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

[Gilou]

Le 09/05/2016 15:33, Alexandre DERUMIER a écrit :
> For v6 (skylake), I think they are new feature implementation in kvm
> http://www.gossamer-threads.com/lists/linux/kernel/2267259
> 
> for v4, I don't see any recent change
> 
> 
> You can reproduce with both v4 and v6 ?

I was able to, yes, lab has been tore down again, but yes, on i5, on i7
4xxx & 6xxx.


> 
> 
> 
> ----- Mail original -----
> De: "Gilou" <contact+dev at gilouweb.com>
> À: "proxmoxve" <pve-user at pve.proxmox.com>
> Envoyé: Lundi 9 Mai 2016 15:12:30
> Objet: Re: [PVE-User] Regression on virtio-net ? (Was: Re: Proxmox VE 4.2 released!)
> 
> 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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