mm: numa: trace tasks that fail migration due to rate limiting

A low local/remote numa hinting fault ratio is potentially explained by
failed migrations.  This patch adds a tracepoint that fires when
migration fails due to migration rate limitation.

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>

1 files changed, 4 insertions, 1 deletions

diff --git a/mm/migrate.c b/mm/migrate.c
index 4612bb2e3677..f9e16350d09c 100644
--- a/mm/migrate.c
+++ b/mm/migrate.c
@@ -1614,8 +1614,11 @@ static bool numamigrate_update_ratelimit(pg_data_t *pgdat,
                         msecs_to_jiffies(migrate_interval_millisecs);
                 spin_unlock(&pgdat->numabalancing_migrate_lock);
         }
-        if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages)
+        if (pgdat->numabalancing_migrate_nr_pages > ratelimit_pages) {
+                trace_mm_numa_migrate_ratelimit(current, pgdat->node_id,
+                                                                nr_pages);
                 return true;
+        }
 
         /*
          * This is an unlocked non-atomic update so errors are possible.