From: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
commit 943dca1a1fcbccb58de944669b833fd38a6c809b upstream.
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@xxxxxxxxxxxxxxxxxxxx: tweak comment]
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Reported-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Tested-by: Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxx>
---
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 5648290..4719985 100644
--- a/include/linux/mmzone.h
+++ b/include/linux/mmzone.h
@@ -494,6 +494,12 @@ 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 3078eaf..c34b582 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3934,6 +3934,7 @@ 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
@@ -3955,6 +3956,12 @@ 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))
@@ -3992,6 +3999,12 @@ 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;
}
/*
--
1.8.4.5
--
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