[Mesa-dev] Performance regression on Tegra/GK20A since commit 363b53f00069

Pekka Paalanen ppaalanen at gmail.com
Tue Nov 18 23:34:06 PST 2014

On Wed, 19 Nov 2014 15:32:38 +0900
Alexandre Courbot <acourbot at nvidia.com> wrote:

> Some more information: CPU usage of the EGL app (glmark2 here) is much 
> higher when this patch is applied, which I presume is what triggers the 
> frame skips.
> On 11/19/2014 03:05 PM, Alexandre Courbot wrote:
> > Hi guys,
> >
> > I am seeing a severe performance regression (lots frame drops when
> > running EGL apps in Weston) on Tegra/GK20A since the following commit:
> >
> > commit 363b53f00069af718f64cf047f19ad5681a8bf6d
> > Author: Marek Olšák <marek.olsak at amd.com>
> > Date:   Sat Nov 1 14:31:09 2014 +0100
> >
> >      egl: remove egl_gallium from the loader
> >
> > Reverting said commit on top of master brings the expected performance
> > back. I am not knowledgeable enough about Mesa to speculate about the
> > reason, but could we try to investigate why this happens and how we
> > could fix this?


that sounds like you used to get egl_gallium as the EGL driver, and
after that patch you get egl_dri2. These two have separate Wayland
platform implementations (and probably all other platforms as well?). I
think that might be a lead for investigation. EGL debug environment
variable (EGL_LOG_LEVEL=debug) should confirm which EGL driver gets
loaded. You can force the EGL driver with e.g. EGL_DRIVER=egl_dri2.

Note, that there are two different EGL platforms in play: DRM/GBM for
Weston, and Wayland for the app. Have you confirmed the problem is in
the app side? That is, does Weston itself run smoothly?

FYI, I've been slowly working on https://github.com/ppaalanen/wesgr but
the Weston patches are not upstream yet, and I'm in the process of
updating them currently. I hope this tool might give some indication
whether the skips/stalls happen in Weston or not.

You say "frame drops", how do you see that? Only on screen, or also in
the app performance profile? How's the average framerate for the app?


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