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From: Johannes Weiner <hannes@cmpxchg.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Mel Gorman <mgorman@techsingularity.net>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	David Rientjes <rientjes@google.com>,
	kernel-team@fb.com
Subject: Re: [PATCH v3 0/8] try to reduce fragmenting fallbacks
Date: Wed, 8 Mar 2017 11:46:31 -0500	[thread overview]
Message-ID: <20170308164631.GA12130@cmpxchg.org> (raw)
In-Reply-To: <20170307131545.28577-1-vbabka@suse.cz>

On Tue, Mar 07, 2017 at 02:15:37PM +0100, Vlastimil Babka wrote:
> Last year, Johannes Weiner has reported a regression in page mobility
> grouping [1] and while the exact cause was not found, I've come up with some
> ways to improve it by reducing the number of allocations falling back to
> different migratetype and causing permanent fragmentation.

I finally managed to get a handful of our machines on 4.10 with these
patches applied and a 4.10 vanilla control group.

The sampling period is over twelve hours, which is on the short side
for evaluating that load, so take the results with a grain of salt.

The allocstall rate (events per second) is down on average, but there
are occasionally fairly high spikes that exceed the peaks in 4.10:

http://cmpxchg.org/antifrag/allocstallrate.png

Activity from the compaction free scanner is down, while the migration
scanner does more work. I would assume most of this is coming from the
same-migratetype restriction on the source blocks:

http://cmpxchg.org/antifrag/compactfreescannedrate.png
http://cmpxchg.org/antifrag/compactmigratescannedrate.png

Unfortunately, the average compaction stall rate is consistently much
higher with the patches. The 1h rate averages are 2-3x higher:

http://cmpxchg.org/antifrag/compactstallrate.png

An increase in direct compaction is a bit worrisome, but the task
completion rates - the bottom line metric for this workload - are
still too chaotic to say whether the increased allocation latency
affects us meaningfully here. I'll give it a few more days.

Is there any other data you would like me to gather?

Thanks!

WARNING: multiple messages have this Message-ID
From: Johannes Weiner <hannes@cmpxchg.org>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-kernel@vger.kernel.org, linux-mm@kvack.org,
	Mel Gorman <mgorman@techsingularity.net>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	David Rientjes <rientjes@google.com>,
	kernel-team@fb.com
Subject: Re: [PATCH v3 0/8] try to reduce fragmenting fallbacks
Date: Wed, 8 Mar 2017 11:46:31 -0500	[thread overview]
Message-ID: <20170308164631.GA12130@cmpxchg.org> (raw)
In-Reply-To: <20170307131545.28577-1-vbabka@suse.cz>

On Tue, Mar 07, 2017 at 02:15:37PM +0100, Vlastimil Babka wrote:
> Last year, Johannes Weiner has reported a regression in page mobility
> grouping [1] and while the exact cause was not found, I've come up with some
> ways to improve it by reducing the number of allocations falling back to
> different migratetype and causing permanent fragmentation.

I finally managed to get a handful of our machines on 4.10 with these
patches applied and a 4.10 vanilla control group.

The sampling period is over twelve hours, which is on the short side
for evaluating that load, so take the results with a grain of salt.

The allocstall rate (events per second) is down on average, but there
are occasionally fairly high spikes that exceed the peaks in 4.10:

http://cmpxchg.org/antifrag/allocstallrate.png

Activity from the compaction free scanner is down, while the migration
scanner does more work. I would assume most of this is coming from the
same-migratetype restriction on the source blocks:

http://cmpxchg.org/antifrag/compactfreescannedrate.png
http://cmpxchg.org/antifrag/compactmigratescannedrate.png

Unfortunately, the average compaction stall rate is consistently much
higher with the patches. The 1h rate averages are 2-3x higher:

http://cmpxchg.org/antifrag/compactstallrate.png

An increase in direct compaction is a bit worrisome, but the task
completion rates - the bottom line metric for this workload - are
still too chaotic to say whether the increased allocation latency
affects us meaningfully here. I'll give it a few more days.

Is there any other data you would like me to gather?

Thanks!

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  parent reply	other threads:[~2017-03-08 17:24 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-07 13:15 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
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 ` Johannes Weiner [this message]
2017-03-08 16:46   ` [PATCH v3 0/8] try to reduce fragmenting fallbacks 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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