From: Mike Galbraith <efault@gmx.de>
To: Jaime Velasco Juan <jsagarribay@gmail.com>
Cc: a.p.zijlstra@hello.nl, linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: Regression (bisected): Lots of wakeups when using battery
Date: Sat, 31 Jul 2010 06:01:42 +0200 [thread overview]
Message-ID: <1280548902.9686.51.camel@marge.simson.net> (raw)
In-Reply-To: <20100730214523.GA5571@pogo>
(corrects cc)
On Fri, 2010-07-30 at 22:45 +0100, Jaime Velasco Juan wrote:
> 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@infradead.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.
And if you revert that, using a serial console becomes.. unpleasant.
The whole ratelimit nohz thing has been dropped for now. It's a nice
little optimization for high frequency switchers on an underutilized
box, but has caused more irritation than it's worth.
-Mike
prev parent reply other threads:[~2010-07-31 4:01 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-07-30 21:45 Regression (bisected): Lots of wakeups when using battery Jaime Velasco Juan
2010-07-31 4:01 ` Mike Galbraith [this message]
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