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

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Message-ID: <51270AD9.9020908@linux.vnet.ibm.com>
Date:	Fri, 22 Feb 2013 14:06:17 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Mike Galbraith <efault@....de>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Ingo Molnar <mingo@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	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 01:08 PM, Mike Galbraith wrote:
> On Fri, 2013-02-22 at 10:37 +0800, Michael Wang wrote:
> 
>> According to the testing result, I could not agree this purpose of
>> wake_affine() benefit us, but I'm sure that wake_affine() is a terrible
>> performance killer when system is busy.
> 
> (hm, result is singular.. pgbench in 1:N mode only?)

I'm not sure about how pgbench implemented, all I know is it will create
several instance and access the database, I suppose no different from
several threads access database (1 server and N clients?).

There are improvement since when system busy, wake_affine() will be skipped.

And in old world, when system is busy, wake_affine() will only be
skipped if prev_cpu and curr_cpu belong to different nodes.

Regards,
Michael Wang

> 
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