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Subject: Re: [RFC PATCH v3 0/3] sched: simplify the select_task_rq_fair()
From: Mike Galbraith <efault@gmx.de>
To: Michael Wang <wangyun@linux.vnet.ibm.com>
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        Ram Pai <linuxram@us.ibm.com>,
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Date: Fri, 22 Feb 2013 09:17:13 +0100
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On Fri, 2013-02-22 at 14:42 +0800, Michael Wang wrote:

> So this is trying to take care the condition when curr_cpu(local) and
> prev_cpu(remote) are on different nodes, which in the old world,
> wake_affine() won't be invoked, correct?

It'll be called any time this_cpu and prev_cpu aren't one and the same.
It'd be pretty silly to asking whether to pull_here or leave_there when
here and there are identical.

> Hmm...I think this maybe a good additional checking before enter balance
> path, but I could not estimate the cost to record the relationship at
> this moment of time...

It'd be pretty cheap, but I'd hate adding any cycles to the fast path
unless those cycles have one hell of a good payoff, so the caching would
have to show most excellent cold hard numbers (talk crazy ideas walk;).

-Mike