Fwd: Re: [PATCH 0/2] Add New XWayland API

Axel Davy axel.davy at ens.fr
Sat Oct 19 13:55:42 CEST 2013

> On Sat, Oct 19, 2013 at 10:49:04AM +0200, Axel Davy wrote:
>> I've tried benchmarking AsyncSwap with the phoronix-test-suite,
>> and I was surprised to see a regression with Openarena and Xonotic.
>> According to dri devs, it is because, since I do an exchange, the
>> application
>> is fullscreen and then Weston uses the buffer as scanout buffer, when
>> the buffer is
>> released and we render again in the buffer, L3 caching is disabled.
> It is simple to demonstrate that hypothesis incorrect by marking all
> colour buffers as uncached.
> -Chirs
> --
> Chris Wilson, Intel Open Source Technology Centre

Unfortunately, I can't test that with wlglamor, since there is too many
abstraction: I don't have access to the caching of the buffers.

I did many tests, and the only conclusion I've came to is that a buffer we
used for the framebuffer
 is slower to render to after.

I've also compared Bypass compositing + no AsyncSwap vs No Bypass
compositing + AsyncSwap, and
as expected, it performs the same (and in the latter case, we don't get
tearings). (And of course,
it performs better than No Bypass compositing + no AsyncSwap, or Bypass
compositing + AsyncSwap + useless copy)

Axel Davy

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