linux-kernel - Re: sched domains oddness.

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Message-ID: <20081031170928.GB10468@linux-os.sc.intel.com>
Date:	Fri, 31 Oct 2008 10:09:29 -0700
From:	Suresh Siddha <suresh.b.siddha@...el.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc:	Dave Jones <davej@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: sched domains oddness.

On Fri, Oct 31, 2008 at 09:51:51AM -0700, Peter Zijlstra wrote:
> On Fri, 2008-10-31 at 12:24 -0400, Dave Jones wrote:
> > The attached dmesg comes from my dual core laptop running 2.6.27
> > What's up with all the sched domains transitions at the bottom?
> > This was just a boot up from power off, no suspend/resume or anything funky.
> 
> > CPU0 attaching NULL sched-domain.
> > CPU1 attaching NULL sched-domain.
> > CPU0 attaching sched-domain:
> >  domain 0: span 0-1 level MC
> >   groups: 0 1
> >   domain 1: span 0-1 level NODE
> >    groups: 0-1
> > CPU1 attaching sched-domain:
> >  domain 0: span 0-1 level MC
> >   groups: 1 0
> >   domain 1: span 0-1 level NODE
> >    groups: 0-1
> 
> 3x
> 
> looks like someone is triggering rebuild_sched_domains(), is something
> poking cpusetfs files or flipping between sched_mc settings?

I remember someone mentioning that some distro's started setting
sched_mc_power_savings to '1' by default during boot. On a dual-core
laptop, this will not give any advantage.

I have to fix the code to not export this tunable, when we have only
socket in the system.

Dave, Is your distro also setting this tunable blindly during boot :(

thanks,
suresh
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