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

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Date:	Thu, 12 Feb 2015 18:09:12 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	riel@...hat.com
Cc:	paulmck@...ux.vnet.ibm.com, luto@...capital.net,
	will.deacon@....com, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, mtosatti@...hat.com, borntraeger@...ibm.com,
	lcapitulino@...hat.com, pbonzini@...hat.com
Subject: Re: [PATCH -v5 0/5] rcu,nohz,kvm: use RCU extended quiescent state
 when running KVM guest

On Tue, Feb 10, 2015 at 03:27:49PM -0500, riel@...hat.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.
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