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cogl/onscreen: Discard depth/stencil before swapping buffers

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Marking the the depth/stencil as discarded before swapping buffers for
the screen signals the GPU that we don't need to keep them around for
the future.
This helps performance by reducing memory bandwidth usage in some GPUs
which may optimize to not write those buffers back to memory at all
after rendering, when they would just be cleared right after that
anyway.
It is not necessary to mark buffers as discarded after swapping buffers.
This should have no effect according to the spec (since that is going to
be followed by new rendering commands which make the buffer valid again)
and removing that has shown no impact in performance tests.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2091>
This commit is contained in:
Erico Nunes 2021-11-16 16:44:39 +01:00 committed by Robert Mader
parent 5fedd065c9
commit 523b27e267
1 changed files with 8 additions and 10 deletions
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18
cogl/cogl/cogl-onscreen.c
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@ -334,17 +334,16 @@ cogl_onscreen_swap_buffers_with_damage (CoglOnscreen *onscreen,
if (G_UNLIKELY (COGL_DEBUG_ENABLED (COGL_DEBUG_SYNC_FRAME)))
cogl_framebuffer_finish (framebuffer);
cogl_framebuffer_discard_buffers (framebuffer,
COGL_BUFFER_BIT_DEPTH |
COGL_BUFFER_BIT_STENCIL);
klass->swap_buffers_with_damage (onscreen,
rectangles,
n_rectangles,
info,
user_data);
cogl_framebuffer_discard_buffers (framebuffer,
COGL_BUFFER_BIT_COLOR |
COGL_BUFFER_BIT_DEPTH |
COGL_BUFFER_BIT_STENCIL);
if (!_cogl_winsys_has_feature (COGL_WINSYS_FEATURE_SYNC_AND_COMPLETE_EVENT))
{
CoglFrameInfo *info;
@ -395,17 +394,16 @@ cogl_onscreen_swap_region (CoglOnscreen *onscreen,
COGL_WINSYS_FEATURE_SWAP_REGION */
g_return_if_fail (klass->swap_region);
cogl_framebuffer_discard_buffers (framebuffer,
COGL_BUFFER_BIT_DEPTH |
COGL_BUFFER_BIT_STENCIL);
klass->swap_region (onscreen,
rectangles,
n_rectangles,
info,
user_data);
cogl_framebuffer_discard_buffers (framebuffer,
COGL_BUFFER_BIT_COLOR |
COGL_BUFFER_BIT_DEPTH |
COGL_BUFFER_BIT_STENCIL);
if (!_cogl_winsys_has_feature (COGL_WINSYS_FEATURE_SYNC_AND_COMPLETE_EVENT))
{
CoglFrameInfo *info;