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Subject: Re: [RFC PATCH v3 0/3] sched: simplify the select_task_rq_fair()
From: Mike Galbraith <efault@gmx.de>
To: Michael Wang <wangyun@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
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Date: Thu, 21 Feb 2013 10:43:09 +0100
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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