Messages in this thread Patch in this message | | | Date | Thu, 14 Nov 2013 11:53:02 +0900 | From | Yasuaki Ishimatsu <> | Subject | [PATCH resend] mm: get rid of unnecessary pageblock scanning in setup_zone_migrate_reserve |
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I resend this patch. I added performance result into description of the patch.
------------------------------------------------------------------ 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 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. 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
Cc: Mel Gorman <mgorman@suse.de> Reported-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com> Tested-by: 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(+)
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 5a98836..da93109 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3908,6 +3908,7 @@ 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 @@ -3929,6 +3930,12 @@ 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)) @@ -3966,6 +3973,12 @@ 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; }
/*
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