linux-kernel - Re: [BUG] sched: fair group's bug

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Message-Id: <1231424195.11687.449.camel@twins>
Date:	Thu, 08 Jan 2009 15:16:35 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	miaox@...fujitsu.com
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: Re: [BUG] sched: fair group's bug

On Thu, 2009-01-08 at 09:30 +0800, Miao Xie wrote:
> I tested fair group scheduler on my hyper-threading x86_64 box(2 CPU * 2 HT)
> and found the deviation of the groups' CPU usage was larger than 2.6.26
> when *offline* a CPU or do hotplug frequently. It is less than 1% On 2.6.26，but
> On current kernel, it is often greater than 4%, even than 10% by accident.

Its not a bug -- a scheduler without smp awareness cannot be compared to
one without -- .26 just wasn't a complete group scheduler.

At best its a regression for your particular workload.

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