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

[Alexandre DERUMIER]

BTW,

what is the host cpu model ?


----- 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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