lkml.org 
[lkml]   [2009]   [Dec]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH 1/4] vmstat: remove zone->lock from walk_zones_in_node
    > * KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> [2009-12-28 16:47:22]:
    >
    > > 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"
    >
    > While this is a noble cause, is printing all this information correct
    > without the lock, I am not worried about old
    > information, but incorrect data. Should the read side be rcu'ed. Is
    > just removing the lock and accessing data safe across architectures?

    Hm.
    Actually,current memory-hotplug implementation change various zone data without zone->lock.
    then, my patch doesn't cause regression. I'm not sure rcu protection is very worth or not.
    but I think it can separate this patch.






    \
     
     \ /
      Last update: 2009-12-30 13:53    [W:0.044 / U:0.120 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site