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From: Johannes Weiner <hannes@cmpxchg.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	David Rientjes <rientjes@google.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH v2 08/10] mm, compaction: finish whole pageblock to reduce fragmentation
Date: Thu, 16 Feb 2017 06:44:10 -0500	[thread overview]
Message-ID: <20170216114410.GA15895@cmpxchg.org> (raw)
In-Reply-To: <20170210172343.30283-9-vbabka@suse.cz>

On Fri, Feb 10, 2017 at 06:23:41PM +0100, Vlastimil Babka wrote:
> The main goal of direct compaction is to form a high-order page for allocation,
> but it should also help against long-term fragmentation when possible. Most
> lower-than-pageblock-order compactions are for non-movable allocations, which
> means that if we compact in a movable pageblock and terminate as soon as we
> create the high-order page, it's unlikely that the fallback heuristics will
> claim the whole block. Instead there might be a single unmovable page in a
> pageblock full of movable pages, and the next unmovable allocation might pick
> another pageblock and increase long-term fragmentation.
> 
> To help against such scenarios, this patch changes the termination criteria for
> compaction so that the current pageblock is finished even though the high-order
> page already exists. Note that it might be possible that the high-order page
> formed elsewhere in the zone due to parallel activity, but this patch doesn't
> try to detect that.
> 
> This is only done with sync compaction, because async compaction is limited to
> pageblock of the same migratetype, where it cannot result in a migratetype
> fallback. (Async compaction also eagerly skips order-aligned blocks where
> isolation fails, which is against the goal of migrating away as much of the
> pageblock as possible.)
> 
> As a result of this patch, long-term memory fragmentation should be reduced.
> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

WARNING: multiple messages have this Message-ID (diff)
From: Johannes Weiner <hannes@cmpxchg.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	David Rientjes <rientjes@google.com>,
	Mel Gorman <mgorman@techsingularity.net>,
	linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH v2 08/10] mm, compaction: finish whole pageblock to reduce fragmentation
Date: Thu, 16 Feb 2017 06:44:10 -0500	[thread overview]
Message-ID: <20170216114410.GA15895@cmpxchg.org> (raw)
In-Reply-To: <20170210172343.30283-9-vbabka@suse.cz>

On Fri, Feb 10, 2017 at 06:23:41PM +0100, Vlastimil Babka wrote:
> The main goal of direct compaction is to form a high-order page for allocation,
> but it should also help against long-term fragmentation when possible. Most
> lower-than-pageblock-order compactions are for non-movable allocations, which
> means that if we compact in a movable pageblock and terminate as soon as we
> create the high-order page, it's unlikely that the fallback heuristics will
> claim the whole block. Instead there might be a single unmovable page in a
> pageblock full of movable pages, and the next unmovable allocation might pick
> another pageblock and increase long-term fragmentation.
> 
> To help against such scenarios, this patch changes the termination criteria for
> compaction so that the current pageblock is finished even though the high-order
> page already exists. Note that it might be possible that the high-order page
> formed elsewhere in the zone due to parallel activity, but this patch doesn't
> try to detect that.
> 
> This is only done with sync compaction, because async compaction is limited to
> pageblock of the same migratetype, where it cannot result in a migratetype
> fallback. (Async compaction also eagerly skips order-aligned blocks where
> isolation fails, which is against the goal of migrating away as much of the
> pageblock as possible.)
> 
> As a result of this patch, long-term memory fragmentation should be reduced.
> 
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Acked-by: Johannes Weiner <hannes@cmpxchg.org>

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  parent reply	other threads:[~2017-02-16 11:44 UTC|newest]

Thread overview: 92+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-02-10 17:23 [PATCH v2 00/10] try to reduce fragmenting fallbacks Vlastimil Babka
2017-02-10 17:23 ` Vlastimil Babka
2017-02-10 17:23 ` [PATCH v2 01/10] mm, compaction: reorder fields in struct compact_control Vlastimil Babka
2017-02-10 17:23   ` Vlastimil Babka
2017-02-13 10:49   ` Mel Gorman
2017-02-13 10:49     ` Mel Gorman
2017-02-14 16:33   ` Johannes Weiner
2017-02-14 16:33     ` Johannes Weiner
2017-02-10 17:23 ` [PATCH v2 02/10] mm, compaction: remove redundant watermark check in compact_finished() Vlastimil Babka
2017-02-10 17:23   ` Vlastimil Babka
2017-02-13 10:49   ` Mel Gorman
2017-02-13 10:49     ` Mel Gorman
2017-02-14 16:34   ` Johannes Weiner
2017-02-14 16:34     ` Johannes Weiner
2017-02-10 17:23 ` [PATCH v2 03/10] mm, page_alloc: split smallest stolen page in fallback Vlastimil Babka
2017-02-10 17:23   ` Vlastimil Babka
2017-02-13 10:51   ` Mel Gorman
2017-02-13 10:51     ` Mel Gorman
2017-02-13 10:54     ` Vlastimil Babka
2017-02-13 10:54       ` Vlastimil Babka
2017-02-14 16:59   ` Johannes Weiner
2017-02-14 16:59     ` Johannes Weiner
2017-02-10 17:23 ` [PATCH v2 04/10] mm, page_alloc: count movable pages when stealing from pageblock Vlastimil Babka
2017-02-10 17:23   ` Vlastimil Babka
2017-02-13 10:53   ` Mel Gorman
2017-02-13 10:53     ` Mel Gorman
2017-02-14 10:07   ` Xishi Qiu
2017-02-14 10:07     ` Xishi Qiu
2017-02-15 10:47     ` Vlastimil Babka
2017-02-15 10:47       ` Vlastimil Babka
2017-02-15 11:56       ` Xishi Qiu
2017-02-15 11:56         ` Xishi Qiu
2017-02-17 16:21         ` Vlastimil Babka
2017-02-17 16:21           ` Vlastimil Babka
2017-02-14 18:10   ` Johannes Weiner
2017-02-14 18:10     ` Johannes Weiner
2017-02-17 16:09     ` Vlastimil Babka
2017-02-17 16:09       ` Vlastimil Babka
2017-02-10 17:23 ` [PATCH v2 05/10] mm, compaction: change migrate_async_suitable() to suitable_migration_source() Vlastimil Babka
2017-02-10 17:23   ` Vlastimil Babka
2017-02-13 10:53   ` Mel Gorman
2017-02-13 10:53     ` Mel Gorman
2017-02-14 18:12   ` Johannes Weiner
2017-02-14 18:12     ` Johannes Weiner
2017-02-10 17:23 ` [PATCH v2 06/10] mm, compaction: add migratetype to compact_control Vlastimil Babka
2017-02-10 17:23   ` Vlastimil Babka
2017-02-13 10:53   ` Mel Gorman
2017-02-13 10:53     ` Mel Gorman
2017-02-14 18:15   ` Johannes Weiner
2017-02-14 18:15     ` Johannes Weiner
2017-02-10 17:23 ` [PATCH v2 07/10] mm, compaction: restrict async compaction to pageblocks of same migratetype Vlastimil Babka
2017-02-10 17:23   ` Vlastimil Babka
2017-02-13 10:56   ` Mel Gorman
2017-02-13 10:56     ` Mel Gorman
2017-02-14 20:10   ` Johannes Weiner
2017-02-14 20:10     ` Johannes Weiner
2017-02-17 16:32     ` Vlastimil Babka
2017-02-17 16:32       ` Vlastimil Babka
2017-02-17 17:39       ` Johannes Weiner
2017-02-17 17:39         ` Johannes Weiner
2017-02-10 17:23 ` [PATCH v2 08/10] mm, compaction: finish whole pageblock to reduce fragmentation Vlastimil Babka
2017-02-10 17:23   ` Vlastimil Babka
2017-02-13 10:57   ` Mel Gorman
2017-02-13 10:57     ` Mel Gorman
2017-02-16 11:44   ` Johannes Weiner [this message]
2017-02-16 11:44     ` Johannes Weiner
2017-02-10 17:23 ` [RFC v2 09/10] mm, page_alloc: disallow migratetype fallback in fastpath Vlastimil Babka
2017-02-10 17:23   ` Vlastimil Babka
2017-02-10 17:23 ` [RFC v2 10/10] mm, page_alloc: introduce MIGRATE_MIXED migratetype Vlastimil Babka
2017-02-10 17:23   ` Vlastimil Babka
2017-03-08  2:16   ` Yisheng Xie
2017-03-08  2:16     ` Yisheng Xie
2017-03-08  7:07     ` Vlastimil Babka
2017-03-08  7:07       ` Vlastimil Babka
2017-03-13  2:16       ` Yisheng Xie
2017-03-13  2:16         ` Yisheng Xie
2017-02-13 11:07 ` [PATCH v2 00/10] try to reduce fragmenting fallbacks Mel Gorman
2017-02-13 11:07   ` Mel Gorman
2017-02-15 14:29   ` Vlastimil Babka
2017-02-15 14:29     ` Vlastimil Babka
2017-02-15 16:11     ` Vlastimil Babka
2017-02-15 16:11       ` Vlastimil Babka
2017-02-15 20:11       ` Vlastimil Babka
2017-02-15 20:11         ` Vlastimil Babka
2017-02-16 15:12     ` Vlastimil Babka
2017-02-16 15:12       ` Vlastimil Babka
2017-02-17 15:24       ` Vlastimil Babka
2017-02-17 15:24         ` Vlastimil Babka
2017-02-20 12:30   ` Vlastimil Babka
2017-02-20 12:30     ` Vlastimil Babka
2017-02-23 16:01     ` Mel Gorman
2017-02-23 16:01       ` Mel Gorman

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