linux-kernel - Re: [RFC PATCH v3 0/3] sched: simplify the select_task_rq

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Date:	Fri, 22 Feb 2013 16:35:36 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Mike Galbraith <efault@....de>
CC:	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Turner <pjt@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>, alex.shi@...el.com,
	Ram Pai <linuxram@...ibm.com>,
	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>,
	Namhyung Kim <namhyung@...nel.org>
Subject: Re: [RFC PATCH v3 0/3] sched: simplify the select_task_rq_fair()

On 02/22/2013 04:17 PM, Mike Galbraith wrote:
> 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.

Agree :)

> 
>> 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;).

It sounds like a good idea, I'm not sure whether it's cheap and how many
benefit we could gain, but it worth some research.

I will thinking more about it after finished the sbm work.

Regards,
Michael Wang

> 
> -Mike
> 

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