From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>, Rik van Riel <riel@redhat.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/5] mm/compaction: do not call suitable_migration_target() on every page
Date: Mon, 10 Feb 2014 09:41:22 +0900 [thread overview]
Message-ID: <20140210004122.GB12049@lge.com> (raw)
In-Reply-To: <52F4A90D.20804@suse.cz>
On Fri, Feb 07, 2014 at 10:36:13AM +0100, Vlastimil Babka wrote:
> On 02/07/2014 06:08 AM, Joonsoo Kim wrote:
> > suitable_migration_target() checks that pageblock is suitable for
> > migration target. In isolate_freepages_block(), it is called on every
> > page and this is inefficient. So make it called once per pageblock.
>
> Hmm but in sync compaction, compact_checklock_irqsave() may drop the zone->lock,
> reschedule and reacquire it and thus possibly invalidate your previous check. Async
> compaction is ok as that will quit immediately. So you could probably communicate that
> this happened and invalidate checked_pageblock in such case. Or maybe this would not
> happen too enough to worry about rare suboptimal migrations?
So, the result of previous check can be changed only if *this* pageblock's migratetype
is changed while we drop the lock. I guess that this is really rare event, and,
in this case, this pageblock already has mixed migratetype pages, so it has
no serious problem.
Thanks.
next prev parent reply other threads:[~2014-02-10 0:41 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-07 5:08 [PATCH 0/5] compaction related commits Joonsoo Kim
2014-02-07 5:08 ` [PATCH 1/5] mm/compaction: disallow high-order page for migration target Joonsoo Kim
2014-02-07 9:20 ` Vlastimil Babka
2014-02-10 13:26 ` Mel Gorman
2014-02-11 7:12 ` Joonsoo Kim
2014-02-07 5:08 ` [PATCH 2/5] mm/compaction: do not call suitable_migration_target() on every page Joonsoo Kim
2014-02-07 9:36 ` Vlastimil Babka
2014-02-10 0:41 ` Joonsoo Kim [this message]
2014-02-07 5:08 ` [PATCH 3/5] mm/compaction: change the timing to check to drop the spinlock Joonsoo Kim
2014-02-07 9:50 ` Vlastimil Babka
2014-02-07 5:08 ` [PATCH 4/5] mm/compaction: check pageblock suitability once per pageblock Joonsoo Kim
2014-02-07 10:30 ` Vlastimil Babka
2014-02-10 0:46 ` Joonsoo Kim
2014-02-07 5:08 ` [PATCH 5/5] mm/compaction: clean-up code on success of ballon isolation Joonsoo Kim
2014-02-07 10:33 ` Vlastimil Babka
2014-02-07 9:14 ` [PATCH 0/5] compaction related commits Vlastimil Babka
2014-02-10 0:24 ` Joonsoo Kim
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