[Mesa-dev] [Bug 97102] [dri][swr] stack overflow / infinite loop with GALLIUM_DRIVER=swr

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=97102

--- Comment #12 from Jan Ziak <0xe2.0x9a.0x9b at gmail.com> ---
(In reply to Bruce Cherniak from comment #11)
> As Tim suggests, pruning empty nodes is probably the best solution for the
> crash.
> 
> For performance, however, I'm not sure how many cores to expose in your
> case.  cpuinfo shows that there are 4 threads across 2 cores, which we
> detect as 2 cores, with 2 hyperthreads.  Due to the way OpenSWR loads the
> processor, we have found that not using the hyperthreads as OpenSWR workers
> yields the best performance.  This may or may not be the case with your
> processor.
> 
> Something you can try is to set the environment variable
> KNOB_MAX_THREADS_PER_CORE=0.  This will allow OpenSWR to use all 4 threads.
> 
> Please report back on how this affects performance.

An AMD dual core x86 module is in terms of performance close to two separate
x86 cores:

- Kaveri/Steamroller module: 1 instruction fetch unit, 2 instruction decoders,
2 integer cores, 1 AVX core, 1 L1i cache, 2 L1d caches

- Two separate cores: 2 instruction {fetch,decode} units, {integer,AVX} cores,
2 L1{i,d} caches

In my experience, the statement that x86 module is close to 2 separate cores is
generally true. Many programs (gcc (make -j4), ...) scale close to what they
scale on two separate x86 cores.

----

# export LIBGL_ALWAYS_SOFTWARE=1
# export GALLIUM_DRIVER=swr
# glxgears
350.080 FPS

# KNOB_MAX_THREADS_PER_CORE=0 glxgears
615.980 FPS

----

Unigine Sanctuary 1.6.3 1024x768_windowed:

Default: 0.166578 FPS
KNOB_MAX_THREADS_PER_CORE=0: 0.440662 FPS

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