Re: massive performance drop after a while when using virtio nics

Henrik Holst
2008-09-09T11:11:15Z

tis 2008-09-09 klockan 11:47 +0100 skrev Mark McLoughlin:
> On Tue, 2008-09-09 at 12:32 +0200, Fabian Deutsch wrote:
> > Am Dienstag, den 09.09.2008, 11:22 +0100 schrieb Mark McLoughlin:
> > > Hi,
> > >
> > > On Sat, 2008-08-23 at 21:21 +0200, Fabian Deutsch wrote:
> > > > Hey.
> > > >
> > > > When running a guest in the following setup, I observ a "massive"
> > > > performance decrease after a couple of gigabytes of transfrerred data.
> > > >
> > > > other guests keep running fine (no regressions) and nothing unusual is
> > > > observed on the host.
> > >
> > > If you do "killall -ALRM qemu-kvm" after the slowdown has occurred, does
> > > it make things speed up again for a while?
> > >
> >
> > It seems so!
> > Fantastic.
> >
> > > If so, the issue is fixed by:
> > >
> > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=ba661292a2bc6ddd305a212b0526e5dc22195fe7
> > >
> > > It also got applied in 2.6.26.3 and 2.6.25.16.
> > >
> >
> > So it was some signaling-bug on the .. client side?
>
> No, it was a kernel race condition causing the qemu-kvm process to stop
> receiving SIGALRM signals.

So is it the host kernel that should be patched?

/Henrik Holst
Witsbits AB