[Mesa-dev] [PATCH 0/4] RadeonSI: Upload constants to VRAM via SDMA

[Dieter Nützel]

Sorry that I step in so late, but the whole family recover slowly from a 
bad flu...

Tried your 'latest" three series altogether with my Polaris 20 (NIR!).
UH and UV hang after some seconds reliable. VM faults. Have to dig 
deeper in (remote) to get some logs.

But my reported Polaris triangle corruptions are solved, now.
W'll try to verify which patches fixed it.

Look here:
https://www.phoronix.com/forums/forum/phoronix/latest-phoronix-articles/1079319-running-the-radeonsi-nir-back-end-with-mesa-19-1-git?p=1079390#post1079390

Greetings,
Dieter

Am 07.02.2019 02:21, schrieb Marek Olšák:
> Hi,
> 
> This patch series increases radeonsi performance in some cases.
> glxgears performance decreases slightly.
> 
> Visible VRAM is usually congested due to CPU accesses, which cause
> buffers to be evicted from that part of VRAM. This removes
> the congestion for all data pushed into const_uploader.
> 
> We have had many problems with const_uploader slowing stuff down due
> to visible VRAM congestion. The most recent one is this Starcraft 2
> issue report on github:
> 
> https://github.com/iXit/Mesa-3D/issues/333
> 
> Since const_uploader reuses buffers from the winsys buffer cache,
> the odds are that the reused buffers are already evicted, so the first
> use is usually slower due to higher shader load latencies.
> 
> This series uses SDMA to get constants into VRAM, so it doesn't have
> any of the above drawbacks.
> 
> SC2 numbers with various other methods (from the github issue report):
> - originally: 50-55 fps
> - changing const_uploader to STREAM: 75-80 fps
> - use stream_uploader for constants in Nine: 90 fps
> - this series: 105-110 fps
> 
> Trivial benchmarks such as glxgears can expect 20% decrease
> in performance due to the added cost of the SDMA CS ioctl that wasn't
> there before.
> 
> CPU-bound apps with many IBs are almost unaffected thanks to winsys
> multithreading.
> 
> Feedback welcome,
> 
> Thanks,
> Marek
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