From: Mel Gorman <mgorman@techsingularity.net>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: linux-mm@kvack.org, Johannes Weiner <hannes@cmpxchg.org>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
David Rientjes <rientjes@google.com>,
linux-kernel@vger.kernel.org, kernel-team@fb.com
Subject: Re: [PATCH v2 07/10] mm, compaction: restrict async compaction to pageblocks of same migratetype
Date: Mon, 13 Feb 2017 10:56:56 +0000 [thread overview]
Message-ID: <20170213105656.2pp5mrdhlkvh73tr@techsingularity.net> (raw)
In-Reply-To: <20170210172343.30283-8-vbabka@suse.cz>
On Fri, Feb 10, 2017 at 06:23:40PM +0100, Vlastimil Babka wrote:
> The migrate scanner in async compaction is currently limited to MIGRATE_MOVABLE
> pageblocks. This is a heuristic intended to reduce latency, based on the
> assumption that non-MOVABLE pageblocks are unlikely to contain movable pages.
>
> However, with the exception of THP's, most high-order allocations are not
> movable. Should the async compaction succeed, this increases the chance that
> the non-MOVABLE allocations will fallback to a MOVABLE pageblock, making the
> long-term fragmentation worse.
>
> This patch attempts to help the situation by changing async direct compaction
> so that the migrate scanner only scans the pageblocks of the requested
> migratetype. If it's a non-MOVABLE type and there are such pageblocks that do
> contain movable pages, chances are that the allocation can succeed within one
> of such pageblocks, removing the need for a fallback. If that fails, the
> subsequent sync attempt will ignore this restriction.
>
> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Ok, I really like this idea. The thinking of async originally was to
reduce latency but that was also at the time when THP allocations were
stalling for long periods of time. Now that the default has changed,
this idea makes a lot of sense. A few months ago I would have thought
that this will increase the changes that a high-order allocation for the
stack may have a higher chance of failing but with VMAP_STACK, this is
much less of a concern. It would be very nice to know for this patch if
the number of times the extfrag tracepoint is triggered is reduced or
increased by this patch. Do you have that data?
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2017-02-13 10:57 UTC|newest]
Thread overview: 46+ 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 ` [PATCH v2 01/10] mm, compaction: reorder fields in struct compact_control Vlastimil Babka
2017-02-13 10:49 ` Mel Gorman
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
2017-02-13 10:49 ` Mel Gorman
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
2017-02-13 10:51 ` Mel Gorman
2017-02-13 10:54 ` Vlastimil Babka
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
2017-02-13 10:53 ` Mel Gorman
2017-02-14 10:07 ` Xishi Qiu
2017-02-15 10:47 ` Vlastimil Babka
2017-02-15 11:56 ` Xishi Qiu
2017-02-17 16:21 ` Vlastimil Babka
2017-02-14 18:10 ` Johannes Weiner
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
2017-02-13 10:53 ` Mel Gorman
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
2017-02-13 10:53 ` Mel Gorman
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
2017-02-13 10:56 ` Mel Gorman [this message]
2017-02-14 20:10 ` Johannes Weiner
2017-02-17 16:32 ` Vlastimil Babka
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
2017-02-13 10:57 ` Mel Gorman
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 ` [RFC v2 10/10] mm, page_alloc: introduce MIGRATE_MIXED migratetype Vlastimil Babka
2017-03-08 2:16 ` Yisheng Xie
2017-03-08 7:07 ` Vlastimil Babka
2017-03-13 2:16 ` Yisheng Xie
2017-02-13 11:07 ` [PATCH v2 00/10] try to reduce fragmenting fallbacks Mel Gorman
2017-02-15 14:29 ` Vlastimil Babka
2017-02-15 16:11 ` Vlastimil Babka
2017-02-15 20:11 ` Vlastimil Babka
2017-02-16 15:12 ` Vlastimil Babka
2017-02-17 15:24 ` Vlastimil Babka
2017-02-20 12:30 ` Vlastimil Babka
2017-02-23 16:01 ` Mel Gorman
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20170213105656.2pp5mrdhlkvh73tr@techsingularity.net \
--to=mgorman@techsingularity.net \
--cc=hannes@cmpxchg.org \
--cc=iamjoonsoo.kim@lge.com \
--cc=kernel-team@fb.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=rientjes@google.com \
--cc=vbabka@suse.cz \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).