Created attachment 107328 [details]
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?).
