From: Joonsoo Kim <iamjoonsoo.kim@lge.com> To: Vlastimil Babka <vbabka@suse.cz> Cc: Andrew Morton <akpm@linux-foundation.org>, <linux-kernel@vger.kernel.org>, <linux-mm@kvack.org>, Johannes Weiner <hannes@cmpxchg.org>, Mel Gorman <mgorman@techsingularity.net>, David Rientjes <rientjes@google.com>, <kernel-team@fb.com>, <kernel-team@lge.com> Subject: Re: [PATCH v3 2/8] mm, compaction: remove redundant watermark check in compact_finished() Date: Thu, 16 Mar 2017 10:30:19 +0900 [thread overview] Message-ID: <20170316013018.GA14063@js1304-P5Q-DELUXE> (raw) In-Reply-To: <20170307131545.28577-3-vbabka@suse.cz> Hello, On Tue, Mar 07, 2017 at 02:15:39PM +0100, Vlastimil Babka wrote: > When detecting whether compaction has succeeded in forming a high-order page, > __compact_finished() employs a watermark check, followed by an own search for > a suitable page in the freelists. This is not ideal for two reasons: > > - The watermark check also searches high-order freelists, but has a less strict > criteria wrt fallback. It's therefore redundant and waste of cycles. This was > different in the past when high-order watermark check attempted to apply > reserves to high-order pages. Although it looks redundant now, I don't like removal of the watermark check here. Criteria in watermark check would be changed to more strict later and we would easily miss to apply it on compaction side if the watermark check is removed. > > - The watermark check might actually fail due to lack of order-0 pages. > Compaction can't help with that, so there's no point in continuing because of > that. It's possible that high-order page still exists and it terminates. If lack of order-0 pages is the reason for stopping compaction, we need to insert the watermark check for order-0 to break the compaction instead of removing it. Am I missing something? Thanks.
WARNING: multiple messages have this Message-ID (diff)
From: Joonsoo Kim <iamjoonsoo.kim@lge.com> To: Vlastimil Babka <vbabka@suse.cz> Cc: Andrew Morton <akpm@linux-foundation.org>, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Johannes Weiner <hannes@cmpxchg.org>, Mel Gorman <mgorman@techsingularity.net>, David Rientjes <rientjes@google.com>, kernel-team@fb.com, kernel-team@lge.com Subject: Re: [PATCH v3 2/8] mm, compaction: remove redundant watermark check in compact_finished() Date: Thu, 16 Mar 2017 10:30:19 +0900 [thread overview] Message-ID: <20170316013018.GA14063@js1304-P5Q-DELUXE> (raw) In-Reply-To: <20170307131545.28577-3-vbabka@suse.cz> Hello, On Tue, Mar 07, 2017 at 02:15:39PM +0100, Vlastimil Babka wrote: > When detecting whether compaction has succeeded in forming a high-order page, > __compact_finished() employs a watermark check, followed by an own search for > a suitable page in the freelists. This is not ideal for two reasons: > > - The watermark check also searches high-order freelists, but has a less strict > criteria wrt fallback. It's therefore redundant and waste of cycles. This was > different in the past when high-order watermark check attempted to apply > reserves to high-order pages. Although it looks redundant now, I don't like removal of the watermark check here. Criteria in watermark check would be changed to more strict later and we would easily miss to apply it on compaction side if the watermark check is removed. > > - The watermark check might actually fail due to lack of order-0 pages. > Compaction can't help with that, so there's no point in continuing because of > that. It's possible that high-order page still exists and it terminates. If lack of order-0 pages is the reason for stopping compaction, we need to insert the watermark check for order-0 to break the compaction instead of removing it. Am I missing something? Thanks. -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2017-03-16 1:29 UTC|newest] Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-03-07 13:15 [PATCH v3 0/8] try to reduce fragmenting fallbacks Vlastimil Babka 2017-03-07 13:15 ` Vlastimil Babka 2017-03-07 13:15 ` [PATCH v3 1/8] mm, compaction: reorder fields in struct compact_control Vlastimil Babka 2017-03-07 13:15 ` Vlastimil Babka 2017-03-07 13:15 ` [PATCH v3 2/8] mm, compaction: remove redundant watermark check in compact_finished() Vlastimil Babka 2017-03-07 13:15 ` Vlastimil Babka 2017-03-16 1:30 ` Joonsoo Kim [this message] 2017-03-16 1:30 ` Joonsoo Kim 2017-03-29 15:30 ` Vlastimil Babka 2017-03-29 15:30 ` Vlastimil Babka 2017-03-07 13:15 ` [PATCH v3 3/8] mm, page_alloc: split smallest stolen page in fallback Vlastimil Babka 2017-03-07 13:15 ` Vlastimil Babka 2017-03-07 13:15 ` [PATCH v3 4/8] mm, page_alloc: count movable pages when stealing from pageblock Vlastimil Babka 2017-03-07 13:15 ` Vlastimil Babka 2017-03-16 1:53 ` Joonsoo Kim 2017-03-16 1:53 ` Joonsoo Kim 2017-03-29 15:49 ` Vlastimil Babka 2017-03-29 15:49 ` Vlastimil Babka 2017-03-07 13:15 ` [PATCH v3 5/8] mm, compaction: change migrate_async_suitable() to suitable_migration_source() Vlastimil Babka 2017-03-07 13:15 ` Vlastimil Babka 2017-03-07 13:15 ` [PATCH v3 6/8] mm, compaction: add migratetype to compact_control Vlastimil Babka 2017-03-07 13:15 ` Vlastimil Babka 2017-03-07 13:15 ` [PATCH v3 7/8] mm, compaction: restrict async compaction to pageblocks of same migratetype Vlastimil Babka 2017-03-07 13:15 ` Vlastimil Babka 2017-03-16 2:14 ` Joonsoo Kim 2017-03-16 2:14 ` Joonsoo Kim 2017-03-29 16:06 ` Vlastimil Babka 2017-03-29 16:06 ` Vlastimil Babka 2017-04-07 0:38 ` Joonsoo Kim 2017-04-07 0:38 ` Joonsoo Kim 2017-05-04 6:12 ` Vlastimil Babka 2017-05-04 6:12 ` Vlastimil Babka 2017-03-07 13:15 ` [PATCH v3 8/8] mm, compaction: finish whole pageblock to reduce fragmentation Vlastimil Babka 2017-03-07 13:15 ` Vlastimil Babka 2017-03-16 2:18 ` Joonsoo Kim 2017-03-16 2:18 ` Joonsoo Kim 2017-03-29 16:13 ` Vlastimil Babka 2017-03-29 16:13 ` Vlastimil Babka 2017-03-08 16:46 ` [PATCH v3 0/8] try to reduce fragmenting fallbacks Johannes Weiner 2017-03-08 16:46 ` Johannes Weiner 2017-03-08 19:17 ` Vlastimil Babka 2017-03-08 19:17 ` Vlastimil Babka 2017-03-16 18:34 ` Johannes Weiner 2017-03-16 18:34 ` Johannes Weiner 2017-03-17 18:29 ` Vlastimil Babka 2017-03-17 18:29 ` Vlastimil Babka 2017-03-19 21:23 ` Johannes Weiner 2017-03-19 21:23 ` Johannes Weiner
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