[vfio-users] Stutter in games

[Quentin Deldycke]

Hello,



This is how I build a cpuset shield at vm boot:

https://github.com/qdel/scripts/blob/master/vfio/scripts/shieldbuild

And how I break it:

https://github.com/qdel/scripts/blob/master/vfio/scripts/shieldbreak

They are called threw libvirt hooks.

In conjunction to tickles cpu, 1kHz frequency,  and rcu offloading.  It
work pretty well.

As I emulate nearly nothing, I can even compile on Linux without feeling
anything on Windows. (i passthrough only pcie, not anything else)


These scripts are old. I will try to update them during the day.

On 24 Jan 2017 5:35 a.m., "Okky Hendriansyah" <okky.htf at gmail.com> wrote:

> On Mon, Jan 23, 2017 at 11:48 PM, Tiit Talts <itvend at gmail.com> wrote:
>
>> QEMU 2.8+
>> Kernel 4.8 @ Debian 8
>>
>> Guest OS: Windows 10
>>
>> H/W: CPU: AMD FX-8300, MB: GA-990XA-UD3, GPU: GTX 1080
>>
>> FPS in games are great 150+/- @ normal details, but i have periodic fps
>> drops from 150 to 30-20fps when i move in game. i noticed that when i stand
>> still in Battlefield 4 no fps drops everything is fine but if is start
>> moving i get fps drops.
>>
>> Other info:
>>
>>
>> perf kvm --host stat live
>> When gaming most VM-Exits are msr and interrupt
>>
>>
>> GRUB:
>>
>> BOOT_IMAGE=/vmlinuz-4.8.0-0.bpo.2-amd64 root=/dev/mapper/debian--vg-root
>> ro iommu=pt amd_iommu=on
>>
>> /etc/modprobe.d/kvm.conf
>>
>> options kvm              ignore_msrs=1
>> options kvm_amd          npt=0
>>
>> /etc/modules
>>
>> kvm
>> kvm_amd
>> vfio
>> vfio_iommu_type1
>> vfio_pci
>> vfio_virqfd
>>
>> Any advice, quit VM or burn down AMD platform ?
>>
>>
> Hi Tiit,
>
> Any chance that your kernel flags for your clock resolution is not high
> enough? What about your pre-emption scheduling? I found my clock resolution
> set to 1000 Hz and voluntary pre-emption scheduling fully eliminates
> stutters in Witcher 3.
>
> Best regards,
> Okky
>
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