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 08/19] mm: numa: Create basic numa page hinting infrastructure
Date: Tue, 13 Nov 2012 11:50:32 +0000 [thread overview]
Message-ID: <20121113115032.GY8218@suse.de> (raw)
In-Reply-To: <20121113102120.GD21522@gmail.com>
On Tue, Nov 13, 2012 at 11:21:20AM +0100, Ingo Molnar wrote:
>
> * Mel Gorman <mgorman@suse.de> wrote:
>
> > Note: This patch started as "mm/mpol: Create special PROT_NONE
> > infrastructure" and preserves the basic idea but steals *very*
> > heavily from "autonuma: numa hinting page faults entry points" for
> > the actual fault handlers without the migration parts. The end
> > result is barely recognisable as either patch so all Signed-off
> > and Reviewed-bys are dropped. If Peter, Ingo and Andrea are ok with
> > this version, I will re-add the signed-offs-by to reflect the history.
>
> Most of the changes you had to do here relates to the earlier
> decision to turn it all the NUMA protection fault demultiplexing
> and setup code into a per arch facility.
>
Yes.
> On one hand I'm 100% fine with making the decision to *use* the
> new NUMA code per arch and explicitly opt-in - we already have
> such a Kconfig switch in our tree already. The decision whether
> to use any of this for an architecture must be considered and
> tested carefully.
>
Agreed.
> But given that most architectures will be just fine reusing the
> already existing generic PROT_NONE machinery, the far better
> approach is to do what we've been doing in generic kernel code
> for the last 10 years: offer a default generic version, and then
> to offer per arch hooks on a strict as-needed basis, if they
> want or need to do something weird ...
>
If they are *not* fine with it, it's a large retrofit because the PROT_NONE
machinery has been hard-coded throughout. It also requires that anyone
looking at the fault paths must remember at almost all times that PROT_NONE
can also mean PROT_NUMA and it depends on context. While that's fine right
now, it'll be harder to maintain in the future.
> So why fork away this logic into per arch code so early and
> without explicit justification? It creates duplication artifacts
> all around and makes porting to a new 'sane' architecture
> harder.
>
I agree that the duplication artifacts was a mistake. I can fix that but
feel that the naming is fine and we shouldn't hard-code that
change_prot_none() can actually mean change_prot_numa() if called from
the right place.
> Also, if there *are* per architecture concerns then I'd very
> much like to see that argued very explicitly, on a per arch
> basis, as it occurs, not obscured through thick "just in case"
> layers of abstraction ...
>
Once there is a generic pte_numa handler for example, an arch-specific
overriding of it should raise a red flag for closer inspection.
--
Mel Gorman
SUSE Labs
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next prev parent reply other threads:[~2012-11-13 11:50 UTC|newest]
Thread overview: 66+ 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 [this message]
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
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
2012-11-08 6:39 ` 杨竹
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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