[Bug 82050] R9270X pyrit benchmark perf regressions with latest kernel/llvm

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=82050

--- Comment #72 from Michel Dänzer <michel at daenzer.net> ---
(In reply to comment #62)
> I do have 2 gig, but looking at the screenshot of elemantal to be attached I
> see that used and requested differ.

That's probably because of VRAM fragmentation. (BTW, I find it easier to keep
track of this with requested-VRAM+VRAM-usage,requested-GTT+GTT-usage instead of
requested-VRAM+requested-GTT,VRAM-usage+GTT-usage)


> This shot doesn't really show how long the pauses are - they are really bad,
> it takes about 2 minutes to render the first few frames with pauses of many
> seconds after that.
> 
> It's so bad it's hard to tell whether the revert helps - probably not, I
> guess it's something different. Have you tried Elemental?

Yes, but even on Kaveri with only 1G of VRAM, it doesn't take two minutes for
it to get going, and I don't notice such long pauses either.

So I think it's better if we track the UE4 issues in a separate report, and it
would be great if you guys could bisect the kernel or Mesa for that.


(In reply to comment #65)
> Keep in mind that revert broke 32bit complitely, lot of corruption :)

I haven't been able to reproduce that. If you still can, please file a bug for
it, as there's nothing preventing the kernel from using GTT instead of VRAM
when the latter is full.


> I am not trying other demos , but seems like newer kernels requests more
> VRAM from the apps :)

The Mesa commit in question makes the r600g and radeonsi drivers try to use
VRAM for more things, but only with newer kernels, because older kernels didn't
guarantee reliability when using VRAM for those things.

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