linux-kernel - Re: [PATCH 5/5] sched/rt: Optimize find_lowest

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Message-ID: <20150127095626.707e434d@gandalf.local.home>
Date:	Tue, 27 Jan 2015 09:56:26 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Xunlei Pang <pang.xunlei@...aro.org>, linux-kernel@...r.kernel.org,
	Juri Lelli <juri.lelli@...il.com>
Subject: Re: [PATCH 5/5] sched/rt: Optimize find_lowest_rq() to select a
 cache hot cpu

On Tue, 27 Jan 2015 15:21:36 +0100
Peter Zijlstra <peterz@...radead.org> wrote:

> On Mon, Jan 19, 2015 at 04:49:40AM +0000, Xunlei Pang wrote:
> > In find_lowest_rq(), if we can't find a wake_affine cpu from
> > sched_domain, then we can actually determine a cache hot cpu
> > instead of simply calling "cpumask_any(lowest_mask)" which
> > always returns the first cpu in the mask.
> > 
> > So, we can determine the cache hot cpu during the interation of
> > sched_domain() in passing.
> 
> Steve, I'm not getting this. Why are we using WAKE_AFFINE here?
> 

It originated from Gregory Haskins topology patches. See 
 6e1254d2c41215da27025add8900ed187bca121d

-- Steve
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