[Bug 84663] New: high cpu usage, poor performance in Borderlands 2 with radeonsi, PRIME

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=84663

            Bug ID: 84663
           Summary: high cpu usage, poor performance in Borderlands 2 with
                    radeonsi, PRIME
           Product: Mesa
           Version: git
          Hardware: Other
                OS: All
            Status: NEW
          Severity: normal
          Priority: medium
         Component: Drivers/Gallium/radeonsi
          Assignee: dri-devel at lists.freedesktop.org
          Reporter: haagch at frickel.club

Created attachment 107328
  --> https://bugs.freedesktop.org/attachment.cgi?id=107328&action=edit
sysprof recording from borderlands 2 only

00:02.0 VGA compatible controller: Intel Corporation 3rd Gen Core processor
Graphics Controller (rev 09)
01:00.0 VGA compatible controller: Advanced Micro Devices, Inc. [AMD/ATI]
Wimbledon XT [Radeon HD 7970M] (rev ff)

xorg stable, mesa git, linux 3.17-rc7.

I have had something similar in some games I think, but most recently with
Borderlands 2.

Here is a random screenshot with the HUD fps display from someone with a HD
7870 that shows that it runs mostly with 60 fps:
https://i.imgur.com/qH0sBkl.jpg

And here is a short clip of how it runs for me that shows it runs with 20-30
fps: https://www.youtube.com/watch?v=ZeZreRntt3k
Radeontop says that the gpu is only used to ~30%.
While running Borderlands 2 the CPU usage is always at 100+% on my i7 3632qm.


I was undecided whether to report this here, but the difference is quite large
so I thought I'd give it a try because I think the game itself is not supposed
to use this much cpu time, so maybe it has something to do with the driver.

Theories:

< glennk> guessing from that output that the game engine uses a lot of
occlusion queries and is stalling on them

I haven't really found anything to test that yet.

< agd5f> haagch, hybrid laptops have to do a lot of extra copying to get the
frame from the rendering GPU to the display GPU

I hope that the overhead is not *that* large because losing 70+% of gpu time
would make it kind of useless for the affected games.

Fortunately many (most?) games run much better, for example unigine valley
shows good gpu usage: https://www.youtube.com/watch?v=sLWvYJlfvWM
which makes me believe that there is a specific bottleneck.

Attached is a sysprof profile of borderlands 2 but I don't know which of it is
normal (like 25% total cpu time for glDrawRangeElements?).

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