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
Date: Thu, 2 Feb 2012 09:01:34 -0800 [thread overview]
Message-ID: <20120202170134.GM2518@linux.vnet.ibm.com> (raw)
In-Reply-To: <4F2AB66C.2030309@redhat.com>
On Thu, Feb 02, 2012 at 06:14:36PM +0200, Avi Kivity wrote:
> On 02/02/2012 05:34 PM, Paul E. McKenney wrote:
> > 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. ;-)
> >
>
> 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.
In any case, this is not yet in mainline.
Thanx, Paul
next prev parent reply other threads:[~2012-02-02 17:02 UTC|newest]
Thread overview: 77+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-26 10:01 [v7 0/8] Reduce cross CPU IPI interference Gilad Ben-Yossef
2012-01-26 10:01 ` [v7 1/8] smp: introduce a generic on_each_cpu_mask function Gilad Ben-Yossef
2012-01-29 12:24 ` Gilad Ben-Yossef
2012-01-30 21:52 ` Andrew Morton
2012-01-31 6:33 ` Gilad Ben-Yossef
2012-01-26 10:01 ` [v7 2/8] arm: move arm over to generic on_each_cpu_mask Gilad Ben-Yossef
2012-01-26 10:01 ` [v7 3/8] tile: move tile to use " Gilad Ben-Yossef
2012-01-26 10:01 ` [v7 4/8] smp: add func to IPI cpus based on parameter func Gilad Ben-Yossef
2012-01-27 23:57 ` Andrew Morton
2012-01-29 12:04 ` Gilad Ben-Yossef
2012-01-26 10:01 ` [v7 5/8] slub: only IPI CPUs that have per cpu obj to flush Gilad Ben-Yossef
2012-01-26 15:09 ` Christoph Lameter
2012-01-26 10:01 ` [v7 6/8] fs: only send IPI to invalidate LRU BH when needed Gilad Ben-Yossef
2012-01-26 10:02 ` [v7 7/8] mm: only IPI CPUs to drain local pages if they exist Gilad Ben-Yossef
2012-01-26 15:13 ` Christoph Lameter
2012-01-28 0:12 ` Andrew Morton
2012-01-29 12:18 ` Gilad Ben-Yossef
2012-01-30 21:49 ` Andrew Morton
2012-01-31 6:32 ` Gilad Ben-Yossef
2012-01-30 14:59 ` Mel Gorman
2012-01-30 15:14 ` Gilad Ben-Yossef
2012-01-30 15:44 ` Mel Gorman
2012-01-26 10:02 ` [v7 8/8] mm: add vmstat counters for tracking PCP drains Gilad Ben-Yossef
2012-01-26 15:19 ` [v7 0/8] Reduce cross CPU IPI interference Peter Zijlstra
2012-01-29 8:25 ` Gilad Ben-Yossef
2012-02-01 17:04 ` Frederic Weisbecker
2012-02-02 8:46 ` Gilad Ben-Yossef
2012-02-02 15:41 ` Chris Metcalf
2012-02-05 11:46 ` Gilad Ben-Yossef
2012-02-10 18:39 ` Peter Zijlstra
2012-02-10 20:13 ` Gilad Ben-Yossef
2012-02-10 20:29 ` Peter Zijlstra
2012-02-10 20:39 ` Gilad Ben-Yossef
2012-02-10 18:33 ` Peter Zijlstra
2012-02-10 20:33 ` Gilad Ben-Yossef
2012-02-15 21:50 ` Chris Metcalf
2012-02-15 22:15 ` Christoph Lameter
2012-02-15 23:44 ` Chris Metcalf
2012-02-21 1:34 ` Frederic Weisbecker
2012-03-01 18:27 ` Chris Metcalf
2012-02-10 18:38 ` Peter Zijlstra
2012-02-10 20:24 ` Gilad Ben-Yossef
2012-02-15 15:11 ` Peter Zijlstra
2012-02-15 15:19 ` Gilad Ben-Yossef
2012-02-15 21:51 ` Chris Metcalf
2012-02-02 16:24 ` Frederic Weisbecker
2012-02-02 16:29 ` Christoph Lameter
2012-02-09 15:52 ` Frederic Weisbecker
2012-02-09 15:59 ` Chris Metcalf
2012-02-09 18:11 ` Frederic Weisbecker
2012-02-09 16:26 ` Christoph Lameter
2012-02-09 18:32 ` Frederic Weisbecker
2012-02-01 17:35 ` Peter Zijlstra
2012-02-01 17:57 ` Peter Zijlstra
2012-02-02 9:42 ` Gilad Ben-Yossef
2012-02-01 18:40 ` Paul E. McKenney
2012-02-01 20:06 ` Christoph Lameter
2012-02-01 20:13 ` Paul E. McKenney
2012-02-02 9:34 ` Avi Kivity
2012-02-02 15:34 ` Paul E. McKenney
2012-02-02 16:14 ` Avi Kivity
2012-02-02 17:01 ` Paul E. McKenney [this message]
2012-02-02 17:23 ` Avi Kivity
2012-02-02 17:51 ` Paul E. McKenney
2012-02-05 12:16 ` Avi Kivity
2012-02-05 16:59 ` Paul E. McKenney
2012-02-09 15:22 ` Frederic Weisbecker
2012-02-09 16:05 ` Avi Kivity
2012-02-09 18:22 ` Frederic Weisbecker
2012-02-09 23:41 ` Paul E. McKenney
2012-02-10 1:39 ` Frederic Weisbecker
2012-02-14 13:18 ` Avi Kivity
2012-02-21 0:02 ` Frederic Weisbecker
2012-02-02 17:25 ` Christoph Lameter
2012-02-05 12:06 ` Gilad Ben-Yossef
2012-02-06 18:19 ` Christoph Lameter
2012-02-09 15:37 ` Frederic Weisbecker
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