linux-kernel - Re: 2.6.32 / RH 6.1 scheduler bloated

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Message-ID: <1318140213.6216.40.camel@marge.simson.net>
Date:	Sun, 09 Oct 2011 08:03:33 +0200
From:	Mike Galbraith <efault@....de>
To:	Robert Kubrick <robertkubrick@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: 2.6.32 / RH 6.1 scheduler bloated

On Sat, 2011-10-08 at 20:26 -0400, Robert Kubrick wrote:
> A simple ftrace wakeup test shows 10us latency during the idle-to-run
> transition:

If you boot nohz=off idle=poll, and measure with cyclictest (measure in
userspace for free), you'll likely see a remarkable difference.

Coming out of idle can be slow, but that has more to do with silicon
than scheduler bloat (not that bloat doesn't exist mind you).  My Q6600
box _sucks_ at getting off it's duff, even intel_idle.max_cstate=1 is
horrid. E5620 gets moving > order of magnitude more quickly with the
same kernel/config/params.

	-Mike

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