[vfio-users] Significant FPS drop with AMD and GTX970

Rokas Kupstys rokups at zoho.com
Mon Oct 10 10:17:54 UTC 2016


I do not think it is powersaving. It could be the case with CPU because
host holds ultimate control of CPU, but GPU is completely controlled by
VM and driver in VM decides at what clock GPU should run.

Maybe CPU is bottleneck here? After all your CPU (and i had similar one)
says it has 8 cores, but in reality every two cores share resources +
single FPU core. On top of that AMD FPUs seem to be not as good as intel
ones so right there could be bottleneck. Also i suggest checking out
your DPC latency - it does cause trouble in some cases.

And i just remembered something that was not listed in first post of
that thread on archlinux forum:
https://bbs.archlinux.org/viewtopic.php?pid=1270311#p1270311 - i think
this actually improved my performance a lot.

P.S. Use [Reply All] or [Reply List] button (whatever is present) when
replying to mailing list messages ;)

Rokas Kupstys

On 2016.10.10 13:07, Andrei Grigore wrote:
>
> Ok. So it's clearly not a hardware failure since on native Windows it
> just works. The GPU is not the issue since there are reports that the
> same GPU performs flawlessly. The CPU is also not an issue, even
> though most people are using Intel. The configuration and passthrough
> procedure is definatelly right (i even wiped the whole system and did
> everything all over again). It's either a drawback with newer
> kernels/qemu for this MB and / or Chipset? It seems to me impossible
> to debug or to find the root cause.
>
> What is certain is that the behavior didn't change after the last
> couple of updates, this issue is there for a couple of months now.
> Just waited and waited for some performance improvements.
>
> It feels to me like the system is not used at it's full strength. I
> can run 100% stress CPU tests, the GPU also is used, RAM is plenty,
> but the fans are not turbo spinning as on native. I have disabled are
> power saving features from the VM and set the host governor to high
> performance. Can it be that some wierd power state / saving feature is
> causing this? Should I disable something more from BIOS / host?
>
>
> On Oct 10, 2016 10:57, "Rokas Kupstys" <rokups at zoho.com
> <mailto:rokups at zoho.com>> wrote:
>
>     You know.. What i am going to tell you will not sound good. My
>     board was Sabertooth 990-fx R2. My little story is that at first
>     it seemed to run ok (with r9 270X card). I sinked enough hours to
>     titanfall and it was great. After good period of time of non-usage
>     (as board was in warranty service and eventually swapped to brand
>     new board), multiple kernel updates and migration to archlinux i
>     no longer could get it running as fast. Now i do not know if i
>     just did not feel slowness initially and it was always there or if
>     something changed, but i know for a fact that testing older kernel
>     releases did yield a little bit better performance (enough that i
>     could notice). So i moved back to dual-booting due to performance
>     reasons. In the end combination of this and r9 270X constantly
>     causing entire PC to go down with a red screen i simply swapped
>     hardware for intel x99 + nvidia gpu. Such is sad story of mine..
>
>     Rokas Kupstys
>
>     On 2016.10.10 11:48, Andrei Grigore wrote:
>>
>>     Could it be an issue caused by the MB chipset (990-fx)? How can
>>     you debug something like this?
>>
>>
>>     On Oct 8, 2016 15:46, "Andrei Grigore" <andrei.grg at gmail.com
>>     <mailto:andrei.grg at gmail.com>> wrote:
>>
>>         Pretty sure, yes. Under: /etc/modprobe.d , then rebuilt the
>>         initramfs with mkinitcpio -p linux and rebooted.
>>
>>
>>         On Oct 8, 2016 15:44, "Rokas Kupstys" <rokups at zoho.com
>>         <mailto:rokups at zoho.com>> wrote:
>>
>>             Sure you put config in the right place? Because depending
>>             on how kernel modules are compiled config go to different
>>             places.
>>
>>
>>
>>             Sent from my Samsung device
>>
>>
>>             -------- Original message --------
>>             From: Andrei Grigore <andrei.grg at gmail.com
>>             <mailto:andrei.grg at gmail.com>>
>>             Date: 10/8/16 16:14 (GMT+02:00)
>>             To: Rokas Kupstys <rokups at zoho.com <mailto:rokups at zoho.com>>
>>             Cc: vfio-users <vfio-users at redhat.com
>>             <mailto:vfio-users at redhat.com>>, Jayme Howard
>>             <g.prime at gmail.com <mailto:g.prime at gmail.com>>
>>             Subject: Re: [vfio-users] Significant FPS drop with AMD
>>             and GTX970
>>
>>             Just tried. No improvement.
>>
>>
>>             On Oct 8, 2016 14:43, "Rokas Kupstys" <rokups at zoho.com
>>             <mailto:rokups at zoho.com>> wrote:
>>
>>                 See https://bbs.archlinux.org/viewtopic.php?id=162768
>>                 <https://bbs.archlinux.org/viewtopic.php?id=162768>
>>                 first post. See if you need ignore_msrs
>>                 or allow_unsafe_interrupts. I had similar issue with
>>                 and board and some module options fixed it I think.
>>
>>
>>                 Sent from my Samsung device
>>
>>
>>                 -------- Original message --------
>>                 From: Andrei Grigore <andrei.grg at gmail.com
>>                 <mailto:andrei.grg at gmail.com>>
>>                 Date: 10/8/16 10:49 (GMT+02:00)
>>                 To: Jayme Howard <g.prime at gmail.com
>>                 <mailto:g.prime at gmail.com>>
>>                 Cc: vfio-users <vfio-users at redhat.com
>>                 <mailto:vfio-users at redhat.com>>
>>                 Subject: Re: [vfio-users] Significant FPS drop with
>>                 AMD and GTX970
>>
>>                 Unfortunately, that didn't help. Thanks for the
>>                 sugestion though!
>>
>>
>>                 On Oct 8, 2016 03:06, "Jayme Howard"
>>                 <g.prime at gmail.com <mailto:g.prime at gmail.com>> wrote:
>>
>>                     Check to see if you have MSI enabled.  That'd be
>>                     my bet.  Alex had a blog post that covered it,
>>                     but I don't have the link handy.
>>
>>                     On Fri, Oct 7, 2016 at 6:39 PM, Andrei Grigore
>>                     <andrei.grg at gmail.com
>>                     <mailto:andrei.grg at gmail.com>> wrote:
>>
>>                         Hi all,
>>
>>                         I was wondering if anyone is experiencing
>>                         this and if there is a known fix for it.
>>
>>                         I am using ArchLinux with latest stable
>>                         Kernel, qemu and libvirt.
>>
>>                         My CPU is FX-8230 with a GTX 970. I've passed
>>                         thorugh the GPU to a Win10 guest.
>>
>>                         In WoW on bare metal i get 90 fps and in the
>>                         same area with the same graphic settings on
>>                         the VM i get around 50. There seems to be no
>>                         cpu and or ram bottlenet and the GPU seems to
>>                         be quite gully used since the fans are
>>                         starting to spin quite soon.
>>
>>                         Can anyone help here with a suggestion? I saw
>>                         reports with about 3% performance drop, but I
>>                         am experiencing a lot more.
>>
>>                         Thanks!
>>                         Andrei.
>>
>>
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