Messages in this thread Patch in this message | | | From | kosaki.motohiro@gmail ... | Subject | [PATCH] mm: get rid of unnecessary pageblock scanning in setup_zone_migrate_reserve | Date | Wed, 23 Oct 2013 17:01:32 -0400 |
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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Yasuaki Ithimatsu reported memory hot-add spent more than 5 _hours_ on 9TB memory machine and we found out setup_zone_migrate_reserve spnet >90% time.
The problem is, setup_zone_migrate_reserve scan all pageblock unconditionally, but it is only necessary number of reserved block was reduced (i.e. memory hot remove). Moreover, maximum MIGRATE_RESERVE per zone are currently 2. It mean, number of reserved pageblock are almost always unchanged.
This patch adds zone->nr_migrate_reserve_block to maintain number of MIGRATE_RESERVE pageblock and it reduce an overhead of setup_zone_migrate_reserve dramatically.
Cc: Mel Gorman <mgorman@suse.de> Reported-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Cc: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> --- include/linux/mmzone.h | 6 ++++++ mm/page_alloc.c | 13 +++++++++++++ 2 files changed, 19 insertions(+), 0 deletions(-)
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index bd791e4..67ab5fe 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; diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 58e67ea..76ca054 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3909,6 +3909,7 @@ static void setup_zone_migrate_reserve(struct zone *zone) struct page *page; unsigned long block_migratetype; int reserve; + int old_reserve; /* * Get the start pfn, end pfn and the number of blocks to reserve @@ -3930,6 +3931,12 @@ static void setup_zone_migrate_reserve(struct zone *zone) * future allocation of hugepages at runtime. */ reserve = min(2, reserve); + old_reserve = zone->nr_migrate_reserve_block; + + /* When memory hot-add, we almost always need to do nothing */ + if (reserve == old_reserve) + return; + zone->nr_migrate_reserve_block = reserve; for (pfn = start_pfn; pfn < end_pfn; pfn += pageblock_nr_pages) { if (!pfn_valid(pfn)) @@ -3967,6 +3974,12 @@ static void setup_zone_migrate_reserve(struct zone *zone) reserve--; continue; } + } else if (!old_reserve) { + /* + * When boot time, we don't need scan whole zone + * for turning off MIGRATE_RESERVE. + */ + break; } /* -- 1.7.1
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