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Re: [Qemu-discuss] [problem]-starting a VM causes RT (latency) problem f

From: Yan Fridland
Subject: Re: [Qemu-discuss] [problem]-starting a VM causes RT (latency) problem for application running on another VM
Date: Tue, 26 Jul 2016 07:48:01 +0000

Hi Yadi,


Thanks a lot for your comment.


Actually I am doing emulator pin to the QEMU process in the XML:


<vcpu placement='static'>3</vcpu>


    <vcpupin vcpu='0' cpuset='1'/>

    <vcpupin vcpu='1' cpuset='2'/>

    <vcpupin vcpu='2' cpuset='3'/>

    <emulatorpin cpuset='8'/>

    <vcpusched vcpus='1-2' scheduler='fifo' priority='99'/>



BUT, looks like it doesn’t help. Is there any way to make ALL the related QEMU threads run within the scope of cores 1,2,3,8 ONLY in the above example?





From: Yadi [mailto:address@hidden
Sent: Tuesday, July 26, 2016 6:12 AM
To: Yan Fridland; address@hidden
Subject: Re: [Qemu-discuss] [problem]-starting a VM causes RT (latency) problem for application running on another VM


On 20160725 23:03, Yan Fridland wrote:

Hello All,


Here is a problem I saw when I ran virsh start to a VM.

I have 2VMs on a server when one of them is running a RT application and the other is in shut down state. Then I executed "virsh start" to the second VM and saw 2-3 seconds later a big latency problem in my RT application running on the first VM.

I want to emphasize that the VMs use dedicated isolated cores of the server and I have the relevant configuration on the server and the vcpu pinning section of virsh xml.


Can anyone tell me why I experience such behavior and how it can be resolved?


I will highly appreciate your help.


Thank you,



I am not very sure, but I suggest you to add emulatorpin in xml file, then see results. actually,  all qemu associated process can use all processors via cgroup configure created by libvirt,


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