linux-kernel - Re: [RFC][PATCH] cache __next_timer

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Message-ID: <alpine.LFD.2.00.0907221632090.2813@localhost.localdomain>
Date:	Wed, 22 Jul 2009 16:38:18 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Martin Schwidefsky <schwidefsky@...ibm.com>
cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	john stultz <johnstul@...ibm.com>,
	Venki Pallipadi <venkatesh.pallipadi@...el.com>
Subject: Re: [RFC][PATCH] cache __next_timer_interrupt result

On Tue, 21 Jul 2009, Martin Schwidefsky wrote:

> From: Martin Schwidefsky <schwidefsky@...ibm.com>
> 
> Each time a cpu goes to sleep on a NOHZ=y system the timer wheel is
> searched for the next timer interrupt. It can take quite a few cycles
> to find the next pending timer. This patch adds a field to tvec_base
> that caches the result of __next_timer_interrupt. The hit ratio is
> around 80% on my thinkpad under normal use, on a server I've seen

Nice, I like it.

> hit ratios from 5% to 95% dependent on the workload.

Which workloads result in lower hit ratios ? Heavy networking ?
 
Thanks,

	tglx
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