diff options
| author | Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> | 2014-01-21 15:49:06 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-01-21 16:19:43 -0800 |
| commit | 943dca1a1fcbccb58de944669b833fd38a6c809b (patch) | |
| tree | a15128dc37e1ebd0e1c01e56b9f69c2872965f76 /mm/page_alloc.c | |
| parent | 34e431b0ae398fc54ea69ff85ec700722c9da773 (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>
Diffstat (limited to 'mm/page_alloc.c')
| -rw-r--r-- | mm/page_alloc.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 5248fe070aa..89d81f4429c 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3901,6 +3901,7 @@ 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 @@ -3922,6 +3923,12 @@ 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)) @@ -3959,6 +3966,12 @@ static void setup_zone_migrate_reserve(struct zone *zone) reserve--; continue; } + } else if (!old_reserve) { + /* + * At boot time we don't need to scan the whole zone + * for turning off MIGRATE_RESERVE. + */ + break; } /* |