linux-kernel - Regression (bisected): Lots of wakeups when using battery

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Date:	Fri, 30 Jul 2010 22:45:23 +0100
From:	Jaime Velasco Juan <jsagarribay@...il.com>
To:	efault@....de, a.p.zijlstra@...lo.nl, tglx@...uxtronix.de,
	linux-kernel@...r.kernel.org
Subject: Regression (bisected): Lots of wakeups when using battery

Hi, testing 2.6.35-rc5 I noticed that when my laptop is on battery,
there are bursts of wakeups (they seem random, but usually happens once
each 5 sec. or so; they cause some audible noise). If the laptop is plugged
it behaves well. In single user mode, there are usually 2 wakeups/sec with
the system idle, but on battery an with the bug, it goes to more than 100 w/s.

Bisection points to:

commit 3310d4d38fbc514e7b18bd3b1eea8effdd63b5aa
Author: Peter Zijlstra <peterz@...radead.org>
Date:   Thu Jun 17 18:02:37 2010 +0200

    nohz: Fix nohz ratelimit
    
    Chris Wedgwood reports that 39c0cbe (sched: Rate-limit nohz) causes a
    serial console regression, unresponsiveness, and indeed it does. The
    reason is that the nohz code is skipped even when the tick was already
    stopped before the nohz_ratelimit(cpu) condition changed.
    
    Move the nohz_ratelimit() check to the other conditions which prevent
    long idle sleeps.

Reverting said commit seems to fix the issue.

Regards
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