linux-kernel - Re: [RFC PATCH 0/4]: affinity-on-next-touch

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Message-id: <4A3FC68A.2030104@lfbs.rwth-aachen.de>
Date:	Mon, 22 Jun 2009 19:59:38 +0200
From:	Stefan Lankes <lankes@...s.rwth-aachen.de>
To:	Brice Goglin <Brice.Goglin@...ia.fr>
Cc:	Lee Schermerhorn <Lee.Schermerhorn@...com>,
	'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



Brice Goglin wrote:
> 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 am not able to reconstruct any performance drawbacks on my system. 
Could you send me your low-level benchmark?

Stefan
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