linux-kernel - Re: sched domains oddness.

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Message-ID: <20081031173737.GA11443@redhat.com>
Date:	Fri, 31 Oct 2008 13:37:37 -0400
From:	Dave Jones <davej@...hat.com>
To:	Suresh Siddha <suresh.b.siddha@...el.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: sched domains oddness.

On Fri, Oct 31, 2008 at 01:17:21PM -0400, Dave Jones wrote:
 > On Fri, Oct 31, 2008 at 10:09:29AM -0700, Suresh Siddha wrote:
 > 
 >  > > 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 :(
 > 
 > (13:15:25:davej@...o:~)$ cat /sys/devices/system/cpu/sched_mc_power_savings
 > 0
 > 
 > So no, unless something set it to 1, and then back to 0.
 > 
 > A grep of etc shows up nothing in initscripts.  Does hal or something
 > play with this?

Even curiouser.. When I unplug AC and replug it, it happens again, but slightly
differently..

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 CPU
   groups: 0-1
   domain 2: 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 CPU
   groups: 0-1
   domain 2: span 0-1 level NODE
    groups: 0-1
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


Note how the CPU level doesn't show up in the 2nd case.

This still doesn't explain the flip-flop I saw just from booting,
as that was on AC the whole time.

I grepped hal and gnome-power-manager, and didn't see anything
touching sched_mc

	Dave

-- 
http://www.codemonkey.org.uk
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