writeback: trace event bdi_dirty_ratelimit

It helps understand how various throttle bandwidths are updated.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 0802d5177997..e3c2d8bf87bb 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -875,6 +875,8 @@ static void bdi_update_dirty_ratelimit(struct backing_dev_info *bdi,
 
         bdi->dirty_ratelimit = max(dirty_ratelimit, 1UL);
         bdi->balanced_dirty_ratelimit = balanced_dirty_ratelimit;
+
+        trace_bdi_dirty_ratelimit(bdi, dirty_rate, task_ratelimit);
 }
 
 void __bdi_update_bandwidth(struct backing_dev_info *bdi,