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Subject[PATCH 1/4] vmstat: remove zone->lock from walk_zones_in_node
Date
The zone->lock is one of performance critical locks. Then, it shouldn't
be hold for long time. Currently, we have four walk_zones_in_node()
usage and almost use-case don't need to hold zone->lock.

Thus, this patch move locking responsibility from walk_zones_in_node
to its sub function. Also this patch kill unnecessary zone->lock taking.

Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
mm/vmstat.c | 8 +++++---
1 files changed, 5 insertions(+), 3 deletions(-)
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 6051fba..a5d45bc 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -418,15 +418,12 @@ static void walk_zones_in_node(struct seq_file *m, pg_data_t *pgdat,
{
struct zone *zone;
struct zone *node_zones = pgdat->node_zones;
- unsigned long flags;

for (zone = node_zones; zone - node_zones < MAX_NR_ZONES; ++zone) {
if (!populated_zone(zone))
continue;

- spin_lock_irqsave(&zone->lock, flags);
print(m, pgdat, zone);
- spin_unlock_irqrestore(&zone->lock, flags);
}
}

@@ -455,6 +452,7 @@ static void pagetypeinfo_showfree_print(struct seq_file *m,
pg_data_t *pgdat, struct zone *zone)
{
int order, mtype;
+ unsigned long flags;

for (mtype = 0; mtype < MIGRATE_TYPES; mtype++) {
seq_printf(m, "Node %4d, zone %8s, type %12s ",
@@ -468,8 +466,11 @@ static void pagetypeinfo_showfree_print(struct seq_file *m,

area = &(zone->free_area[order]);

+ spin_lock_irqsave(&zone->lock, flags);
list_for_each(curr, &area->free_list[mtype])
freecount++;
+ spin_unlock_irqrestore(&zone->lock, flags);
+
seq_printf(m, "%6lu ", freecount);
}
seq_putc(m, '\n');
@@ -709,6 +710,7 @@ static void zoneinfo_show_print(struct seq_file *m, pg_data_t *pgdat,
struct zone *zone)
{
int i;
+
seq_printf(m, "Node %d, zone %8s", pgdat->node_id, zone->name);
seq_printf(m,
"\n pages free %lu"
--
1.6.5.2





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