linux-kernel - Re: High CPU load when machine is idle (related to PROBLEM: Unusually high load average when idle in 2.6.35, 2.6.35.1 and later)

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Message-ID: <20101023021338.GA8205@roll>
Date:	Fri, 22 Oct 2010 22:13:38 -0400
From:	tmhikaru@...il.com
To:	Venkatesh Pallipadi <venki@...gle.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Damien Wyart <damien.wyart@...e.fr>,
	Chase Douglas <chase.douglas@...onical.com>,
	Ingo Molnar <mingo@...e.hu>, tmhikaru@...il.com,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org
Subject: Re: High CPU load when machine is idle (related to PROBLEM: Unusually high load average when idle in 2.6.35, 2.6.35.1 and later)

On Fri, Oct 22, 2010 at 04:03:42PM -0700, Venkatesh Pallipadi wrote:
> (Sorry about the subjectless earlier mail)
> 
> I started making small changes to the code, but none of the change helped much.
> I think the problem with the current code is that, even though idle CPUs
> update load, the fold only happens when one of the CPU is busy
> and we end up taking its load into global load.
> 
> So, I tried to simplify things and doing the updates directly from idle loop.
> This is only a test patch, and eventually we need to hook it off somewhere
> else, instead of idle loop and also this is expected work only as x86_64
> right now.
> 
> Peter: Do you think something like this will work? loadavg went
> quite on two of my test systems after this change (4 cpu and 24 cpu).
> 
> Thanks,
> Venki

	I'd really like to be able to help test this, but with a 32bit x86
machine I guess this patch won't do anything for me. How hard would it be to
mangle this into working for my machine or should I just wait?

Tim McGrath

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