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

Sat Jan 9 13:59:28 UTC 2016

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 1000~1500
> μs.
> 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>
>>> 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>
>>>> 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>
>>>>> 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>
>>>>>> sergey at vlasov.me> wrote:
>>>>>>
>>>>>>> On 27 October 2015 at 18:38, LordZiru < <lordziru at gmail.com>
>>>>>>> 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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>>>>>>
>>>>>
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