linux-kernel - Re: [PATCH 07/41] cpuset: Set up interface for nohz flag

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Message-ID: <1336506601.7400.21.camel@marge.simpson.net>
Date:	Tue, 08 May 2012 21:50:01 +0200
From:	Mike Galbraith <efault@....de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Christoph Lameter <cl@...ux.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	linaro-sched-sig@...ts.linaro.org,
	Alessio Igor Bogani <abogani@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Avi Kivity <avi@...hat.com>,
	Chris Metcalf <cmetcalf@...era.com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	Geoff Levand <geoff@...radead.org>,
	Gilad Ben Yossef <gilad@...yossef.com>,
	Hakan Akkan <hakanakkan@...il.com>,
	Ingo Molnar <mingo@...nel.org>, Kevin Hilman <khilman@...com>,
	Max Krasnyansky <maxk@...lcomm.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Stephen Hemminger <shemminger@...tta.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Sven-Thorsten Dietrich <thebigcorporation@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 07/41] cpuset: Set up interface for nohz flag

On Tue, 2012-05-08 at 18:16 +0200, Peter Zijlstra wrote: 
> On Tue, 2012-05-08 at 10:57 -0500, Christoph Lameter wrote:

> isolcpus is a very limited hack that adds more pain that its worth. Its
> yet another mask to check and its functionality is completely available
> through cpusets.

Agreed.

> You cannot create multi-cpu partitions using isolcpus, you cannot
> dynamically reconfigure it.

Big plus for cpusets.

> And on the scheduler side cpusets doesn't add runtime overhead to normal
> things, only sched_setaffinity() and a few other rare operations get
> slightly more expensive. And it allows to reduce runtime overhead by
> making the load-balancer domains smaller.

Very big deal if you have a load that doesn't do all the performance 'i'
dotting and 't' crossing it maybe could have, but ends up on a big box.

-Mike

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