diff options
| author | Michel Dänzer <mdaenzer@redhat.com> | 2020-10-02 15:55:05 +0200 |
|---|---|---|
| committer | Dylan Baker <dylan.c.baker@intel.com> | 2020-11-02 07:48:26 -0800 |
| commit | cacca2aaa1ceb4690d3800d3f0f918a5696e6e8b (patch) | |
| tree | 3c2edf6cb9472589c03991c1da8360ed8531c782 | |
| parent | fa73f34f79cc1a8b6deca0d7760b0a615eb97713 (diff) | |
loader/dri3: Allocate up to 4 back buffers for page flips
With swap interval 0, i.e. sync-to-vblank disabled.
This can be necessary for unthrottled drawing with Xwayland:
1) One buffer can be scanned out
2) One buffer can be pending in the kernel for a page flip
3) One buffer can be pending in the Wayland compositor
Therefore, with 3 buffers, the frame-rate could be capped much lower
than the throughput the GPU is capable of, in the worst case at the
Wayland compositor refresh rate.
(The native Wayland EGL backend always uses up to 4 buffers)
Leave the maximum number of buffers at 3 for swap interval != 0, it's
sufficient in that case to always be able to queue one frame ahead of
time.
https://gitlab.gnome.org/GNOME/mutter/-/issues/1455
https://gitlab.gnome.org/GNOME/mutter/-/issues/1462
Cc: mesa-stable
Reviewed-by: Eric Anholt <eric@anholt.net>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/7033>
(cherry picked from commit 31e9de9c8ac72399427cb0fc15f19205dd8182c9)
| -rw-r--r-- | .pick_status.json | 2 | ||||
| -rw-r--r-- | src/loader/loader_dri3_helper.c | 25 |
2 files changed, 23 insertions, 4 deletions
diff --git a/.pick_status.json b/.pick_status.json index 10de6697160..dbf617eb5d7 100644 --- a/.pick_status.json +++ b/.pick_status.json @@ -1201,7 +1201,7 @@ "description": "loader/dri3: Allocate up to 4 back buffers for page flips", "nominated": true, "nomination_type": 0, - "resolution": 0, + "resolution": 1, "master_sha": null, "because_sha": null }, diff --git a/src/loader/loader_dri3_helper.c b/src/loader/loader_dri3_helper.c index 14af1eb0661..78cf14b9ff7 100644 --- a/src/loader/loader_dri3_helper.c +++ b/src/loader/loader_dri3_helper.c @@ -275,10 +275,29 @@ static void dri3_update_max_num_back(struct loader_dri3_drawable *draw) { switch (draw->last_present_mode) { - case XCB_PRESENT_COMPLETE_MODE_FLIP: - /* Leave cur_num_back unchanged, it'll grow as needed */ - draw->max_num_back = 3; + case XCB_PRESENT_COMPLETE_MODE_FLIP: { + int new_max; + + if (draw->swap_interval == 0) + new_max = 4; + else + new_max = 3; + + assert(new_max <= LOADER_DRI3_MAX_BACK); + + if (new_max != draw->max_num_back) { + /* On transition from swap interval == 0 to != 0, start with two + * buffers again. Otherwise keep the current number of buffers. Either + * way, more will be allocated if needed. + */ + if (new_max < draw->max_num_back) + draw->cur_num_back = 2; + + draw->max_num_back = new_max; + } + break; + } case XCB_PRESENT_COMPLETE_MODE_SKIP: break; |