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From: Mel Gorman <mgorman@suse.de>
To: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
	Andrea Arcangeli <aarcange@redhat.com>,
	Rik van Riel <riel@redhat.com>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Hugh Dickins <hughd@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	Linux-MM <linux-mm@kvack.org>,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 14/19] mm: mempolicy: Add MPOL_MF_LAZY
Date: Tue, 13 Nov 2012 12:02:48 +0000	[thread overview]
Message-ID: <20121113120248.GA8218@suse.de> (raw)
In-Reply-To: <20121113102555.GE21522@gmail.com>

On Tue, Nov 13, 2012 at 11:25:55AM +0100, Ingo Molnar wrote:
> 
> * Mel Gorman <mgorman@suse.de> wrote:
> 
> > From: Lee Schermerhorn <lee.schermerhorn@hp.com>
> > 
> > NOTE: Once again there is a lot of patch stealing and the end result
> > 	is sufficiently different that I had to drop the signed-offs.
> > 	Will re-add if the original authors are ok with that.
> > 
> > This patch adds another mbind() flag to request "lazy migration".  The
> > flag, MPOL_MF_LAZY, modifies MPOL_MF_MOVE* such that the selected
> > pages are marked PROT_NONE. The pages will be migrated in the fault
> > path on "first touch", if the policy dictates at that time.
> > 
> > <SNIP>
> 
> Here you are paying a heavy price for the earlier design 
> mistake, for forking into per arch approach - the NUMA version 
> of change_protection() had to be open-coded:
> 

I considered this when looking at the two trees.

At the time I also had the option of making change_prot_numa() to be a
wrapper around change_protection() and if pte_numa is made generic, that
becomes more attractive.

One of the reasons I went with this version from Andrea's tree is simply
because it does less work than change_protect() but what should be
sufficient for _PAGE_NUMA. I avoid the TLB flush if there are no PTE
updates for example but could shuffle change_protection() and get the
same thing.

> >  include/linux/mm.h             |    3 +
> >  include/uapi/linux/mempolicy.h |   13 ++-
> >  mm/mempolicy.c                 |  176 ++++++++++++++++++++++++++++++++++++----
> >  3 files changed, 174 insertions(+), 18 deletions(-)
> 
> Compare it to the generic version that Peter used:
> 
>  include/uapi/linux/mempolicy.h | 13 ++++++++---
>  mm/mempolicy.c                 | 49 +++++++++++++++++++++++++++---------------
>  2 files changed, 42 insertions(+), 20 deletions(-)
> 
> and the cleanliness and maintainability advantages are obvious.
> 
> So without some really good arguments in favor of your approach 
> NAK on that complex approach really.
> 

I will reimplement around change_protection() and see what effect, if any,
it has on overhead.

-- 
Mel Gorman
SUSE Labs

  reply	other threads:[~2012-11-13 12:02 UTC|newest]

Thread overview: 65+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-11-06  9:14 [RFC PATCH 00/19] Foundation for automatic NUMA balancing Mel Gorman
2012-11-06  9:14 ` [PATCH 01/19] mm: compaction: Move migration fail/success stats to migrate.c Mel Gorman
2012-11-06 17:32   ` Rik van Riel
2012-11-06  9:14 ` [PATCH 02/19] mm: migrate: Add a tracepoint for migrate_pages Mel Gorman
2012-11-06 17:33   ` Rik van Riel
2012-11-06  9:14 ` [PATCH 03/19] mm: compaction: Add scanned and isolated counters for compaction Mel Gorman
2012-11-06 17:35   ` Rik van Riel
2012-11-06  9:14 ` [PATCH 04/19] mm: numa: define _PAGE_NUMA Mel Gorman
2012-11-06 18:35   ` Rik van Riel
2012-11-06  9:14 ` [PATCH 05/19] mm: numa: pte_numa() and pmd_numa() Mel Gorman
2012-11-13  9:54   ` Ingo Molnar
2012-11-13 11:24     ` Mel Gorman
2012-11-06  9:14 ` [PATCH 06/19] mm: numa: teach gup_fast about pmd_numa Mel Gorman
2012-11-13 10:07   ` Ingo Molnar
2012-11-13 11:37     ` Mel Gorman
2012-11-13 13:51       ` Ingo Molnar
2012-11-06  9:14 ` [PATCH 07/19] mm: numa: split_huge_page: transfer the NUMA type from the pmd to the pte Mel Gorman
2012-11-06  9:14 ` [PATCH 08/19] mm: numa: Create basic numa page hinting infrastructure Mel Gorman
2012-11-06 18:58   ` Rik van Riel
2012-11-07 10:38     ` Mel Gorman
2012-11-07 10:48       ` Rik van Riel
2012-11-07 11:00         ` Mel Gorman
2012-11-13 10:21   ` Ingo Molnar
2012-11-13 11:50     ` Mel Gorman
2012-11-13 13:49       ` Ingo Molnar
2012-11-13 14:26         ` Mel Gorman
2012-11-06  9:14 ` [PATCH 09/19] mm: mempolicy: Make MPOL_LOCAL a real policy Mel Gorman
2012-11-06  9:14 ` [PATCH 10/19] mm: mempolicy: Add MPOL_MF_NOOP Mel Gorman
2012-11-06  9:14 ` [PATCH 11/19] mm: mempolicy: Check for misplaced page Mel Gorman
2012-11-06  9:14 ` [PATCH 12/19] mm: migrate: Introduce migrate_misplaced_page() Mel Gorman
2012-11-06 19:10   ` Rik van Riel
2012-11-13  9:36   ` Ingo Molnar
2012-11-13 11:43     ` Ingo Molnar
2012-11-13 11:56       ` Mel Gorman
2012-11-13 14:49       ` Rik van Riel
2012-11-06  9:14 ` [PATCH 13/19] mm: mempolicy: Use _PAGE_NUMA to migrate pages Mel Gorman
2012-11-06 19:18   ` Rik van Riel
2012-11-07 12:32     ` Mel Gorman
2012-11-06  9:14 ` [PATCH 14/19] mm: mempolicy: Add MPOL_MF_LAZY Mel Gorman
2012-11-06 19:19   ` Rik van Riel
2012-11-13 10:25   ` Ingo Molnar
2012-11-13 12:02     ` Mel Gorman [this message]
2012-11-06  9:14 ` [PATCH 15/19] mm: numa: Add fault driven placement and migration Mel Gorman
2012-11-06 19:41   ` Rik van Riel
2012-11-07 10:49     ` Mel Gorman
2012-11-07 11:46       ` Rik van Riel
2012-11-13 10:45   ` Ingo Molnar
2012-11-13 12:09     ` Mel Gorman
2012-11-13 13:39       ` Ingo Molnar
2012-11-06  9:14 ` [PATCH 16/19] mm: numa: Add pte updates, hinting and migration stats Mel Gorman
2012-11-06 19:55   ` Rik van Riel
2012-11-07 10:57     ` Mel Gorman
2012-11-07 11:47       ` Rik van Riel
2012-11-06  9:14 ` [PATCH 17/19] mm: numa: Migrate on reference policy Mel Gorman
2012-11-07 11:56   ` Rik van Riel
2012-11-06  9:14 ` [PATCH 18/19] mm: sched: numa: Implement constant, per task Working Set Sampling (WSS) rate Mel Gorman
2012-11-06 19:55   ` Rik van Riel
2012-11-06  9:14 ` [PATCH 19/19] mm: sched: numa: Implement slow start for working set sampling Mel Gorman
2012-11-06 19:56   ` Rik van Riel
2012-11-07  9:27 ` [RFC PATCH 00/19] Foundation for automatic NUMA balancing Zhouping Liu
2012-11-07 15:25   ` Mel Gorman
2012-11-08  6:37     ` Zhouping Liu
     [not found]       ` <CAOHXNFG=T63dmc3smkJ2juE7HpxTv6qbavBXycRsXiLBzAwMGw@mail.gmail.com>
2012-11-08  7:03         ` Zhouping Liu
2012-11-09 14:42 ` Andrea Arcangeli
2012-11-09 16:12   ` Mel Gorman

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