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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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