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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:	Sat, 31 Jul 2010 06:01:42 +0200
From:	Mike Galbraith <efault@....de>
To:	Jaime Velasco Juan <jsagarribay@...il.com>
Cc:	a.p.zijlstra@...lo.nl, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Regression (bisected): Lots of wakeups when using battery

(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@...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.

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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/