[PVE-User] Regression on virtio-net ? (Was: Re: Proxmox VE 4.2 released!)

[Gilou]

Le 09/05/2016 14:58, Alexandre DERUMIER a écrit :
> BTW,
> 
> what is the host cpu model ?

My tests were mostly done on "recent" intel CPUs, i5 & i7 (4th gen, 6th
gen) mostly.

Gilles


> 
> 
> ----- Mail original -----
> De: "aderumier" <aderumier at odiso.com>
> À: "proxmoxve" <pve-user at pve.proxmox.com>
> Envoyé: Mercredi 4 Mai 2016 14:52:14
> Objet: Re: [PVE-User] Regression on virtio-net ? (Was: Re: Proxmox VE 4.2 released!)
> 
> Same problem here: 
> 
> https://forum.proxmox.com/threads/wrong-cpu-usage.27080/ 
> 
> ----- Mail original ----- 
> De: "Wolfgang Bumiller" <w.bumiller at proxmox.com> 
> À: "Gilou" <contact+dev at gilouweb.com> 
> Cc: "proxmoxve" <pve-user at pve.proxmox.com> 
> Envoyé: Mercredi 4 Mai 2016 14:42:51 
> Objet: Re: [PVE-User] Regression on virtio-net ? (Was: Re: Proxmox VE 4.2 released!) 
> 
> On Tue, May 03, 2016 at 12:40:08PM +0200, Gilou wrote: 
>> Le 30/04/2016 07:20, Alexandre DERUMIER a écrit : 
>>> ok, 
>>>
>>> can you check with perf command ? 
>>>
>>> check both qemu and vhost process 
>>>
>>>
>>> "perf top -p pidofqemu" 
>>>
>>> "perf top -p pidofvhost" 
>>
>>
>> OK, I did it, and hit the bug again, on a different hardware. 
>> Context is: 
>> Ubuntu 16.04 VM, single core, host CPU, using virtio-net to blast at 1 
>> Gbps through the physical NIC. I still have 100% of a core used by the 
>> kvm process, and the perf top results are here: 
>>
>> https://gist.github.com/gilou/15b620a7a067fd1d58a7616942e025b4#file-perf_virtionet_4-4-txt 
>>
>> This was done again on a 4.1 updated to a 4.2. I will probably try on a 
>> fresh 4.2 install to check it out, but I doubt it will change much. 
>> If I fall back to the 4.2.6 kernel, bug isn't there. 
> 
> I'll try to bisect this next week. I was able to produce a similar perf 
> output (read_tsc() at >25% with 4.4, and far below with 4.2). 
> 
>> I can grant you access to the host should you need that, but I'm pretty 
>> sure anybody can reproduce that issue. Which brings quite some worries. 
>>
>> Regards, 
>>
>> Gilles Pietri 
> 
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