From: Mel Gorman <mgorman@suse.de>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Linux-MM <linux-mm@kvack.org>, Jiri Slaby <jslaby@suse.cz>,
Valdis Kletnieks <Valdis.Kletnieks@vt.edu>,
Rik van Riel <riel@redhat.com>,
Zlatko Calusic <zcalusic@bitsync.net>,
dormando <dormando@rydia.net>,
Satoru Moriya <satoru.moriya@hds.com>,
Michal Hocko <mhocko@suse.cz>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority
Date: Thu, 21 Mar 2013 16:47:37 +0000 [thread overview]
Message-ID: <20130321164737.GL1878@suse.de> (raw)
In-Reply-To: <20130321155705.GA27848@cmpxchg.org>
On Thu, Mar 21, 2013 at 11:57:05AM -0400, Johannes Weiner wrote:
> On Sun, Mar 17, 2013 at 01:04:07PM +0000, Mel Gorman wrote:
> > The number of pages kswapd can reclaim is bound by the number of pages it
> > scans which is related to the size of the zone and the scanning priority. In
> > many cases the priority remains low because it's reset every SWAP_CLUSTER_MAX
> > reclaimed pages but in the event kswapd scans a large number of pages it
> > cannot reclaim, it will raise the priority and potentially discard a large
> > percentage of the zone as sc->nr_to_reclaim is ULONG_MAX. The user-visible
> > effect is a reclaim "spike" where a large percentage of memory is suddenly
> > freed. It would be bad enough if this was just unused memory but because
> > of how anon/file pages are balanced it is possible that applications get
> > pushed to swap unnecessarily.
> >
> > This patch limits the number of pages kswapd will reclaim to the high
> > watermark. Reclaim will will overshoot due to it not being a hard limit as
>
> will -> still?
>
> > shrink_lruvec() will ignore the sc.nr_to_reclaim at DEF_PRIORITY but it
> > prevents kswapd reclaiming the world at higher priorities. The number of
> > pages it reclaims is not adjusted for high-order allocations as kswapd will
> > reclaim excessively if it is to balance zones for high-order allocations.
>
> I don't really understand this last sentence. Is the excessive
> reclaim a result of the patch, a description of what's happening
> now...?
>
It's a very basic description of what happens now and with the patch
applied. Until patch 5 is applied, kswapd can still reclaim the world if
it reaches priority 0.
> > Signed-off-by: Mel Gorman <mgorman@suse.de>
>
> Nice, thank you. Using the high watermark for larger zones is more
> reasonable than my hack that just always went with SWAP_CLUSTER_MAX,
> what with inter-zone LRU cycle time balancing and all.
>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Thanks.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2013-03-21 16:47 UTC|newest]
Thread overview: 124+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-17 13:04 [RFC PATCH 0/8] Reduce system disruption due to kswapd Mel Gorman
2013-03-17 13:04 ` [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority Mel Gorman
2013-03-18 23:53 ` Simon Jeons
2013-03-19 9:55 ` Mel Gorman
2013-03-19 10:16 ` Simon Jeons
2013-03-19 10:59 ` Mel Gorman
2013-03-20 16:18 ` Michal Hocko
2013-03-21 0:52 ` Rik van Riel
2013-03-22 0:08 ` Will Huck
2013-03-21 9:47 ` Mel Gorman
2013-03-21 12:59 ` Michal Hocko
2013-03-21 0:51 ` Rik van Riel
2013-03-21 15:57 ` Johannes Weiner
2013-03-21 16:47 ` Mel Gorman [this message]
2013-03-22 0:05 ` Will Huck
2013-03-22 3:52 ` Rik van Riel
2013-03-22 3:56 ` Will Huck
2013-03-22 4:59 ` Will Huck
2013-03-22 13:01 ` Rik van Riel
2013-04-05 0:05 ` Will Huck
2013-04-07 7:32 ` Will Huck
2013-04-07 7:35 ` Will Huck
2013-04-11 5:54 ` Will Huck
2013-04-11 5:58 ` Will Huck
2013-04-12 5:46 ` Ric Mason
2013-04-12 9:34 ` Mel Gorman
2013-04-12 13:40 ` Rik van Riel
2013-03-25 9:07 ` Michal Hocko
2013-03-25 9:13 ` Jiri Slaby
2013-03-28 22:31 ` Jiri Slaby
2013-03-29 8:22 ` Michal Hocko
2013-03-30 22:07 ` Jiri Slaby
2013-04-02 11:15 ` Mel Gorman
2013-03-17 13:04 ` [PATCH 02/10] mm: vmscan: Obey proportional scanning requirements for kswapd Mel Gorman
2013-03-17 14:39 ` Andi Kleen
2013-03-17 15:08 ` Mel Gorman
2013-03-21 1:10 ` Rik van Riel
2013-03-21 9:54 ` Mel Gorman
2013-03-21 14:01 ` Michal Hocko
2013-03-21 14:31 ` Mel Gorman
2013-03-21 15:07 ` Michal Hocko
2013-03-21 15:34 ` Mel Gorman
2013-03-22 7:54 ` Michal Hocko
2013-03-22 8:37 ` Mel Gorman
2013-03-22 10:04 ` Michal Hocko
2013-03-22 10:47 ` Michal Hocko
2013-03-21 16:25 ` Johannes Weiner
2013-03-21 18:02 ` Mel Gorman
2013-03-22 16:53 ` Johannes Weiner
2013-03-22 18:25 ` Mel Gorman
2013-03-22 19:09 ` Johannes Weiner
2013-03-22 19:46 ` Mel Gorman
2013-03-17 13:04 ` [PATCH 03/10] mm: vmscan: Flatten kswapd priority loop Mel Gorman
2013-03-17 14:36 ` Andi Kleen
2013-03-17 15:09 ` Mel Gorman
2013-03-18 23:58 ` Simon Jeons
2013-03-19 10:12 ` Mel Gorman
2013-03-19 3:08 ` Simon Jeons
2013-03-19 8:23 ` Michal Hocko
2013-03-19 10:14 ` Mel Gorman
2013-03-19 10:26 ` Simon Jeons
2013-03-19 11:01 ` Mel Gorman
2013-03-21 14:54 ` Michal Hocko
2013-03-21 15:26 ` Mel Gorman
2013-03-21 15:38 ` Michal Hocko
2013-03-17 13:04 ` [PATCH 04/10] mm: vmscan: Decide whether to compact the pgdat based on reclaim progress Mel Gorman
2013-03-18 11:35 ` Hillf Danton
2013-03-19 10:27 ` Mel Gorman
[not found] ` <20130318111130.GA7245@hacker.(null)>
2013-03-19 10:19 ` Mel Gorman
2013-03-21 15:32 ` Michal Hocko
2013-03-21 15:47 ` Mel Gorman
2013-03-21 15:50 ` Michal Hocko
2013-03-17 13:04 ` [PATCH 05/10] mm: vmscan: Do not allow kswapd to scan at maximum priority Mel Gorman
2013-03-21 1:20 ` Rik van Riel
2013-03-21 10:12 ` Mel Gorman
2013-03-21 12:30 ` Rik van Riel
2013-03-21 15:48 ` Michal Hocko
2013-03-17 13:04 ` [PATCH 06/10] mm: vmscan: Have kswapd writeback pages based on dirty pages encountered, not priority Mel Gorman
2013-03-17 14:42 ` Andi Kleen
2013-03-17 15:11 ` Mel Gorman
2013-03-21 17:53 ` Rik van Riel
2013-03-21 18:15 ` Mel Gorman
2013-03-21 18:21 ` Rik van Riel
[not found] ` <20130318110850.GA7144@hacker.(null)>
2013-03-19 10:35 ` Mel Gorman
2013-03-17 13:04 ` [PATCH 07/10] mm: vmscan: Block kswapd if it is encountering pages under writeback Mel Gorman
2013-03-17 14:49 ` Andi Kleen
2013-03-17 15:19 ` Mel Gorman
2013-03-17 15:40 ` Andi Kleen
2013-03-19 11:06 ` Mel Gorman
2013-03-18 11:37 ` Simon Jeons
2013-03-19 10:57 ` Mel Gorman
[not found] ` <20130318115827.GB7245@hacker.(null)>
2013-03-19 10:58 ` Mel Gorman
2013-03-21 16:32 ` [PATCH 07/10 -v2r1] " Michal Hocko
2013-03-21 18:42 ` [PATCH 07/10] " Rik van Riel
2013-03-22 8:27 ` Mel Gorman
2013-03-17 13:04 ` [PATCH 08/10] mm: vmscan: Have kswapd shrink slab only once per priority Mel Gorman
2013-03-17 14:53 ` Andi Kleen
2013-03-21 16:47 ` Michal Hocko
2013-03-21 19:47 ` Rik van Riel
2013-04-09 6:53 ` Joonsoo Kim
2013-04-09 8:41 ` Simon Jeons
2013-04-09 11:13 ` Mel Gorman
2013-04-10 1:07 ` Dave Chinner
2013-04-10 5:23 ` Joonsoo Kim
2013-04-11 9:53 ` Mel Gorman
2013-04-10 5:21 ` Joonsoo Kim
2013-04-11 10:01 ` Mel Gorman
2013-04-11 10:29 ` Ric Mason
2013-03-17 13:04 ` [PATCH 09/10] mm: vmscan: Check if kswapd should writepage " Mel Gorman
2013-03-21 16:58 ` Michal Hocko
2013-03-21 18:07 ` Mel Gorman
2013-03-21 19:52 ` Rik van Riel
2013-03-17 13:04 ` [PATCH 10/10] mm: vmscan: Move logic from balance_pgdat() to kswapd_shrink_zone() Mel Gorman
2013-03-17 14:55 ` Andi Kleen
2013-03-17 15:25 ` Mel Gorman
2013-03-21 17:18 ` Michal Hocko
2013-03-21 18:13 ` Mel Gorman
2013-03-22 14:37 ` [RFC PATCH 0/8] Reduce system disruption due to kswapd Mel Gorman
2013-03-24 19:00 ` Jiri Slaby
2013-03-25 8:17 ` Michal Hocko
-- strict thread matches above, loose matches on Subject: below --
2013-04-09 11:06 [PATCH 0/10] Reduce system disruption due to kswapd V2 Mel Gorman
2013-04-09 11:06 ` [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority Mel Gorman
2013-04-09 13:27 ` Michal Hocko
2013-04-10 6:47 ` Kamezawa Hiroyuki
2013-04-11 19:57 [PATCH 0/10] Reduce system disruption due to kswapd V3 Mel Gorman
2013-04-11 19:57 ` [PATCH 01/10] mm: vmscan: Limit the number of pages kswapd reclaims at each priority Mel Gorman
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