linux-kernel - Re: [patch 0/2] sched, timers: simplify calc

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Message-ID: <20090514172328.GA25691@sgi.com>
Date:	Thu, 14 May 2009 12:23:28 -0500
From:	Dimitri Sivanich <sivanich@....com>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [patch 0/2] sched, timers: simplify calc_load and avoid cpu
	iteration loop

I ran this patchset on a 64p ia64 machine and latency-wise it looks good.  I can't really speak for the loadavg calculation.

On Thu, May 14, 2009 at 11:21:14AM -0000, Thomas Gleixner wrote:
> Dimitri Sivanich pointed out that calc_load iterates over all online
> CPUs under xtime lock which can cause long latencies on large SMP
> systems.
> 
> The following patch series removes the iteration loop and lets
> scheduler_tick() on each CPU update the number of active tasks. The
> calc_load() function just uses this variable and updates avenrun from
> do_timer().
> 
> Dimitri, can you please test run this on one of your large machines ?
> 
> Thanks,
> 
> 	tglx
> 
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