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| author | Mel Gorman <mel@csn.ul.ie> | 2010-10-26 14:21:41 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2010-10-26 16:52:07 -0700 |
| commit | 52bb9198668968506f9d12bf35d7f5d3f094921e (patch) | |
| tree | 6e1f79c46de902c4462054803eb13115673f8c8c /mm/backing-dev.c | |
| parent | e11da5b4fdf01d71d73c21cb92b00595b917d7fd (diff) | |
| download | lwn-52bb9198668968506f9d12bf35d7f5d3f094921e.tar.gz lwn-52bb9198668968506f9d12bf35d7f5d3f094921e.zip | |
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.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/mm/backing-dev.c b/mm/backing-dev.c index 65d420499a61..55627306abe0 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); |