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

[Wolfgang Bumiller]

On Tue, May 10, 2016 at 01:37:27PM +0200, Gilou wrote:
> 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 ?
> 
> Yes, though again m y lab is unavailable for this, so I can't do it
> "again". But it was a 4xxx  & 6xxx that showed the issue in the first place.
> 
> I just tried on a 4xxx I have on my laptop, it has the issue (using
> kvm/ubuntu rather than Proxmox, but still)

After bisecting it seems this commit is the issue:
https://github.com/torvalds/linux/commit/aca6ff29c4063a8d467cdee241e6b3bf7dc4a171

Can you try loading the kvm module with these options:
  halt_poll_ns_grow=0 halt_poll_ns_shrink=0

(/etc/modprobe.d + reboot, or grub boot commandline (with the `kvm.`
prefix to the options), or just:
  # rmmod kvm-intel
  # rmmod kvm
  # modprobe kvm halt_poll_ns_grow=0 halt_poll_ns_shrink=0
  # modprobe kvm-intel
)

This should revert the behavior of this commit. In my test VM this
commit bumps my load from 60% to 100% with the same 'perf' output you
had, and setting these options revert it back to normal.