writeback: trace event balance_dirty_pages

Useful for analyzing the dynamics of the throttling algorithms and
debugging user reported problems.

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

1 files changed, 22 insertions, 0 deletions

diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index e3c2d8bf87bb..45d36f7dc169 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1103,12 +1103,34 @@ static void balance_dirty_pages(struct address_space *mapping,
                                         pos_ratio >> RATELIMIT_CALC_SHIFT;
                 pause = (HZ * pages_dirtied) / (task_ratelimit | 1);
                 if (unlikely(pause <= 0)) {
+                        trace_balance_dirty_pages(bdi,
+                                                  dirty_thresh,
+                                                  background_thresh,
+                                                  nr_dirty,
+                                                  bdi_thresh,
+                                                  bdi_dirty,
+                                                  dirty_ratelimit,
+                                                  task_ratelimit,
+                                                  pages_dirtied,
+                                                  pause,
+                                                  start_time);
                         pause = 1; /* avoid resetting nr_dirtied_pause below */
                         break;
                 }
                 pause = min(pause, max_pause);
 
 pause:
+                trace_balance_dirty_pages(bdi,
+                                          dirty_thresh,
+                                          background_thresh,
+                                          nr_dirty,
+                                          bdi_thresh,
+                                          bdi_dirty,
+                                          dirty_ratelimit,
+                                          task_ratelimit,
+                                          pages_dirtied,
+                                          pause,
+                                          start_time);
                 __set_current_state(TASK_UNINTERRUPTIBLE);
                 io_schedule_timeout(pause);