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authorYasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>2014-01-22 03:49:06 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-01-22 04:19:43 +0400
commit943dca1a1fcbccb58de944669b833fd38a6c809b (patch)
treea15128dc37e1ebd0e1c01e56b9f69c2872965f76 /include/linux/mmzone.h
parent34e431b0ae398fc54ea69ff85ec700722c9da773 (diff)
downloadlinux-943dca1a1fcbccb58de944669b833fd38a6c809b.tar.xz
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>
Diffstat (limited to 'include/linux/mmzone.h')
-rw-r--r--include/linux/mmzone.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h
index bd791e452ad7..67ab5febabf7 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -490,6 +490,12 @@ struct zone {
unsigned long managed_pages;
/*
+ * Number of MIGRATE_RESEVE page block. To maintain for just
+ * optimization. Protected by zone->lock.
+ */
+ int nr_migrate_reserve_block;
+
+ /*
* rarely used fields:
*/
const char *name;