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: Arjan van de Ven <arjan@linux.intel.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/trace/events/workqueue.h b/include/trace/events/workqueue.h
new file mode 100644
index 0000000..49682d7
--- /dev/null
+++ b/include/trace/events/workqueue.h
@@ -0,0 +1,62 @@
+#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>
diff --git a/kernel/workqueue.c b/kernel/workqueue.c
index 2994a0e..8bd600c 100644
--- a/kernel/workqueue.c
+++ b/kernel/workqueue.c
@@ -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 @@
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);