[Mesa-dev] [PATCH 4/6] gallium/radeon: fix performance of buffer readbacks

[Emil Velikov]

On 13 February 2017 at 03:24, Michel Dänzer <michel at daenzer.net> wrote:
> On 10/02/17 08:27 PM, Marek Olšák wrote:
>> On Fri, Feb 10, 2017 at 12:22 PM, Emil Velikov <emil.l.velikov at gmail.com> wrote:
>>>  On 9 February 2017 at 11:56, Marek Olšák <maraeo at gmail.com> wrote:
>>>> From: Marek Olšák <marek.olsak at amd.com>
>>>>
>>>> We want cached GTT for all non-persistent read mappings.
>>>> Set level = 0 on purpose.
>>>>
>>>> Use dma_copy, because resource_copy_region causes a failure in the PBO
>>>> read of piglit/getteximage-luminance.
>>>>
>>>> If Rocket League used the READ flag, it should get cached GTT.
>>>>
>>> Does this patch resolve/mitigate the reported performance issues with
>>> Rocket League ?
>>>
>>> Strictly speaking performance patches are a no-go for stable, although
>>> we had exceptions in the past.
>>> I will pick this up, but for future do provide numbers which indicate
>>> the severity of the issue.
>>
>> It will help only if Rocket League is fixed to use GL_MAP_READ_BIT. It
>> doesn't fix the current release of Rocket League.
>
> That's incorrect, it always used GL_MAP_READ_BIT. So this fix should
> (and reportedly does) help with unpatched Rocket League.
>
> As can be seen from https://bugs.freedesktop.org/show_bug.cgi?id=97879
> (which should have been referenced by the commit log :), the problem is
> freezes of up to several seconds, which makes the game essentially
> unplayable, especially for online multiplayer.
>
> OTOH the game itself has now been fixed to no longer run into the
> problem, and I suspect most users will probably get the game update
> before any future Mesa stable release.
>
I'm concerned about the reports that although this(?) commit makes the
stalls shorter, it also decreases performance (do to ~80%).

Fabio (Oibaf) is fairly responsive so getting the extra patch in his
PPA should be trivial. I'd imagine that others, say padoka (Paulo),
would also gladly assist.

Thanks
Emil