Messages in this thread | | | Subject | Re: AMD graphics performance regression in 4.15 and later | From | Jean-Marc Valin <> | Date | Fri, 6 Apr 2018 12:42:11 -0400 |
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Hi Christian,
On 04/09/2018 07:48 AM, Christian König wrote: > Am 06.04.2018 um 17:30 schrieb Jean-Marc Valin: >> Hi Christian, >> >> Is there a way to turn off these huge pages at boot-time/run-time? > > Only at compile time by not setting CONFIG_TRANSPARENT_HUGEPAGE.
Any reason why echo never > /sys/kernel/mm/transparent_hugepage/enabled doesn't solve the problem?
Also, I assume that disabling CONFIG_TRANSPARENT_HUGEPAGE will disable them for everything and not just what your patch added, right?
>> I'm not sure what you mean by "We mitigated the problem by avoiding the >> slow coherent DMA code path on almost all platforms on newer kernels". I >> tested up to 4.16 and the performance regression is just as bad as it is >> for 4.15. > > Indeed 4.16 still doesn't have that. You could use the > amd-staging-drm-next branch or wait for 4.17.
Is there a way to pull just that change or is there too much interactions with other changes?
> That isn't related to the GFX hardware, but to your CPU/motherboard and > whatever else you have in the system.
Well, I have an nvidia GPU in the same system (normally only used for CUDA) and if I use it instead of my RX 560 then I'm not seeing any performance issue with 4.15.
> Some part of your system needs SWIOTLB and that makes allocating memory > much slower.
What would that part be? FTR, I have a complete description of my system at https://jmvalin.dreamwidth.org/15583.html
I don't know if it's related, but I can maybe see one thing in common between my machine and the Core 2 Quad from the other bug report and that's the "NUMA part". I have a dual-socket Xeon and (AFAIK) the Core 2 Quad is made of two two-core CPUs glued together with little communication between them.
> Intel doesn't use TTM because they don't have dedicated VRAM, but the > open source nvidia driver should be affected as well.
I'm using the proprietary nvidia driver (because CUDA). Is that supposed to be affected as well?
> We already mitigated that problem and I don't see any solution which > will arrive faster than 4.17.
Is that supposed to make the slowdown unnoticeable or just slightly better?
> The only quick workaround I can see is to avoid firefox, chrome for > example is reported to work perfectly fine.
Or use an unaffected GPU/driver ;-)
Cheers,
Jean-Marc
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