linux-kernel - Re: [PATCH] Track accurate idle time with tick_sched.idle

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Message-ID: <20070831182212.GA3568@elte.hu>
Date:	Fri, 31 Aug 2007 20:22:12 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Venki Pallipadi <venkatesh.pallipadi@...el.com>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Track accurate idle time with tick_sched.idle_sleeptime


* Venki Pallipadi <venkatesh.pallipadi@...el.com> wrote:

> Current idle time in kstat is based on jiffies and is coarse grained. 
> tick_sched.idle_sleeptime is making some attempt to keep track of idle 
> time in a fine grained manner. But, it is not handling the time spent 
> in interrupts fully.
> 
> Make tick_sched.idle_sleeptime accurate with respect to time spent on 
> handling interrupts and also add tick_sched.idle_lastupdate, which 
> keeps track of last time when idle_sleeptime was updated.
> 
> This statistics will be crucial for cpufreq-ondemand governor, which 
> can shed some conservative gaurd band that is uses today while setting 
> the frequency. The ondemand changes that uses the exact idle time is 
> coming soon.

nice stuff! I've added your patch to the scheduler queue - but this will 
probably be 2.6.24 material.

Acked-by: Ingo Molnar <mingo@...e.hu>

	Ingo
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