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authorMel Gorman <mgorman@suse.de>2012-11-19 05:59:15 -0500
committerMel Gorman <mgorman@suse.de>2012-12-11 09:42:51 -0500
commite14808b49f55e0e1135da5e4a154a540dd9f3662 (patch)
treed66708455dcc1b6e2e15937d732ab12c121e623a /mm
parenta8f6077213d285ca08dbf6d4a67470787388138b (diff)
mm: numa: Rate limit setting of pte_numa if node is saturated
If there are a large number of NUMA hinting faults and all of them are resulting in migrations it may indicate that memory is just bouncing uselessly around. NUMA balancing cost is likely exceeding any benefit from locality. Rate limit the PTE updates if the node is migration rate-limited. As noted in the comments, this distorts the NUMA faulting statistics. Signed-off-by: Mel Gorman <mgorman@suse.de>
Diffstat (limited to 'mm')
-rw-r--r--mm/migrate.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 4b8267f1842f..32a1afca6009 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1464,10 +1464,30 @@ static struct page *alloc_misplaced_dst_page(struct page *page,
1464 * page migration rate limiting control. 1464 * page migration rate limiting control.
1465 * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs 1465 * Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
1466 * window of time. Default here says do not migrate more than 1280M per second. 1466 * window of time. Default here says do not migrate more than 1280M per second.
1467 * If a node is rate-limited then PTE NUMA updates are also rate-limited. However
1468 * as it is faults that reset the window, pte updates will happen unconditionally
1469 * if there has not been a fault since @pteupdate_interval_millisecs after the
1470 * throttle window closed.
1467 */ 1471 */
1468static unsigned int migrate_interval_millisecs __read_mostly = 100; 1472static unsigned int migrate_interval_millisecs __read_mostly = 100;
1473static unsigned int pteupdate_interval_millisecs __read_mostly = 1000;
1469static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT); 1474static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
1470 1475
1476/* Returns true if NUMA migration is currently rate limited */
1477bool migrate_ratelimited(int node)
1478{
1479 pg_data_t *pgdat = NODE_DATA(node);
1480
1481 if (time_after(jiffies, pgdat->numabalancing_migrate_next_window +
1482 msecs_to_jiffies(pteupdate_interval_millisecs)))
1483 return false;
1484
1485 if (pgdat->numabalancing_migrate_nr_pages < ratelimit_pages)
1486 return false;
1487
1488 return true;
1489}
1490
1471/* 1491/*
1472 * Attempt to migrate a misplaced page to the specified destination 1492 * Attempt to migrate a misplaced page to the specified destination
1473 * node. Caller is expected to have an elevated reference count on 1493 * node. Caller is expected to have an elevated reference count on