Re [nova]Bug #1829696: qemu-kvm process takes 100% CPU usage whenrunning redhat/centos 7.6 guest OS

QianXi qianxi416 at
Thu Jun 27 01:29:10 UTC 2019

I tested two newest QEMU versions these days(v3.1.0 and v4.0.0), and sadly, the problem still happens.

I tried to find the reason why the qemu process take 100% usage of cpu, and collected some facts about it.
I compared the facts with other normal vm's qemu process(who's cpu usage is normal) and didn't find out any interesting result.

Please give me some guides to debug this problem if you could, thanks very much.
(The full content of facts is in the attachment and I also leave a message in


    Thanks a lot!
Best Regards


------------------ Original ------------------
From:  "QianXi";<qianxi416 at>;
Date:  Jun 21, 2019
To:  "Kashyap Chamarthy"<kchamart at>; "1829696"<1829696 at>; 
Cc:  "openstack-discuss"<openstack-discuss at>; 
Subject:  Reply: [nova]Bug #1829696: qemu-kvm process takes 100% CPU usage whenrunning redhat/centos 7.6 guest OS

Thanks very much. I will upgrade the virt tools software on the host and check if it still happens. Later, I hope I could update you guys. Thanks again. Best regards QianXi------------------ 原始邮件 ------------------
发件人: "Kashyap Chamarthy"<kchamart at>
发送时间: 2019年6月21日(星期五) 凌晨0:32
收件人: "钱熙"<qianxi416 at>;
抄送: "openstack-discuss"<openstack-discuss at>;
主题: Re: [nova]Bug #1829696: qemu-kvm process takes 100% CPU usage whenrunning redhat/centos 7.6 guest OS

On Thu, Jun 20, 2019 at 10:06:11PM +0800, 钱熙 wrote:
> Hi there,


> I am struggling with qemu-kvm 100% CPU usage problem.
> When running redhat or centos 7.6 guest os on vm,
> the cpu usage is very low on vm(almost 100% idle when no tasks run), but on the host,
> qemu-kvm reports 100% cpu busy usage.
> I opened the bug above, however it did not find some interest.
> After searching some related bugs report,
> I suspect that it is due to the clock settings in vm's domain xml.
> My settings are as follows:
>     <clock offset='utc'>
>       <timer name='rtc' tickpolicy='catchup'/>
>       <timer name='pit' tickpolicy='delay'/>
>       <timer name='hpet' present='no'/>
>     </clock>
> And details about the bug, please see

I don't think it is related to clock settings at all.

> It shows that only the version 7.6 of redhat or centos affected by this bug behavior.
> In my cluster, it is OK for versions from redhat or centos 6.8 to 7.5.
> Any clue or suggestion?

Please see DanPB's response in comment#2; I agree with it.  (Note that
I've changed the bug component from 'openstack-nova' --> 'qemu')

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