diff options
| author | Mel Gorman <mgorman@suse.de> | 2014-01-21 15:50:59 -0800 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2014-01-21 16:19:48 -0800 |
| commit | 1c5e9c27cbd966c7f0038698d5dcd5ada3574f47 (patch) | |
| tree | a546cec0019aa3b726ba06e50ce38f960ee8f222 | |
| parent | 1c30e0177e4f41a11cb88b0f1f056ccebfe0fff4 (diff) | |
mm: numa: limit scope of lock for NUMA migrate rate limiting
NUMA migrate rate limiting protects a migration counter and window using
a lock but in some cases this can be a contended lock. It is not
critical that the number of pages be perfect, lost updates are
acceptable. Reduce the importance of this lock.
Signed-off-by: Mel Gorman <mgorman@suse.de>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
| -rw-r--r-- | include/linux/mmzone.h | 5 | ||||
| -rw-r--r-- | mm/migrate.c | 21 |
2 files changed, 13 insertions, 13 deletions
diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 67ab5febabf7..5f2052c83154 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -764,10 +764,7 @@ typedef struct pglist_data { int kswapd_max_order; enum zone_type classzone_idx; #ifdef CONFIG_NUMA_BALANCING - /* - * Lock serializing the per destination node AutoNUMA memory - * migration rate limiting data. - */ + /* Lock serializing the migrate rate limiting window */ spinlock_t numabalancing_migrate_lock; /* Rate limiting time interval */ diff --git a/mm/migrate.c b/mm/migrate.c index 41eba21f10ba..4612bb2e3677 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -1602,26 +1602,29 @@ bool migrate_ratelimited(int node) static bool numamigrate_update_ratelimit(pg_data_t *pgdat, unsigned long nr_pages) { - bool rate_limited = false; - /* * Rate-limit the amount of data that is being migrated to a node. * Optimal placement is no good if the memory bus is saturated and * all the time is being spent migrating! */ - spin_lock(&pgdat->numabalancing_migrate_lock); if (time_after(jiffies, pgdat->numabalancing_migrate_next_window)) { + spin_lock(&pgdat->numabalancing_migrate_lock); pgdat->numabalancing_migrate_nr_pages = 0; pgdat->numabalancing_migrate_next_window = jiffies + msecs_to_jiffies(migrate_interval_millisecs); + spin_unlock(&pgdat->numabalancing_migrate_lock); } if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) - rate_limited = true; - else - pgdat->numabalancing_migrate_nr_pages += nr_pages; - spin_unlock(&pgdat->numabalancing_migrate_lock); - - return rate_limited; + return true; + + /* + * This is an unlocked non-atomic update so errors are possible. + * The consequences are failing to migrate when we potentiall should + * have which is not severe enough to warrant locking. If it is ever + * a problem, it can be converted to a per-cpu counter. + */ + pgdat->numabalancing_migrate_nr_pages += nr_pages; + return false; } static int numamigrate_isolate_page(pg_data_t *pgdat, struct page *page) |