vo/gpu-next/opengl: frame timing statistics for compute shader passes are always zero

mpv Information

mpv v0.38.0-77-g0318174273 Copyright © 2000-2024 mpv/MPlayer/mplayer2 projects
libplacebo version: v7.349.0
FFmpeg version: 6.0.1
FFmpeg library versions:
   libavutil       58.2.100
   libavcodec      60.3.100
   libavformat     60.3.100
   libswscale      7.1.100
   libavfilter     9.3.100
   libswresample   4.10.100

Other Information

• Linux version: Fedora Linux 40.20240519.0 (Silverblue)
• Kernel Version: 6.8.9-300.fc40.x86_64
• GPU Model: Intel Corporation DG2 [Arc A750] [8086:56a1]
• Mesa/GPU Driver Version: 4.6 (Core Profile) Mesa 24.0.6 (git-c659c7e660)
• Window Manager and Version: Mutter (GNOME 46.1)
• Source mpv: Built from HEAD
• Introduced in version: IDK

Reproduction Steps

Get a compute shader. Here I use ravu-zoom-ar-r3-yuv.hook as an example.

Run:

mpv test.mkv --no-config --msg-level=vo/gpu-next=trace --fs --vo=gpu-next --gpu-api=opengl --glsl-shader=ravu-zoom-ar-r3-yuv-compute.hook --log-file=mpv.log

Ensure the compute shader is hooked and takes effect.

See frame timing in Shift+I page 2.

Expected Behavior

The timing of the pass of compute shader should be correct. In my machine, compared with:

• --vo=gpu
• --vo=gpu-next --gpu-api=opengl
  the duration of this pass should be near 4000us.

Actual Behavior

The timing of this pass is always zero; I have confirmed it in the log file as well:

[vo/gpu-next/libplacebo] Spent 0.000 ms on shader: RAVU-Zoom-AR (yuv, r3, compute)

I tried adding a gl->MemoryBarrier immediately after gl->DispatchCompute in gl_pass_run() in libplacebo/src/opengl/gpu_pass.c, but the result did not change.

I've confirmed that the results got from gl->GetQueryObjectui64v for the pass are very small values like 0 and 52.

I've tried MESA_LOADER_DRIVER_OVERRIDE=zink and confirmed that it is unlikely a vendor-specific issue.

Log File

mpv.log

Sample Files

No response

I carefully read all instruction and confirm that I did the following:

• I tested with the latest mpv version to validate that the issue is not already fixed.
• I provided all required information including system and mpv version.
• I produced the log file with the exact same set of files, parameters, and conditions used in "Reproduction Steps", with the addition of --log-file=output.txt.
• I produced the log file while the behaviors described in "Actual Behavior" were actively observed.
• I attached the full, untruncated log file.
• I attached the backtrace in the case of a crash.

Start with libplacebo/src/opengl/gpu_pass.c and gl_pass_run(), then reproduce the compute-shader case with the provided mpv command and trace logging. Inspect the glGetQueryObjectui64v results alongside the gpu-next shader timing output; done means the compute pass reports its actual duration rather than zero.