Re: [PATCH -v5 0/5] rcu,nohz,kvm: use RCU extended quiescent state when running KVM guest

Frederic Weisbecker
2015-02-12T17:09:18Z

On Tue, Feb 10, 2015 at 03:27:49PM -0500, riel@redhat.com wrote:
> When running a KVM guest on a system with NOHZ_FULL enabled, and the
> KVM guest running with idle=poll mode, we still get wakeups of the
> rcuos/N threads.
>
> This problem has already been solved for user space by telling the
> RCU subsystem that the CPU is in an extended quiescent state while
> running user space code.
>
> This patch series extends that code a little bit to make it usable
> to track KVM guest space, too.
>
> I tested the code by booting a KVM guest with idle=poll, on a system
> with NOHZ_FULL enabled on most CPUs, and a VCPU thread bound to a
> CPU. In a 10 second interval, rcuos/N threads on other CPUs got woken
> up several times, while the rcuos thread on the CPU running the bound
> and alwasy running VCPU thread never got woken up once.
>
> Thanks to Christian Borntraeger, Paul McKenney, Paulo Bonzini,
> Frederic Weisbecker, and Will Deacon for reviewing and improving
> earlier versions of this patch series.
>

So the patchset look good, thanks everyone. I'm applying the series
and will see anything explode.

I'll wait until the end of the merge window to push it to Ingo.

Thanks.