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