From: Andrew Morton <akpm@linux-foundation.org>
To: Mel Gorman <mgorman@suse.de>
Cc: Jiri Slaby <jslaby@suse.cz>,
Valdis Kletnieks <Valdis.Kletnieks@vt.edu>,
Rik van Riel <riel@redhat.com>,
Zlatko Calusic <zcalusic@bitsync.net>,
Johannes Weiner <hannes@cmpxchg.org>,
dormando <dormando@rydia.net>, Michal Hocko <mhocko@suse.cz>,
Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Linux-MM <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 0/9] Reduce system disruption due to kswapd V4
Date: Wed, 15 May 2013 13:37:48 -0700 [thread overview]
Message-ID: <20130515133748.5db2c6fb61c72ec61381d941@linux-foundation.org> (raw)
In-Reply-To: <1368432760-21573-1-git-send-email-mgorman@suse.de>
On Mon, 13 May 2013 09:12:31 +0100 Mel Gorman <mgorman@suse.de> wrote:
> This series does not fix all the current known problems with reclaim but
> it addresses one important swapping bug when there is background IO.
>
> ...
>
> This was tested using memcached+memcachetest while some background IO
> was in progress as implemented by the parallel IO tests implement in MM
> Tests. memcachetest benchmarks how many operations/second memcached can
> service and it is run multiple times. It starts with no background IO and
> then re-runs the test with larger amounts of IO in the background to roughly
> simulate a large copy in progress. The expectation is that the IO should
> have little or no impact on memcachetest which is running entirely in memory.
>
> 3.10.0-rc1 3.10.0-rc1
> vanilla lessdisrupt-v4
> Ops memcachetest-0M 22155.00 ( 0.00%) 22180.00 ( 0.11%)
> Ops memcachetest-715M 22720.00 ( 0.00%) 22355.00 ( -1.61%)
> Ops memcachetest-2385M 3939.00 ( 0.00%) 23450.00 (495.33%)
> Ops memcachetest-4055M 3628.00 ( 0.00%) 24341.00 (570.92%)
> Ops io-duration-0M 0.00 ( 0.00%) 0.00 ( 0.00%)
> Ops io-duration-715M 12.00 ( 0.00%) 7.00 ( 41.67%)
> Ops io-duration-2385M 118.00 ( 0.00%) 21.00 ( 82.20%)
> Ops io-duration-4055M 162.00 ( 0.00%) 36.00 ( 77.78%)
> Ops swaptotal-0M 0.00 ( 0.00%) 0.00 ( 0.00%)
> Ops swaptotal-715M 140134.00 ( 0.00%) 18.00 ( 99.99%)
> Ops swaptotal-2385M 392438.00 ( 0.00%) 0.00 ( 0.00%)
> Ops swaptotal-4055M 449037.00 ( 0.00%) 27864.00 ( 93.79%)
> Ops swapin-0M 0.00 ( 0.00%) 0.00 ( 0.00%)
> Ops swapin-715M 0.00 ( 0.00%) 0.00 ( 0.00%)
> Ops swapin-2385M 148031.00 ( 0.00%) 0.00 ( 0.00%)
> Ops swapin-4055M 135109.00 ( 0.00%) 0.00 ( 0.00%)
> Ops minorfaults-0M 1529984.00 ( 0.00%) 1530235.00 ( -0.02%)
> Ops minorfaults-715M 1794168.00 ( 0.00%) 1613750.00 ( 10.06%)
> Ops minorfaults-2385M 1739813.00 ( 0.00%) 1609396.00 ( 7.50%)
> Ops minorfaults-4055M 1754460.00 ( 0.00%) 1614810.00 ( 7.96%)
> Ops majorfaults-0M 0.00 ( 0.00%) 0.00 ( 0.00%)
> Ops majorfaults-715M 185.00 ( 0.00%) 180.00 ( 2.70%)
> Ops majorfaults-2385M 24472.00 ( 0.00%) 101.00 ( 99.59%)
> Ops majorfaults-4055M 22302.00 ( 0.00%) 229.00 ( 98.97%)
I doubt if many people have the context to understand what these
numbers really mean. I don't.
> Note how the vanilla kernels performance collapses when there is enough
> IO taking place in the background. This drop in performance is part of
> what users complain of when they start backups. Note how the swapin and
> major fault figures indicate that processes were being pushed to swap
> prematurely. With the series applied, there is no noticable performance
> drop and while there is still some swap activity, it's tiny.
>
> 3.10.0-rc1 3.10.0-rc1
> vanilla lessdisrupt-v4
> Page Ins 1234608 101892
> Page Outs 12446272 11810468
> Swap Ins 283406 0
> Swap Outs 698469 27882
> Direct pages scanned 0 136480
> Kswapd pages scanned 6266537 5369364
> Kswapd pages reclaimed 1088989 930832
> Direct pages reclaimed 0 120901
> Kswapd efficiency 17% 17%
> Kswapd velocity 5398.371 4635.115
> Direct efficiency 100% 88%
> Direct velocity 0.000 117.817
> Percentage direct scans 0% 2%
> Page writes by reclaim 1655843 4009929
> Page writes file 957374 3982047
> Page writes anon 698469 27882
> Page reclaim immediate 5245 1745
> Page rescued immediate 0 0
> Slabs scanned 33664 25216
> Direct inode steals 0 0
> Kswapd inode steals 19409 778
The reduction in inode steals might be a significant thing?
prune_icache_sb() does invalidate_mapping_pages() and can have the bad
habit of shooting down a vast number of pagecache pages (for a large
file) in a single hit. Did this workload use large (and clean) files?
Did you run any test which would expose this effect?
> ...
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next prev parent reply other threads:[~2013-05-15 20:37 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-13 8:12 Mel Gorman
2013-05-13 8:12 ` [PATCH 1/9] mm: vmscan: Limit the number of pages kswapd reclaims at each priority Mel Gorman
2013-05-13 8:12 ` [PATCH 2/9] mm: vmscan: Obey proportional scanning requirements for kswapd Mel Gorman
2013-05-14 10:21 ` Michal Hocko
2013-05-17 3:41 ` Kamezawa Hiroyuki
2013-05-13 8:12 ` [PATCH 3/9] mm: vmscan: Flatten kswapd priority loop Mel Gorman
2013-05-14 10:38 ` Michal Hocko
2013-05-13 8:12 ` [PATCH 4/9] mm: vmscan: Decide whether to compact the pgdat based on reclaim progress Mel Gorman
2013-05-14 10:51 ` Michal Hocko
2013-05-13 8:12 ` [PATCH 5/9] mm: vmscan: Do not allow kswapd to scan at maximum priority Mel Gorman
2013-05-13 8:12 ` [PATCH 6/9] mm: vmscan: Have kswapd writeback pages based on dirty pages encountered, not priority Mel Gorman
2013-05-14 11:25 ` Michal Hocko
2013-05-13 8:12 ` [PATCH 7/9] mm: vmscan: Block kswapd if it is encountering pages under writeback Mel Gorman
2013-05-14 21:06 ` Rik van Riel
2013-05-15 21:39 ` Andrew Morton
2013-05-16 13:07 ` Mel Gorman
2013-05-13 8:12 ` [PATCH 8/9] mm: vmscan: Check if kswapd should writepage once per pgdat scan Mel Gorman
2013-05-13 8:12 ` [PATCH 9/9] mm: vmscan: Move logic from balance_pgdat() to kswapd_shrink_zone() Mel Gorman
2013-05-14 12:23 ` Michal Hocko
2013-05-14 21:06 ` Rik van Riel
2013-05-15 20:37 ` Andrew Morton [this message]
2013-05-16 10:33 ` [PATCH 0/9] Reduce system disruption due to kswapd V4 Mel Gorman
2013-05-16 13:54 ` Michal Hocko
2013-05-16 14:11 ` Mel Gorman
2013-05-18 21:15 ` Zlatko Calusic
2013-05-21 23:13 ` Dave Chinner
2013-05-22 8:48 ` Mel Gorman
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