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From: Peter Clifton <pcjc2@cam.ac.uk>
To: "mesa-dev@lists.freedesktop.org" <mesa-dev@lists.freedesktop.org>
Cc: "intel-gfx@lists.freedesktop.org" <intel-gfx@lists.freedesktop.org>
Subject: Re: [Intel-gfx] Strange performance cliff...
Date: Tue, 12 Oct 2010 21:54:08 +0100	[thread overview]
Message-ID: <1286916848.2716.1.camel@pcjc2lap> (raw)
In-Reply-To: <1286905525.2807.7.camel@pcjc2lap>

On Tue, 2010-10-12 at 18:45 +0100, Peter Clifton wrote:
> Using glxgears as a tool to exercise the GPU with some simple rendering,
> I have noted a strange cliff in the intel_gpu_top output when resizing
> the glxgears window:
> 
> Below a certain size e.g.:
> 
>   -geometry 576x868+0+29

>                    render busy:  21%: ████▎                                  render space: 10/126976 (0%)
> When I increase the window size just a fraction, to:
> 
>   -geometry 576x871+0+29

> The CS (command streamer) unit jumps to 100% busy, along with the render
> busy graph. Does anyone have any ideas why?
> 
>                    render busy: 100%: ████████████████████                   render space: 61/126976 (0%)


It would appear that this transition occurs at the point when glxgears
executed with vblank_mode=0 set, gives approx 60Hz (vblank rate).

I can only presume therefore, that the command stream shows as 100% when
it is stalling the CPU.. is that right?

-- 
Peter Clifton

Electrical Engineering Division,
Engineering Department,
University of Cambridge,
9, JJ Thomson Avenue,
Cambridge
CB3 0FA

Tel: +44 (0)7729 980173 - (No signal in the lab!)
Tel: +44 (0)1223 748328 - (Shared lab phone, ask for me)

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      reply	other threads:[~2010-10-12 20:54 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-10-12 17:45 Strange performance cliff Peter Clifton
2010-10-12 20:54 ` Peter Clifton [this message]

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