Re: Frame rate drops dramatically with high resolution on embedded device using EGL backend

[Emmanuele Bassi <ebassi gmail com>]

hi;

are you perchance using FBOs (directly or through
ClutterOffscreenEffect)? in my experience, using FBOs on some
platforms increases drastically the time spent inside eglMakeCurrent.

ciao,
 Emmanuele.


On 2 May 2013 11:51, Reza Ghassemi <reza robin1 gmail com> wrote:
> An update.
>
> By doing some profiling, we found that the culprit for slow FPS seems to be
> one of the COGL API’s, bind_onscreen_with_context.  It is taking 70-100msec!
> From what we can tell, this function is pretty much a wrapper around
> eglMakeCurrent.
>
>
> On Mon, Apr 29, 2013 at 7:03 PM, Reza Ghassemi <reza robin1 gmail com>
> wrote:
> > My team and I working on porting clutter to an embedded linux system which
> > requires using the EGL backend (CLUTTER_BACKEND=eglnative). I created a test
> > application that renders a number of playing card images and scrolls them
> > around the scene. When doing this at a resolution of 300x200 everything ran
> > perfectly fine. CLUTTER_SHOW_FPS shows a frame rate varying around 60fps.
> > However, as we increase the resolution, the frame rate drops dramatically.
> > At our target resolution of 1920x1080, the frame rate completely tanked,
> > dropping to an average of about 15fps. The frame rate is low with or without
> > animations running. In addition, the high resolution version exhibits
> > noticeable visual tearing.
> >
> > At first my assumption was that OpenGLES2 was not being used to render,
> > since, as I understand it, OpenGL uses double buffering and should not cause
> > tearing. So we ran the same test using one of the Cogl samples
> > (cogl-gles-gears), with its resolution turned up to 1920x1080, but the same
> > thing happened: dramatic decrease in frame rate and noticeable tearing.
> >
> > We've tested implementations of the same card scrolling app in several
> > other gui frameworks on the same device, at the same resolution, and none of
> > them exhibited this problem. Qt, for example, ran smoothly at around 60fps
> > with no tearing.
> >
> > Does anyone have any insight into what might cause this? Could it have to
> > do with the 'experimental' nature of the EGL backend? What could cause the
> > tearing when rendering with OpenGL?
> >
> > Here are some samples of the frame rate reported by cogl-gles-gears at
> > different resolutions:
> >
> > 1920x1080 => ~16fps
> > 1280x720 => ~32fps
> > 854x480 => ~55fps
>
>
>
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-- 
W: http://www.emmanuelebassi.name
B: http://blogs.gnome.org/ebassi/