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Message-ID: <4A3FBA11.8030304@inria.fr>
Date: Mon, 22 Jun 2009 19:06:25 +0200
From: Brice Goglin <Brice.Goglin@...ia.fr>
To: Lee Schermerhorn <Lee.Schermerhorn@...com>
CC: Stefan Lankes <lankes@...s.rwth-aachen.de>,
'Andi Kleen' <andi@...stfloor.org>,
linux-kernel@...r.kernel.org, linux-numa@...r.kernel.org,
Boris Bierbaum <boris@...s.rwth-aachen.de>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
Balbir Singh <balbir@...ux.vnet.ibm.com>,
KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Subject: Re: [RFC PATCH 0/4]: affinity-on-next-touch
Lee Schermerhorn wrote:
> The primary difference should be at unmap time, right? In the fault
> path, I only update the pte of the faulting task. That's why I require
> the [anon] pages to be in the swap cache [or something similar]. I
> don't want to be fixing up other tasks' page tables in the context of
> the faulting task's fault handler. If, later, another task touches the
> page, it will take a minor fault and find the [possibly migrated] page
> in the cache. Hmmm, I guess all tasks WILL incur the minor fault if
> they touch the page after the unmap. That could be part of the
> difference if you compare on the same kernel version.
>
Agreed.
> Try booting with cgroup_disable=memory on the command line, if you have
> the memory resource controller configured in. See what that does to
> your measurements.
>
It doesn't seem to help. I'll try to bisect and find where the
performance dropped.
> ??? I would expect low level page copying to be highly optimized per
> arch, and also fairly stable.
I just did a quick copy_page benchmark and didn't see any performance
difference between 2.6.27 and mmotm.
thanks,
Brice
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