From: Mel Gorman <mgorman@techsingularity.net>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Linux-MM <linux-mm@kvack.org>,
David Rientjes <rientjes@google.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Michal Hocko <mhocko@kernel.org>,
ying.huang@intel.com, kirill@shutemov.name,
Andrew Morton <akpm@linux-foundation.org>,
Linux List Kernel Mailing <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 06/14] mm, migrate: Immediately fail migration of a page with no migration handler
Date: Tue, 18 Dec 2018 09:55:10 +0000 [thread overview]
Message-ID: <20181218095510.GJ29005@techsingularity.net> (raw)
In-Reply-To: <0ef5c1d0-1853-8fdb-1a68-7482297cb802@suse.cz>
On Tue, Dec 18, 2018 at 10:06:31AM +0100, Vlastimil Babka wrote:
> On 12/15/18 12:03 AM, Mel Gorman wrote:
> > Pages with no migration handler use a fallback hander which sometimes
> > works and sometimes persistently fails such as blockdev pages. Migration
> > will retry a number of times on these persistent pages which is wasteful
> > during compaction. This patch will fail migration immediately unless the
> > caller is in MIGRATE_SYNC mode which indicates the caller is willing to
> > wait while being persistent.
>
> Right.
>
> > This is not expected to help THP allocation success rates but it does
> > reduce latencies slightly.
> >
> > 1-socket thpfioscale
> > 4.20.0-rc6 4.20.0-rc6
> > noreserved-v1r4 failfast-v1r4
> > Amean fault-both-1 0.00 ( 0.00%) 0.00 * 0.00%*
> > Amean fault-both-3 2276.15 ( 0.00%) 3867.54 * -69.92%*
>
> This is rather weird.
>
Fault latency is extremely variable and there can be very large outliers
that skew the mean (the full report includes quartiles but it makes for an
excessive changelog). It can be down to luck about how often the migrate
scanner advances and how often it gets reset. For this series, it'll
not be unusual to see jitter in the latencies for individual patches
that will not get nailed down reliably until later in the series. The
alternative is massive patches that do multiple things which will look
nice in changelogs and be horrible to review.
> > Amean fault-both-5 4992.20 ( 0.00%) 5313.20 ( -6.43%)
> > Amean fault-both-7 7373.30 ( 0.00%) 7039.11 ( 4.53%)
> > Amean fault-both-12 11911.52 ( 0.00%) 11328.29 ( 4.90%)
> > Amean fault-both-18 17209.42 ( 0.00%) 16455.34 ( 4.38%)
> > Amean fault-both-24 20943.71 ( 0.00%) 20448.94 ( 2.36%)
> > Amean fault-both-30 22703.00 ( 0.00%) 21655.07 ( 4.62%)
> > Amean fault-both-32 22461.41 ( 0.00%) 21415.35 ( 4.66%)
> >
> > The 2-socket results are not materially different. Scan rates are
> > similar as expected.
> >
> > Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
>
> Acked-by: Vlastimil Babka <vbabka@suse.cz>
>
Thanks.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2018-12-18 9:55 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-12-14 23:02 [RFC PATCH 00/14] Increase success rates and reduce latency of compaction v1 Mel Gorman
2018-12-14 23:02 ` [PATCH 01/14] mm, compaction: Shrink compact_control Mel Gorman
2018-12-17 12:27 ` Vlastimil Babka
2018-12-14 23:02 ` [PATCH 02/14] mm, compaction: Rearrange compact_control Mel Gorman
2018-12-17 13:20 ` Vlastimil Babka
2018-12-14 23:02 ` [PATCH 03/14] mm, compaction: Remove last_migrated_pfn from compact_control Mel Gorman
2018-12-17 13:50 ` Vlastimil Babka
2018-12-14 23:03 ` [PATCH 04/14] mm, compaction: Rename map_pages to split_map_pages Mel Gorman
2018-12-17 14:06 ` Vlastimil Babka
2018-12-17 14:30 ` Mel Gorman
2018-12-14 23:03 ` [PATCH 05/14] mm, compaction: Skip pageblocks with reserved pages Mel Gorman
2018-12-18 8:08 ` Vlastimil Babka
2018-12-18 8:38 ` Mel Gorman
2018-12-14 23:03 ` [PATCH 06/14] mm, migrate: Immediately fail migration of a page with no migration handler Mel Gorman
2018-12-18 9:06 ` Vlastimil Babka
2018-12-18 9:55 ` Mel Gorman [this message]
2018-12-20 19:44 ` Yang Shi
2018-12-20 19:44 ` Yang Shi
2018-12-20 20:31 ` Mel Gorman
2018-12-14 23:03 ` [PATCH 07/14] mm, compaction: Always finish scanning of a full pageblock Mel Gorman
2018-12-18 9:23 ` Vlastimil Babka
2018-12-14 23:03 ` [PATCH 08/14] mm, compaction: Use the page allocator bulk-free helper for lists of pages Mel Gorman
2018-12-18 9:55 ` Vlastimil Babka
2018-12-19 16:04 ` Mel Gorman
2018-12-14 23:03 ` [PATCH 09/14] mm, compaction: Ignore the fragmentation avoidance boost for isolation and compaction Mel Gorman
2018-12-18 12:36 ` Vlastimil Babka
2018-12-18 13:51 ` Mel Gorman
2018-12-18 13:58 ` Vlastimil Babka
2018-12-18 14:29 ` Mel Gorman
2018-12-14 23:04 ` [PATCH 10/14] mm, compaction: Use free lists to quickly locate a migration source Mel Gorman
2018-12-14 23:05 ` [PATCH 11/14] mm, compaction: Keep migration source private to a single compaction instance Mel Gorman
2018-12-14 23:05 ` [PATCH 12/14] mm, compaction: Use free lists to quickly locate a migration target Mel Gorman
2018-12-14 23:05 ` [PATCH 13/14] mm, compaction: Capture a page under direct compaction Mel Gorman
2018-12-14 23:06 ` [PATCH 14/14] mm, compaction: Do not direct compact remote memory Mel Gorman
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