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

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Message-ID: <1361439789.5861.70.camel@marge.simpson.net>
Date:	Thu, 21 Feb 2013 10:43:09 +0100
From:	Mike Galbraith <efault@....de>
To:	Michael Wang <wangyun@...ux.vnet.ibm.com>
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 Thu, 2013-02-21 at 17:08 +0800, Michael Wang wrote:

> But is this patch set really cause regression on your Q6600? It may
> sacrificed some thing, but I still think it will benefit far more,
> especially on huge systems.

We spread on FORK/EXEC, and will no longer will pull communicating tasks
back to a shared cache with the new logic preferring to leave wakee
remote, so while no, I haven't tested (will try to find round tuit) it
seems  it _must_ hurt.  Dragging data from one llc to the other on Q6600
hurts a LOT.  Every time a client and server are cross llc, it's a huge
hit.  The previous logic pulled communicating tasks together right when
it matters the most, intermittent load... or interactive use.

-Mike

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