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



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 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 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 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 gmail com> wrote:
Sorry, but how to check DPC Latency?

2015-10-29 10:08 GMT+08:00 Nick Sukharev <nicksukharev 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 vlasov me> wrote:
On 27 October 2015 at 18:38, LordZiru <lordziru 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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