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

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Message-ID: <4A3FEAF0.2060301@inria.fr>
Date:	Mon, 22 Jun 2009 22:34:56 +0200
From:	Brice Goglin <Brice.Goglin@...ia.fr>
To:	Stefan Lankes <lankes@...s.rwth-aachen.de>
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

Stefan Lankes wrote:
> By the way, do you also add Lee's "shared policy" patches? These
> patches add MPOL_MF_SHARED, which is specified as 3. Afterwards, you
> have to define MPOL_MF_LAZY as 4.

Yes, I applied shared-policy-* since migrate-on-fault doesn't apply
without them :)

But I have the following in include/linux/mempolicy.h after applying all
patches:
#define MPOL_MF_LAZY     (1<<3) /* Modifies '_MOVE:  lazy migrate on
fault */
#define MPOL_F_SHARED  (1 << 0) /* identify shared policies */
Where did you get your F_SHARED=3 and MF_LAZY=4?

> I got following performance results with MPOL_NOOP:
>
> # Nb_pages      Cost(ns)
> 32768   50431375
> 65536   101970000
> 131072  216200500
> 262144  511706000

Is there any migration here? Don't you just have unmap and fault without
migration? In my test program, the initialization does MPOL_BIND. So the
following MPOL_NOOP should just do nothing since the page is already
correctly placed with regard to the previous MPOL_BIND. I feel like 2us
per page looks too low for a migration and it's also very high for just
unmap and fault-in.

> I got following performance results with MPOL_PREFERRED:
>
> # Nb_pages      Cost(ns)
> 32768   141738000

That's about 60% faster than on my machine (quad-barcelona 8347HE
1.9GHz). What machine are you running on?

Brice

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