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| 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 /mm | |
| parent | 1c30e0177e4f41a11cb88b0f1f056ccebfe0fff4 (diff) | |
| download | op-kernel-dev-1c5e9c27cbd966c7f0038698d5dcd5ada3574f47.zip op-kernel-dev-1c5e9c27cbd966c7f0038698d5dcd5ada3574f47.tar.gz | |
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>
Diffstat (limited to 'mm')
| -rw-r--r-- | mm/migrate.c | 21 |
1 files changed, 12 insertions, 9 deletions
diff --git a/mm/migrate.c b/mm/migrate.c index 41eba21..4612bb2 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) |
