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authorMel Gorman <mel@csn.ul.ie>2010-10-26 14:21:41 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-10-26 16:52:07 -0700
commit52bb9198668968506f9d12bf35d7f5d3f094921e (patch)
tree6e1f79c46de902c4462054803eb13115673f8c8c /mm/backing-dev.c
parente11da5b4fdf01d71d73c21cb92b00595b917d7fd (diff)
downloadlinux-52bb9198668968506f9d12bf35d7f5d3f094921e.tar.gz
writeback: account for time spent congestion_waited
There is strong evidence to indicate a lot of time is being spent in congestion_wait(), some of it unnecessarily. This patch adds a tracepoint for congestion_wait to record when congestion_wait() was called, how long the timeout was for and how long it actually slept. Signed-off-by: Mel Gorman <mel@csn.ul.ie> Reviewed-by: Minchan Kim <minchan.kim@gmail.com> Reviewed-by: Johannes Weiner <hannes@cmpxchg.org> Cc: Wu Fengguang <fengguang.wu@intel.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Rik van Riel <riel@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/backing-dev.c')
-rw-r--r--mm/backing-dev.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 65d420499a6..55627306abe 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -764,12 +764,17 @@ EXPORT_SYMBOL(set_bdi_congested);
long congestion_wait(int sync, long timeout)
{
long ret;
+ unsigned long start = jiffies;
DEFINE_WAIT(wait);
wait_queue_head_t *wqh = &congestion_wqh[sync];
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
ret = io_schedule_timeout(timeout);
finish_wait(wqh, &wait);
+
+ trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
+ jiffies_to_usecs(jiffies - start));
+
return ret;
}
EXPORT_SYMBOL(congestion_wait);