[vfio-users] Brutal DPC Latency - how is yours? check it please and report back

Quentin Deldycke quentindeldycke at gmail.com
Mon Jan 11 08:39:55 UTC 2016 

Also, i juste saw something:

You use ultra (4k?) settings on a 770gtx. This is too heavy for it. You
have less than 10fps. So in fact if you loose let's say 10% of performance,
you will barely see it.

What we search is a very high reponse time. Could you please compare your
system with a less heavy benchmark. It is easier to see the difference at
~50-70 fps.

In my case, this configuration work. But my fps fluctuate quite a lot. If
you are a bit a serious gamer, this falls are not an option during game :)

--
Deldycke Quentin


On 11 January 2016 at 08:54, Quentin Deldycke <quentindeldycke at gmail.com>
wrote:

> Using this mode,
>
> DPC Latency is hugely buggy using this mode.
>
> My fps are also moving on an apocaliptic way: from 80 to 45 fps without
> moving on ungine valley.
>
> Do you have anything working on your linux? (i have plasma doing nothing
> on another screen)
>
> Ungine heaven went back to 2600 points from 3100
> Cinebench r15: single core 124
>
>
> Could you please send your whole xml file, qemu version and kernel config
> / boot?
>
> I will try to get 3dmark and verify host / virtual comparison
>
> --
> Deldycke Quentin
>
>
> On 9 January 2016 at 20:24, Milos Kaurin <milos.kaurin at gmail.com> wrote:
>
>> My details:
>> Intel(R) Core(TM) i7-4770 CPU @ 3.40GHz
>> 32GB total ram
>> hugetables at 16x1GB for the guest (didn't have much to do with 3dmark
>> results)
>>
>> I have had the best performance with:
>>
>>   <vcpu placement='static'>8</vcpu>
>>   <cpu mode='custom' match='exact'>
>>     <model fallback='allow'>host-passthrough</model>
>>     <topology sockets='1' cores='4' threads='2'/>
>>   </cpu>
>>
>> No CPU pinning on either guest or host
>>
>> Benchmark example (Bare metal Win10 vs Fedora Guest Win10)
>> http://www.3dmark.com/compare/fs/7076732/fs/7076627#
>>
>>
>> Could you try my settings and report back?
>>
>> On Sat, Jan 9, 2016 at 3:14 PM, Quentin Deldycke
>> <quentindeldycke at gmail.com> wrote:
>> > I use virsh:
>> >
>> > ===SNIP===
>> >   <vcpu placement='static'>3</vcpu>
>> >   <cputune>
>> >     <vcpupin vcpu='0' cpuset='1'/>
>> >     <vcpupin vcpu='1' cpuset='2'/>
>> >     <vcpupin vcpu='2' cpuset='3'/>
>> >     <emulatorpin cpuset='6-7'/>
>> >   </cputune>
>> > ===SNAP===
>> >
>> > I have a prepare script running:
>> >
>> > ===SNIP===
>> > sudo mkdir /cpuset
>> > sudo mount -t cpuset none /cpuset/
>> > cd /cpuset
>> > echo 0 | sudo tee -a cpuset.cpu_exclusive
>> > echo 0 | sudo tee -a cpuset.mem_exclusive
>> >
>> > sudo mkdir sys
>> > echo 'Building shield for core system... threads 0 and 4, and we place
>> all
>> > runnning tasks there'
>> > /bin/echo 0,4 | sudo tee -a sys/cpuset.cpus
>> > /bin/echo 0 | sudo tee -a sys/cpuset.mems
>> > /bin/echo 0 | sudo tee -a sys/cpuset.cpu_exclusive
>> > /bin/echo 0 | sudo tee -a sys/cpuset.mem_exclusive
>> > for T in `cat tasks`; do sudo bash -c "/bin/echo $T >
>> sys/tasks">/dev/null
>> > 2>&1 ; done
>> > cd -
>> > ===SNAP===
>> >
>> > Note that i use this command line for the kernel
>> > nohz_full=1,2,3,4,5,6,7 rcu_nocbs=1,2,3,4,5,6,7 default_hugepagesz=1G
>> > hugepagesz=1G hugepages=12
>> >
>> >
>> > --
>> > Deldycke Quentin
>> >
>> >
>> > On 9 January 2016 at 15:40, rndbit <rndbit at sysret.net> wrote:
>> >>
>> >> Mind posting actual commands how you achieved this?
>> >>
>> >> All im doing now is this:
>> >>
>> >> cset set -c 0-3 system
>> >> cset proc -m -f root -t system -k
>> >>
>> >>   <vcpu placement='static'>4</vcpu>
>> >>   <cputune>
>> >>     <vcpupin vcpu='0' cpuset='4'/>
>> >>     <vcpupin vcpu='1' cpuset='5'/>
>> >>     <vcpupin vcpu='2' cpuset='6'/>
>> >>     <vcpupin vcpu='3' cpuset='7'/>
>> >>     <emulatorpin cpuset='0-3'/>
>> >>   </cputune>
>> >>
>> >> Basically this puts most of threads to 0-3 cores including emulator
>> >> threads. Some threads cant be moved though so they remain on 4-7
>> cores. VM
>> >> is given 4-7 cores. It works better but there is still much to be
>> desired.
>> >>
>> >>
>> >>
>> >> On 2016.01.09 15:59, Quentin Deldycke wrote:
>> >>
>> >> Hello,
>> >>
>> >> Using cpuset, i was using the vm with:
>> >>
>> >> Core 0: threads 0 & 4: linux + emulator pin
>> >> Core 1,2,3: threads 1,2,3,5,6,7: windows
>> >>
>> >> I tested with:
>> >> Core 0: threads 0 & 4: linux
>> >> Core 1,2,3: threads 1,2,3: windows
>> >> Core 1,2,3: threads 5,6,7: emulator
>> >>
>> >> The difference between both is huge (DPC latency is mush more stable):
>> >> Performance on single core went up to 50% (cinebench ratio by core from
>> >> 100 to 150 points)
>> >> Performance on gpu went up to 20% (cinebench from 80fps to 100+)
>> >> Performance on "heroes of the storm" went from 20~30 fps to stable 60
>> (and
>> >> much time more than 100)
>> >>
>> >> (performance of Unigine Heaven went from 2700 points to 3100 points)
>> >>
>> >> The only sad thing is that i have the 3 idle threads which are barely
>> >> used... Is there any way to put them back to windows?
>> >>
>> >> --
>> >> Deldycke Quentin
>> >>
>> >>
>> >> On 29 December 2015 at 17:38, Michael Bauer <michael at m-bauer.org>
>> wrote:
>> >>>
>> >>> I noticed that attaching a DVD-Drive from the host leads to HUGE
>> delays.
>> >>> I had attached my /dev/sr0 to the guest and even without a DVD in the
>> drive
>> >>> this was causing huge lag about once per second.
>> >>>
>> >>> Best regards
>> >>> Michael
>> >>>
>> >>>
>> >>> Am 28.12.2015 um 19:30 schrieb rndbit:
>> >>>
>> >>> 4000μs-16000μs here, its terrible.
>> >>> Tried whats said on
>> >>> https://lime-technology.com/forum/index.php?topic=43126.15
>> >>> Its a bit better with this:
>> >>>
>> >>>   <vcpu placement='static'>4</vcpu>
>> >>>   <cputune>
>> >>>     <vcpupin vcpu='0' cpuset='4'/>
>> >>>     <vcpupin vcpu='1' cpuset='5'/>
>> >>>     <vcpupin vcpu='2' cpuset='6'/>
>> >>>     <vcpupin vcpu='3' cpuset='7'/>
>> >>>     <emulatorpin cpuset='0-3'/>
>> >>>   </cputune>
>> >>>
>> >>> I tried isolcpus but it did not yield visible benefits. ndis.sys is
>> big
>> >>> offender here but i dont really understand why. Removing network
>> interface
>> >>> from VM makes usbport.sys take over as biggest offender. All this
>> happens
>> >>> with performance governor of all cpu cores:
>> >>>
>> >>> echo performance | tee
>> >>> /sys/devices/system/cpu/cpu*/cpufreq/scaling_governor >/dev/null
>> >>>
>> >>> Cores remain clocked at 4k mhz. I dont know what else i could try.
>> Does
>> >>> anyone have any ideas..?
>> >>>
>> >>> On 2015.10.29 08:03, Eddie Yen wrote:
>> >>>
>> >>> I tested again with VM reboot, I found that this time is about
>> >>> 1000~1500μs.
>> >>> Also I found that it easily get high while hard drive is loading, but
>> >>> only few times.
>> >>>
>> >>> Which specs you're using? Maybe it depends on CPU or patches.
>> >>>
>> >>> 2015-10-29 13:44 GMT+08:00 Blank Field <ihatethisfield at gmail.com>:
>> >>>>
>> >>>> If i understand it right, this software has a fixed latency error of
>> 1
>> >>>> ms(1000us) in windows 8-10 due to different kernel timer
>> implementation. So
>> >>>> i guess your latency is very good.
>> >>>>
>> >>>> On Oct 29, 2015 8:40 AM, "Eddie Yen" <missile0407 at gmail.com> wrote:
>> >>>>>
>> >>>>> Thanks for information! And sorry I don'r read carefully at
>> beginning
>> >>>>> message.
>> >>>>>
>> >>>>> For my result, I got about 1000μs below and only few times got
>> 1000μs
>> >>>>> above when idling.
>> >>>>>
>> >>>>> I'm using 4820K and used 4 threads to VM, also  I set these 4
>> threads
>> >>>>> as 4 cores in VM settings.
>> >>>>> The OS is Windows 10.
>> >>>>>
>> >>>>> 2015-10-29 13:21 GMT+08:00 Blank Field <ihatethisfield at gmail.com>:
>> >>>>>>
>> >>>>>> I think they're using this:
>> >>>>>> www.thesycon.de/deu/latency_check.shtml
>> >>>>>>
>> >>>>>> On Oct 29, 2015 6:11 AM, "Eddie Yen" <missile0407 at gmail.com>
>> wrote:
>> >>>>>>>
>> >>>>>>> Sorry, but how to check DPC Latency?
>> >>>>>>>
>> >>>>>>> 2015-10-29 10:08 GMT+08:00 Nick Sukharev <nicksukharev at gmail.com
>> >:
>> >>>>>>>>
>> >>>>>>>> I just checked on W7 and I get 3000μs-4000μs one one of the
>> guests
>> >>>>>>>> when 3 guests are running.
>> >>>>>>>>
>> >>>>>>>> On Wed, Oct 28, 2015 at 4:52 AM, Sergey Vlasov <sergey at vlasov.me
>> >
>> >>>>>>>> wrote:
>> >>>>>>>>>
>> >>>>>>>>> On 27 October 2015 at 18:38, LordZiru <lordziru at gmail.com>
>> wrote:
>> >>>>>>>>>>
>> >>>>>>>>>> I have brutal DPC Latency on qemu, no matter if using
>> pci-assign
>> >>>>>>>>>> or vfio-pci or without any passthrought,
>> >>>>>>>>>>
>> >>>>>>>>>> my DPC Latency is like:
>> >>>>>>>>>> 10000,500,8000,6000,800,300,12000,9000,700,2000,9000
>> >>>>>>>>>> and on native windows 7 is like:
>> >>>>>>>>>> 20,30,20,50,20,30,20,20,30
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>> In Windows 10 guest I constantly have red bars around 3000μs
>> >>>>>>>>> (microseconds), spiking sometimes up to 10000μs.
>> >>>>>>>>>
>> >>>>>>>>>>
>> >>>>>>>>>> I don't know how to fix it.
>> >>>>>>>>>> this matter for me because i are using USB Sound Card for my
>> VMs,
>> >>>>>>>>>> and i get sound drop-outs every 0-4 secounds
>> >>>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>> That bugs me a lot too. I also use an external USB card and my
>> DAW
>> >>>>>>>>> periodically drops out :(
>> >>>>>>>>>
>> >>>>>>>>> I haven't tried CPU pinning yet though. And perhaps I should try
>> >>>>>>>>> Windows 7.
>> >>>>>>>>>
>> >>>>>>>>>
>> >>>>>>>>> _______________________________________________
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>> >>>>>>>>>
>> >>>>>>>>
>> >>>>>>>>
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