linux-kernel - Re: sched: Avoid SMT siblings in select_idle

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Message-ID: <20120221080954.GJ2350@linux.vnet.ibm.com>
Date:	Tue, 21 Feb 2012 13:39:54 +0530
From:	Srivatsa Vaddagiri <vatsa@...ux.vnet.ibm.com>
To:	Mike Galbraith <efault@....de>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Suresh Siddha <suresh.b.siddha@...el.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>, Paul Turner <pjt@...gle.com>
Subject: Re: sched: Avoid SMT siblings in select_idle_sibling() if possible

* Mike Galbraith <efault@....de> [2012-02-21 07:37:14]:

> On Tue, 2012-02-21 at 05:36 +0530, Srivatsa Vaddagiri wrote:
> 
> > fwiw the patch I had sent does a wakeup balance within prev_cpu's
> > cache_domain (and not outside).
> 
> Yeah, the testing I did was turn on the flag, and measure.  With single
> domain scans, maybe select_idle_sibling() could just go away.

Yeah that's what I was thinking. Essentially find_idlest_group/cpu
should accomplish that job pretty much for us ...

> It ain't free either.

Will find out how much difference it makes ..

- vatsa

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