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Subject: Re: sched: Avoid SMT siblings in select_idle_sibling() if possible
From: Mike Galbraith <efault@gmx.de>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Suresh Siddha <suresh.b.siddha@intel.com>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@elte.hu>, Paul Turner <pjt@google.com>
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Date: Fri, 18 Nov 2011 16:26:10 +0100
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On Fri, 2011-11-18 at 16:12 +0100, Peter Zijlstra wrote:
> On Thu, 2011-11-17 at 11:08 -0800, Suresh Siddha wrote:
> > 
> > From: Suresh Siddha <suresh.b.siddha@intel.com>
> > Subject: sched: cleanup domain traversal in select_idle_sibling
> > 
> > Instead of going through the scheduler domain hierarchy multiple times
> > (for giving priority to an idle core over an idle SMT sibling in a busy
> > core), start with the highest scheduler domain with the SD_SHARE_PKG_RESOURCES
> > flag and traverse the domain hierarchy down till we find an idle group.
> > 
> > This cleanup also addresses an issue reported by Mike where the recent
> > changes returned the busy thread even in the presence of an idle SMT
> > sibling in single socket platforms.
> > 
> > Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
> > Cc: Mike Galbraith <efault@gmx.de> 
> 
> Thanks Suresh!

Tested-by: Mike Galbraith <efault@gmx.de>