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Commit ece13ac3 authored by Wu Fengguang's avatar Wu Fengguang
Browse files

writeback: trace event balance_dirty_pages 



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

Signed-off-by: default avatarWu Fengguang <fengguang.wu@intel.com>
parent b48c104d

include/trace/events/writeback.h

+73 −0
Original line number Diff line number Diff line
@@ -271,6 +271,79 @@ TRACE_EVENT(bdi_dirty_ratelimit, 
	)

);



TRACE_EVENT(balance_dirty_pages,



	TP_PROTO(struct backing_dev_info *bdi,

		 unsigned long thresh,

		 unsigned long bg_thresh,

		 unsigned long dirty,

		 unsigned long bdi_thresh,

		 unsigned long bdi_dirty,

		 unsigned long dirty_ratelimit,

		 unsigned long task_ratelimit,

		 unsigned long dirtied,

		 long pause,

		 unsigned long start_time),



	TP_ARGS(bdi, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty,

		dirty_ratelimit, task_ratelimit,

		dirtied, pause, start_time),



	TP_STRUCT__entry(

		__array(	 char,	bdi, 32)

		__field(unsigned long,	limit)

		__field(unsigned long,	setpoint)

		__field(unsigned long,	dirty)

		__field(unsigned long,	bdi_setpoint)

		__field(unsigned long,	bdi_dirty)

		__field(unsigned long,	dirty_ratelimit)

		__field(unsigned long,	task_ratelimit)

		__field(unsigned int,	dirtied)

		__field(unsigned int,	dirtied_pause)

		__field(unsigned long,	paused)

		__field(	 long,	pause)

	),



	TP_fast_assign(

		unsigned long freerun = (thresh + bg_thresh) / 2;

		strlcpy(__entry->bdi, dev_name(bdi->dev), 32);



		__entry->limit		= global_dirty_limit;

		__entry->setpoint	= (global_dirty_limit + freerun) / 2;

		__entry->dirty		= dirty;

		__entry->bdi_setpoint	= __entry->setpoint *

						bdi_thresh / (thresh + 1);

		__entry->bdi_dirty	= bdi_dirty;

		__entry->dirty_ratelimit = KBps(dirty_ratelimit);

		__entry->task_ratelimit	= KBps(task_ratelimit);

		__entry->dirtied	= dirtied;

		__entry->dirtied_pause	= current->nr_dirtied_pause;

		__entry->pause		= pause * 1000 / HZ;

		__entry->paused		= (jiffies - start_time) * 1000 / HZ;

	),





	TP_printk("bdi %s: "

		  "limit=%lu setpoint=%lu dirty=%lu "

		  "bdi_setpoint=%lu bdi_dirty=%lu "

		  "dirty_ratelimit=%lu task_ratelimit=%lu "

		  "dirtied=%u dirtied_pause=%u "

		  "paused=%lu pause=%ld",

		  __entry->bdi,

		  __entry->limit,

		  __entry->setpoint,

		  __entry->dirty,

		  __entry->bdi_setpoint,

		  __entry->bdi_dirty,

		  __entry->dirty_ratelimit,

		  __entry->task_ratelimit,

		  __entry->dirtied,

		  __entry->dirtied_pause,

		  __entry->paused,	/* ms */

		  __entry->pause	/* ms */

	  )

);



DECLARE_EVENT_CLASS(writeback_congest_waited_template,



	TP_PROTO(unsigned int usec_timeout, unsigned int usec_delayed),

mm/page-writeback.c

+22 −0
Original line number Diff line number Diff line
@@ -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);