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authorYasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>2014-01-21 15:49:06 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-21 16:19:43 -0800
commit943dca1a1fcbccb58de944669b833fd38a6c809b (patch)
treea15128dc37e1ebd0e1c01e56b9f69c2872965f76 /init
parent34e431b0ae398fc54ea69ff85ec700722c9da773 (diff)
mm: get rid of unnecessary pageblock scanning in setup_zone_migrate_reserve
Yasuaki Ishimatsu reported memory hot-add spent more than 5 _hours_ on 9TB memory machine since onlining memory sections is too slow. And we found out setup_zone_migrate_reserve spent >90% of the time. The problem is, setup_zone_migrate_reserve scans all pageblocks unconditionally, but it is only necessary if the number of reserved block was reduced (i.e. memory hot remove). Moreover, maximum MIGRATE_RESERVE per zone is currently 2. It means that the number of reserved pageblocks is almost always unchanged. This patch adds zone->nr_migrate_reserve_block to maintain the number of MIGRATE_RESERVE pageblocks and it reduces the overhead of setup_zone_migrate_reserve dramatically. The following table shows time of onlining a memory section. Amount of memory | 128GB | 192GB | 256GB| --------------------------------------------- linux-3.12 | 23.9 | 31.4 | 44.5 | This patch | 8.3 | 8.3 | 8.6 | Mel's proposal patch | 10.9 | 19.2 | 31.3 | --------------------------------------------- (millisecond) 128GB : 4 nodes and each node has 32GB of memory 192GB : 6 nodes and each node has 32GB of memory 256GB : 8 nodes and each node has 32GB of memory (*1) Mel proposed his idea by the following threads. https://lkml.org/lkml/2013/10/30/272 [akpm@linux-foundation.org: tweak comment] Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Reported-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Tested-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Cc: Mel Gorman <mgorman@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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