From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
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@xxxxxxx>
Reported-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Cc: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
---
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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