linux-kernel - Re: [PATCH] sched: Reduce the rate of needless idle load balancing

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Message-ID: <20140521063826.GC30445@twins.programming.kicks-ass.net>
Date:	Wed, 21 May 2014 08:38:26 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Tim Chen <tim.c.chen@...ux.intel.com>
Cc:	Jason Low <jason.low2@...com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Len Brown <len.brown@...el.com>, Russ Anderson <rja@....com>,
	Dimitri Sivanich <sivanich@....com>,
	Hedi Berriche <hedi@....com>, Andi Kleen <andi@...stfloor.org>,
	Michel Lespinasse <walken@...gle.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Hurley <peter@...leysoftware.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched: Reduce the rate of needless idle load balancing

On Tue, May 20, 2014 at 02:39:27PM -0700, Tim Chen wrote:
> From: Tim Chen <tim.c.chen@...ux.intel.com>
> Subject: [PATCH v2] sched: Reduce the rate of needless idle load balancing
> 
> 
> The current no_hz idle load balancer do load balancing for *all* idle cpus,
> even though the time due to load balance for a particular
> idle cpu could be still a while in the future.  This introduces a much
> higher load balancing rate than what is necessary.  The patch
> changes the behavior by only doing idle load balancing on
> behalf of an idle cpu only when it is due for load balancing.
> 
> On SGI's systems with over 3000 cores, the cpu responsible for idle balancing
> got overwhelmed with idle balancing, and introduces a lot of OS noise
> to workloads.  This patch fixes the issue.
> 
> Acked-by: Russ Anderson <rja@....com>
> Reviewed-by: Rik van Riel <riel@...hat.com>
> Reviewed-by: Jason Low <jason.low2@...com>
> Signed-off-by: Tim Chen <tim.c.chen@...ux.intel.com>
> ---

Thanks!

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