linux-kernel - Re: [PATCH] sched: smart wake-affine

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Message-ID: <51D2708C.1050901@linux.vnet.ibm.com>
Date:	Tue, 02 Jul 2013 14:17:48 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Mike Galbraith <efault@....de>
CC:	LKML <linux-kernel@...r.kernel.org>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Alex Shi <alex.shi@...el.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Paul Turner <pjt@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Nikunj A. Dadhania" <nikunj@...ux.vnet.ibm.com>,
	Ram Pai <linuxram@...ibm.com>
Subject: Re: [PATCH] sched: smart wake-affine

On 07/02/2013 01:54 PM, Mike Galbraith wrote:
> On Tue, 2013-07-02 at 12:43 +0800, Michael Wang wrote: 
>> Since RFC:
>> 	Tested again with the latest tip 3.10.0-rc7.
>>
>> wake-affine stuff is always trying to pull wakee close to waker, by theory,
>> this will bring benefit if waker's cpu cached hot data for wakee, or the
>> extreme ping-pong case.
>>
>> And testing show it could benefit hackbench 15% at most.
> 
> How much does this still help with Alex's patches integrated?

I remember Alex already tested hackbench, and for wake_affine(), his
patch set is some kind of load filter, mine is nr_wakee filter, they are
separated, but I will do more test on this point when it become the last
concern.

> 
> aside: were I a maintainer, I'd be a little concerned that what this
> helps with collides somewhat with the ongoing numa work.

As Peter mentioned before, we currently need some solution like the
buddy-idea, and when folks report regression (I suppose they won't...),
we will have more data then.

So we could firstly try to regain the lost performance of pgbench, if it
strip the benefit of other benchmarks, let's fix it, and at last we will
have a real smart wake-affine and no one will complain ;-)

Regards,
Michael Wang

> 
> -Mike
> 
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