Date: Thu, 2 Feb 2012 07:34:37 -0800
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Avi Kivity <avi@redhat.com>
Cc: Christoph Lameter <cl@linux.com>, Peter Zijlstra <a.p.zijlstra@chello.nl>,
        Gilad Ben-Yossef <gilad@benyossef.com>, linux-kernel@vger.kernel.org,
        Chris Metcalf <cmetcalf@tilera.com>,
        Frederic Weisbecker <fweisbec@gmail.com>, linux-mm@kvack.org,
        Pekka Enberg <penberg@kernel.org>, Matt Mackall <mpm@selenic.com>,
        Sasha Levin <levinsasha928@gmail.com>, Rik van Riel <riel@redhat.com>,
        Andi Kleen <andi@firstfloor.org>, Mel Gorman <mel@csn.ul.ie>,
        Andrew Morton <akpm@linux-foundation.org>,
        Alexander Viro <viro@zeniv.linux.org.uk>,
        Michal Nazarewicz <mina86@mina86.com>,
        Kosaki Motohiro <kosaki.motohiro@gmail.com>,
        Milton Miller <miltonm@bga.com>
Subject: Re: [v7 0/8] Reduce cross CPU IPI interference
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On Thu, Feb 02, 2012 at 11:34:25AM +0200, Avi Kivity wrote:
> On 02/01/2012 10:13 PM, Paul E. McKenney wrote:
> > > 
> > > Could we also apply the same approach to processors busy doing
> > > computational work? In that case the OS is also not needed. Interrupting
> > > these activities is impacting on performance and latency.
> >
> > Yep, that is in fact what Frederic's dyntick-idle userspace work does.
> 
> Running in a guest is a special case of running in userspace, so we'd
> need to extend this work to kvm as well.

As long as rcu_idle_enter() is called at the appropriate time, RCU will
happily ignore the CPU.  ;-)

							Thanx, Paul

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