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Date: Thu, 2 Feb 2012 09:51:55 -0800
From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To: Avi Kivity <avi@...hat.com>
Cc: Christoph Lameter <cl@...ux.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Gilad Ben-Yossef <gilad@...yossef.com>,
linux-kernel@...r.kernel.org, Chris Metcalf <cmetcalf@...era.com>,
Frederic Weisbecker <fweisbec@...il.com>, linux-mm@...ck.org,
Pekka Enberg <penberg@...nel.org>,
Matt Mackall <mpm@...enic.com>,
Sasha Levin <levinsasha928@...il.com>,
Rik van Riel <riel@...hat.com>,
Andi Kleen <andi@...stfloor.org>, Mel Gorman <mel@....ul.ie>,
Andrew Morton <akpm@...ux-foundation.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
Michal Nazarewicz <mina86@...a86.com>,
Kosaki Motohiro <kosaki.motohiro@...il.com>,
Milton Miller <miltonm@....com>
Subject: Re: [v7 0/8] Reduce cross CPU IPI interference
On Thu, Feb 02, 2012 at 07:23:39PM +0200, Avi Kivity wrote:
> On 02/02/2012 07:01 PM, Paul E. McKenney wrote:
> > >
> > > It's not called (since the cpu is not idle). Instead we call
> > > rcu_virt_note_context_switch().
> >
> > Frederic's work checks to see if there is only one runnable user task
> > on a given CPU. If there is only one, then the scheduling-clock interrupt
> > is turned off for that CPU, and RCU is told to ignore it while it is
> > executing in user space. Not sure whether this covers KVM guests.
>
> Conceptually it's the same. Maybe it needs adjustments, since kvm
> enters a guest in a different way than the kernel exits to userspace.
>
> > In any case, this is not yet in mainline.
>
> Let me know when it's in, and I'll have a look.
Could you please touch base with Frederic Weisbecker to make sure that
what he is doing works for you?
Thanx, Paul
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