[Mesa-dev] [Bug 86690] glmark2-es2-wayland shortly freezes on some frames with egl_dri2 backend (Nouveau/GK20A)

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=86690

            Bug ID: 86690
           Summary: glmark2-es2-wayland shortly freezes on some frames
                    with egl_dri2 backend (Nouveau/GK20A)
           Product: Mesa
           Version: git
          Hardware: ARM
                OS: Linux (All)
            Status: NEW
          Severity: normal
          Priority: medium
         Component: EGL/Wayland
          Assignee: wayland-bugs at lists.freedesktop.org
          Reporter: gnurou at gmail.com
        QA Contact: mesa-dev at lists.freedesktop.org

When using the egl_dri2 driver, glmark2 will sometimes keep displaying the same
frame for up to 1/2 second before resuming normally. This also affects the
reported frame rate, which drops dramatically with each occurence.

This only seems to happen for applications that set eglSwapInterval to 0 in
order to exceed the monitor frame rate. With applications that do not set
eglSwapInterval (like weston-simple-egl) or the (recently removed) egl_gallium
driver that also does not allow more than 60fps, the issue is not visible.

Relevant comments from Pekka Paalanen when discussing this on the mailing-list:

"I have a hunch (wl_buffer.release not delivered in time, and client
side EGL running out of available buffers), but confirming that would
require a Wayland protocol dump up to such hickup. You could try to get
one by setting the enviroment variable WAYLAND_DEBUG=client for
glmark2. It will be a flood, especially if glmark2 succeeds in running
at uncapped framerates. The trace will come to stderr, so you want to
redirect that to file. You need to find out where in the trace the
hickup happened. The timestamps are in milliseconds. I could then take
a look (will need the whole trace)."

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