From: Minchan Kim <minchan@kernel.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Greg Thelen <gthelen@google.com>, Mel Gorman <mgorman@suse.de>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Michal Nazarewicz <mina86@mina86.com>,
Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
Christoph Lameter <cl@linux.com>, Rik van Riel <riel@redhat.com>
Subject: Re: [PATCH 01/10] mm, compaction: do not recheck suitable_migration_target under lock
Date: Wed, 11 Jun 2014 09:33:23 +0900 [thread overview]
Message-ID: <20140611003322.GB15630@bbox> (raw)
In-Reply-To: <1402305982-6928-1-git-send-email-vbabka@suse.cz>
On Mon, Jun 09, 2014 at 11:26:13AM +0200, Vlastimil Babka wrote:
> isolate_freepages_block() rechecks if the pageblock is suitable to be a target
> for migration after it has taken the zone->lock. However, the check has been
> optimized to occur only once per pageblock, and compact_checklock_irqsave()
> might be dropping and reacquiring lock, which means somebody else might have
> changed the pageblock's migratetype meanwhile.
>
> Furthermore, nothing prevents the migratetype to change right after
> isolate_freepages_block() has finished isolating. Given how imperfect this is,
> it's simpler to just rely on the check done in isolate_freepages() without
> lock, and not pretend that the recheck under lock guarantees anything. It is
> just a heuristic after all.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Minchan Kim <minchan@kernel.org>
--
Kind regards,
Minchan Kim
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next prev parent reply other threads:[~2014-06-11 0:33 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-09 9:26 [PATCH 01/10] mm, compaction: do not recheck suitable_migration_target under lock Vlastimil Babka
2014-06-09 9:26 ` [PATCH 02/10] mm, compaction: report compaction as contended only due to lock contention Vlastimil Babka
2014-06-09 23:50 ` David Rientjes
2014-06-10 7:11 ` Vlastimil Babka
2014-06-10 23:40 ` David Rientjes
2014-06-11 1:10 ` Minchan Kim
2014-06-11 12:22 ` Vlastimil Babka
2014-06-11 23:49 ` Minchan Kim
2014-06-12 14:02 ` Vlastimil Babka
2014-06-13 2:40 ` Minchan Kim
2014-06-20 11:47 ` Vlastimil Babka
2014-06-09 9:26 ` [PATCH 03/10] mm, compaction: periodically drop lock and restore IRQs in scanners Vlastimil Babka
2014-06-09 23:58 ` David Rientjes
2014-06-10 7:15 ` Vlastimil Babka
2014-06-10 23:41 ` David Rientjes
2014-06-11 1:32 ` Minchan Kim
2014-06-11 11:24 ` Vlastimil Babka
2014-06-09 9:26 ` [PATCH 04/10] mm, compaction: skip rechecks when lock was already held Vlastimil Babka
2014-06-10 0:00 ` David Rientjes
2014-06-11 1:50 ` Minchan Kim
2014-06-09 9:26 ` [PATCH 05/10] mm, compaction: remember position within pageblock in free pages scanner Vlastimil Babka
2014-06-10 0:07 ` David Rientjes
2014-06-11 2:12 ` Minchan Kim
2014-06-11 8:16 ` Joonsoo Kim
2014-06-11 11:41 ` Vlastimil Babka
2014-06-11 11:33 ` Vlastimil Babka
2014-06-11 3:29 ` Zhang Yanfei
2014-06-09 9:26 ` [PATCH 06/10] mm, compaction: skip buddy pages by their order in the migrate scanner Vlastimil Babka
2014-06-10 0:08 ` David Rientjes
2014-06-09 9:26 ` [PATCH 07/10] mm: rename allocflags_to_migratetype for clarity Vlastimil Babka
2014-06-11 2:41 ` Minchan Kim
2014-06-11 3:38 ` Zhang Yanfei
2014-06-09 9:26 ` [PATCH 08/10] mm, compaction: pass gfp mask to compact_control Vlastimil Babka
2014-06-11 2:48 ` Minchan Kim
2014-06-11 11:46 ` Vlastimil Babka
2014-06-12 0:24 ` David Rientjes
2014-06-09 9:26 ` [RFC PATCH 09/10] mm, compaction: try to capture the just-created high-order freepage Vlastimil Babka
2014-06-11 14:56 ` Vlastimil Babka
2014-06-12 2:20 ` Minchan Kim
2014-06-12 8:21 ` Vlastimil Babka
2014-06-09 9:26 ` [RFC PATCH 10/10] mm, compaction: do not migrate pages when that cannot satisfy page fault allocation Vlastimil Babka
2014-06-09 23:41 ` [PATCH 01/10] mm, compaction: do not recheck suitable_migration_target under lock David Rientjes
2014-06-11 0:33 ` Minchan Kim [this message]
2014-06-11 2:45 ` Zhang Yanfei
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