[vfio-users] Stutter in games

[Andrei Grigore]

I had the same issues and I solved them by installing Windows 10 on bare
metal. I am really interested if there is a fix for this. From my research,
(I've spent 2 full months in trying to find all kinds of causes and fixes)
I've just come to the conclusion that somehow the AMD CPU and/or the
Motherboard IOMMU is the root cause and you just can't fix it from the
configuration side of things. I guess it would also be hard to provide a
fix for QEMU/Kernel KVM since there is no easy way to reproduce it, or by
the fact that mostly everything is optimized for the Intel platform.

My Configuration: AMD FX-8320, 990FXA-UD3 (Rev. 3.0), GTX 970.

On Mon, Jan 23, 2017 at 8:02 PM, Alex Williamson <
alex.l.williamson at gmail.com> wrote:

> [Please copy the mailing list, use reply-all.  The mailing list is not
> intended to spawn private conversations]
>
> On Mon, Jan 23, 2017 at 11:30 AM, <itvend at gmail.com> wrote:
>
>> I have no clue what to Google even. All cpu pinning topics are for virt
>>
>
> isolcpus
> http://git.kernel.org/cgit/linux/kernel/git/torvalds/
> linux.git/tree/Documentation/admin-guide/kernel-parameters.txt#n1669
>
> libvirt vcpu pinning
> https://libvirt.org/formatdomain.html#elementsCPUTuning
>
> libvirt hugepage support
> https://libvirt.org/formatdomain.html#elementsMemoryTuning
>
> man irqbalance
>
> If you intend to continue using the QEMU commandline directly, be prepared
> to do your own research, libvirt is common way to do these things.  Thanks,
>
> Alex
>
>
>
>>
>> *Saatja: *Alex Williamson <alex.l.williamson at gmail.com>
>> *Saadetud: *esmaspäev, 23. jaanuar 2017 19:18
>> *Adressaat: *Tiit Talts <itvend at gmail.com>
>> *Koopia: *vfio-users <vfio-users at redhat.com>
>> *Teema: *Re: [vfio-users] Stutter in games
>>
>>
>>
>> [re-adding vfio-users]
>>
>>
>>
>> On Mon, Jan 23, 2017 at 10:11 AM, <itvend at gmail.com> wrote:
>>
>> QEMU command is :
>>
>>
>>
>> #!/bin/bash
>>
>>
>>
>> ## PARAMS        ##############################
>> ##############################
>>
>> CMD="-name vm2 -enable-kvm"
>>
>> CMD="$CMD -machine type=pc,accel=kvm,kernel_irqchip=on,mem-merge=off"
>>
>>
>>
>> CMD="$CMD -rtc base=localtime,clock=host,driftfix=none"
>>
>>
>>
>> CMD="$CMD -drive if=pflash,format=raw,readonly,
>> file=/usr/share/ovmf/OVMF_CODE.fd"
>>
>> CMD="$CMD -drive if=pflash,format=raw,file=/root/vm/vm2.fd"
>>
>>
>>
>> ## CPU                 ############################################################
>> +nx
>>
>> CMD="$CMD -cpu host,kvm=off,hv_time,hv_relaxe
>> d,hv_vapic,hv_spinlocks=0x1fff,hv_vendor_id=Nvidia43FIX -smp cores=6"
>>
>>
>>
>> ## MEM                              ##############################
>> ##############################
>>
>> CMD="$CMD -m $((8*1024))"  ## HOST HAS 16GB
>>
>>
>>
>> ## PCI-E               ##############################
>> ##############################
>>
>> CMD="$CMD -device vfio-pci,host=01:00.0,multifunction=on"
>>
>> CMD="$CMD -device vfio-pci,host=01:00.1"
>>
>>
>>
>> CMD="$CMD -device vfio-pci,host=02:00.0" ## USB 3.0 EATRON
>>
>> CMD="$CMD -device vfio-pci,host=04:00.0" ## USB 3.0 EATRON
>>
>>
>>
>> ## NET                 ##############################
>> ##############################
>>
>> CMD="$CMD -net nic,model=virtio -net bridge,br=bridge0"
>>
>>
>>
>> ## DRIVES           ##############################
>> ##############################
>>
>> CMD="$CMD -device virtio-blk-pci,drive=device_blk_one"
>>
>> CMD="$CMD -drive file=/dev/mapper/debian--vg-wi
>> ndows,format=raw,if=none,aio=native,cache.direct=on,cache=
>> none,id=device_blk_one"
>>
>>
>>
>> ## OTHER            ##############################
>> ##############################
>>
>> CMD="$CMD -monitor stdio"
>>
>> CMD="$CMD -display none"
>>
>> CMD="$CMD -vga none"
>>
>> CMD="$CMD -nodefaults -nodefconfig"
>>
>>
>>
>> ## STAR OF THE SHOW
>>
>> qemu-system-x86_64 $CMD
>>
>>
>>
>>
>>
>> So the good news is you're already leaving 2 cores for the host, the bad
>> news is that the next level of tuning you need to do is very difficult when
>> using QEMU directly from the commandline.  libvirt makes is so much easier.
>>
>>
>>
>>
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>
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