Commit 52bb9198 authored by Mel Gorman's avatar Mel Gorman Committed by Linus Torvalds

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: default avatarMel Gorman <mel@csn.ul.ie>
Reviewed-by: default avatarMinchan Kim <minchan.kim@gmail.com>
Reviewed-by: default avatarJohannes 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e11da5b4
...@@ -151,6 +151,34 @@ DEFINE_WBC_EVENT(wbc_balance_dirty_written); ...@@ -151,6 +151,34 @@ DEFINE_WBC_EVENT(wbc_balance_dirty_written);
DEFINE_WBC_EVENT(wbc_balance_dirty_wait); DEFINE_WBC_EVENT(wbc_balance_dirty_wait);
DEFINE_WBC_EVENT(wbc_writepage); DEFINE_WBC_EVENT(wbc_writepage);
DECLARE_EVENT_CLASS(writeback_congest_waited_template,
TP_PROTO(unsigned int usec_timeout, unsigned int usec_delayed),
TP_ARGS(usec_timeout, usec_delayed),
TP_STRUCT__entry(
__field( unsigned int, usec_timeout )
__field( unsigned int, usec_delayed )
),
TP_fast_assign(
__entry->usec_timeout = usec_timeout;
__entry->usec_delayed = usec_delayed;
),
TP_printk("usec_timeout=%u usec_delayed=%u",
__entry->usec_timeout,
__entry->usec_delayed)
);
DEFINE_EVENT(writeback_congest_waited_template, writeback_congestion_wait,
TP_PROTO(unsigned int usec_timeout, unsigned int usec_delayed),
TP_ARGS(usec_timeout, usec_delayed)
);
#endif /* _TRACE_WRITEBACK_H */ #endif /* _TRACE_WRITEBACK_H */
/* This part must be outside protection */ /* This part must be outside protection */
......
...@@ -764,12 +764,17 @@ EXPORT_SYMBOL(set_bdi_congested); ...@@ -764,12 +764,17 @@ EXPORT_SYMBOL(set_bdi_congested);
long congestion_wait(int sync, long timeout) long congestion_wait(int sync, long timeout)
{ {
long ret; long ret;
unsigned long start = jiffies;
DEFINE_WAIT(wait); DEFINE_WAIT(wait);
wait_queue_head_t *wqh = &congestion_wqh[sync]; wait_queue_head_t *wqh = &congestion_wqh[sync];
prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE); prepare_to_wait(wqh, &wait, TASK_UNINTERRUPTIBLE);
ret = io_schedule_timeout(timeout); ret = io_schedule_timeout(timeout);
finish_wait(wqh, &wait); finish_wait(wqh, &wait);
trace_writeback_congestion_wait(jiffies_to_usecs(timeout),
jiffies_to_usecs(jiffies - start));
return ret; return ret;
} }
EXPORT_SYMBOL(congestion_wait); EXPORT_SYMBOL(congestion_wait);
......
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