[pve-devel] qemu kvm_steal_time bug

[Alexandre DERUMIER]

Some news info about this bug:

https://bugs.launchpad.net/qemu/+bug/1494350?comments=all


I have hited the bug again. 
(No production impact, but my monitoring probes become crazy because of cpu steal at 100%)

I don't know if we could setup -kvm_steal_time by default for now ?
(it'll not break migration)

or maybe add cpuflags options to vmid.conf ?


----- Mail original -----
De: "aderumier" <aderumier at odiso.com>
À: "Stefan Priebe" <s.priebe at profihost.ag>
Cc: "pve-devel" <pve-devel at pve.proxmox.com>
Envoyé: Vendredi 28 Août 2015 20:09:18
Objet: Re: [pve-devel] qemu kvm_steal_time bug

>>Is it only with 3.16 kernel? Haven't seen this yet. 

Yes, I have reproduce it on 3 debian jessie kernel 3.16. 

But other jessie migration have worked before... 

I have asked to the qemu mailing, waiting for more information. 

----- Mail original ----- 
De: "Stefan Priebe" <s.priebe at profihost.ag> 
À: "aderumier" <aderumier at odiso.com> 
Cc: "pve-devel" <pve-devel at pve.proxmox.com> 
Envoyé: Vendredi 28 Août 2015 17:07:07 
Objet: Re: [pve-devel] qemu kvm_steal_time bug 

Is it only with 3.16 kernel? Haven't seen this yet. 

Stefan 
Excuse my typo s ent from my mobile phone. 

Am 28.08.2015 um 16:31 schrieb Alexandre DERUMIER < aderumier at odiso.com >: 




Hi, 

I have add this bug, which occur after live migration: 

https://code.google.com/p/ganeti/issues/detail?id=986 
https://groups.google.com/forum/#!topic/ganeti/D2Yos3BShmc 
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=785557#64 


qemu 2.4 or 2.1 and guest kernel 3.16 (debian jessie). 


The bug is that after a live migration, the steal cpu counter just freeze at 100% 

# mpstat 
Linux 3.16.0-4-amd64 (radinsapi1) 28/08/2015 _x86_64_ (8 CPU) 

16:24:51 CPU %usr %nice %sys %iowait %irq %soft %steal %guest %gnice %idle 
16:24:51 all 0,00 0,00 0,00 0,00 0,00 0,00 99,92 0,00 0,00 0,08 


Seem to be a qemu bug, the workaround seem to use -kvm_steal_time cpu flag. 
But I don't known if they are an performance impact or not. 

Does somebody already have had this bug ? 

Alexandre 
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