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authorMel Gorman <mgorman@suse.de>2012-11-19 10:59:15 +0000
committerMel Gorman <mgorman@suse.de>2012-12-11 14:42:51 +0000
commite14808b49f55e0e1135da5e4a154a540dd9f3662 (patch)
treed66708455dcc1b6e2e15937d732ab12c121e623a /mm/migrate.c
parenta8f6077213d285ca08dbf6d4a67470787388138b (diff)
downloadop-kernel-dev-e14808b49f55e0e1135da5e4a154a540dd9f3662.zip
op-kernel-dev-e14808b49f55e0e1135da5e4a154a540dd9f3662.tar.gz
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/migrate.c')
-rw-r--r--mm/migrate.c20
1 files changed, 20 insertions, 0 deletions
diff --git a/mm/migrate.c b/mm/migrate.c
index 4b8267f..32a1afc 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1464,10 +1464,30 @@ static struct page *alloc_misplaced_dst_page(struct page *page,
* page migration rate limiting control.
* Do not migrate more than @pages_to_migrate in a @migrate_interval_millisecs
* window of time. Default here says do not migrate more than 1280M per second.
+ * If a node is rate-limited then PTE NUMA updates are also rate-limited. However
+ * as it is faults that reset the window, pte updates will happen unconditionally
+ * if there has not been a fault since @pteupdate_interval_millisecs after the
+ * throttle window closed.
*/
static unsigned int migrate_interval_millisecs __read_mostly = 100;
+static unsigned int pteupdate_interval_millisecs __read_mostly = 1000;
static unsigned int ratelimit_pages __read_mostly = 128 << (20 - PAGE_SHIFT);
+/* Returns true if NUMA migration is currently rate limited */
+bool migrate_ratelimited(int node)
+{
+ pg_data_t *pgdat = NODE_DATA(node);
+
+ if (time_after(jiffies, pgdat->numabalancing_migrate_next_window +
+ msecs_to_jiffies(pteupdate_interval_millisecs)))
+ return false;
+
+ if (pgdat->numabalancing_migrate_nr_pages < ratelimit_pages)
+ return false;
+
+ return true;
+}
+
/*
* Attempt to migrate a misplaced page to the specified destination
* node. Caller is expected to have an elevated reference count on
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