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
Showing the changes to kernel/workqueue.c (1 of 2 files). Show all
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| @@ -35,6 +35,9 @@ · 34 unmodified lines | ||
| 35 | 35 | #include <linux/lockdep.h> |
| 36 | 36 | #include <linux/idr.h> |
| 37 | 37 | |
| 38 | +#define CREATE_TRACE_POINTS | |
| 39 | +#include <trace/events/workqueue.h> | |
| 40 | + | |
| 38 | 41 | #include "workqueue_sched.h" |
| 39 | 42 | |
| 40 | 43 | enum { |
| @@ -1790,7 +1793,13 @@ static void process_one_work(struct worker *worker, struct work_struct *work) · 1749 unmodified lines | ||
| 1790 | 1793 | work_clear_pending(work); |
| 1791 | 1794 | lock_map_acquire(&cwq->wq->lockdep_map); |
| 1792 | 1795 | lock_map_acquire(&lockdep_map); |
| 1796 | + trace_workqueue_execute_start(work); | |
| 1793 | 1797 | f(work); |
| 1798 | + /* | |
| 1799 | + * While we must be careful to not use "work" after this, the trace | |
| 1800 | + * point will only record its address. | |
| 1801 | + */ | |
| 1802 | + trace_workqueue_execute_end(work); | |
| 1794 | 1803 | lock_map_release(&lockdep_map); |
| 1795 | 1804 | lock_map_release(&cwq->wq->lockdep_map); |
| 1796 | 1805 | |