (140.211.169.59:80)
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linux-2.6.19.2.tar.b 100% |***************************************************| 41727k 0:00:00 ETA
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Performance counter stats for 'wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>':
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4597.223902 task-clock # 0.077 CPUs utilized
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23568 context-switches # 0.005 M/sec
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68 CPU-migrations # 0.015 K/sec
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241 page-faults # 0.052 K/sec
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3045817293 cycles # 0.663 GHz
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<not supported> stalled-cycles-frontend
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<not supported> stalled-cycles-backend
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858909167 instructions # 0.28 insns per cycle
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165441165 branches # 35.987 M/sec
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19550329 branch-misses # 11.82% of all branches
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59.836627620 seconds time elapsed
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</literallayout>
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Many times such a simple-minded test doesn't yield much of
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interest, but sometimes it does (see Real-world Yocto bug
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(slow loop-mounted write speed)).
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</para>
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<para>
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Also, note that 'perf stat' isn't restricted to a fixed set of
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counters - basically any event listed in the output of 'perf list'
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can be tallied by 'perf stat'. For example, suppose we wanted to
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see a summary of all the events related to kernel memory
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allocation/freeing along with cache hits and misses:
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<literallayout class='monospaced'>
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root@crownbay:~# perf stat -e kmem:* -e cache-references -e cache-misses wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>
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Connecting to downloads.yoctoproject.org (140.211.169.59:80)
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linux-2.6.19.2.tar.b 100% |***************************************************| 41727k 0:00:00 ETA
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Performance counter stats for 'wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>':
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5566 kmem:kmalloc
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125517 kmem:kmem_cache_alloc
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0 kmem:kmalloc_node
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0 kmem:kmem_cache_alloc_node
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34401 kmem:kfree
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69920 kmem:kmem_cache_free
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133 kmem:mm_page_free
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41 kmem:mm_page_free_batched
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11502 kmem:mm_page_alloc
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11375 kmem:mm_page_alloc_zone_locked
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0 kmem:mm_page_pcpu_drain
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0 kmem:mm_page_alloc_extfrag
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66848602 cache-references
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2917740 cache-misses # 4.365 % of all cache refs
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44.831023415 seconds time elapsed
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</literallayout>
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So 'perf stat' gives us a nice easy way to get a quick overview of
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what might be happening for a set of events, but normally we'd
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need a little more detail in order to understand what's going on
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in a way that we can act on in a useful way.
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</para>
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<para>
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To dive down into a next level of detail, we can use 'perf
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record'/'perf report' which will collect profiling data and
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present it to use using an interactive text-based UI (or
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simply as text if we specify --stdio to 'perf report').
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</para>
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<para>
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As our first attempt at profiling this workload, we'll simply
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run 'perf record', handing it the workload we want to profile
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(everything after 'perf record' and any perf options we hand
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it - here none - will be executed in a new shell). perf collects
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samples until the process exits and records them in a file named
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'perf.data' in the current working directory.
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<literallayout class='monospaced'>
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root@crownbay:~# perf record wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>
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Connecting to downloads.yoctoproject.org (140.211.169.59:80)
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linux-2.6.19.2.tar.b 100% |************************************************| 41727k 0:00:00 ETA
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[ perf record: Woken up 1 times to write data ]
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[ perf record: Captured and wrote 0.176 MB perf.data (~7700 samples) ]
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</literallayout>
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To see the results in a 'text-based UI' (tui), simply run
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'perf report', which will read the perf.data file in the current
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working directory and display the results in an interactive UI:
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<literallayout class='monospaced'>
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root@crownbay:~# perf report
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</literallayout>
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</para>
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<para>
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<imagedata fileref="figures/perf-wget-flat-stripped.png" width="6in" depth="7in" align="center" scalefit="1" />
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</para>
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<para>
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The above screenshot displays a 'flat' profile, one entry for
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each 'bucket' corresponding to the functions that were profiled
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during the profiling run, ordered from the most popular to the
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least (perf has options to sort in various orders and keys as
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well as display entries only above a certain threshold and so
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on - see the perf documentation for details). Note that this
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includes both userspace functions (entries containing a [.]) and
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kernel functions accounted to the process (entries containing
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a [k]). (perf has command-line modifiers that can be used to
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restrict the profiling to kernel or userspace, among others).
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</para>
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<para>
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Notice also that the above report shows an entry for 'busybox',
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which is the executable that implements 'wget' in Yocto, but that
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instead of a useful function name in that entry, it displays
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a not-so-friendly hex value instead. The steps below will show
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how to fix that problem.
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</para>
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<para>
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Before we do that, however, let's try running a different profile,
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one which shows something a little more interesting. The only
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difference between the new profile and the previous one is that
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we'll add the -g option, which will record not just the address
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of a sampled function, but the entire callchain to the sampled
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function as well:
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<literallayout class='monospaced'>
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root@crownbay:~# perf record -g wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>
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Connecting to downloads.yoctoproject.org (140.211.169.59:80)
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linux-2.6.19.2.tar.b 100% |************************************************| 41727k 0:00:00 ETA
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[ perf record: Woken up 3 times to write data ]
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[ perf record: Captured and wrote 0.652 MB perf.data (~28476 samples) ]
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root@crownbay:~# perf report
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</literallayout>
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</para>
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<para>
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<imagedata fileref="figures/perf-wget-g-copy-to-user-expanded-stripped.png" width="6in" depth="7in" align="center" scalefit="1" />
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</para>
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<para>
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Using the callgraph view, we can actually see not only which
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functions took the most time, but we can also see a summary of
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how those functions were called and learn something about how the
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program interacts with the kernel in the process.
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</para>
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<para>
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Notice that each entry in the above screenshot now contains a '+'
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on the left-hand side. This means that we can expand the entry and
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drill down into the callchains that feed into that entry.
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Pressing 'enter' on any one of them will expand the callchain
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(you can also press 'E' to expand them all at the same time or 'C'
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to collapse them all).
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</para>
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<para>
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In the screenshot above, we've toggled the __copy_to_user_ll()
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entry and several subnodes all the way down. This lets us see
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which callchains contributed to the profiled __copy_to_user_ll()
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function which contributed 1.77% to the total profile.
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</para>
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<para>
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As a bit of background explanation for these callchains, think
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about what happens at a high level when you run wget to get a file
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out on the network. Basically what happens is that the data comes
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into the kernel via the network connection (socket) and is passed
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to the userspace program 'wget' (which is actually a part of
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busybox, but that's not important for now), which takes the buffers
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the kernel passes to it and writes it to a disk file to save it.
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</para>
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<para>
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The part of this process that we're looking at in the above call
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stacks is the part where the kernel passes the data it's read from
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the socket down to wget i.e. a copy-to-user.
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</para>
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<para>
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Notice also that here there's also a case where the hex value
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is displayed in the callstack, here in the expanded
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sys_clock_gettime() function. Later we'll see it resolve to a
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userspace function call in busybox.
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</para>
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<para>
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<imagedata fileref="figures/perf-wget-g-copy-from-user-expanded-stripped.png" width="6in" depth="7in" align="center" scalefit="1" />
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</para>
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|
|
<para>
|
||
|
|
The above screenshot shows the other half of the journey for the
|
||
|
|
data - from the wget program's userspace buffers to disk. To get
|
||
|
|
the buffers to disk, the wget program issues a write(2), which
|
||
|
|
does a copy-from-user to the kernel, which then takes care via
|
||
|
|
some circuitous path (probably also present somewhere in the
|
||
|
|
profile data), to get it safely to disk.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Now that we've seen the basic layout of the profile data and the
|
||
|
|
basics of how to extract useful information out of it, let's get
|
||
|
|
back to the task at hand and see if we can get some basic idea
|
||
|
|
about where the time is spent in the program we're profiling,
|
||
|
|
wget. Remember that wget is actually implemented as an applet
|
||
|
|
in busybox, so while the process name is 'wget', the executable
|
||
|
|
we're actually interested in is busybox. So let's expand the
|
||
|
|
first entry containing busybox:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/perf-wget-busybox-expanded-stripped.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Again, before we expanded we saw that the function was labeled
|
||
|
|
with a hex value instead of a symbol as with most of the kernel
|
||
|
|
entries. Expanding the busybox entry doesn't make it any better.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The problem is that perf can't find the symbol information for the
|
||
|
|
busybox binary, which is actually stripped out by the Yocto build
|
||
|
|
system.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
One way around that is to put the following in your
|
||
|
|
<filename>local.conf</filename> file when you build the image:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
<ulink url='&YOCTO_DOCS_REF_URL;#var-INHIBIT_PACKAGE_STRIP'>INHIBIT_PACKAGE_STRIP</ulink> = "1"
|
||
|
|
</literallayout>
|
||
|
|
However, we already have an image with the binaries stripped,
|
||
|
|
so what can we do to get perf to resolve the symbols? Basically
|
||
|
|
we need to install the debuginfo for the busybox package.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
To generate the debug info for the packages in the image, we can
|
||
|
|
add dbg-pkgs to EXTRA_IMAGE_FEATURES in local.conf. For example:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
EXTRA_IMAGE_FEATURES = "debug-tweaks tools-profile dbg-pkgs"
|
||
|
|
</literallayout>
|
||
|
|
Additionally, in order to generate the type of debuginfo that
|
||
|
|
perf understands, we also need to add the following to local.conf:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
PACKAGE_DEBUG_SPLIT_STYLE = 'debug-file-directory'
|
||
|
|
</literallayout>
|
||
|
|
Once we've done that, we can install the debuginfo for busybox.
|
||
|
|
The debug packages once built can be found in
|
||
|
|
build/tmp/deploy/rpm/* on the host system. Find the
|
||
|
|
busybox-dbg-...rpm file and copy it to the target. For example:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
[trz@empanada core2]$ scp /home/trz/yocto/crownbay-tracing-dbg/build/tmp/deploy/rpm/core2_32/busybox-dbg-1.20.2-r2.core2_32.rpm root@192.168.1.31:
|
||
|
|
root@192.168.1.31's password:
|
||
|
|
busybox-dbg-1.20.2-r2.core2_32.rpm 100% 1826KB 1.8MB/s 00:01
|
||
|
|
</literallayout>
|
||
|
|
Now install the debug rpm on the target:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# rpm -i busybox-dbg-1.20.2-r2.core2_32.rpm
|
||
|
|
</literallayout>
|
||
|
|
Now that the debuginfo is installed, we see that the busybox
|
||
|
|
entries now display their functions symbolically:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/perf-wget-busybox-debuginfo.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
If we expand one of the entries and press 'enter' on a leaf node,
|
||
|
|
we're presented with a menu of actions we can take to get more
|
||
|
|
information related to that entry:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/perf-wget-busybox-dso-zoom-menu.png" width="6in" depth="2in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
One of these actions allows us to show a view that displays a
|
||
|
|
busybox-centric view of the profiled functions (in this case we've
|
||
|
|
also expanded all the nodes using the 'E' key):
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/perf-wget-busybox-dso-zoom.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Finally, we can see that now that the busybox debuginfo is
|
||
|
|
installed, the previously unresolved symbol in the
|
||
|
|
sys_clock_gettime() entry mentioned previously is now resolved,
|
||
|
|
and shows that the sys_clock_gettime system call that was the
|
||
|
|
source of 6.75% of the copy-to-user overhead was initiated by
|
||
|
|
the handle_input() busybox function:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/perf-wget-g-copy-to-user-expanded-debuginfo.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
At the lowest level of detail, we can dive down to the assembly
|
||
|
|
level and see which instructions caused the most overhead in a
|
||
|
|
function. Pressing 'enter' on the 'udhcpc_main' function, we're
|
||
|
|
again presented with a menu:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/perf-wget-busybox-annotate-menu.png" width="6in" depth="2in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Selecting 'Annotate udhcpc_main', we get a detailed listing of
|
||
|
|
percentages by instruction for the udhcpc_main function. From the
|
||
|
|
display, we can see that over 50% of the time spent in this
|
||
|
|
function is taken up by a couple tests and the move of a
|
||
|
|
constant (1) to a register:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/perf-wget-busybox-annotate-udhcpc.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
As a segue into tracing, let's try another profile using a
|
||
|
|
different counter, something other than the default 'cycles'.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The tracing and profiling infrastructure in Linux has become
|
||
|
|
unified in a way that allows us to use the same tool with a
|
||
|
|
completely different set of counters, not just the standard
|
||
|
|
hardware counters that traditional tools have had to restrict
|
||
|
|
themselves to (of course the traditional tools can also make use
|
||
|
|
of the expanded possibilities now available to them, and in some
|
||
|
|
cases have, as mentioned previously).
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
We can get a list of the available events that can be used to
|
||
|
|
profile a workload via 'perf list':
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf list
|
||
|
|
|
||
|
|
List of pre-defined events (to be used in -e):
|
||
|
|
cpu-cycles OR cycles [Hardware event]
|
||
|
|
stalled-cycles-frontend OR idle-cycles-frontend [Hardware event]
|
||
|
|
stalled-cycles-backend OR idle-cycles-backend [Hardware event]
|
||
|
|
instructions [Hardware event]
|
||
|
|
cache-references [Hardware event]
|
||
|
|
cache-misses [Hardware event]
|
||
|
|
branch-instructions OR branches [Hardware event]
|
||
|
|
branch-misses [Hardware event]
|
||
|
|
bus-cycles [Hardware event]
|
||
|
|
ref-cycles [Hardware event]
|
||
|
|
|
||
|
|
cpu-clock [Software event]
|
||
|
|
task-clock [Software event]
|
||
|
|
page-faults OR faults [Software event]
|
||
|
|
minor-faults [Software event]
|
||
|
|
major-faults [Software event]
|
||
|
|
context-switches OR cs [Software event]
|
||
|
|
cpu-migrations OR migrations [Software event]
|
||
|
|
alignment-faults [Software event]
|
||
|
|
emulation-faults [Software event]
|
||
|
|
|
||
|
|
L1-dcache-loads [Hardware cache event]
|
||
|
|
L1-dcache-load-misses [Hardware cache event]
|
||
|
|
L1-dcache-prefetch-misses [Hardware cache event]
|
||
|
|
L1-icache-loads [Hardware cache event]
|
||
|
|
L1-icache-load-misses [Hardware cache event]
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
rNNN [Raw hardware event descriptor]
|
||
|
|
cpu/t1=v1[,t2=v2,t3 ...]/modifier [Raw hardware event descriptor]
|
||
|
|
(see 'perf list --help' on how to encode it)
|
||
|
|
|
||
|
|
mem:<addr>[:access] [Hardware breakpoint]
|
||
|
|
|
||
|
|
sunrpc:rpc_call_status [Tracepoint event]
|
||
|
|
sunrpc:rpc_bind_status [Tracepoint event]
|
||
|
|
sunrpc:rpc_connect_status [Tracepoint event]
|
||
|
|
sunrpc:rpc_task_begin [Tracepoint event]
|
||
|
|
skb:kfree_skb [Tracepoint event]
|
||
|
|
skb:consume_skb [Tracepoint event]
|
||
|
|
skb:skb_copy_datagram_iovec [Tracepoint event]
|
||
|
|
net:net_dev_xmit [Tracepoint event]
|
||
|
|
net:net_dev_queue [Tracepoint event]
|
||
|
|
net:netif_receive_skb [Tracepoint event]
|
||
|
|
net:netif_rx [Tracepoint event]
|
||
|
|
napi:napi_poll [Tracepoint event]
|
||
|
|
sock:sock_rcvqueue_full [Tracepoint event]
|
||
|
|
sock:sock_exceed_buf_limit [Tracepoint event]
|
||
|
|
udp:udp_fail_queue_rcv_skb [Tracepoint event]
|
||
|
|
hda:hda_send_cmd [Tracepoint event]
|
||
|
|
hda:hda_get_response [Tracepoint event]
|
||
|
|
hda:hda_bus_reset [Tracepoint event]
|
||
|
|
scsi:scsi_dispatch_cmd_start [Tracepoint event]
|
||
|
|
scsi:scsi_dispatch_cmd_error [Tracepoint event]
|
||
|
|
scsi:scsi_eh_wakeup [Tracepoint event]
|
||
|
|
drm:drm_vblank_event [Tracepoint event]
|
||
|
|
drm:drm_vblank_event_queued [Tracepoint event]
|
||
|
|
drm:drm_vblank_event_delivered [Tracepoint event]
|
||
|
|
random:mix_pool_bytes [Tracepoint event]
|
||
|
|
random:mix_pool_bytes_nolock [Tracepoint event]
|
||
|
|
random:credit_entropy_bits [Tracepoint event]
|
||
|
|
gpio:gpio_direction [Tracepoint event]
|
||
|
|
gpio:gpio_value [Tracepoint event]
|
||
|
|
block:block_rq_abort [Tracepoint event]
|
||
|
|
block:block_rq_requeue [Tracepoint event]
|
||
|
|
block:block_rq_issue [Tracepoint event]
|
||
|
|
block:block_bio_bounce [Tracepoint event]
|
||
|
|
block:block_bio_complete [Tracepoint event]
|
||
|
|
block:block_bio_backmerge [Tracepoint event]
|
||
|
|
.
|
||
|
|
.
|
||
|
|
writeback:writeback_wake_thread [Tracepoint event]
|
||
|
|
writeback:writeback_wake_forker_thread [Tracepoint event]
|
||
|
|
writeback:writeback_bdi_register [Tracepoint event]
|
||
|
|
.
|
||
|
|
.
|
||
|
|
writeback:writeback_single_inode_requeue [Tracepoint event]
|
||
|
|
writeback:writeback_single_inode [Tracepoint event]
|
||
|
|
kmem:kmalloc [Tracepoint event]
|
||
|
|
kmem:kmem_cache_alloc [Tracepoint event]
|
||
|
|
kmem:mm_page_alloc [Tracepoint event]
|
||
|
|
kmem:mm_page_alloc_zone_locked [Tracepoint event]
|
||
|
|
kmem:mm_page_pcpu_drain [Tracepoint event]
|
||
|
|
kmem:mm_page_alloc_extfrag [Tracepoint event]
|
||
|
|
vmscan:mm_vmscan_kswapd_sleep [Tracepoint event]
|
||
|
|
vmscan:mm_vmscan_kswapd_wake [Tracepoint event]
|
||
|
|
vmscan:mm_vmscan_wakeup_kswapd [Tracepoint event]
|
||
|
|
vmscan:mm_vmscan_direct_reclaim_begin [Tracepoint event]
|
||
|
|
.
|
||
|
|
.
|
||
|
|
module:module_get [Tracepoint event]
|
||
|
|
module:module_put [Tracepoint event]
|
||
|
|
module:module_request [Tracepoint event]
|
||
|
|
sched:sched_kthread_stop [Tracepoint event]
|
||
|
|
sched:sched_wakeup [Tracepoint event]
|
||
|
|
sched:sched_wakeup_new [Tracepoint event]
|
||
|
|
sched:sched_process_fork [Tracepoint event]
|
||
|
|
sched:sched_process_exec [Tracepoint event]
|
||
|
|
sched:sched_stat_runtime [Tracepoint event]
|
||
|
|
rcu:rcu_utilization [Tracepoint event]
|
||
|
|
workqueue:workqueue_queue_work [Tracepoint event]
|
||
|
|
workqueue:workqueue_execute_end [Tracepoint event]
|
||
|
|
signal:signal_generate [Tracepoint event]
|
||
|
|
signal:signal_deliver [Tracepoint event]
|
||
|
|
timer:timer_init [Tracepoint event]
|
||
|
|
timer:timer_start [Tracepoint event]
|
||
|
|
timer:hrtimer_cancel [Tracepoint event]
|
||
|
|
timer:itimer_state [Tracepoint event]
|
||
|
|
timer:itimer_expire [Tracepoint event]
|
||
|
|
irq:irq_handler_entry [Tracepoint event]
|
||
|
|
irq:irq_handler_exit [Tracepoint event]
|
||
|
|
irq:softirq_entry [Tracepoint event]
|
||
|
|
irq:softirq_exit [Tracepoint event]
|
||
|
|
irq:softirq_raise [Tracepoint event]
|
||
|
|
printk:console [Tracepoint event]
|
||
|
|
task:task_newtask [Tracepoint event]
|
||
|
|
task:task_rename [Tracepoint event]
|
||
|
|
syscalls:sys_enter_socketcall [Tracepoint event]
|
||
|
|
syscalls:sys_exit_socketcall [Tracepoint event]
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
syscalls:sys_enter_unshare [Tracepoint event]
|
||
|
|
syscalls:sys_exit_unshare [Tracepoint event]
|
||
|
|
raw_syscalls:sys_enter [Tracepoint event]
|
||
|
|
raw_syscalls:sys_exit [Tracepoint event]
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<informalexample>
|
||
|
|
<emphasis>Tying it Together:</emphasis> These are exactly the same set of events defined
|
||
|
|
by the trace event subsystem and exposed by
|
||
|
|
ftrace/tracecmd/kernelshark as files in
|
||
|
|
/sys/kernel/debug/tracing/events, by SystemTap as
|
||
|
|
kernel.trace("tracepoint_name") and (partially) accessed by LTTng.
|
||
|
|
</informalexample>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Only a subset of these would be of interest to us when looking at
|
||
|
|
this workload, so let's choose the most likely subsystems
|
||
|
|
(identified by the string before the colon in the Tracepoint events)
|
||
|
|
and do a 'perf stat' run using only those wildcarded subsystems:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf stat -e skb:* -e net:* -e napi:* -e sched:* -e workqueue:* -e irq:* -e syscalls:* wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>
|
||
|
|
Performance counter stats for 'wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>':
|
||
|
|
|
||
|
|
23323 skb:kfree_skb
|
||
|
|
0 skb:consume_skb
|
||
|
|
49897 skb:skb_copy_datagram_iovec
|
||
|
|
6217 net:net_dev_xmit
|
||
|
|
6217 net:net_dev_queue
|
||
|
|
7962 net:netif_receive_skb
|
||
|
|
2 net:netif_rx
|
||
|
|
8340 napi:napi_poll
|
||
|
|
0 sched:sched_kthread_stop
|
||
|
|
0 sched:sched_kthread_stop_ret
|
||
|
|
3749 sched:sched_wakeup
|
||
|
|
0 sched:sched_wakeup_new
|
||
|
|
0 sched:sched_switch
|
||
|
|
29 sched:sched_migrate_task
|
||
|
|
0 sched:sched_process_free
|
||
|
|
1 sched:sched_process_exit
|
||
|
|
0 sched:sched_wait_task
|
||
|
|
0 sched:sched_process_wait
|
||
|
|
0 sched:sched_process_fork
|
||
|
|
1 sched:sched_process_exec
|
||
|
|
0 sched:sched_stat_wait
|
||
|
|
2106519415641 sched:sched_stat_sleep
|
||
|
|
0 sched:sched_stat_iowait
|
||
|
|
147453613 sched:sched_stat_blocked
|
||
|
|
12903026955 sched:sched_stat_runtime
|
||
|
|
0 sched:sched_pi_setprio
|
||
|
|
3574 workqueue:workqueue_queue_work
|
||
|
|
3574 workqueue:workqueue_activate_work
|
||
|
|
0 workqueue:workqueue_execute_start
|
||
|
|
0 workqueue:workqueue_execute_end
|
||
|
|
16631 irq:irq_handler_entry
|
||
|
|
16631 irq:irq_handler_exit
|
||
|
|
28521 irq:softirq_entry
|
||
|
|
28521 irq:softirq_exit
|
||
|
|
28728 irq:softirq_raise
|
||
|
|
1 syscalls:sys_enter_sendmmsg
|
||
|
|
1 syscalls:sys_exit_sendmmsg
|
||
|
|
0 syscalls:sys_enter_recvmmsg
|
||
|
|
0 syscalls:sys_exit_recvmmsg
|
||
|
|
14 syscalls:sys_enter_socketcall
|
||
|
|
14 syscalls:sys_exit_socketcall
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
16965 syscalls:sys_enter_read
|
||
|
|
16965 syscalls:sys_exit_read
|
||
|
|
12854 syscalls:sys_enter_write
|
||
|
|
12854 syscalls:sys_exit_write
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
|
||
|
|
58.029710972 seconds time elapsed
|
||
|
|
</literallayout>
|
||
|
|
Let's pick one of these tracepoints and tell perf to do a profile
|
||
|
|
using it as the sampling event:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf record -g -e sched:sched_wakeup wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/sched-wakeup-profile.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The screenshot above shows the results of running a profile using
|
||
|
|
sched:sched_switch tracepoint, which shows the relative costs of
|
||
|
|
various paths to sched_wakeup (note that sched_wakeup is the
|
||
|
|
name of the tracepoint - it's actually defined just inside
|
||
|
|
ttwu_do_wakeup(), which accounts for the function name actually
|
||
|
|
displayed in the profile:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
/*
|
||
|
|
* Mark the task runnable and perform wakeup-preemption.
|
||
|
|
*/
|
||
|
|
static void
|
||
|
|
ttwu_do_wakeup(struct rq *rq, struct task_struct *p, int wake_flags)
|
||
|
|
{
|
||
|
|
trace_sched_wakeup(p, true);
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
}
|
||
|
|
</literallayout>
|
||
|
|
A couple of the more interesting callchains are expanded and
|
||
|
|
displayed above, basically some network receive paths that
|
||
|
|
presumably end up waking up wget (busybox) when network data is
|
||
|
|
ready.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Note that because tracepoints are normally used for tracing,
|
||
|
|
the default sampling period for tracepoints is 1 i.e. for
|
||
|
|
tracepoints perf will sample on every event occurrence (this
|
||
|
|
can be changed using the -c option). This is in contrast to
|
||
|
|
hardware counters such as for example the default 'cycles'
|
||
|
|
hardware counter used for normal profiling, where sampling
|
||
|
|
periods are much higher (in the thousands) because profiling should
|
||
|
|
have as low an overhead as possible and sampling on every cycle
|
||
|
|
would be prohibitively expensive.
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='using-perf-to-do-basic-tracing'>
|
||
|
|
<title>Using perf to do Basic Tracing</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Profiling is a great tool for solving many problems or for
|
||
|
|
getting a high-level view of what's going on with a workload or
|
||
|
|
across the system. It is however by definition an approximation,
|
||
|
|
as suggested by the most prominent word associated with it,
|
||
|
|
'sampling'. On the one hand, it allows a representative picture of
|
||
|
|
what's going on in the system to be cheaply taken, but on the other
|
||
|
|
hand, that cheapness limits its utility when that data suggests a
|
||
|
|
need to 'dive down' more deeply to discover what's really going
|
||
|
|
on. In such cases, the only way to see what's really going on is
|
||
|
|
to be able to look at (or summarize more intelligently) the
|
||
|
|
individual steps that go into the higher-level behavior exposed
|
||
|
|
by the coarse-grained profiling data.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
As a concrete example, we can trace all the events we think might
|
||
|
|
be applicable to our workload:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf record -g -e skb:* -e net:* -e napi:* -e sched:sched_switch -e sched:sched_wakeup -e irq:*
|
||
|
|
-e syscalls:sys_enter_read -e syscalls:sys_exit_read -e syscalls:sys_enter_write -e syscalls:sys_exit_write
|
||
|
|
wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>
|
||
|
|
</literallayout>
|
||
|
|
We can look at the raw trace output using 'perf script' with no
|
||
|
|
arguments:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf script
|
||
|
|
|
||
|
|
perf 1262 [000] 11624.857082: sys_exit_read: 0x0
|
||
|
|
perf 1262 [000] 11624.857193: sched_wakeup: comm=migration/0 pid=6 prio=0 success=1 target_cpu=000
|
||
|
|
wget 1262 [001] 11624.858021: softirq_raise: vec=1 [action=TIMER]
|
||
|
|
wget 1262 [001] 11624.858074: softirq_entry: vec=1 [action=TIMER]
|
||
|
|
wget 1262 [001] 11624.858081: softirq_exit: vec=1 [action=TIMER]
|
||
|
|
wget 1262 [001] 11624.858166: sys_enter_read: fd: 0x0003, buf: 0xbf82c940, count: 0x0200
|
||
|
|
wget 1262 [001] 11624.858177: sys_exit_read: 0x200
|
||
|
|
wget 1262 [001] 11624.858878: kfree_skb: skbaddr=0xeb248d80 protocol=0 location=0xc15a5308
|
||
|
|
wget 1262 [001] 11624.858945: kfree_skb: skbaddr=0xeb248000 protocol=0 location=0xc15a5308
|
||
|
|
wget 1262 [001] 11624.859020: softirq_raise: vec=1 [action=TIMER]
|
||
|
|
wget 1262 [001] 11624.859076: softirq_entry: vec=1 [action=TIMER]
|
||
|
|
wget 1262 [001] 11624.859083: softirq_exit: vec=1 [action=TIMER]
|
||
|
|
wget 1262 [001] 11624.859167: sys_enter_read: fd: 0x0003, buf: 0xb7720000, count: 0x0400
|
||
|
|
wget 1262 [001] 11624.859192: sys_exit_read: 0x1d7
|
||
|
|
wget 1262 [001] 11624.859228: sys_enter_read: fd: 0x0003, buf: 0xb7720000, count: 0x0400
|
||
|
|
wget 1262 [001] 11624.859233: sys_exit_read: 0x0
|
||
|
|
wget 1262 [001] 11624.859573: sys_enter_read: fd: 0x0003, buf: 0xbf82c580, count: 0x0200
|
||
|
|
wget 1262 [001] 11624.859584: sys_exit_read: 0x200
|
||
|
|
wget 1262 [001] 11624.859864: sys_enter_read: fd: 0x0003, buf: 0xb7720000, count: 0x0400
|
||
|
|
wget 1262 [001] 11624.859888: sys_exit_read: 0x400
|
||
|
|
wget 1262 [001] 11624.859935: sys_enter_read: fd: 0x0003, buf: 0xb7720000, count: 0x0400
|
||
|
|
wget 1262 [001] 11624.859944: sys_exit_read: 0x400
|
||
|
|
</literallayout>
|
||
|
|
This gives us a detailed timestamped sequence of events that
|
||
|
|
occurred within the workload with respect to those events.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
In many ways, profiling can be viewed as a subset of tracing -
|
||
|
|
theoretically, if you have a set of trace events that's sufficient
|
||
|
|
to capture all the important aspects of a workload, you can derive
|
||
|
|
any of the results or views that a profiling run can.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Another aspect of traditional profiling is that while powerful in
|
||
|
|
many ways, it's limited by the granularity of the underlying data.
|
||
|
|
Profiling tools offer various ways of sorting and presenting the
|
||
|
|
sample data, which make it much more useful and amenable to user
|
||
|
|
experimentation, but in the end it can't be used in an open-ended
|
||
|
|
way to extract data that just isn't present as a consequence of
|
||
|
|
the fact that conceptually, most of it has been thrown away.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Full-blown detailed tracing data does however offer the opportunity
|
||
|
|
to manipulate and present the information collected during a
|
||
|
|
tracing run in an infinite variety of ways.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Another way to look at it is that there are only so many ways that
|
||
|
|
the 'primitive' counters can be used on their own to generate
|
||
|
|
interesting output; to get anything more complicated than simple
|
||
|
|
counts requires some amount of additional logic, which is typically
|
||
|
|
very specific to the problem at hand. For example, if we wanted to
|
||
|
|
make use of a 'counter' that maps to the value of the time
|
||
|
|
difference between when a process was scheduled to run on a
|
||
|
|
processor and the time it actually ran, we wouldn't expect such
|
||
|
|
a counter to exist on its own, but we could derive one called say
|
||
|
|
'wakeup_latency' and use it to extract a useful view of that metric
|
||
|
|
from trace data. Likewise, we really can't figure out from standard
|
||
|
|
profiling tools how much data every process on the system reads and
|
||
|
|
writes, along with how many of those reads and writes fail
|
||
|
|
completely. If we have sufficient trace data, however, we could
|
||
|
|
with the right tools easily extract and present that information,
|
||
|
|
but we'd need something other than pre-canned profiling tools to
|
||
|
|
do that.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Luckily, there is a general-purpose way to handle such needs,
|
||
|
|
called 'programming languages'. Making programming languages
|
||
|
|
easily available to apply to such problems given the specific
|
||
|
|
format of data is called a 'programming language binding' for
|
||
|
|
that data and language. Perf supports two programming language
|
||
|
|
bindings, one for Python and one for Perl.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<informalexample>
|
||
|
|
<emphasis>Tying it Together:</emphasis> Language bindings for manipulating and
|
||
|
|
aggregating trace data are of course not a new
|
||
|
|
idea. One of the first projects to do this was IBM's DProbes
|
||
|
|
dpcc compiler, an ANSI C compiler which targeted a low-level
|
||
|
|
assembly language running on an in-kernel interpreter on the
|
||
|
|
target system. This is exactly analogous to what Sun's DTrace
|
||
|
|
did, except that DTrace invented its own language for the purpose.
|
||
|
|
Systemtap, heavily inspired by DTrace, also created its own
|
||
|
|
one-off language, but rather than running the product on an
|
||
|
|
in-kernel interpreter, created an elaborate compiler-based
|
||
|
|
machinery to translate its language into kernel modules written
|
||
|
|
in C.
|
||
|
|
</informalexample>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Now that we have the trace data in perf.data, we can use
|
||
|
|
'perf script -g' to generate a skeleton script with handlers
|
||
|
|
for the read/write entry/exit events we recorded:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf script -g python
|
||
|
|
generated Python script: perf-script.py
|
||
|
|
</literallayout>
|
||
|
|
The skeleton script simply creates a python function for each
|
||
|
|
event type in the perf.data file. The body of each function simply
|
||
|
|
prints the event name along with its parameters. For example:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
def net__netif_rx(event_name, context, common_cpu,
|
||
|
|
common_secs, common_nsecs, common_pid, common_comm,
|
||
|
|
skbaddr, len, name):
|
||
|
|
print_header(event_name, common_cpu, common_secs, common_nsecs,
|
||
|
|
common_pid, common_comm)
|
||
|
|
|
||
|
|
print "skbaddr=%u, len=%u, name=%s\n" % (skbaddr, len, name),
|
||
|
|
</literallayout>
|
||
|
|
We can run that script directly to print all of the events
|
||
|
|
contained in the perf.data file:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf script -s perf-script.py
|
||
|
|
|
||
|
|
in trace_begin
|
||
|
|
syscalls__sys_exit_read 0 11624.857082795 1262 perf nr=3, ret=0
|
||
|
|
sched__sched_wakeup 0 11624.857193498 1262 perf comm=migration/0, pid=6, prio=0, success=1, target_cpu=0
|
||
|
|
irq__softirq_raise 1 11624.858021635 1262 wget vec=TIMER
|
||
|
|
irq__softirq_entry 1 11624.858074075 1262 wget vec=TIMER
|
||
|
|
irq__softirq_exit 1 11624.858081389 1262 wget vec=TIMER
|
||
|
|
syscalls__sys_enter_read 1 11624.858166434 1262 wget nr=3, fd=3, buf=3213019456, count=512
|
||
|
|
syscalls__sys_exit_read 1 11624.858177924 1262 wget nr=3, ret=512
|
||
|
|
skb__kfree_skb 1 11624.858878188 1262 wget skbaddr=3945041280, location=3243922184, protocol=0
|
||
|
|
skb__kfree_skb 1 11624.858945608 1262 wget skbaddr=3945037824, location=3243922184, protocol=0
|
||
|
|
irq__softirq_raise 1 11624.859020942 1262 wget vec=TIMER
|
||
|
|
irq__softirq_entry 1 11624.859076935 1262 wget vec=TIMER
|
||
|
|
irq__softirq_exit 1 11624.859083469 1262 wget vec=TIMER
|
||
|
|
syscalls__sys_enter_read 1 11624.859167565 1262 wget nr=3, fd=3, buf=3077701632, count=1024
|
||
|
|
syscalls__sys_exit_read 1 11624.859192533 1262 wget nr=3, ret=471
|
||
|
|
syscalls__sys_enter_read 1 11624.859228072 1262 wget nr=3, fd=3, buf=3077701632, count=1024
|
||
|
|
syscalls__sys_exit_read 1 11624.859233707 1262 wget nr=3, ret=0
|
||
|
|
syscalls__sys_enter_read 1 11624.859573008 1262 wget nr=3, fd=3, buf=3213018496, count=512
|
||
|
|
syscalls__sys_exit_read 1 11624.859584818 1262 wget nr=3, ret=512
|
||
|
|
syscalls__sys_enter_read 1 11624.859864562 1262 wget nr=3, fd=3, buf=3077701632, count=1024
|
||
|
|
syscalls__sys_exit_read 1 11624.859888770 1262 wget nr=3, ret=1024
|
||
|
|
syscalls__sys_enter_read 1 11624.859935140 1262 wget nr=3, fd=3, buf=3077701632, count=1024
|
||
|
|
syscalls__sys_exit_read 1 11624.859944032 1262 wget nr=3, ret=1024
|
||
|
|
</literallayout>
|
||
|
|
That in itself isn't very useful; after all, we can accomplish
|
||
|
|
pretty much the same thing by simply running 'perf script'
|
||
|
|
without arguments in the same directory as the perf.data file.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
We can however replace the print statements in the generated
|
||
|
|
function bodies with whatever we want, and thereby make it
|
||
|
|
infinitely more useful.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
As a simple example, let's just replace the print statements in
|
||
|
|
the function bodies with a simple function that does nothing but
|
||
|
|
increment a per-event count. When the program is run against a
|
||
|
|
perf.data file, each time a particular event is encountered,
|
||
|
|
a tally is incremented for that event. For example:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
def net__netif_rx(event_name, context, common_cpu,
|
||
|
|
common_secs, common_nsecs, common_pid, common_comm,
|
||
|
|
skbaddr, len, name):
|
||
|
|
inc_counts(event_name)
|
||
|
|
</literallayout>
|
||
|
|
Each event handler function in the generated code is modified
|
||
|
|
to do this. For convenience, we define a common function called
|
||
|
|
inc_counts() that each handler calls; inc_counts() simply tallies
|
||
|
|
a count for each event using the 'counts' hash, which is a
|
||
|
|
specialized hash function that does Perl-like autovivification, a
|
||
|
|
capability that's extremely useful for kinds of multi-level
|
||
|
|
aggregation commonly used in processing traces (see perf's
|
||
|
|
documentation on the Python language binding for details):
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
counts = autodict()
|
||
|
|
|
||
|
|
def inc_counts(event_name):
|
||
|
|
try:
|
||
|
|
counts[event_name] += 1
|
||
|
|
except TypeError:
|
||
|
|
counts[event_name] = 1
|
||
|
|
</literallayout>
|
||
|
|
Finally, at the end of the trace processing run, we want to
|
||
|
|
print the result of all the per-event tallies. For that, we
|
||
|
|
use the special 'trace_end()' function:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
def trace_end():
|
||
|
|
for event_name, count in counts.iteritems():
|
||
|
|
print "%-40s %10s\n" % (event_name, count)
|
||
|
|
</literallayout>
|
||
|
|
The end result is a summary of all the events recorded in the
|
||
|
|
trace:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
skb__skb_copy_datagram_iovec 13148
|
||
|
|
irq__softirq_entry 4796
|
||
|
|
irq__irq_handler_exit 3805
|
||
|
|
irq__softirq_exit 4795
|
||
|
|
syscalls__sys_enter_write 8990
|
||
|
|
net__net_dev_xmit 652
|
||
|
|
skb__kfree_skb 4047
|
||
|
|
sched__sched_wakeup 1155
|
||
|
|
irq__irq_handler_entry 3804
|
||
|
|
irq__softirq_raise 4799
|
||
|
|
net__net_dev_queue 652
|
||
|
|
syscalls__sys_enter_read 17599
|
||
|
|
net__netif_receive_skb 1743
|
||
|
|
syscalls__sys_exit_read 17598
|
||
|
|
net__netif_rx 2
|
||
|
|
napi__napi_poll 1877
|
||
|
|
syscalls__sys_exit_write 8990
|
||
|
|
</literallayout>
|
||
|
|
Note that this is pretty much exactly the same information we get
|
||
|
|
from 'perf stat', which goes a little way to support the idea
|
||
|
|
mentioned previously that given the right kind of trace data,
|
||
|
|
higher-level profiling-type summaries can be derived from it.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Documentation on using the
|
||
|
|
<ulink url='http://linux.die.net/man/1/perf-script-python'>'perf script' python binding</ulink>.
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='system-wide-tracing-and-profiling'>
|
||
|
|
<title>System-Wide Tracing and Profiling</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The examples so far have focused on tracing a particular program or
|
||
|
|
workload - in other words, every profiling run has specified the
|
||
|
|
program to profile in the command-line e.g. 'perf record wget ...'.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
It's also possible, and more interesting in many cases, to run a
|
||
|
|
system-wide profile or trace while running the workload in a
|
||
|
|
separate shell.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
To do system-wide profiling or tracing, you typically use
|
||
|
|
the -a flag to 'perf record'.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
To demonstrate this, open up one window and start the profile
|
||
|
|
using the -a flag (press Ctrl-C to stop tracing):
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf record -g -a
|
||
|
|
^C[ perf record: Woken up 6 times to write data ]
|
||
|
|
[ perf record: Captured and wrote 1.400 MB perf.data (~61172 samples) ]
|
||
|
|
</literallayout>
|
||
|
|
In another window, run the wget test:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>
|
||
|
|
Connecting to downloads.yoctoproject.org (140.211.169.59:80)
|
||
|
|
linux-2.6.19.2.tar.b 100% |*******************************| 41727k 0:00:00 ETA
|
||
|
|
</literallayout>
|
||
|
|
Here we see entries not only for our wget load, but for other
|
||
|
|
processes running on the system as well:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/perf-systemwide.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
In the snapshot above, we can see callchains that originate in
|
||
|
|
libc, and a callchain from Xorg that demonstrates that we're
|
||
|
|
using a proprietary X driver in userspace (notice the presence
|
||
|
|
of 'PVR' and some other unresolvable symbols in the expanded
|
||
|
|
Xorg callchain).
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Note also that we have both kernel and userspace entries in the
|
||
|
|
above snapshot. We can also tell perf to focus on userspace but
|
||
|
|
providing a modifier, in this case 'u', to the 'cycles' hardware
|
||
|
|
counter when we record a profile:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf record -g -a -e cycles:u
|
||
|
|
^C[ perf record: Woken up 2 times to write data ]
|
||
|
|
[ perf record: Captured and wrote 0.376 MB perf.data (~16443 samples) ]
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/perf-report-cycles-u.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Notice in the screenshot above, we see only userspace entries ([.])
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Finally, we can press 'enter' on a leaf node and select the 'Zoom
|
||
|
|
into DSO' menu item to show only entries associated with a
|
||
|
|
specific DSO. In the screenshot below, we've zoomed into the
|
||
|
|
'libc' DSO which shows all the entries associated with the
|
||
|
|
libc-xxx.so DSO.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/perf-systemwide-libc.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
We can also use the system-wide -a switch to do system-wide
|
||
|
|
tracing. Here we'll trace a couple of scheduler events:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf record -a -e sched:sched_switch -e sched:sched_wakeup
|
||
|
|
^C[ perf record: Woken up 38 times to write data ]
|
||
|
|
[ perf record: Captured and wrote 9.780 MB perf.data (~427299 samples) ]
|
||
|
|
</literallayout>
|
||
|
|
We can look at the raw output using 'perf script' with no
|
||
|
|
arguments:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf script
|
||
|
|
|
||
|
|
perf 1383 [001] 6171.460045: sched_wakeup: comm=kworker/1:1 pid=21 prio=120 success=1 target_cpu=001
|
||
|
|
perf 1383 [001] 6171.460066: sched_switch: prev_comm=perf prev_pid=1383 prev_prio=120 prev_state=R+ ==> next_comm=kworker/1:1 next_pid=21 next_prio=120
|
||
|
|
kworker/1:1 21 [001] 6171.460093: sched_switch: prev_comm=kworker/1:1 prev_pid=21 prev_prio=120 prev_state=S ==> next_comm=perf next_pid=1383 next_prio=120
|
||
|
|
swapper 0 [000] 6171.468063: sched_wakeup: comm=kworker/0:3 pid=1209 prio=120 success=1 target_cpu=000
|
||
|
|
swapper 0 [000] 6171.468107: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=kworker/0:3 next_pid=1209 next_prio=120
|
||
|
|
kworker/0:3 1209 [000] 6171.468143: sched_switch: prev_comm=kworker/0:3 prev_pid=1209 prev_prio=120 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120
|
||
|
|
perf 1383 [001] 6171.470039: sched_wakeup: comm=kworker/1:1 pid=21 prio=120 success=1 target_cpu=001
|
||
|
|
perf 1383 [001] 6171.470058: sched_switch: prev_comm=perf prev_pid=1383 prev_prio=120 prev_state=R+ ==> next_comm=kworker/1:1 next_pid=21 next_prio=120
|
||
|
|
kworker/1:1 21 [001] 6171.470082: sched_switch: prev_comm=kworker/1:1 prev_pid=21 prev_prio=120 prev_state=S ==> next_comm=perf next_pid=1383 next_prio=120
|
||
|
|
perf 1383 [001] 6171.480035: sched_wakeup: comm=kworker/1:1 pid=21 prio=120 success=1 target_cpu=001
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<section id='perf-filtering'>
|
||
|
|
<title>Filtering</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Notice that there are a lot of events that don't really have
|
||
|
|
anything to do with what we're interested in, namely events
|
||
|
|
that schedule 'perf' itself in and out or that wake perf up.
|
||
|
|
We can get rid of those by using the '--filter' option -
|
||
|
|
for each event we specify using -e, we can add a --filter
|
||
|
|
after that to filter out trace events that contain fields
|
||
|
|
with specific values:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf record -a -e sched:sched_switch --filter 'next_comm != perf && prev_comm != perf' -e sched:sched_wakeup --filter 'comm != perf'
|
||
|
|
^C[ perf record: Woken up 38 times to write data ]
|
||
|
|
[ perf record: Captured and wrote 9.688 MB perf.data (~423279 samples) ]
|
||
|
|
|
||
|
|
|
||
|
|
root@crownbay:~# perf script
|
||
|
|
|
||
|
|
swapper 0 [000] 7932.162180: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=kworker/0:3 next_pid=1209 next_prio=120
|
||
|
|
kworker/0:3 1209 [000] 7932.162236: sched_switch: prev_comm=kworker/0:3 prev_pid=1209 prev_prio=120 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120
|
||
|
|
perf 1407 [001] 7932.170048: sched_wakeup: comm=kworker/1:1 pid=21 prio=120 success=1 target_cpu=001
|
||
|
|
perf 1407 [001] 7932.180044: sched_wakeup: comm=kworker/1:1 pid=21 prio=120 success=1 target_cpu=001
|
||
|
|
perf 1407 [001] 7932.190038: sched_wakeup: comm=kworker/1:1 pid=21 prio=120 success=1 target_cpu=001
|
||
|
|
perf 1407 [001] 7932.200044: sched_wakeup: comm=kworker/1:1 pid=21 prio=120 success=1 target_cpu=001
|
||
|
|
perf 1407 [001] 7932.210044: sched_wakeup: comm=kworker/1:1 pid=21 prio=120 success=1 target_cpu=001
|
||
|
|
perf 1407 [001] 7932.220044: sched_wakeup: comm=kworker/1:1 pid=21 prio=120 success=1 target_cpu=001
|
||
|
|
swapper 0 [001] 7932.230111: sched_wakeup: comm=kworker/1:1 pid=21 prio=120 success=1 target_cpu=001
|
||
|
|
swapper 0 [001] 7932.230146: sched_switch: prev_comm=swapper/1 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=kworker/1:1 next_pid=21 next_prio=120
|
||
|
|
kworker/1:1 21 [001] 7932.230205: sched_switch: prev_comm=kworker/1:1 prev_pid=21 prev_prio=120 prev_state=S ==> next_comm=swapper/1 next_pid=0 next_prio=120
|
||
|
|
swapper 0 [000] 7932.326109: sched_wakeup: comm=kworker/0:3 pid=1209 prio=120 success=1 target_cpu=000
|
||
|
|
swapper 0 [000] 7932.326171: sched_switch: prev_comm=swapper/0 prev_pid=0 prev_prio=120 prev_state=R ==> next_comm=kworker/0:3 next_pid=1209 next_prio=120
|
||
|
|
kworker/0:3 1209 [000] 7932.326214: sched_switch: prev_comm=kworker/0:3 prev_pid=1209 prev_prio=120 prev_state=S ==> next_comm=swapper/0 next_pid=0 next_prio=120
|
||
|
|
</literallayout>
|
||
|
|
In this case, we've filtered out all events that have 'perf'
|
||
|
|
in their 'comm' or 'comm_prev' or 'comm_next' fields. Notice
|
||
|
|
that there are still events recorded for perf, but notice
|
||
|
|
that those events don't have values of 'perf' for the filtered
|
||
|
|
fields. To completely filter out anything from perf will
|
||
|
|
require a bit more work, but for the purpose of demonstrating
|
||
|
|
how to use filters, it's close enough.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<informalexample>
|
||
|
|
<emphasis>Tying it Together:</emphasis> These are exactly the same set of event
|
||
|
|
filters defined by the trace event subsystem. See the
|
||
|
|
ftrace/tracecmd/kernelshark section for more discussion about
|
||
|
|
these event filters.
|
||
|
|
</informalexample>
|
||
|
|
|
||
|
|
<informalexample>
|
||
|
|
<emphasis>Tying it Together:</emphasis> These event filters are implemented by a
|
||
|
|
special-purpose pseudo-interpreter in the kernel and are an
|
||
|
|
integral and indispensable part of the perf design as it
|
||
|
|
relates to tracing. kernel-based event filters provide a
|
||
|
|
mechanism to precisely throttle the event stream that appears
|
||
|
|
in user space, where it makes sense to provide bindings to real
|
||
|
|
programming languages for postprocessing the event stream.
|
||
|
|
This architecture allows for the intelligent and flexible
|
||
|
|
partitioning of processing between the kernel and user space.
|
||
|
|
Contrast this with other tools such as SystemTap, which does
|
||
|
|
all of its processing in the kernel and as such requires a
|
||
|
|
special project-defined language in order to accommodate that
|
||
|
|
design, or LTTng, where everything is sent to userspace and
|
||
|
|
as such requires a super-efficient kernel-to-userspace
|
||
|
|
transport mechanism in order to function properly. While
|
||
|
|
perf certainly can benefit from for instance advances in
|
||
|
|
the design of the transport, it doesn't fundamentally depend
|
||
|
|
on them. Basically, if you find that your perf tracing
|
||
|
|
application is causing buffer I/O overruns, it probably
|
||
|
|
means that you aren't taking enough advantage of the
|
||
|
|
kernel filtering engine.
|
||
|
|
</informalexample>
|
||
|
|
</section>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='using-dynamic-tracepoints'>
|
||
|
|
<title>Using Dynamic Tracepoints</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
perf isn't restricted to the fixed set of static tracepoints
|
||
|
|
listed by 'perf list'. Users can also add their own 'dynamic'
|
||
|
|
tracepoints anywhere in the kernel. For instance, suppose we
|
||
|
|
want to define our own tracepoint on do_fork(). We can do that
|
||
|
|
using the 'perf probe' perf subcommand:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf probe do_fork
|
||
|
|
Added new event:
|
||
|
|
probe:do_fork (on do_fork)
|
||
|
|
|
||
|
|
You can now use it in all perf tools, such as:
|
||
|
|
|
||
|
|
perf record -e probe:do_fork -aR sleep 1
|
||
|
|
</literallayout>
|
||
|
|
Adding a new tracepoint via 'perf probe' results in an event
|
||
|
|
with all the expected files and format in
|
||
|
|
/sys/kernel/debug/tracing/events, just the same as for static
|
||
|
|
tracepoints (as discussed in more detail in the trace events
|
||
|
|
subsystem section:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:/sys/kernel/debug/tracing/events/probe/do_fork# ls -al
|
||
|
|
drwxr-xr-x 2 root root 0 Oct 28 11:42 .
|
||
|
|
drwxr-xr-x 3 root root 0 Oct 28 11:42 ..
|
||
|
|
-rw-r--r-- 1 root root 0 Oct 28 11:42 enable
|
||
|
|
-rw-r--r-- 1 root root 0 Oct 28 11:42 filter
|
||
|
|
-r--r--r-- 1 root root 0 Oct 28 11:42 format
|
||
|
|
-r--r--r-- 1 root root 0 Oct 28 11:42 id
|
||
|
|
|
||
|
|
root@crownbay:/sys/kernel/debug/tracing/events/probe/do_fork# cat format
|
||
|
|
name: do_fork
|
||
|
|
ID: 944
|
||
|
|
format:
|
||
|
|
field:unsigned short common_type; offset:0; size:2; signed:0;
|
||
|
|
field:unsigned char common_flags; offset:2; size:1; signed:0;
|
||
|
|
field:unsigned char common_preempt_count; offset:3; size:1; signed:0;
|
||
|
|
field:int common_pid; offset:4; size:4; signed:1;
|
||
|
|
field:int common_padding; offset:8; size:4; signed:1;
|
||
|
|
|
||
|
|
field:unsigned long __probe_ip; offset:12; size:4; signed:0;
|
||
|
|
|
||
|
|
print fmt: "(%lx)", REC->__probe_ip
|
||
|
|
</literallayout>
|
||
|
|
We can list all dynamic tracepoints currently in existence:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf probe -l
|
||
|
|
probe:do_fork (on do_fork)
|
||
|
|
probe:schedule (on schedule)
|
||
|
|
</literallayout>
|
||
|
|
Let's record system-wide ('sleep 30' is a trick for recording
|
||
|
|
system-wide but basically do nothing and then wake up after
|
||
|
|
30 seconds):
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf record -g -a -e probe:do_fork sleep 30
|
||
|
|
[ perf record: Woken up 1 times to write data ]
|
||
|
|
[ perf record: Captured and wrote 0.087 MB perf.data (~3812 samples) ]
|
||
|
|
</literallayout>
|
||
|
|
Using 'perf script' we can see each do_fork event that fired:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# perf script
|
||
|
|
|
||
|
|
# ========
|
||
|
|
# captured on: Sun Oct 28 11:55:18 2012
|
||
|
|
# hostname : crownbay
|
||
|
|
# os release : 3.4.11-yocto-standard
|
||
|
|
# perf version : 3.4.11
|
||
|
|
# arch : i686
|
||
|
|
# nrcpus online : 2
|
||
|
|
# nrcpus avail : 2
|
||
|
|
# cpudesc : Intel(R) Atom(TM) CPU E660 @ 1.30GHz
|
||
|
|
# cpuid : GenuineIntel,6,38,1
|
||
|
|
# total memory : 1017184 kB
|
||
|
|
# cmdline : /usr/bin/perf record -g -a -e probe:do_fork sleep 30
|
||
|
|
# event : name = probe:do_fork, type = 2, config = 0x3b0, config1 = 0x0, config2 = 0x0, excl_usr = 0, excl_kern
|
||
|
|
= 0, id = { 5, 6 }
|
||
|
|
# HEADER_CPU_TOPOLOGY info available, use -I to display
|
||
|
|
# ========
|
||
|
|
#
|
||
|
|
matchbox-deskto 1197 [001] 34211.378318: do_fork: (c1028460)
|
||
|
|
matchbox-deskto 1295 [001] 34211.380388: do_fork: (c1028460)
|
||
|
|
pcmanfm 1296 [000] 34211.632350: do_fork: (c1028460)
|
||
|
|
pcmanfm 1296 [000] 34211.639917: do_fork: (c1028460)
|
||
|
|
matchbox-deskto 1197 [001] 34217.541603: do_fork: (c1028460)
|
||
|
|
matchbox-deskto 1299 [001] 34217.543584: do_fork: (c1028460)
|
||
|
|
gthumb 1300 [001] 34217.697451: do_fork: (c1028460)
|
||
|
|
gthumb 1300 [001] 34219.085734: do_fork: (c1028460)
|
||
|
|
gthumb 1300 [000] 34219.121351: do_fork: (c1028460)
|
||
|
|
gthumb 1300 [001] 34219.264551: do_fork: (c1028460)
|
||
|
|
pcmanfm 1296 [000] 34219.590380: do_fork: (c1028460)
|
||
|
|
matchbox-deskto 1197 [001] 34224.955965: do_fork: (c1028460)
|
||
|
|
matchbox-deskto 1306 [001] 34224.957972: do_fork: (c1028460)
|
||
|
|
matchbox-termin 1307 [000] 34225.038214: do_fork: (c1028460)
|
||
|
|
matchbox-termin 1307 [001] 34225.044218: do_fork: (c1028460)
|
||
|
|
matchbox-termin 1307 [000] 34225.046442: do_fork: (c1028460)
|
||
|
|
matchbox-deskto 1197 [001] 34237.112138: do_fork: (c1028460)
|
||
|
|
matchbox-deskto 1311 [001] 34237.114106: do_fork: (c1028460)
|
||
|
|
gaku 1312 [000] 34237.202388: do_fork: (c1028460)
|
||
|
|
</literallayout>
|
||
|
|
And using 'perf report' on the same file, we can see the
|
||
|
|
callgraphs from starting a few programs during those 30 seconds:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/perf-probe-do_fork-profile.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<informalexample>
|
||
|
|
<emphasis>Tying it Together:</emphasis> The trace events subsystem accommodate static
|
||
|
|
and dynamic tracepoints in exactly the same way - there's no
|
||
|
|
difference as far as the infrastructure is concerned. See the
|
||
|
|
ftrace section for more details on the trace event subsystem.
|
||
|
|
</informalexample>
|
||
|
|
|
||
|
|
<informalexample>
|
||
|
|
<emphasis>Tying it Together:</emphasis> Dynamic tracepoints are implemented under the
|
||
|
|
covers by kprobes and uprobes. kprobes and uprobes are also used
|
||
|
|
by and in fact are the main focus of SystemTap.
|
||
|
|
</informalexample>
|
||
|
|
</section>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='perf-documentation'>
|
||
|
|
<title>Documentation</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Online versions of the man pages for the commands discussed in this
|
||
|
|
section can be found here:
|
||
|
|
<itemizedlist>
|
||
|
|
<listitem><para>The <ulink url='http://linux.die.net/man/1/perf-stat'>'perf stat' manpage</ulink>.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para>The <ulink url='http://linux.die.net/man/1/perf-record'>'perf record' manpage</ulink>.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para>The <ulink url='http://linux.die.net/man/1/perf-report'>'perf report' manpage</ulink>.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para>The <ulink url='http://linux.die.net/man/1/perf-probe'>'perf probe' manpage</ulink>.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para>The <ulink url='http://linux.die.net/man/1/perf-script'>'perf script' manpage</ulink>.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para>Documentation on using the
|
||
|
|
<ulink url='http://linux.die.net/man/1/perf-script-python'>'perf script' python binding</ulink>.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para>The top-level
|
||
|
|
<ulink url='http://linux.die.net/man/1/perf'>perf(1) manpage</ulink>.
|
||
|
|
</para></listitem>
|
||
|
|
</itemizedlist>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Normally, you should be able to invoke the man pages via perf
|
||
|
|
itself e.g. 'perf help' or 'perf help record'.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
However, by default Yocto doesn't install man pages, but perf
|
||
|
|
invokes the man pages for most help functionality. This is a bug
|
||
|
|
and is being addressed by a Yocto bug:
|
||
|
|
<ulink url='https://bugzilla.yoctoproject.org/show_bug.cgi?id=3388'>Bug 3388 - perf: enable man pages for basic 'help' functionality</ulink>.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The man pages in text form, along with some other files, such as
|
||
|
|
a set of examples, can be found in the 'perf' directory of the
|
||
|
|
kernel tree:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
tools/perf/Documentation
|
||
|
|
</literallayout>
|
||
|
|
There's also a nice perf tutorial on the perf wiki that goes
|
||
|
|
into more detail than we do here in certain areas:
|
||
|
|
<ulink url='https://perf.wiki.kernel.org/index.php/Tutorial'>Perf Tutorial</ulink>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='profile-manual-ftrace'>
|
||
|
|
<title>ftrace</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
'ftrace' literally refers to the 'ftrace function tracer' but in
|
||
|
|
reality this encompasses a number of related tracers along with
|
||
|
|
the infrastructure that they all make use of.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<section id='ftrace-setup'>
|
||
|
|
<title>Setup</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
For this section, we'll assume you've already performed the basic
|
||
|
|
setup outlined in the General Setup section.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
ftrace, trace-cmd, and kernelshark run on the target system,
|
||
|
|
and are ready to go out-of-the-box - no additional setup is
|
||
|
|
necessary. For the rest of this section we assume you've ssh'ed
|
||
|
|
to the host and will be running ftrace on the target. kernelshark
|
||
|
|
is a GUI application and if you use the '-X' option to ssh you
|
||
|
|
can have the kernelshark GUI run on the target but display
|
||
|
|
remotely on the host if you want.
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='basic-ftrace-usage'>
|
||
|
|
<title>Basic ftrace usage</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
'ftrace' essentially refers to everything included in
|
||
|
|
the /tracing directory of the mounted debugfs filesystem
|
||
|
|
(Yocto follows the standard convention and mounts it
|
||
|
|
at /sys/kernel/debug). Here's a listing of all the files
|
||
|
|
found in /sys/kernel/debug/tracing on a Yocto system:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# ls
|
||
|
|
README kprobe_events trace
|
||
|
|
available_events kprobe_profile trace_clock
|
||
|
|
available_filter_functions options trace_marker
|
||
|
|
available_tracers per_cpu trace_options
|
||
|
|
buffer_size_kb printk_formats trace_pipe
|
||
|
|
buffer_total_size_kb saved_cmdlines tracing_cpumask
|
||
|
|
current_tracer set_event tracing_enabled
|
||
|
|
dyn_ftrace_total_info set_ftrace_filter tracing_on
|
||
|
|
enabled_functions set_ftrace_notrace tracing_thresh
|
||
|
|
events set_ftrace_pid
|
||
|
|
free_buffer set_graph_function
|
||
|
|
</literallayout>
|
||
|
|
The files listed above are used for various purposes -
|
||
|
|
some relate directly to the tracers themselves, others are
|
||
|
|
used to set tracing options, and yet others actually contain
|
||
|
|
the tracing output when a tracer is in effect. Some of the
|
||
|
|
functions can be guessed from their names, others need
|
||
|
|
explanation; in any case, we'll cover some of the files we
|
||
|
|
see here below but for an explanation of the others, please
|
||
|
|
see the ftrace documentation.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
We'll start by looking at some of the available built-in
|
||
|
|
tracers.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
cat'ing the 'available_tracers' file lists the set of
|
||
|
|
available tracers:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# cat available_tracers
|
||
|
|
blk function_graph function nop
|
||
|
|
</literallayout>
|
||
|
|
The 'current_tracer' file contains the tracer currently in
|
||
|
|
effect:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# cat current_tracer
|
||
|
|
nop
|
||
|
|
</literallayout>
|
||
|
|
The above listing of current_tracer shows that
|
||
|
|
the 'nop' tracer is in effect, which is just another
|
||
|
|
way of saying that there's actually no tracer
|
||
|
|
currently in effect.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
echo'ing one of the available_tracers into current_tracer
|
||
|
|
makes the specified tracer the current tracer:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# echo function > current_tracer
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# cat current_tracer
|
||
|
|
function
|
||
|
|
</literallayout>
|
||
|
|
The above sets the current tracer to be the
|
||
|
|
'function tracer'. This tracer traces every function
|
||
|
|
call in the kernel and makes it available as the
|
||
|
|
contents of the 'trace' file. Reading the 'trace' file
|
||
|
|
lists the currently buffered function calls that have been
|
||
|
|
traced by the function tracer:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# cat trace | less
|
||
|
|
|
||
|
|
# tracer: function
|
||
|
|
#
|
||
|
|
# entries-in-buffer/entries-written: 310629/766471 #P:8
|
||
|
|
#
|
||
|
|
# _-----=> irqs-off
|
||
|
|
# / _----=> need-resched
|
||
|
|
# | / _---=> hardirq/softirq
|
||
|
|
# || / _--=> preempt-depth
|
||
|
|
# ||| / delay
|
||
|
|
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
|
||
|
|
# | | | |||| | |
|
||
|
|
<idle>-0 [004] d..1 470.867169: ktime_get_real <-intel_idle
|
||
|
|
<idle>-0 [004] d..1 470.867170: getnstimeofday <-ktime_get_real
|
||
|
|
<idle>-0 [004] d..1 470.867171: ns_to_timeval <-intel_idle
|
||
|
|
<idle>-0 [004] d..1 470.867171: ns_to_timespec <-ns_to_timeval
|
||
|
|
<idle>-0 [004] d..1 470.867172: smp_apic_timer_interrupt <-apic_timer_interrupt
|
||
|
|
<idle>-0 [004] d..1 470.867172: native_apic_mem_write <-smp_apic_timer_interrupt
|
||
|
|
<idle>-0 [004] d..1 470.867172: irq_enter <-smp_apic_timer_interrupt
|
||
|
|
<idle>-0 [004] d..1 470.867172: rcu_irq_enter <-irq_enter
|
||
|
|
<idle>-0 [004] d..1 470.867173: rcu_idle_exit_common.isra.33 <-rcu_irq_enter
|
||
|
|
<idle>-0 [004] d..1 470.867173: local_bh_disable <-irq_enter
|
||
|
|
<idle>-0 [004] d..1 470.867173: add_preempt_count <-local_bh_disable
|
||
|
|
<idle>-0 [004] d.s1 470.867174: tick_check_idle <-irq_enter
|
||
|
|
<idle>-0 [004] d.s1 470.867174: tick_check_oneshot_broadcast <-tick_check_idle
|
||
|
|
<idle>-0 [004] d.s1 470.867174: ktime_get <-tick_check_idle
|
||
|
|
<idle>-0 [004] d.s1 470.867174: tick_nohz_stop_idle <-tick_check_idle
|
||
|
|
<idle>-0 [004] d.s1 470.867175: update_ts_time_stats <-tick_nohz_stop_idle
|
||
|
|
<idle>-0 [004] d.s1 470.867175: nr_iowait_cpu <-update_ts_time_stats
|
||
|
|
<idle>-0 [004] d.s1 470.867175: tick_do_update_jiffies64 <-tick_check_idle
|
||
|
|
<idle>-0 [004] d.s1 470.867175: _raw_spin_lock <-tick_do_update_jiffies64
|
||
|
|
<idle>-0 [004] d.s1 470.867176: add_preempt_count <-_raw_spin_lock
|
||
|
|
<idle>-0 [004] d.s2 470.867176: do_timer <-tick_do_update_jiffies64
|
||
|
|
<idle>-0 [004] d.s2 470.867176: _raw_spin_lock <-do_timer
|
||
|
|
<idle>-0 [004] d.s2 470.867176: add_preempt_count <-_raw_spin_lock
|
||
|
|
<idle>-0 [004] d.s3 470.867177: ntp_tick_length <-do_timer
|
||
|
|
<idle>-0 [004] d.s3 470.867177: _raw_spin_lock_irqsave <-ntp_tick_length
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
</literallayout>
|
||
|
|
Each line in the trace above shows what was happening in
|
||
|
|
the kernel on a given cpu, to the level of detail of
|
||
|
|
function calls. Each entry shows the function called,
|
||
|
|
followed by its caller (after the arrow).
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The function tracer gives you an extremely detailed idea
|
||
|
|
of what the kernel was doing at the point in time the trace
|
||
|
|
was taken, and is a great way to learn about how the kernel
|
||
|
|
code works in a dynamic sense.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<informalexample>
|
||
|
|
<emphasis>Tying it Together:</emphasis> The ftrace function tracer is also
|
||
|
|
available from within perf, as the ftrace:function tracepoint.
|
||
|
|
</informalexample>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
It is a little more difficult to follow the call chains than
|
||
|
|
it needs to be - luckily there's a variant of the function
|
||
|
|
tracer that displays the callchains explicitly, called the
|
||
|
|
'function_graph' tracer:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# echo function_graph > current_tracer
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# cat trace | less
|
||
|
|
|
||
|
|
tracer: function_graph
|
||
|
|
|
||
|
|
CPU DURATION FUNCTION CALLS
|
||
|
|
| | | | | | |
|
||
|
|
7) 0.046 us | pick_next_task_fair();
|
||
|
|
7) 0.043 us | pick_next_task_stop();
|
||
|
|
7) 0.042 us | pick_next_task_rt();
|
||
|
|
7) 0.032 us | pick_next_task_fair();
|
||
|
|
7) 0.030 us | pick_next_task_idle();
|
||
|
|
7) | _raw_spin_unlock_irq() {
|
||
|
|
7) 0.033 us | sub_preempt_count();
|
||
|
|
7) 0.258 us | }
|
||
|
|
7) 0.032 us | sub_preempt_count();
|
||
|
|
7) + 13.341 us | } /* __schedule */
|
||
|
|
7) 0.095 us | } /* sub_preempt_count */
|
||
|
|
7) | schedule() {
|
||
|
|
7) | __schedule() {
|
||
|
|
7) 0.060 us | add_preempt_count();
|
||
|
|
7) 0.044 us | rcu_note_context_switch();
|
||
|
|
7) | _raw_spin_lock_irq() {
|
||
|
|
7) 0.033 us | add_preempt_count();
|
||
|
|
7) 0.247 us | }
|
||
|
|
7) | idle_balance() {
|
||
|
|
7) | _raw_spin_unlock() {
|
||
|
|
7) 0.031 us | sub_preempt_count();
|
||
|
|
7) 0.246 us | }
|
||
|
|
7) | update_shares() {
|
||
|
|
7) 0.030 us | __rcu_read_lock();
|
||
|
|
7) 0.029 us | __rcu_read_unlock();
|
||
|
|
7) 0.484 us | }
|
||
|
|
7) 0.030 us | __rcu_read_lock();
|
||
|
|
7) | load_balance() {
|
||
|
|
7) | find_busiest_group() {
|
||
|
|
7) 0.031 us | idle_cpu();
|
||
|
|
7) 0.029 us | idle_cpu();
|
||
|
|
7) 0.035 us | idle_cpu();
|
||
|
|
7) 0.906 us | }
|
||
|
|
7) 1.141 us | }
|
||
|
|
7) 0.022 us | msecs_to_jiffies();
|
||
|
|
7) | load_balance() {
|
||
|
|
7) | find_busiest_group() {
|
||
|
|
7) 0.031 us | idle_cpu();
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
4) 0.062 us | msecs_to_jiffies();
|
||
|
|
4) 0.062 us | __rcu_read_unlock();
|
||
|
|
4) | _raw_spin_lock() {
|
||
|
|
4) 0.073 us | add_preempt_count();
|
||
|
|
4) 0.562 us | }
|
||
|
|
4) + 17.452 us | }
|
||
|
|
4) 0.108 us | put_prev_task_fair();
|
||
|
|
4) 0.102 us | pick_next_task_fair();
|
||
|
|
4) 0.084 us | pick_next_task_stop();
|
||
|
|
4) 0.075 us | pick_next_task_rt();
|
||
|
|
4) 0.062 us | pick_next_task_fair();
|
||
|
|
4) 0.066 us | pick_next_task_idle();
|
||
|
|
------------------------------------------
|
||
|
|
4) kworker-74 => <idle>-0
|
||
|
|
------------------------------------------
|
||
|
|
|
||
|
|
4) | finish_task_switch() {
|
||
|
|
4) | _raw_spin_unlock_irq() {
|
||
|
|
4) 0.100 us | sub_preempt_count();
|
||
|
|
4) 0.582 us | }
|
||
|
|
4) 1.105 us | }
|
||
|
|
4) 0.088 us | sub_preempt_count();
|
||
|
|
4) ! 100.066 us | }
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
3) | sys_ioctl() {
|
||
|
|
3) 0.083 us | fget_light();
|
||
|
|
3) | security_file_ioctl() {
|
||
|
|
3) 0.066 us | cap_file_ioctl();
|
||
|
|
3) 0.562 us | }
|
||
|
|
3) | do_vfs_ioctl() {
|
||
|
|
3) | drm_ioctl() {
|
||
|
|
3) 0.075 us | drm_ut_debug_printk();
|
||
|
|
3) | i915_gem_pwrite_ioctl() {
|
||
|
|
3) | i915_mutex_lock_interruptible() {
|
||
|
|
3) 0.070 us | mutex_lock_interruptible();
|
||
|
|
3) 0.570 us | }
|
||
|
|
3) | drm_gem_object_lookup() {
|
||
|
|
3) | _raw_spin_lock() {
|
||
|
|
3) 0.080 us | add_preempt_count();
|
||
|
|
3) 0.620 us | }
|
||
|
|
3) | _raw_spin_unlock() {
|
||
|
|
3) 0.085 us | sub_preempt_count();
|
||
|
|
3) 0.562 us | }
|
||
|
|
3) 2.149 us | }
|
||
|
|
3) 0.133 us | i915_gem_object_pin();
|
||
|
|
3) | i915_gem_object_set_to_gtt_domain() {
|
||
|
|
3) 0.065 us | i915_gem_object_flush_gpu_write_domain();
|
||
|
|
3) 0.065 us | i915_gem_object_wait_rendering();
|
||
|
|
3) 0.062 us | i915_gem_object_flush_cpu_write_domain();
|
||
|
|
3) 1.612 us | }
|
||
|
|
3) | i915_gem_object_put_fence() {
|
||
|
|
3) 0.097 us | i915_gem_object_flush_fence.constprop.36();
|
||
|
|
3) 0.645 us | }
|
||
|
|
3) 0.070 us | add_preempt_count();
|
||
|
|
3) 0.070 us | sub_preempt_count();
|
||
|
|
3) 0.073 us | i915_gem_object_unpin();
|
||
|
|
3) 0.068 us | mutex_unlock();
|
||
|
|
3) 9.924 us | }
|
||
|
|
3) + 11.236 us | }
|
||
|
|
3) + 11.770 us | }
|
||
|
|
3) + 13.784 us | }
|
||
|
|
3) | sys_ioctl() {
|
||
|
|
</literallayout>
|
||
|
|
As you can see, the function_graph display is much easier to
|
||
|
|
follow. Also note that in addition to the function calls and
|
||
|
|
associated braces, other events such as scheduler events
|
||
|
|
are displayed in context. In fact, you can freely include
|
||
|
|
any tracepoint available in the trace events subsystem described
|
||
|
|
in the next section by simply enabling those events, and they'll
|
||
|
|
appear in context in the function graph display. Quite a
|
||
|
|
powerful tool for understanding kernel dynamics.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Also notice that there are various annotations on the left
|
||
|
|
hand side of the display. For example if the total time it
|
||
|
|
took for a given function to execute is above a certain
|
||
|
|
threshold, an exclamation point or plus sign appears on the
|
||
|
|
left hand side. Please see the ftrace documentation for
|
||
|
|
details on all these fields.
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='the-trace-events-subsystem'>
|
||
|
|
<title>The 'trace events' Subsystem</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
One especially important directory contained within
|
||
|
|
the /sys/kernel/debug/tracing directory is the 'events'
|
||
|
|
subdirectory, which contains representations of every
|
||
|
|
tracepoint in the system. Listing out the contents of
|
||
|
|
the 'events' subdirectory, we see mainly another set of
|
||
|
|
subdirectories:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# cd events
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing/events# ls -al
|
||
|
|
drwxr-xr-x 38 root root 0 Nov 14 23:19 .
|
||
|
|
drwxr-xr-x 5 root root 0 Nov 14 23:19 ..
|
||
|
|
drwxr-xr-x 19 root root 0 Nov 14 23:19 block
|
||
|
|
drwxr-xr-x 32 root root 0 Nov 14 23:19 btrfs
|
||
|
|
drwxr-xr-x 5 root root 0 Nov 14 23:19 drm
|
||
|
|
-rw-r--r-- 1 root root 0 Nov 14 23:19 enable
|
||
|
|
drwxr-xr-x 40 root root 0 Nov 14 23:19 ext3
|
||
|
|
drwxr-xr-x 79 root root 0 Nov 14 23:19 ext4
|
||
|
|
drwxr-xr-x 14 root root 0 Nov 14 23:19 ftrace
|
||
|
|
drwxr-xr-x 8 root root 0 Nov 14 23:19 hda
|
||
|
|
-r--r--r-- 1 root root 0 Nov 14 23:19 header_event
|
||
|
|
-r--r--r-- 1 root root 0 Nov 14 23:19 header_page
|
||
|
|
drwxr-xr-x 25 root root 0 Nov 14 23:19 i915
|
||
|
|
drwxr-xr-x 7 root root 0 Nov 14 23:19 irq
|
||
|
|
drwxr-xr-x 12 root root 0 Nov 14 23:19 jbd
|
||
|
|
drwxr-xr-x 14 root root 0 Nov 14 23:19 jbd2
|
||
|
|
drwxr-xr-x 14 root root 0 Nov 14 23:19 kmem
|
||
|
|
drwxr-xr-x 7 root root 0 Nov 14 23:19 module
|
||
|
|
drwxr-xr-x 3 root root 0 Nov 14 23:19 napi
|
||
|
|
drwxr-xr-x 6 root root 0 Nov 14 23:19 net
|
||
|
|
drwxr-xr-x 3 root root 0 Nov 14 23:19 oom
|
||
|
|
drwxr-xr-x 12 root root 0 Nov 14 23:19 power
|
||
|
|
drwxr-xr-x 3 root root 0 Nov 14 23:19 printk
|
||
|
|
drwxr-xr-x 8 root root 0 Nov 14 23:19 random
|
||
|
|
drwxr-xr-x 4 root root 0 Nov 14 23:19 raw_syscalls
|
||
|
|
drwxr-xr-x 3 root root 0 Nov 14 23:19 rcu
|
||
|
|
drwxr-xr-x 6 root root 0 Nov 14 23:19 rpm
|
||
|
|
drwxr-xr-x 20 root root 0 Nov 14 23:19 sched
|
||
|
|
drwxr-xr-x 7 root root 0 Nov 14 23:19 scsi
|
||
|
|
drwxr-xr-x 4 root root 0 Nov 14 23:19 signal
|
||
|
|
drwxr-xr-x 5 root root 0 Nov 14 23:19 skb
|
||
|
|
drwxr-xr-x 4 root root 0 Nov 14 23:19 sock
|
||
|
|
drwxr-xr-x 10 root root 0 Nov 14 23:19 sunrpc
|
||
|
|
drwxr-xr-x 538 root root 0 Nov 14 23:19 syscalls
|
||
|
|
drwxr-xr-x 4 root root 0 Nov 14 23:19 task
|
||
|
|
drwxr-xr-x 14 root root 0 Nov 14 23:19 timer
|
||
|
|
drwxr-xr-x 3 root root 0 Nov 14 23:19 udp
|
||
|
|
drwxr-xr-x 21 root root 0 Nov 14 23:19 vmscan
|
||
|
|
drwxr-xr-x 3 root root 0 Nov 14 23:19 vsyscall
|
||
|
|
drwxr-xr-x 6 root root 0 Nov 14 23:19 workqueue
|
||
|
|
drwxr-xr-x 26 root root 0 Nov 14 23:19 writeback
|
||
|
|
</literallayout>
|
||
|
|
Each one of these subdirectories corresponds to a
|
||
|
|
'subsystem' and contains yet again more subdirectories,
|
||
|
|
each one of those finally corresponding to a tracepoint.
|
||
|
|
For example, here are the contents of the 'kmem' subsystem:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing/events# cd kmem
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing/events/kmem# ls -al
|
||
|
|
drwxr-xr-x 14 root root 0 Nov 14 23:19 .
|
||
|
|
drwxr-xr-x 38 root root 0 Nov 14 23:19 ..
|
||
|
|
-rw-r--r-- 1 root root 0 Nov 14 23:19 enable
|
||
|
|
-rw-r--r-- 1 root root 0 Nov 14 23:19 filter
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 kfree
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 kmalloc
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 kmalloc_node
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 kmem_cache_alloc
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 kmem_cache_alloc_node
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 kmem_cache_free
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 mm_page_alloc
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 mm_page_alloc_extfrag
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 mm_page_alloc_zone_locked
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 mm_page_free
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 mm_page_free_batched
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 mm_page_pcpu_drain
|
||
|
|
</literallayout>
|
||
|
|
Let's see what's inside the subdirectory for a specific
|
||
|
|
tracepoint, in this case the one for kmalloc:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing/events/kmem# cd kmalloc
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing/events/kmem/kmalloc# ls -al
|
||
|
|
drwxr-xr-x 2 root root 0 Nov 14 23:19 .
|
||
|
|
drwxr-xr-x 14 root root 0 Nov 14 23:19 ..
|
||
|
|
-rw-r--r-- 1 root root 0 Nov 14 23:19 enable
|
||
|
|
-rw-r--r-- 1 root root 0 Nov 14 23:19 filter
|
||
|
|
-r--r--r-- 1 root root 0 Nov 14 23:19 format
|
||
|
|
-r--r--r-- 1 root root 0 Nov 14 23:19 id
|
||
|
|
</literallayout>
|
||
|
|
The 'format' file for the tracepoint describes the event
|
||
|
|
in memory, which is used by the various tracing tools
|
||
|
|
that now make use of these tracepoint to parse the event
|
||
|
|
and make sense of it, along with a 'print fmt' field that
|
||
|
|
allows tools like ftrace to display the event as text.
|
||
|
|
Here's what the format of the kmalloc event looks like:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing/events/kmem/kmalloc# cat format
|
||
|
|
name: kmalloc
|
||
|
|
ID: 313
|
||
|
|
format:
|
||
|
|
field:unsigned short common_type; offset:0; size:2; signed:0;
|
||
|
|
field:unsigned char common_flags; offset:2; size:1; signed:0;
|
||
|
|
field:unsigned char common_preempt_count; offset:3; size:1; signed:0;
|
||
|
|
field:int common_pid; offset:4; size:4; signed:1;
|
||
|
|
field:int common_padding; offset:8; size:4; signed:1;
|
||
|
|
|
||
|
|
field:unsigned long call_site; offset:16; size:8; signed:0;
|
||
|
|
field:const void * ptr; offset:24; size:8; signed:0;
|
||
|
|
field:size_t bytes_req; offset:32; size:8; signed:0;
|
||
|
|
field:size_t bytes_alloc; offset:40; size:8; signed:0;
|
||
|
|
field:gfp_t gfp_flags; offset:48; size:4; signed:0;
|
||
|
|
|
||
|
|
print fmt: "call_site=%lx ptr=%p bytes_req=%zu bytes_alloc=%zu gfp_flags=%s", REC->call_site, REC->ptr, REC->bytes_req, REC->bytes_alloc,
|
||
|
|
(REC->gfp_flags) ? __print_flags(REC->gfp_flags, "|", {(unsigned long)(((( gfp_t)0x10u) | (( gfp_t)0x40u) | (( gfp_t)0x80u) | ((
|
||
|
|
gfp_t)0x20000u) | (( gfp_t)0x02u) | (( gfp_t)0x08u)) | (( gfp_t)0x4000u) | (( gfp_t)0x10000u) | (( gfp_t)0x1000u) | (( gfp_t)0x200u) | ((
|
||
|
|
gfp_t)0x400000u)), "GFP_TRANSHUGE"}, {(unsigned long)((( gfp_t)0x10u) | (( gfp_t)0x40u) | (( gfp_t)0x80u) | (( gfp_t)0x20000u) | ((
|
||
|
|
gfp_t)0x02u) | (( gfp_t)0x08u)), "GFP_HIGHUSER_MOVABLE"}, {(unsigned long)((( gfp_t)0x10u) | (( gfp_t)0x40u) | (( gfp_t)0x80u) | ((
|
||
|
|
gfp_t)0x20000u) | (( gfp_t)0x02u)), "GFP_HIGHUSER"}, {(unsigned long)((( gfp_t)0x10u) | (( gfp_t)0x40u) | (( gfp_t)0x80u) | ((
|
||
|
|
gfp_t)0x20000u)), "GFP_USER"}, {(unsigned long)((( gfp_t)0x10u) | (( gfp_t)0x40u) | (( gfp_t)0x80u) | (( gfp_t)0x80000u)), GFP_TEMPORARY"},
|
||
|
|
{(unsigned long)((( gfp_t)0x10u) | (( gfp_t)0x40u) | (( gfp_t)0x80u)), "GFP_KERNEL"}, {(unsigned long)((( gfp_t)0x10u) | (( gfp_t)0x40u)),
|
||
|
|
"GFP_NOFS"}, {(unsigned long)((( gfp_t)0x20u)), "GFP_ATOMIC"}, {(unsigned long)((( gfp_t)0x10u)), "GFP_NOIO"}, {(unsigned long)((
|
||
|
|
gfp_t)0x20u), "GFP_HIGH"}, {(unsigned long)(( gfp_t)0x10u), "GFP_WAIT"}, {(unsigned long)(( gfp_t)0x40u), "GFP_IO"}, {(unsigned long)((
|
||
|
|
gfp_t)0x100u), "GFP_COLD"}, {(unsigned long)(( gfp_t)0x200u), "GFP_NOWARN"}, {(unsigned long)(( gfp_t)0x400u), "GFP_REPEAT"}, {(unsigned
|
||
|
|
long)(( gfp_t)0x800u), "GFP_NOFAIL"}, {(unsigned long)(( gfp_t)0x1000u), "GFP_NORETRY"}, {(unsigned long)(( gfp_t)0x4000u), "GFP_COMP"},
|
||
|
|
{(unsigned long)(( gfp_t)0x8000u), "GFP_ZERO"}, {(unsigned long)(( gfp_t)0x10000u), "GFP_NOMEMALLOC"}, {(unsigned long)(( gfp_t)0x20000u),
|
||
|
|
"GFP_HARDWALL"}, {(unsigned long)(( gfp_t)0x40000u), "GFP_THISNODE"}, {(unsigned long)(( gfp_t)0x80000u), "GFP_RECLAIMABLE"}, {(unsigned
|
||
|
|
long)(( gfp_t)0x08u), "GFP_MOVABLE"}, {(unsigned long)(( gfp_t)0), "GFP_NOTRACK"}, {(unsigned long)(( gfp_t)0x400000u), "GFP_NO_KSWAPD"},
|
||
|
|
{(unsigned long)(( gfp_t)0x800000u), "GFP_OTHER_NODE"} ) : "GFP_NOWAIT"
|
||
|
|
</literallayout>
|
||
|
|
The 'enable' file in the tracepoint directory is what allows
|
||
|
|
the user (or tools such as trace-cmd) to actually turn the
|
||
|
|
tracepoint on and off. When enabled, the corresponding
|
||
|
|
tracepoint will start appearing in the ftrace 'trace'
|
||
|
|
file described previously. For example, this turns on the
|
||
|
|
kmalloc tracepoint:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing/events/kmem/kmalloc# echo 1 > enable
|
||
|
|
</literallayout>
|
||
|
|
At the moment, we're not interested in the function tracer or
|
||
|
|
some other tracer that might be in effect, so we first turn
|
||
|
|
it off, but if we do that, we still need to turn tracing on in
|
||
|
|
order to see the events in the output buffer:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# echo nop > current_tracer
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# echo 1 > tracing_on
|
||
|
|
</literallayout>
|
||
|
|
Now, if we look at the the 'trace' file, we see nothing
|
||
|
|
but the kmalloc events we just turned on:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing# cat trace | less
|
||
|
|
# tracer: nop
|
||
|
|
#
|
||
|
|
# entries-in-buffer/entries-written: 1897/1897 #P:8
|
||
|
|
#
|
||
|
|
# _-----=> irqs-off
|
||
|
|
# / _----=> need-resched
|
||
|
|
# | / _---=> hardirq/softirq
|
||
|
|
# || / _--=> preempt-depth
|
||
|
|
# ||| / delay
|
||
|
|
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
|
||
|
|
# | | | |||| | |
|
||
|
|
dropbear-1465 [000] ...1 18154.620753: kmalloc: call_site=ffffffff816650d4 ptr=ffff8800729c3000 bytes_req=2048 bytes_alloc=2048 gfp_flags=GFP_KERNEL
|
||
|
|
<idle>-0 [000] ..s3 18154.621640: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d555800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
<idle>-0 [000] ..s3 18154.621656: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d555800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
matchbox-termin-1361 [001] ...1 18154.755472: kmalloc: call_site=ffffffff81614050 ptr=ffff88006d5f0e00 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_KERNEL|GFP_REPEAT
|
||
|
|
Xorg-1264 [002] ...1 18154.755581: kmalloc: call_site=ffffffff8141abe8 ptr=ffff8800734f4cc0 bytes_req=168 bytes_alloc=192 gfp_flags=GFP_KERNEL|GFP_NOWARN|GFP_NORETRY
|
||
|
|
Xorg-1264 [002] ...1 18154.755583: kmalloc: call_site=ffffffff814192a3 ptr=ffff88001f822520 bytes_req=24 bytes_alloc=32 gfp_flags=GFP_KERNEL|GFP_ZERO
|
||
|
|
Xorg-1264 [002] ...1 18154.755589: kmalloc: call_site=ffffffff81419edb ptr=ffff8800721a2f00 bytes_req=64 bytes_alloc=64 gfp_flags=GFP_KERNEL|GFP_ZERO
|
||
|
|
matchbox-termin-1361 [001] ...1 18155.354594: kmalloc: call_site=ffffffff81614050 ptr=ffff88006db35400 bytes_req=576 bytes_alloc=1024 gfp_flags=GFP_KERNEL|GFP_REPEAT
|
||
|
|
Xorg-1264 [002] ...1 18155.354703: kmalloc: call_site=ffffffff8141abe8 ptr=ffff8800734f4cc0 bytes_req=168 bytes_alloc=192 gfp_flags=GFP_KERNEL|GFP_NOWARN|GFP_NORETRY
|
||
|
|
Xorg-1264 [002] ...1 18155.354705: kmalloc: call_site=ffffffff814192a3 ptr=ffff88001f822520 bytes_req=24 bytes_alloc=32 gfp_flags=GFP_KERNEL|GFP_ZERO
|
||
|
|
Xorg-1264 [002] ...1 18155.354711: kmalloc: call_site=ffffffff81419edb ptr=ffff8800721a2f00 bytes_req=64 bytes_alloc=64 gfp_flags=GFP_KERNEL|GFP_ZERO
|
||
|
|
<idle>-0 [000] ..s3 18155.673319: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d555800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
dropbear-1465 [000] ...1 18155.673525: kmalloc: call_site=ffffffff816650d4 ptr=ffff8800729c3000 bytes_req=2048 bytes_alloc=2048 gfp_flags=GFP_KERNEL
|
||
|
|
<idle>-0 [000] ..s3 18155.674821: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d554800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
<idle>-0 [000] ..s3 18155.793014: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d554800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
dropbear-1465 [000] ...1 18155.793219: kmalloc: call_site=ffffffff816650d4 ptr=ffff8800729c3000 bytes_req=2048 bytes_alloc=2048 gfp_flags=GFP_KERNEL
|
||
|
|
<idle>-0 [000] ..s3 18155.794147: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d555800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
<idle>-0 [000] ..s3 18155.936705: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d555800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
dropbear-1465 [000] ...1 18155.936910: kmalloc: call_site=ffffffff816650d4 ptr=ffff8800729c3000 bytes_req=2048 bytes_alloc=2048 gfp_flags=GFP_KERNEL
|
||
|
|
<idle>-0 [000] ..s3 18155.937869: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d554800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
matchbox-termin-1361 [001] ...1 18155.953667: kmalloc: call_site=ffffffff81614050 ptr=ffff88006d5f2000 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_KERNEL|GFP_REPEAT
|
||
|
|
Xorg-1264 [002] ...1 18155.953775: kmalloc: call_site=ffffffff8141abe8 ptr=ffff8800734f4cc0 bytes_req=168 bytes_alloc=192 gfp_flags=GFP_KERNEL|GFP_NOWARN|GFP_NORETRY
|
||
|
|
Xorg-1264 [002] ...1 18155.953777: kmalloc: call_site=ffffffff814192a3 ptr=ffff88001f822520 bytes_req=24 bytes_alloc=32 gfp_flags=GFP_KERNEL|GFP_ZERO
|
||
|
|
Xorg-1264 [002] ...1 18155.953783: kmalloc: call_site=ffffffff81419edb ptr=ffff8800721a2f00 bytes_req=64 bytes_alloc=64 gfp_flags=GFP_KERNEL|GFP_ZERO
|
||
|
|
<idle>-0 [000] ..s3 18156.176053: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d554800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
dropbear-1465 [000] ...1 18156.176257: kmalloc: call_site=ffffffff816650d4 ptr=ffff8800729c3000 bytes_req=2048 bytes_alloc=2048 gfp_flags=GFP_KERNEL
|
||
|
|
<idle>-0 [000] ..s3 18156.177717: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d555800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
<idle>-0 [000] ..s3 18156.399229: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d555800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
dropbear-1465 [000] ...1 18156.399434: kmalloc: call_site=ffffffff816650d4 ptr=ffff8800729c3000 bytes_http://rostedt.homelinux.com/kernelshark/req=2048 bytes_alloc=2048 gfp_flags=GFP_KERNEL
|
||
|
|
<idle>-0 [000] ..s3 18156.400660: kmalloc: call_site=ffffffff81619b36 ptr=ffff88006d554800 bytes_req=512 bytes_alloc=512 gfp_flags=GFP_ATOMIC
|
||
|
|
matchbox-termin-1361 [001] ...1 18156.552800: kmalloc: call_site=ffffffff81614050 ptr=ffff88006db34800 bytes_req=576 bytes_alloc=1024 gfp_flags=GFP_KERNEL|GFP_REPEAT
|
||
|
|
</literallayout>
|
||
|
|
To again disable the kmalloc event, we need to send 0 to the
|
||
|
|
enable file:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:/sys/kernel/debug/tracing/events/kmem/kmalloc# echo 0 > enable
|
||
|
|
</literallayout>
|
||
|
|
You can enable any number of events or complete subsystems
|
||
|
|
(by using the 'enable' file in the subsystem directory) and
|
||
|
|
get an arbitrarily fine-grained idea of what's going on in the
|
||
|
|
system by enabling as many of the appropriate tracepoints
|
||
|
|
as applicable.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
A number of the tools described in this HOWTO do just that,
|
||
|
|
including trace-cmd and kernelshark in the next section.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<informalexample>
|
||
|
|
<emphasis>Tying it Together:</emphasis> These tracepoints and their representation
|
||
|
|
are used not only by ftrace, but by many of the other tools
|
||
|
|
covered in this document and they form a central point of
|
||
|
|
integration for the various tracers available in Linux.
|
||
|
|
They form a central part of the instrumentation for the
|
||
|
|
following tools: perf, lttng, ftrace, blktrace and SystemTap
|
||
|
|
</informalexample>
|
||
|
|
|
||
|
|
<informalexample>
|
||
|
|
<emphasis>Tying it Together:</emphasis> Eventually all the special-purpose tracers
|
||
|
|
currently available in /sys/kernel/debug/tracing will be
|
||
|
|
removed and replaced with equivalent tracers based on the
|
||
|
|
'trace events' subsystem.
|
||
|
|
</informalexample>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='trace-cmd-kernelshark'>
|
||
|
|
<title>trace-cmd/kernelshark</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
trace-cmd is essentially an extensive command-line 'wrapper'
|
||
|
|
interface that hides the details of all the individual files
|
||
|
|
in /sys/kernel/debug/tracing, allowing users to specify
|
||
|
|
specific particular events within the
|
||
|
|
/sys/kernel/debug/tracing/events/ subdirectory and to collect
|
||
|
|
traces and avoid having to deal with those details directly.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
As yet another layer on top of that, kernelshark provides a GUI
|
||
|
|
that allows users to start and stop traces and specify sets
|
||
|
|
of events using an intuitive interface, and view the
|
||
|
|
output as both trace events and as a per-CPU graphical
|
||
|
|
display. It directly uses 'trace-cmd' as the plumbing
|
||
|
|
that accomplishes all that underneath the covers (and
|
||
|
|
actually displays the trace-cmd command it uses, as we'll see).
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
To start a trace using kernelshark, first start kernelshark:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@sugarbay:~# kernelshark
|
||
|
|
</literallayout>
|
||
|
|
Then bring up the 'Capture' dialog by choosing from the
|
||
|
|
kernelshark menu:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
Capture | Record
|
||
|
|
</literallayout>
|
||
|
|
That will display the following dialog, which allows you to
|
||
|
|
choose one or more events (or even one or more complete
|
||
|
|
subsystems) to trace:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/kernelshark-choose-events.png" width="6in" depth="6in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Note that these are exactly the same sets of events described
|
||
|
|
in the previous trace events subsystem section, and in fact
|
||
|
|
is where trace-cmd gets them for kernelshark.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
In the above screenshot, we've decided to explore the
|
||
|
|
graphics subsystem a bit and so have chosen to trace all
|
||
|
|
the tracepoints contained within the 'i915' and 'drm'
|
||
|
|
subsystems.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
After doing that, we can start and stop the trace using
|
||
|
|
the 'Run' and 'Stop' button on the lower right corner of
|
||
|
|
the dialog (the same button will turn into the 'Stop'
|
||
|
|
button after the trace has started):
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/kernelshark-output-display.png" width="6in" depth="6in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Notice that the right-hand pane shows the exact trace-cmd
|
||
|
|
command-line that's used to run the trace, along with the
|
||
|
|
results of the trace-cmd run.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Once the 'Stop' button is pressed, the graphical view magically
|
||
|
|
fills up with a colorful per-cpu display of the trace data,
|
||
|
|
along with the detailed event listing below that:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/kernelshark-i915-display.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Here's another example, this time a display resulting
|
||
|
|
from tracing 'all events':
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/kernelshark-all.png" width="6in" depth="7in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The tool is pretty self-explanatory, but for more detailed
|
||
|
|
information on navigating through the data, see the
|
||
|
|
<ulink url='http://rostedt.homelinux.com/kernelshark/'>kernelshark website</ulink>.
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='ftrace-documentation'>
|
||
|
|
<title>Documentation</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The documentation for ftrace can be found in the kernel
|
||
|
|
Documentation directory:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
Documentation/trace/ftrace.txt
|
||
|
|
</literallayout>
|
||
|
|
The documentation for the trace event subsystem can also
|
||
|
|
be found in the kernel Documentation directory:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
Documentation/trace/events.txt
|
||
|
|
</literallayout>
|
||
|
|
There is a nice series of articles on using
|
||
|
|
ftrace and trace-cmd at LWN:
|
||
|
|
<itemizedlist>
|
||
|
|
<listitem><para><ulink url='http://lwn.net/Articles/365835/'>Debugging the kernel using Ftrace - part 1</ulink>
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><ulink url='http://lwn.net/Articles/366796/'>Debugging the kernel using Ftrace - part 2</ulink>
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><ulink url='http://lwn.net/Articles/370423/'>Secrets of the Ftrace function tracer</ulink>
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><ulink url='https://lwn.net/Articles/410200/'>trace-cmd: A front-end for Ftrace</ulink>
|
||
|
|
</para></listitem>
|
||
|
|
</itemizedlist>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
There's more detailed documentation kernelshark usage here:
|
||
|
|
<ulink url='http://rostedt.homelinux.com/kernelshark/'>KernelShark</ulink>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
An amusing yet useful README (a tracing mini-HOWTO) can be
|
||
|
|
found in /sys/kernel/debug/tracing/README.
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='profile-manual-systemtap'>
|
||
|
|
<title>systemtap</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
SystemTap is a system-wide script-based tracing and profiling tool.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
SystemTap scripts are C-like programs that are executed in the
|
||
|
|
kernel to gather/print/aggregate data extracted from the context
|
||
|
|
they end up being invoked under.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
For example, this probe from the
|
||
|
|
<ulink url='http://sourceware.org/systemtap/tutorial/'>SystemTap tutorial</ulink>
|
||
|
|
simply prints a line every time any process on the system open()s
|
||
|
|
a file. For each line, it prints the executable name of the
|
||
|
|
program that opened the file, along with its PID, and the name
|
||
|
|
of the file it opened (or tried to open), which it extracts
|
||
|
|
from the open syscall's argstr.
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
probe syscall.open
|
||
|
|
{
|
||
|
|
printf ("%s(%d) open (%s)\n", execname(), pid(), argstr)
|
||
|
|
}
|
||
|
|
|
||
|
|
probe timer.ms(4000) # after 4 seconds
|
||
|
|
{
|
||
|
|
exit ()
|
||
|
|
}
|
||
|
|
</literallayout>
|
||
|
|
Normally, to execute this probe, you'd simply install
|
||
|
|
systemtap on the system you want to probe, and directly run
|
||
|
|
the probe on that system e.g. assuming the name of the file
|
||
|
|
containing the above text is trace_open.stp:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
# stap trace_open.stp
|
||
|
|
</literallayout>
|
||
|
|
What systemtap does under the covers to run this probe is 1)
|
||
|
|
parse and convert the probe to an equivalent 'C' form, 2)
|
||
|
|
compile the 'C' form into a kernel module, 3) insert the
|
||
|
|
module into the kernel, which arms it, and 4) collect the data
|
||
|
|
generated by the probe and display it to the user.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
In order to accomplish steps 1 and 2, the 'stap' program needs
|
||
|
|
access to the kernel build system that produced the kernel
|
||
|
|
that the probed system is running. In the case of a typical
|
||
|
|
embedded system (the 'target'), the kernel build system
|
||
|
|
unfortunately isn't typically part of the image running on
|
||
|
|
the target. It is normally available on the 'host' system
|
||
|
|
that produced the target image however; in such cases,
|
||
|
|
steps 1 and 2 are executed on the host system, and steps
|
||
|
|
3 and 4 are executed on the target system, using only the
|
||
|
|
systemtap 'runtime'.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The systemtap support in Yocto assumes that only steps
|
||
|
|
3 and 4 are run on the target; it is possible to do
|
||
|
|
everything on the target, but this section assumes only
|
||
|
|
the typical embedded use-case.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
So basically what you need to do in order to run a systemtap
|
||
|
|
script on the target is to 1) on the host system, compile the
|
||
|
|
probe into a kernel module that makes sense to the target, 2)
|
||
|
|
copy the module onto the target system and 3) insert the
|
||
|
|
module into the target kernel, which arms it, and 4) collect
|
||
|
|
the data generated by the probe and display it to the user.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<section id='systemtap-setup'>
|
||
|
|
<title>Setup</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Those are a lot of steps and a lot of details, but
|
||
|
|
fortunately Yocto includes a script called 'crosstap'
|
||
|
|
that will take care of those details, allowing you to
|
||
|
|
simply execute a systemtap script on the remote target,
|
||
|
|
with arguments if necessary.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
In order to do this from a remote host, however, you
|
||
|
|
need to have access to the build for the image you
|
||
|
|
booted. The 'crosstap' script provides details on how
|
||
|
|
to do this if you run the script on the host without having
|
||
|
|
done a build:
|
||
|
|
<note>
|
||
|
|
SystemTap, which uses 'crosstap', assumes you can establish an
|
||
|
|
ssh connection to the remote target.
|
||
|
|
Please refer to the crosstap wiki page for details on verifying
|
||
|
|
ssh connections at
|
||
|
|
<ulink url='https://wiki.yoctoproject.org/wiki/Tracing_and_Profiling#systemtap'></ulink>.
|
||
|
|
Also, the ability to ssh into the target system is not enabled
|
||
|
|
by default in *-minimal images.
|
||
|
|
</note>
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ crosstap root@192.168.1.88 trace_open.stp
|
||
|
|
|
||
|
|
Error: No target kernel build found.
|
||
|
|
Did you forget to create a local build of your image?
|
||
|
|
|
||
|
|
'crosstap' requires a local sdk build of the target system
|
||
|
|
(or a build that includes 'tools-profile') in order to build
|
||
|
|
kernel modules that can probe the target system.
|
||
|
|
|
||
|
|
Practically speaking, that means you need to do the following:
|
||
|
|
- If you're running a pre-built image, download the release
|
||
|
|
and/or BSP tarballs used to build the image.
|
||
|
|
- If you're working from git sources, just clone the metadata
|
||
|
|
and BSP layers needed to build the image you'll be booting.
|
||
|
|
- Make sure you're properly set up to build a new image (see
|
||
|
|
the BSP README and/or the widely available basic documentation
|
||
|
|
that discusses how to build images).
|
||
|
|
- Build an -sdk version of the image e.g.:
|
||
|
|
$ bitbake core-image-sato-sdk
|
||
|
|
OR
|
||
|
|
- Build a non-sdk image but include the profiling tools:
|
||
|
|
[ edit local.conf and add 'tools-profile' to the end of
|
||
|
|
the EXTRA_IMAGE_FEATURES variable ]
|
||
|
|
$ bitbake core-image-sato
|
||
|
|
|
||
|
|
Once you've build the image on the host system, you're ready to
|
||
|
|
boot it (or the equivalent pre-built image) and use 'crosstap'
|
||
|
|
to probe it (you need to source the environment as usual first):
|
||
|
|
|
||
|
|
$ source oe-init-build-env
|
||
|
|
$ cd ~/my/systemtap/scripts
|
||
|
|
$ crosstap root@192.168.1.xxx myscript.stp
|
||
|
|
</literallayout>
|
||
|
|
So essentially what you need to do is build an SDK image or
|
||
|
|
image with 'tools-profile' as detailed in the
|
||
|
|
"<link linkend='profile-manual-general-setup'>General Setup</link>"
|
||
|
|
section of this manual, and boot the resulting target image.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<note>
|
||
|
|
If you have a build directory containing multiple machines,
|
||
|
|
you need to have the MACHINE you're connecting to selected
|
||
|
|
in local.conf, and the kernel in that machine's build
|
||
|
|
directory must match the kernel on the booted system exactly,
|
||
|
|
or you'll get the above 'crosstap' message when you try to
|
||
|
|
invoke a script.
|
||
|
|
</note>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='running-a-script-on-a-target'>
|
||
|
|
<title>Running a Script on a Target</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Once you've done that, you should be able to run a systemtap
|
||
|
|
script on the target:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ cd /path/to/yocto
|
||
|
|
$ source oe-init-build-env
|
||
|
|
|
||
|
|
### Shell environment set up for builds. ###
|
||
|
|
|
||
|
|
You can now run 'bitbake <target>'
|
||
|
|
|
||
|
|
Common targets are:
|
||
|
|
core-image-minimal
|
||
|
|
core-image-sato
|
||
|
|
meta-toolchain
|
||
|
|
meta-ide-support
|
||
|
|
|
||
|
|
You can also run generated qemu images with a command like 'runqemu qemux86'
|
||
|
|
|
||
|
|
</literallayout>
|
||
|
|
Once you've done that, you can cd to whatever directory
|
||
|
|
contains your scripts and use 'crosstap' to run the script:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ cd /path/to/my/systemap/script
|
||
|
|
$ crosstap root@192.168.7.2 trace_open.stp
|
||
|
|
</literallayout>
|
||
|
|
If you get an error connecting to the target e.g.:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ crosstap root@192.168.7.2 trace_open.stp
|
||
|
|
error establishing ssh connection on remote 'root@192.168.7.2'
|
||
|
|
</literallayout>
|
||
|
|
Try ssh'ing to the target and see what happens:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ ssh root@192.168.7.2
|
||
|
|
</literallayout>
|
||
|
|
A lot of the time, connection problems are due specifying a
|
||
|
|
wrong IP address or having a 'host key verification error'.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
If everything worked as planned, you should see something
|
||
|
|
like this (enter the password when prompted, or press enter
|
||
|
|
if it's set up to use no password):
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ crosstap root@192.168.7.2 trace_open.stp
|
||
|
|
root@192.168.7.2's password:
|
||
|
|
matchbox-termin(1036) open ("/tmp/vte3FS2LW", O_RDWR|O_CREAT|O_EXCL|O_LARGEFILE, 0600)
|
||
|
|
matchbox-termin(1036) open ("/tmp/vteJMC7LW", O_RDWR|O_CREAT|O_EXCL|O_LARGEFILE, 0600)
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='systemtap-documentation'>
|
||
|
|
<title>Documentation</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The SystemTap language reference can be found here:
|
||
|
|
<ulink url='http://sourceware.org/systemtap/langref/'>SystemTap Language Reference</ulink>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Links to other SystemTap documents, tutorials, and examples can be
|
||
|
|
found here:
|
||
|
|
<ulink url='http://sourceware.org/systemtap/documentation.html'>SystemTap documentation page</ulink>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='profile-manual-sysprof'>
|
||
|
|
<title>Sysprof</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Sysprof is a very easy to use system-wide profiler that consists
|
||
|
|
of a single window with three panes and a few buttons which allow
|
||
|
|
you to start, stop, and view the profile from one place.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<section id='sysprof-setup'>
|
||
|
|
<title>Setup</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
For this section, we'll assume you've already performed the
|
||
|
|
basic setup outlined in the General Setup section.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Sysprof is a GUI-based application that runs on the target
|
||
|
|
system. For the rest of this document we assume you've
|
||
|
|
ssh'ed to the host and will be running Sysprof on the
|
||
|
|
target (you can use the '-X' option to ssh and have the
|
||
|
|
Sysprof GUI run on the target but display remotely on the
|
||
|
|
host if you want).
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='sysprof-basic-usage'>
|
||
|
|
<title>Basic Usage</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
To start profiling the system, you simply press the 'Start'
|
||
|
|
button. To stop profiling and to start viewing the profile data
|
||
|
|
in one easy step, press the 'Profile' button.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Once you've pressed the profile button, the three panes will
|
||
|
|
fill up with profiling data:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/sysprof-copy-to-user.png" width="6in" depth="4in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The left pane shows a list of functions and processes.
|
||
|
|
Selecting one of those expands that function in the right
|
||
|
|
pane, showing all its callees. Note that this caller-oriented
|
||
|
|
display is essentially the inverse of perf's default
|
||
|
|
callee-oriented callchain display.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
In the screenshot above, we're focusing on __copy_to_user_ll()
|
||
|
|
and looking up the callchain we can see that one of the callers
|
||
|
|
of __copy_to_user_ll is sys_read() and the complete callpath
|
||
|
|
between them. Notice that this is essentially a portion of the
|
||
|
|
same information we saw in the perf display shown in the perf
|
||
|
|
section of this page.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/sysprof-copy-from-user.png" width="6in" depth="4in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Similarly, the above is a snapshot of the Sysprof display of a
|
||
|
|
copy-from-user callchain.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Finally, looking at the third Sysprof pane in the lower left,
|
||
|
|
we can see a list of all the callers of a particular function
|
||
|
|
selected in the top left pane. In this case, the lower pane is
|
||
|
|
showing all the callers of __mark_inode_dirty:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/sysprof-callers.png" width="6in" depth="4in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Double-clicking on one of those functions will in turn change the
|
||
|
|
focus to the selected function, and so on.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<informalexample>
|
||
|
|
<emphasis>Tying it Together:</emphasis> If you like sysprof's 'caller-oriented'
|
||
|
|
display, you may be able to approximate it in other tools as
|
||
|
|
well. For example, 'perf report' has the -g (--call-graph)
|
||
|
|
option that you can experiment with; one of the options is
|
||
|
|
'caller' for an inverted caller-based callgraph display.
|
||
|
|
</informalexample>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='sysprof-documentation'>
|
||
|
|
<title>Documentation</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
There doesn't seem to be any documentation for Sysprof, but
|
||
|
|
maybe that's because it's pretty self-explanatory.
|
||
|
|
The Sysprof website, however, is here:
|
||
|
|
<ulink url='http://sysprof.com/'>Sysprof, System-wide Performance Profiler for Linux</ulink>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='lttng-linux-trace-toolkit-next-generation'>
|
||
|
|
<title>LTTng (Linux Trace Toolkit, next generation)</title>
|
||
|
|
|
||
|
|
<section id='lttng-setup'>
|
||
|
|
<title>Setup</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
For this section, we'll assume you've already performed the
|
||
|
|
basic setup outlined in the General Setup section.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
LTTng is run on the target system by ssh'ing to it.
|
||
|
|
However, if you want to see the traces graphically,
|
||
|
|
install Eclipse as described in section
|
||
|
|
"<link linkend='manually-copying-a-trace-to-the-host-and-viewing-it-in-eclipse'>Manually copying a trace to the host and viewing it in Eclipse (i.e. using Eclipse without network support)</link>"
|
||
|
|
and follow the directions to manually copy traces to the host and
|
||
|
|
view them in Eclipse (i.e. using Eclipse without network support).
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<note>
|
||
|
|
Be sure to download and install/run the 'SR1' or later Juno release
|
||
|
|
of eclipse e.g.:
|
||
|
|
<ulink url='http://www.eclipse.org/downloads/download.php?file=/technology/epp/downloads/release/juno/SR1/eclipse-cpp-juno-SR1-linux-gtk-x86_64.tar.gz'>http://www.eclipse.org/downloads/download.php?file=/technology/epp/downloads/release/juno/SR1/eclipse-cpp-juno-SR1-linux-gtk-x86_64.tar.gz</ulink>
|
||
|
|
</note>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='collecting-and-viewing-traces'>
|
||
|
|
<title>Collecting and Viewing Traces</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Once you've applied the above commits and built and booted your
|
||
|
|
image (you need to build the core-image-sato-sdk image or use one of the
|
||
|
|
other methods described in the General Setup section), you're
|
||
|
|
ready to start tracing.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<section id='collecting-and-viewing-a-trace-on-the-target-inside-a-shell'>
|
||
|
|
<title>Collecting and viewing a trace on the target (inside a shell)</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
First, from the host, ssh to the target:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ ssh -l root 192.168.1.47
|
||
|
|
The authenticity of host '192.168.1.47 (192.168.1.47)' can't be established.
|
||
|
|
RSA key fingerprint is 23:bd:c8:b1:a8:71:52:00:ee:00:4f:64:9e:10:b9:7e.
|
||
|
|
Are you sure you want to continue connecting (yes/no)? yes
|
||
|
|
Warning: Permanently added '192.168.1.47' (RSA) to the list of known hosts.
|
||
|
|
root@192.168.1.47's password:
|
||
|
|
</literallayout>
|
||
|
|
Once on the target, use these steps to create a trace:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng create
|
||
|
|
Spawning a session daemon
|
||
|
|
Session auto-20121015-232120 created.
|
||
|
|
Traces will be written in /home/root/lttng-traces/auto-20121015-232120
|
||
|
|
</literallayout>
|
||
|
|
Enable the events you want to trace (in this case all
|
||
|
|
kernel events):
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng enable-event --kernel --all
|
||
|
|
All kernel events are enabled in channel channel0
|
||
|
|
</literallayout>
|
||
|
|
Start the trace:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng start
|
||
|
|
Tracing started for session auto-20121015-232120
|
||
|
|
</literallayout>
|
||
|
|
And then stop the trace after awhile or after running
|
||
|
|
a particular workload that you want to trace:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng stop
|
||
|
|
Tracing stopped for session auto-20121015-232120
|
||
|
|
</literallayout>
|
||
|
|
You can now view the trace in text form on the target:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng view
|
||
|
|
[23:21:56.989270399] (+?.?????????) sys_geteuid: { 1 }, { }
|
||
|
|
[23:21:56.989278081] (+0.000007682) exit_syscall: { 1 }, { ret = 0 }
|
||
|
|
[23:21:56.989286043] (+0.000007962) sys_pipe: { 1 }, { fildes = 0xB77B9E8C }
|
||
|
|
[23:21:56.989321802] (+0.000035759) exit_syscall: { 1 }, { ret = 0 }
|
||
|
|
[23:21:56.989329345] (+0.000007543) sys_mmap_pgoff: { 1 }, { addr = 0x0, len = 10485760, prot = 3, flags = 131362, fd = 4294967295, pgoff = 0 }
|
||
|
|
[23:21:56.989351694] (+0.000022349) exit_syscall: { 1 }, { ret = -1247805440 }
|
||
|
|
[23:21:56.989432989] (+0.000081295) sys_clone: { 1 }, { clone_flags = 0x411, newsp = 0xB5EFFFE4, parent_tid = 0xFFFFFFFF, child_tid = 0x0 }
|
||
|
|
[23:21:56.989477129] (+0.000044140) sched_stat_runtime: { 1 }, { comm = "lttng-consumerd", tid = 1193, runtime = 681660, vruntime = 43367983388 }
|
||
|
|
[23:21:56.989486697] (+0.000009568) sched_migrate_task: { 1 }, { comm = "lttng-consumerd", tid = 1193, prio = 20, orig_cpu = 1, dest_cpu = 1 }
|
||
|
|
[23:21:56.989508418] (+0.000021721) hrtimer_init: { 1 }, { hrtimer = 3970832076, clockid = 1, mode = 1 }
|
||
|
|
[23:21:56.989770462] (+0.000262044) hrtimer_cancel: { 1 }, { hrtimer = 3993865440 }
|
||
|
|
[23:21:56.989771580] (+0.000001118) hrtimer_cancel: { 0 }, { hrtimer = 3993812192 }
|
||
|
|
[23:21:56.989776957] (+0.000005377) hrtimer_expire_entry: { 1 }, { hrtimer = 3993865440, now = 79815980007057, function = 3238465232 }
|
||
|
|
[23:21:56.989778145] (+0.000001188) hrtimer_expire_entry: { 0 }, { hrtimer = 3993812192, now = 79815980008174, function = 3238465232 }
|
||
|
|
[23:21:56.989791695] (+0.000013550) softirq_raise: { 1 }, { vec = 1 }
|
||
|
|
[23:21:56.989795396] (+0.000003701) softirq_raise: { 0 }, { vec = 1 }
|
||
|
|
[23:21:56.989800635] (+0.000005239) softirq_raise: { 0 }, { vec = 9 }
|
||
|
|
[23:21:56.989807130] (+0.000006495) sched_stat_runtime: { 1 }, { comm = "lttng-consumerd", tid = 1193, runtime = 330710, vruntime = 43368314098 }
|
||
|
|
[23:21:56.989809993] (+0.000002863) sched_stat_runtime: { 0 }, { comm = "lttng-sessiond", tid = 1181, runtime = 1015313, vruntime = 36976733240 }
|
||
|
|
[23:21:56.989818514] (+0.000008521) hrtimer_expire_exit: { 0 }, { hrtimer = 3993812192 }
|
||
|
|
[23:21:56.989819631] (+0.000001117) hrtimer_expire_exit: { 1 }, { hrtimer = 3993865440 }
|
||
|
|
[23:21:56.989821866] (+0.000002235) hrtimer_start: { 0 }, { hrtimer = 3993812192, function = 3238465232, expires = 79815981000000, softexpires = 79815981000000 }
|
||
|
|
[23:21:56.989822984] (+0.000001118) hrtimer_start: { 1 }, { hrtimer = 3993865440, function = 3238465232, expires = 79815981000000, softexpires = 79815981000000 }
|
||
|
|
[23:21:56.989832762] (+0.000009778) softirq_entry: { 1 }, { vec = 1 }
|
||
|
|
[23:21:56.989833879] (+0.000001117) softirq_entry: { 0 }, { vec = 1 }
|
||
|
|
[23:21:56.989838069] (+0.000004190) timer_cancel: { 1 }, { timer = 3993871956 }
|
||
|
|
[23:21:56.989839187] (+0.000001118) timer_cancel: { 0 }, { timer = 3993818708 }
|
||
|
|
[23:21:56.989841492] (+0.000002305) timer_expire_entry: { 1 }, { timer = 3993871956, now = 79515980, function = 3238277552 }
|
||
|
|
[23:21:56.989842819] (+0.000001327) timer_expire_entry: { 0 }, { timer = 3993818708, now = 79515980, function = 3238277552 }
|
||
|
|
[23:21:56.989854831] (+0.000012012) sched_stat_runtime: { 1 }, { comm = "lttng-consumerd", tid = 1193, runtime = 49237, vruntime = 43368363335 }
|
||
|
|
[23:21:56.989855949] (+0.000001118) sched_stat_runtime: { 0 }, { comm = "lttng-sessiond", tid = 1181, runtime = 45121, vruntime = 36976778361 }
|
||
|
|
[23:21:56.989861257] (+0.000005308) sched_stat_sleep: { 1 }, { comm = "kworker/1:1", tid = 21, delay = 9451318 }
|
||
|
|
[23:21:56.989862374] (+0.000001117) sched_stat_sleep: { 0 }, { comm = "kworker/0:0", tid = 4, delay = 9958820 }
|
||
|
|
[23:21:56.989868241] (+0.000005867) sched_wakeup: { 0 }, { comm = "kworker/0:0", tid = 4, prio = 120, success = 1, target_cpu = 0 }
|
||
|
|
[23:21:56.989869358] (+0.000001117) sched_wakeup: { 1 }, { comm = "kworker/1:1", tid = 21, prio = 120, success = 1, target_cpu = 1 }
|
||
|
|
[23:21:56.989877460] (+0.000008102) timer_expire_exit: { 1 }, { timer = 3993871956 }
|
||
|
|
[23:21:56.989878577] (+0.000001117) timer_expire_exit: { 0 }, { timer = 3993818708 }
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
</literallayout>
|
||
|
|
You can now safely destroy the trace session (note that
|
||
|
|
this doesn't delete the trace - it's still there
|
||
|
|
in ~/lttng-traces):
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng destroy
|
||
|
|
Session auto-20121015-232120 destroyed at /home/root
|
||
|
|
</literallayout>
|
||
|
|
Note that the trace is saved in a directory of the same
|
||
|
|
name as returned by 'lttng create', under the ~/lttng-traces
|
||
|
|
directory (note that you can change this by supplying your
|
||
|
|
own name to 'lttng create'):
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# ls -al ~/lttng-traces
|
||
|
|
drwxrwx--- 3 root root 1024 Oct 15 23:21 .
|
||
|
|
drwxr-xr-x 5 root root 1024 Oct 15 23:57 ..
|
||
|
|
drwxrwx--- 3 root root 1024 Oct 15 23:21 auto-20121015-232120
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='collecting-and-viewing-a-userspace-trace-on-the-target-inside-a-shell'>
|
||
|
|
<title>Collecting and viewing a userspace trace on the target (inside a shell)</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
For LTTng userspace tracing, you need to have a properly
|
||
|
|
instrumented userspace program. For this example, we'll use
|
||
|
|
the 'hello' test program generated by the lttng-ust build.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The 'hello' test program isn't installed on the rootfs by
|
||
|
|
the lttng-ust build, so we need to copy it over manually.
|
||
|
|
First cd into the build directory that contains the hello
|
||
|
|
executable:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ cd build/tmp/work/core2_32-poky-linux/lttng-ust/2.0.5-r0/git/tests/hello/.libs
|
||
|
|
</literallayout>
|
||
|
|
Copy that over to the target machine:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ scp hello root@192.168.1.20:
|
||
|
|
</literallayout>
|
||
|
|
You now have the instrumented lttng 'hello world' test
|
||
|
|
program on the target, ready to test.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
First, from the host, ssh to the target:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ ssh -l root 192.168.1.47
|
||
|
|
The authenticity of host '192.168.1.47 (192.168.1.47)' can't be established.
|
||
|
|
RSA key fingerprint is 23:bd:c8:b1:a8:71:52:00:ee:00:4f:64:9e:10:b9:7e.
|
||
|
|
Are you sure you want to continue connecting (yes/no)? yes
|
||
|
|
Warning: Permanently added '192.168.1.47' (RSA) to the list of known hosts.
|
||
|
|
root@192.168.1.47's password:
|
||
|
|
</literallayout>
|
||
|
|
Once on the target, use these steps to create a trace:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng create
|
||
|
|
Session auto-20190303-021943 created.
|
||
|
|
Traces will be written in /home/root/lttng-traces/auto-20190303-021943
|
||
|
|
</literallayout>
|
||
|
|
Enable the events you want to trace (in this case all
|
||
|
|
userspace events):
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng enable-event --userspace --all
|
||
|
|
All UST events are enabled in channel channel0
|
||
|
|
</literallayout>
|
||
|
|
Start the trace:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng start
|
||
|
|
Tracing started for session auto-20190303-021943
|
||
|
|
</literallayout>
|
||
|
|
Run the instrumented hello world program:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# ./hello
|
||
|
|
Hello, World!
|
||
|
|
Tracing... done.
|
||
|
|
</literallayout>
|
||
|
|
And then stop the trace after awhile or after running a
|
||
|
|
particular workload that you want to trace:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng stop
|
||
|
|
Tracing stopped for session auto-20190303-021943
|
||
|
|
</literallayout>
|
||
|
|
You can now view the trace in text form on the target:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng view
|
||
|
|
[02:31:14.906146544] (+?.?????????) hello:1424 ust_tests_hello:tptest: { cpu_id = 1 }, { intfield = 0, intfield2 = 0x0, longfield = 0, netintfield = 0, netintfieldhex = 0x0, arrfield1 = [ [0] = 1, [1] = 2, [2] = 3 ], arrfield2 = "test", _seqfield1_length = 4, seqfield1 = [ [0] = 116, [1] = 101, [2] = 115, [3] = 116 ], _seqfield2_length = 4, seqfield2 = "test", stringfield = "test", floatfield = 2222, doublefield = 2, boolfield = 1 }
|
||
|
|
[02:31:14.906170360] (+0.000023816) hello:1424 ust_tests_hello:tptest: { cpu_id = 1 }, { intfield = 1, intfield2 = 0x1, longfield = 1, netintfield = 1, netintfieldhex = 0x1, arrfield1 = [ [0] = 1, [1] = 2, [2] = 3 ], arrfield2 = "test", _seqfield1_length = 4, seqfield1 = [ [0] = 116, [1] = 101, [2] = 115, [3] = 116 ], _seqfield2_length = 4, seqfield2 = "test", stringfield = "test", floatfield = 2222, doublefield = 2, boolfield = 1 }
|
||
|
|
[02:31:14.906183140] (+0.000012780) hello:1424 ust_tests_hello:tptest: { cpu_id = 1 }, { intfield = 2, intfield2 = 0x2, longfield = 2, netintfield = 2, netintfieldhex = 0x2, arrfield1 = [ [0] = 1, [1] = 2, [2] = 3 ], arrfield2 = "test", _seqfield1_length = 4, seqfield1 = [ [0] = 116, [1] = 101, [2] = 115, [3] = 116 ], _seqfield2_length = 4, seqfield2 = "test", stringfield = "test", floatfield = 2222, doublefield = 2, boolfield = 1 }
|
||
|
|
[02:31:14.906194385] (+0.000011245) hello:1424 ust_tests_hello:tptest: { cpu_id = 1 }, { intfield = 3, intfield2 = 0x3, longfield = 3, netintfield = 3, netintfieldhex = 0x3, arrfield1 = [ [0] = 1, [1] = 2, [2] = 3 ], arrfield2 = "test", _seqfield1_length = 4, seqfield1 = [ [0] = 116, [1] = 101, [2] = 115, [3] = 116 ], _seqfield2_length = 4, seqfield2 = "test", stringfield = "test", floatfield = 2222, doublefield = 2, boolfield = 1 }
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
</literallayout>
|
||
|
|
You can now safely destroy the trace session (note that
|
||
|
|
this doesn't delete the trace - it's still
|
||
|
|
there in ~/lttng-traces):
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# lttng destroy
|
||
|
|
Session auto-20190303-021943 destroyed at /home/root
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='manually-copying-a-trace-to-the-host-and-viewing-it-in-eclipse'>
|
||
|
|
<title>Manually copying a trace to the host and viewing it in Eclipse (i.e. using Eclipse without network support)</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
If you already have an LTTng trace on a remote target and
|
||
|
|
would like to view it in Eclipse on the host, you can easily
|
||
|
|
copy it from the target to the host and import it into
|
||
|
|
Eclipse to view it using the LTTng Eclipse plug-in already
|
||
|
|
bundled in the Eclipse (Juno SR1 or greater).
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Using the trace we created in the previous section, archive
|
||
|
|
it and copy it to your host system:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~/lttng-traces# tar zcvf auto-20121015-232120.tar.gz auto-20121015-232120
|
||
|
|
auto-20121015-232120/
|
||
|
|
auto-20121015-232120/kernel/
|
||
|
|
auto-20121015-232120/kernel/metadata
|
||
|
|
auto-20121015-232120/kernel/channel0_1
|
||
|
|
auto-20121015-232120/kernel/channel0_0
|
||
|
|
|
||
|
|
$ scp root@192.168.1.47:lttng-traces/auto-20121015-232120.tar.gz .
|
||
|
|
root@192.168.1.47's password:
|
||
|
|
auto-20121015-232120.tar.gz 100% 1566KB 1.5MB/s 00:01
|
||
|
|
</literallayout>
|
||
|
|
Unarchive it on the host:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ gunzip -c auto-20121015-232120.tar.gz | tar xvf -
|
||
|
|
auto-20121015-232120/
|
||
|
|
auto-20121015-232120/kernel/
|
||
|
|
auto-20121015-232120/kernel/metadata
|
||
|
|
auto-20121015-232120/kernel/channel0_1
|
||
|
|
auto-20121015-232120/kernel/channel0_0
|
||
|
|
</literallayout>
|
||
|
|
We can now import the trace into Eclipse and view it:
|
||
|
|
<orderedlist>
|
||
|
|
<listitem><para>First, start eclipse and open the
|
||
|
|
'LTTng Kernel' perspective by selecting the following
|
||
|
|
menu item:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
Window | Open Perspective | Other...
|
||
|
|
</literallayout></para></listitem>
|
||
|
|
<listitem><para>In the dialog box that opens, select
|
||
|
|
'LTTng Kernel' from the list.</para></listitem>
|
||
|
|
<listitem><para>Back at the main menu, select the
|
||
|
|
following menu item:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
File | New | Project...
|
||
|
|
</literallayout></para></listitem>
|
||
|
|
<listitem><para>In the dialog box that opens, select
|
||
|
|
the 'Tracing | Tracing Project' wizard and press
|
||
|
|
'Next>'.</para></listitem>
|
||
|
|
<listitem><para>Give the project a name and press
|
||
|
|
'Finish'.</para></listitem>
|
||
|
|
<listitem><para>In the 'Project Explorer' pane under
|
||
|
|
the project you created, right click on the
|
||
|
|
'Traces' item.</para></listitem>
|
||
|
|
<listitem><para>Select 'Import..." and in the dialog
|
||
|
|
that's displayed:</para></listitem>
|
||
|
|
<listitem><para>Browse the filesystem and find the
|
||
|
|
select the 'kernel' directory containing the trace
|
||
|
|
you copied from the target
|
||
|
|
e.g. auto-20121015-232120/kernel</para></listitem>
|
||
|
|
<listitem><para>'Checkmark' the directory in the tree
|
||
|
|
that's displayed for the trace</para></listitem>
|
||
|
|
<listitem><para>Below that, select 'Common Trace Format:
|
||
|
|
Kernel Trace' for the 'Trace Type'</para></listitem>
|
||
|
|
<listitem><para>Press 'Finish' to close the dialog
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para>Back in the 'Project Explorer' pane,
|
||
|
|
double-click on the 'kernel' item for the
|
||
|
|
trace you just imported under 'Traces'
|
||
|
|
</para></listitem>
|
||
|
|
</orderedlist>
|
||
|
|
You should now see your trace data displayed graphically
|
||
|
|
in several different views in Eclipse:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
<imagedata fileref="figures/lttngmain0.png" width="6in" depth="6in" align="center" scalefit="1" />
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
You can access extensive help information on how to use
|
||
|
|
the LTTng plug-in to search and analyze captured traces via
|
||
|
|
the Eclipse help system:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
Help | Help Contents | LTTng Plug-in User Guide
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='collecting-and-viewing-a-trace-in-eclipse'>
|
||
|
|
<title>Collecting and viewing a trace in Eclipse</title>
|
||
|
|
|
||
|
|
<note>
|
||
|
|
This section on collecting traces remotely doesn't currently
|
||
|
|
work because of Eclipse 'RSE' connectivity problems. Manually
|
||
|
|
tracing on the target, copying the trace files to the host,
|
||
|
|
and viewing the trace in Eclipse on the host as outlined in
|
||
|
|
previous steps does work however - please use the manual
|
||
|
|
steps outlined above to view traces in Eclipse.
|
||
|
|
</note>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
In order to trace a remote target, you also need to add
|
||
|
|
a 'tracing' group on the target and connect as a user
|
||
|
|
who's part of that group e.g:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
# adduser tomz
|
||
|
|
# groupadd -r tracing
|
||
|
|
# usermod -a -G tracing tomz
|
||
|
|
</literallayout>
|
||
|
|
<orderedlist>
|
||
|
|
<listitem><para>First, start eclipse and open the
|
||
|
|
'LTTng Kernel' perspective by selecting the following
|
||
|
|
menu item:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
Window | Open Perspective | Other...
|
||
|
|
</literallayout></para></listitem>
|
||
|
|
<listitem><para>In the dialog box that opens, select
|
||
|
|
'LTTng Kernel' from the list.</para></listitem>
|
||
|
|
<listitem><para>Back at the main menu, select the
|
||
|
|
following menu item:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
File | New | Project...
|
||
|
|
</literallayout></para></listitem>
|
||
|
|
<listitem><para>In the dialog box that opens, select
|
||
|
|
the 'Tracing | Tracing Project' wizard and
|
||
|
|
press 'Next>'.</para></listitem>
|
||
|
|
<listitem><para>Give the project a name and press
|
||
|
|
'Finish'. That should result in an entry in the
|
||
|
|
'Project' subwindow.</para></listitem>
|
||
|
|
<listitem><para>In the 'Control' subwindow just below
|
||
|
|
it, press 'New Connection'.</para></listitem>
|
||
|
|
<listitem><para>Add a new connection, giving it the
|
||
|
|
hostname or IP address of the target system.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para>Provide the username and password
|
||
|
|
of a qualified user (a member of the 'tracing' group)
|
||
|
|
or root account on the target system.
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para>Provide appropriate answers to whatever
|
||
|
|
else is asked for e.g. 'secure storage password'
|
||
|
|
can be anything you want.
|
||
|
|
If you get an 'RSE Error' it may be due to proxies.
|
||
|
|
It may be possible to get around the problem by
|
||
|
|
changing the following setting:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
Window | Preferences | Network Connections
|
||
|
|
</literallayout>
|
||
|
|
Switch 'Active Provider' to 'Direct'
|
||
|
|
</para></listitem>
|
||
|
|
</orderedlist>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='lltng-documentation'>
|
||
|
|
<title>Documentation</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
You can find the primary LTTng Documentation on the
|
||
|
|
<ulink url='https://lttng.org/docs/'>LTTng Documentation</ulink>
|
||
|
|
site.
|
||
|
|
The documentation on this site is appropriate for intermediate to
|
||
|
|
advanced software developers who are working in a Linux environment
|
||
|
|
and are interested in efficient software tracing.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
For information on LTTng in general, visit the
|
||
|
|
<ulink url='http://lttng.org/lttng2.0'>LTTng Project</ulink>
|
||
|
|
site.
|
||
|
|
You can find a "Getting Started" link on this site that takes
|
||
|
|
you to an LTTng Quick Start.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Finally, you can access extensive help information on how to use
|
||
|
|
the LTTng plug-in to search and analyze captured traces via the
|
||
|
|
Eclipse help system:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
Help | Help Contents | LTTng Plug-in User Guide
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='profile-manual-blktrace'>
|
||
|
|
<title>blktrace</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
blktrace is a tool for tracing and reporting low-level disk I/O.
|
||
|
|
blktrace provides the tracing half of the equation; its output can
|
||
|
|
be piped into the blkparse program, which renders the data in a
|
||
|
|
human-readable form and does some basic analysis:
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<section id='blktrace-setup'>
|
||
|
|
<title>Setup</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
For this section, we'll assume you've already performed the
|
||
|
|
basic setup outlined in the
|
||
|
|
"<link linkend='profile-manual-general-setup'>General Setup</link>"
|
||
|
|
section.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
blktrace is an application that runs on the target system.
|
||
|
|
You can run the entire blktrace and blkparse pipeline on the
|
||
|
|
target, or you can run blktrace in 'listen' mode on the target
|
||
|
|
and have blktrace and blkparse collect and analyze the data on
|
||
|
|
the host (see the
|
||
|
|
"<link linkend='using-blktrace-remotely'>Using blktrace Remotely</link>"
|
||
|
|
section below).
|
||
|
|
For the rest of this section we assume you've ssh'ed to the
|
||
|
|
host and will be running blkrace on the target.
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='blktrace-basic-usage'>
|
||
|
|
<title>Basic Usage</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
To record a trace, simply run the 'blktrace' command, giving it
|
||
|
|
the name of the block device you want to trace activity on:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# blktrace /dev/sdc
|
||
|
|
</literallayout>
|
||
|
|
In another shell, execute a workload you want to trace.
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:/media/sdc# rm linux-2.6.19.2.tar.bz2; wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>; sync
|
||
|
|
Connecting to downloads.yoctoproject.org (140.211.169.59:80)
|
||
|
|
linux-2.6.19.2.tar.b 100% |*******************************| 41727k 0:00:00 ETA
|
||
|
|
</literallayout>
|
||
|
|
Press Ctrl-C in the blktrace shell to stop the trace. It will
|
||
|
|
display how many events were logged, along with the per-cpu file
|
||
|
|
sizes (blktrace records traces in per-cpu kernel buffers and
|
||
|
|
simply dumps them to userspace for blkparse to merge and sort
|
||
|
|
later).
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
^C=== sdc ===
|
||
|
|
CPU 0: 7082 events, 332 KiB data
|
||
|
|
CPU 1: 1578 events, 74 KiB data
|
||
|
|
Total: 8660 events (dropped 0), 406 KiB data
|
||
|
|
</literallayout>
|
||
|
|
If you examine the files saved to disk, you see multiple files,
|
||
|
|
one per CPU and with the device name as the first part of the
|
||
|
|
filename:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# ls -al
|
||
|
|
drwxr-xr-x 6 root root 1024 Oct 27 22:39 .
|
||
|
|
drwxr-sr-x 4 root root 1024 Oct 26 18:24 ..
|
||
|
|
-rw-r--r-- 1 root root 339938 Oct 27 22:40 sdc.blktrace.0
|
||
|
|
-rw-r--r-- 1 root root 75753 Oct 27 22:40 sdc.blktrace.1
|
||
|
|
</literallayout>
|
||
|
|
To view the trace events, simply invoke 'blkparse' in the
|
||
|
|
directory containing the trace files, giving it the device name
|
||
|
|
that forms the first part of the filenames:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# blkparse sdc
|
||
|
|
|
||
|
|
8,32 1 1 0.000000000 1225 Q WS 3417048 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 2 0.000025213 1225 G WS 3417048 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 3 0.000033384 1225 P N [jbd2/sdc-8]
|
||
|
|
8,32 1 4 0.000043301 1225 I WS 3417048 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 0 0.000057270 0 m N cfq1225 insert_request
|
||
|
|
8,32 1 0 0.000064813 0 m N cfq1225 add_to_rr
|
||
|
|
8,32 1 5 0.000076336 1225 U N [jbd2/sdc-8] 1
|
||
|
|
8,32 1 0 0.000088559 0 m N cfq workload slice:150
|
||
|
|
8,32 1 0 0.000097359 0 m N cfq1225 set_active wl_prio:0 wl_type:1
|
||
|
|
8,32 1 0 0.000104063 0 m N cfq1225 Not idling. st->count:1
|
||
|
|
8,32 1 0 0.000112584 0 m N cfq1225 fifo= (null)
|
||
|
|
8,32 1 0 0.000118730 0 m N cfq1225 dispatch_insert
|
||
|
|
8,32 1 0 0.000127390 0 m N cfq1225 dispatched a request
|
||
|
|
8,32 1 0 0.000133536 0 m N cfq1225 activate rq, drv=1
|
||
|
|
8,32 1 6 0.000136889 1225 D WS 3417048 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 7 0.000360381 1225 Q WS 3417056 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 8 0.000377422 1225 G WS 3417056 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 9 0.000388876 1225 P N [jbd2/sdc-8]
|
||
|
|
8,32 1 10 0.000397886 1225 Q WS 3417064 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 11 0.000404800 1225 M WS 3417064 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 12 0.000412343 1225 Q WS 3417072 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 13 0.000416533 1225 M WS 3417072 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 14 0.000422121 1225 Q WS 3417080 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 15 0.000425194 1225 M WS 3417080 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 16 0.000431968 1225 Q WS 3417088 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 17 0.000435251 1225 M WS 3417088 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 18 0.000440279 1225 Q WS 3417096 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 19 0.000443911 1225 M WS 3417096 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 20 0.000450336 1225 Q WS 3417104 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 21 0.000454038 1225 M WS 3417104 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 22 0.000462070 1225 Q WS 3417112 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 23 0.000465422 1225 M WS 3417112 + 8 [jbd2/sdc-8]
|
||
|
|
8,32 1 24 0.000474222 1225 I WS 3417056 + 64 [jbd2/sdc-8]
|
||
|
|
8,32 1 0 0.000483022 0 m N cfq1225 insert_request
|
||
|
|
8,32 1 25 0.000489727 1225 U N [jbd2/sdc-8] 1
|
||
|
|
8,32 1 0 0.000498457 0 m N cfq1225 Not idling. st->count:1
|
||
|
|
8,32 1 0 0.000503765 0 m N cfq1225 dispatch_insert
|
||
|
|
8,32 1 0 0.000512914 0 m N cfq1225 dispatched a request
|
||
|
|
8,32 1 0 0.000518851 0 m N cfq1225 activate rq, drv=2
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
8,32 0 0 58.515006138 0 m N cfq3551 complete rqnoidle 1
|
||
|
|
8,32 0 2024 58.516603269 3 C WS 3156992 + 16 [0]
|
||
|
|
8,32 0 0 58.516626736 0 m N cfq3551 complete rqnoidle 1
|
||
|
|
8,32 0 0 58.516634558 0 m N cfq3551 arm_idle: 8 group_idle: 0
|
||
|
|
8,32 0 0 58.516636933 0 m N cfq schedule dispatch
|
||
|
|
8,32 1 0 58.516971613 0 m N cfq3551 slice expired t=0
|
||
|
|
8,32 1 0 58.516982089 0 m N cfq3551 sl_used=13 disp=6 charge=13 iops=0 sect=80
|
||
|
|
8,32 1 0 58.516985511 0 m N cfq3551 del_from_rr
|
||
|
|
8,32 1 0 58.516990819 0 m N cfq3551 put_queue
|
||
|
|
|
||
|
|
CPU0 (sdc):
|
||
|
|
Reads Queued: 0, 0KiB Writes Queued: 331, 26,284KiB
|
||
|
|
Read Dispatches: 0, 0KiB Write Dispatches: 485, 40,484KiB
|
||
|
|
Reads Requeued: 0 Writes Requeued: 0
|
||
|
|
Reads Completed: 0, 0KiB Writes Completed: 511, 41,000KiB
|
||
|
|
Read Merges: 0, 0KiB Write Merges: 13, 160KiB
|
||
|
|
Read depth: 0 Write depth: 2
|
||
|
|
IO unplugs: 23 Timer unplugs: 0
|
||
|
|
CPU1 (sdc):
|
||
|
|
Reads Queued: 0, 0KiB Writes Queued: 249, 15,800KiB
|
||
|
|
Read Dispatches: 0, 0KiB Write Dispatches: 42, 1,600KiB
|
||
|
|
Reads Requeued: 0 Writes Requeued: 0
|
||
|
|
Reads Completed: 0, 0KiB Writes Completed: 16, 1,084KiB
|
||
|
|
Read Merges: 0, 0KiB Write Merges: 40, 276KiB
|
||
|
|
Read depth: 0 Write depth: 2
|
||
|
|
IO unplugs: 30 Timer unplugs: 1
|
||
|
|
|
||
|
|
Total (sdc):
|
||
|
|
Reads Queued: 0, 0KiB Writes Queued: 580, 42,084KiB
|
||
|
|
Read Dispatches: 0, 0KiB Write Dispatches: 527, 42,084KiB
|
||
|
|
Reads Requeued: 0 Writes Requeued: 0
|
||
|
|
Reads Completed: 0, 0KiB Writes Completed: 527, 42,084KiB
|
||
|
|
Read Merges: 0, 0KiB Write Merges: 53, 436KiB
|
||
|
|
IO unplugs: 53 Timer unplugs: 1
|
||
|
|
|
||
|
|
Throughput (R/W): 0KiB/s / 719KiB/s
|
||
|
|
Events (sdc): 6,592 entries
|
||
|
|
Skips: 0 forward (0 - 0.0%)
|
||
|
|
Input file sdc.blktrace.0 added
|
||
|
|
Input file sdc.blktrace.1 added
|
||
|
|
</literallayout>
|
||
|
|
The report shows each event that was found in the blktrace data,
|
||
|
|
along with a summary of the overall block I/O traffic during
|
||
|
|
the run. You can look at the
|
||
|
|
<ulink url='http://linux.die.net/man/1/blkparse'>blkparse</ulink>
|
||
|
|
manpage to learn the
|
||
|
|
meaning of each field displayed in the trace listing.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<section id='blktrace-live-mode'>
|
||
|
|
<title>Live Mode</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
blktrace and blkparse are designed from the ground up to
|
||
|
|
be able to operate together in a 'pipe mode' where the
|
||
|
|
stdout of blktrace can be fed directly into the stdin of
|
||
|
|
blkparse:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# blktrace /dev/sdc -o - | blkparse -i -
|
||
|
|
</literallayout>
|
||
|
|
This enables long-lived tracing sessions to run without
|
||
|
|
writing anything to disk, and allows the user to look for
|
||
|
|
certain conditions in the trace data in 'real-time' by
|
||
|
|
viewing the trace output as it scrolls by on the screen or
|
||
|
|
by passing it along to yet another program in the pipeline
|
||
|
|
such as grep which can be used to identify and capture
|
||
|
|
conditions of interest.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
There's actually another blktrace command that implements
|
||
|
|
the above pipeline as a single command, so the user doesn't
|
||
|
|
have to bother typing in the above command sequence:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# btrace /dev/sdc
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='using-blktrace-remotely'>
|
||
|
|
<title>Using blktrace Remotely</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Because blktrace traces block I/O and at the same time
|
||
|
|
normally writes its trace data to a block device, and
|
||
|
|
in general because it's not really a great idea to make
|
||
|
|
the device being traced the same as the device the tracer
|
||
|
|
writes to, blktrace provides a way to trace without
|
||
|
|
perturbing the traced device at all by providing native
|
||
|
|
support for sending all trace data over the network.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
To have blktrace operate in this mode, start blktrace on
|
||
|
|
the target system being traced with the -l option, along with
|
||
|
|
the device to trace:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:~# blktrace -l /dev/sdc
|
||
|
|
server: waiting for connections...
|
||
|
|
</literallayout>
|
||
|
|
On the host system, use the -h option to connect to the
|
||
|
|
target system, also passing it the device to trace:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ blktrace -d /dev/sdc -h 192.168.1.43
|
||
|
|
blktrace: connecting to 192.168.1.43
|
||
|
|
blktrace: connected!
|
||
|
|
</literallayout>
|
||
|
|
On the target system, you should see this:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
server: connection from 192.168.1.43
|
||
|
|
</literallayout>
|
||
|
|
In another shell, execute a workload you want to trace.
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:/media/sdc# rm linux-2.6.19.2.tar.bz2; wget <ulink url='http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2'>http://downloads.yoctoproject.org/mirror/sources/linux-2.6.19.2.tar.bz2</ulink>; sync
|
||
|
|
Connecting to downloads.yoctoproject.org (140.211.169.59:80)
|
||
|
|
linux-2.6.19.2.tar.b 100% |*******************************| 41727k 0:00:00 ETA
|
||
|
|
</literallayout>
|
||
|
|
When it's done, do a Ctrl-C on the host system to
|
||
|
|
stop the trace:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
^C=== sdc ===
|
||
|
|
CPU 0: 7691 events, 361 KiB data
|
||
|
|
CPU 1: 4109 events, 193 KiB data
|
||
|
|
Total: 11800 events (dropped 0), 554 KiB data
|
||
|
|
</literallayout>
|
||
|
|
On the target system, you should also see a trace
|
||
|
|
summary for the trace just ended:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
server: end of run for 192.168.1.43:sdc
|
||
|
|
=== sdc ===
|
||
|
|
CPU 0: 7691 events, 361 KiB data
|
||
|
|
CPU 1: 4109 events, 193 KiB data
|
||
|
|
Total: 11800 events (dropped 0), 554 KiB data
|
||
|
|
</literallayout>
|
||
|
|
The blktrace instance on the host will save the target
|
||
|
|
output inside a hostname-timestamp directory:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ ls -al
|
||
|
|
drwxr-xr-x 10 root root 1024 Oct 28 02:40 .
|
||
|
|
drwxr-sr-x 4 root root 1024 Oct 26 18:24 ..
|
||
|
|
drwxr-xr-x 2 root root 1024 Oct 28 02:40 192.168.1.43-2012-10-28-02:40:56
|
||
|
|
</literallayout>
|
||
|
|
cd into that directory to see the output files:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ ls -l
|
||
|
|
-rw-r--r-- 1 root root 369193 Oct 28 02:44 sdc.blktrace.0
|
||
|
|
-rw-r--r-- 1 root root 197278 Oct 28 02:44 sdc.blktrace.1
|
||
|
|
</literallayout>
|
||
|
|
And run blkparse on the host system using the device name:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ blkparse sdc
|
||
|
|
|
||
|
|
8,32 1 1 0.000000000 1263 Q RM 6016 + 8 [ls]
|
||
|
|
8,32 1 0 0.000036038 0 m N cfq1263 alloced
|
||
|
|
8,32 1 2 0.000039390 1263 G RM 6016 + 8 [ls]
|
||
|
|
8,32 1 3 0.000049168 1263 I RM 6016 + 8 [ls]
|
||
|
|
8,32 1 0 0.000056152 0 m N cfq1263 insert_request
|
||
|
|
8,32 1 0 0.000061600 0 m N cfq1263 add_to_rr
|
||
|
|
8,32 1 0 0.000075498 0 m N cfq workload slice:300
|
||
|
|
.
|
||
|
|
.
|
||
|
|
.
|
||
|
|
8,32 0 0 177.266385696 0 m N cfq1267 arm_idle: 8 group_idle: 0
|
||
|
|
8,32 0 0 177.266388140 0 m N cfq schedule dispatch
|
||
|
|
8,32 1 0 177.266679239 0 m N cfq1267 slice expired t=0
|
||
|
|
8,32 1 0 177.266689297 0 m N cfq1267 sl_used=9 disp=6 charge=9 iops=0 sect=56
|
||
|
|
8,32 1 0 177.266692649 0 m N cfq1267 del_from_rr
|
||
|
|
8,32 1 0 177.266696560 0 m N cfq1267 put_queue
|
||
|
|
|
||
|
|
CPU0 (sdc):
|
||
|
|
Reads Queued: 0, 0KiB Writes Queued: 270, 21,708KiB
|
||
|
|
Read Dispatches: 59, 2,628KiB Write Dispatches: 495, 39,964KiB
|
||
|
|
Reads Requeued: 0 Writes Requeued: 0
|
||
|
|
Reads Completed: 90, 2,752KiB Writes Completed: 543, 41,596KiB
|
||
|
|
Read Merges: 0, 0KiB Write Merges: 9, 344KiB
|
||
|
|
Read depth: 2 Write depth: 2
|
||
|
|
IO unplugs: 20 Timer unplugs: 1
|
||
|
|
CPU1 (sdc):
|
||
|
|
Reads Queued: 688, 2,752KiB Writes Queued: 381, 20,652KiB
|
||
|
|
Read Dispatches: 31, 124KiB Write Dispatches: 59, 2,396KiB
|
||
|
|
Reads Requeued: 0 Writes Requeued: 0
|
||
|
|
Reads Completed: 0, 0KiB Writes Completed: 11, 764KiB
|
||
|
|
Read Merges: 598, 2,392KiB Write Merges: 88, 448KiB
|
||
|
|
Read depth: 2 Write depth: 2
|
||
|
|
IO unplugs: 52 Timer unplugs: 0
|
||
|
|
|
||
|
|
Total (sdc):
|
||
|
|
Reads Queued: 688, 2,752KiB Writes Queued: 651, 42,360KiB
|
||
|
|
Read Dispatches: 90, 2,752KiB Write Dispatches: 554, 42,360KiB
|
||
|
|
Reads Requeued: 0 Writes Requeued: 0
|
||
|
|
Reads Completed: 90, 2,752KiB Writes Completed: 554, 42,360KiB
|
||
|
|
Read Merges: 598, 2,392KiB Write Merges: 97, 792KiB
|
||
|
|
IO unplugs: 72 Timer unplugs: 1
|
||
|
|
|
||
|
|
Throughput (R/W): 15KiB/s / 238KiB/s
|
||
|
|
Events (sdc): 9,301 entries
|
||
|
|
Skips: 0 forward (0 - 0.0%)
|
||
|
|
</literallayout>
|
||
|
|
You should see the trace events and summary just as
|
||
|
|
you would have if you'd run the same command on the target.
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='tracing-block-io-via-ftrace'>
|
||
|
|
<title>Tracing Block I/O via 'ftrace'</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
It's also possible to trace block I/O using only
|
||
|
|
<link linkend='the-trace-events-subsystem'>trace events subsystem</link>,
|
||
|
|
which can be useful for casual tracing
|
||
|
|
if you don't want to bother dealing with the userspace tools.
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
To enable tracing for a given device, use
|
||
|
|
/sys/block/xxx/trace/enable, where xxx is the device name.
|
||
|
|
This for example enables tracing for /dev/sdc:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:/sys/kernel/debug/tracing# echo 1 > /sys/block/sdc/trace/enable
|
||
|
|
</literallayout>
|
||
|
|
Once you've selected the device(s) you want to trace,
|
||
|
|
selecting the 'blk' tracer will turn the blk tracer on:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:/sys/kernel/debug/tracing# cat available_tracers
|
||
|
|
blk function_graph function nop
|
||
|
|
|
||
|
|
root@crownbay:/sys/kernel/debug/tracing# echo blk > current_tracer
|
||
|
|
</literallayout>
|
||
|
|
Execute the workload you're interested in:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:/sys/kernel/debug/tracing# cat /media/sdc/testfile.txt
|
||
|
|
</literallayout>
|
||
|
|
And look at the output (note here that we're using
|
||
|
|
'trace_pipe' instead of trace to capture this trace -
|
||
|
|
this allows us to wait around on the pipe for data to
|
||
|
|
appear):
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:/sys/kernel/debug/tracing# cat trace_pipe
|
||
|
|
cat-3587 [001] d..1 3023.276361: 8,32 Q R 1699848 + 8 [cat]
|
||
|
|
cat-3587 [001] d..1 3023.276410: 8,32 m N cfq3587 alloced
|
||
|
|
cat-3587 [001] d..1 3023.276415: 8,32 G R 1699848 + 8 [cat]
|
||
|
|
cat-3587 [001] d..1 3023.276424: 8,32 P N [cat]
|
||
|
|
cat-3587 [001] d..2 3023.276432: 8,32 I R 1699848 + 8 [cat]
|
||
|
|
cat-3587 [001] d..1 3023.276439: 8,32 m N cfq3587 insert_request
|
||
|
|
cat-3587 [001] d..1 3023.276445: 8,32 m N cfq3587 add_to_rr
|
||
|
|
cat-3587 [001] d..2 3023.276454: 8,32 U N [cat] 1
|
||
|
|
cat-3587 [001] d..1 3023.276464: 8,32 m N cfq workload slice:150
|
||
|
|
cat-3587 [001] d..1 3023.276471: 8,32 m N cfq3587 set_active wl_prio:0 wl_type:2
|
||
|
|
cat-3587 [001] d..1 3023.276478: 8,32 m N cfq3587 fifo= (null)
|
||
|
|
cat-3587 [001] d..1 3023.276483: 8,32 m N cfq3587 dispatch_insert
|
||
|
|
cat-3587 [001] d..1 3023.276490: 8,32 m N cfq3587 dispatched a request
|
||
|
|
cat-3587 [001] d..1 3023.276497: 8,32 m N cfq3587 activate rq, drv=1
|
||
|
|
cat-3587 [001] d..2 3023.276500: 8,32 D R 1699848 + 8 [cat]
|
||
|
|
</literallayout>
|
||
|
|
And this turns off tracing for the specified device:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
root@crownbay:/sys/kernel/debug/tracing# echo 0 > /sys/block/sdc/trace/enable
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
</section>
|
||
|
|
|
||
|
|
<section id='blktrace-documentation'>
|
||
|
|
<title>Documentation</title>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
Online versions of the man pages for the commands discussed
|
||
|
|
in this section can be found here:
|
||
|
|
<itemizedlist>
|
||
|
|
<listitem><para><ulink url='http://linux.die.net/man/8/blktrace'>http://linux.die.net/man/8/blktrace</ulink>
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><ulink url='http://linux.die.net/man/1/blkparse'>http://linux.die.net/man/1/blkparse</ulink>
|
||
|
|
</para></listitem>
|
||
|
|
<listitem><para><ulink url='http://linux.die.net/man/8/btrace'>http://linux.die.net/man/8/btrace</ulink>
|
||
|
|
</para></listitem>
|
||
|
|
</itemizedlist>
|
||
|
|
</para>
|
||
|
|
|
||
|
|
<para>
|
||
|
|
The above manpages, along with manpages for the other
|
||
|
|
blktrace utilities (btt, blkiomon, etc) can be found in the
|
||
|
|
/doc directory of the blktrace tools git repo:
|
||
|
|
<literallayout class='monospaced'>
|
||
|
|
$ git clone git://git.kernel.dk/blktrace.git
|
||
|
|
</literallayout>
|
||
|
|
</para>
|
||
|
|
</section>
|
||
|
|
</section>
|
||
|
|
</chapter>
|
||
|
|
<!--
|
||
|
|
vim: expandtab tw=80 ts=4
|
||
|
|
-->
|