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workqueue: Add basic tracepoints to track workqueue execution

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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: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Arjan van de Ven 2010-08-21 13:07:26 -07:00 • committed by Linus Torvalds
parent 69b26c7ad0
commit e36c886a0f
2 changed files with 71 additions and 0 deletions
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9
kernel/workqueue.c
View file

@ -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);