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Commit e36c886a authored by Arjan van de Ven's avatar Arjan van de Ven Committed by Linus Torvalds
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workqueue: Add basic tracepoints to track workqueue execution 



With the introduction of the new unified work queue thread pools,
we lost one feature: It's no longer possible to know which worker
is causing the CPU to wake out of idle. The result is that PowerTOP
now reports a lot of "kworker/a:b" instead of more readable results.

This patch adds a pair of tracepoints to the new workqueue code,
similar in style to the timer/hrtimer tracepoints.

With this pair of tracepoints, the next PowerTOP can correctly
report which work item caused the wakeup (and how long it took):

Interrupt (43)            i915      time   3.51ms    wakeups 141
Work      ieee80211_iface_work      time   0.81ms    wakeups  29
Work              do_dbs_timer      time   0.55ms    wakeups  24
Process                   Xorg      time  21.36ms    wakeups   4
Timer    sched_rt_period_timer      time   0.01ms    wakeups   1

Signed-off-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 69b26c7a

include/trace/events/workqueue.h

0 → 100644
+62 −0
Original line number Diff line number Diff line 
#undef TRACE_SYSTEM

#define TRACE_SYSTEM workqueue



#if !defined(_TRACE_WORKQUEUE_H) || defined(TRACE_HEADER_MULTI_READ)

#define _TRACE_WORKQUEUE_H



#include <linux/tracepoint.h>

#include <linux/workqueue.h>



/**

 * workqueue_execute_start - called immediately before the workqueue callback

 * @work:	pointer to struct work_struct

 *

 * Allows to track workqueue execution.

 */

TRACE_EVENT(workqueue_execute_start,



	TP_PROTO(struct work_struct *work),



	TP_ARGS(work),



	TP_STRUCT__entry(

		__field( void *,	work	)

		__field( void *,	function)

	),



	TP_fast_assign(

		__entry->work		= work;

		__entry->function	= work->func;

	),



	TP_printk("work struct %p: function %pf", __entry->work, __entry->function)

);



/**

 * workqueue_execute_end - called immediately before the workqueue callback

 * @work:	pointer to struct work_struct

 *

 * Allows to track workqueue execution.

 */

TRACE_EVENT(workqueue_execute_end,



	TP_PROTO(struct work_struct *work),



	TP_ARGS(work),



	TP_STRUCT__entry(

		__field( void *,	work	)

	),



	TP_fast_assign(

		__entry->work		= work;

	),



	TP_printk("work struct %p", __entry->work)

);





#endif /*  _TRACE_WORKQUEUE_H */



/* This part must be outside protection */

#include <trace/define_trace.h>

kernel/workqueue.c

+9 −0
Original line number Diff line number Diff line
@@ -35,6 +35,9 @@ 
#include <linux/lockdep.h>

#include <linux/idr.h>



#define CREATE_TRACE_POINTS

#include <trace/events/workqueue.h>



#include "workqueue_sched.h"



enum {
@@ -1790,7 +1793,13 @@ static void process_one_work(struct worker *worker, struct work_struct *work) 
	work_clear_pending(work);

	lock_map_acquire(&cwq->wq->lockdep_map);

	lock_map_acquire(&lockdep_map);

	trace_workqueue_execute_start(work);

	f(work);

	/*

	 * While we must be careful to not use "work" after this, the trace

	 * point will only record its address.

	 */

	trace_workqueue_execute_end(work);

	lock_map_release(&lockdep_map);

	lock_map_release(&cwq->wq->lockdep_map);