From: Rob Clark <[email protected]>
While migrating some code from wq to kthread_worker, I found that I
missed the execute_start/end tracepoints. So add similar tracepoints
for kthread_work. And for completeness, queue_work tracepoint (although
this one differs slightly from the matching workqueue tracepoint).
Signed-off-by: Rob Clark <[email protected]>
---
include/trace/events/sched.h | 84 ++++++++++++++++++++++++++++++++++++
kernel/kthread.c | 9 ++++
2 files changed, 93 insertions(+)
diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index fec25b9cfbaf..349d9872e807 100644
--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -5,6 +5,7 @@
#if !defined(_TRACE_SCHED_H) || defined(TRACE_HEADER_MULTI_READ)
#define _TRACE_SCHED_H
+#include <linux/kthread.h>
#include <linux/sched/numa_balancing.h>
#include <linux/tracepoint.h>
#include <linux/binfmts.h>
@@ -51,6 +52,89 @@ TRACE_EVENT(sched_kthread_stop_ret,
TP_printk("ret=%d", __entry->ret)
);
+/**
+ * sched_kthread_work_queue_work - called when a work gets queued
+ * @worker: pointer to the kthread_worker
+ * @work: pointer to struct kthread_work
+ *
+ * This event occurs when a work is queued immediately or once a
+ * delayed work is actually queued (ie: once the delay has been
+ * reached).
+ */
+TRACE_EVENT(sched_kthread_work_queue_work,
+
+ TP_PROTO(struct kthread_worker *worker,
+ struct kthread_work *work),
+
+ TP_ARGS(worker, work),
+
+ TP_STRUCT__entry(
+ __field( void *, work )
+ __field( void *, function)
+ __field( void *, worker)
+ ),
+
+ TP_fast_assign(
+ __entry->work = work;
+ __entry->function = work->func;
+ __entry->worker = worker;
+ ),
+
+ TP_printk("work struct=%p function=%ps worker=%p",
+ __entry->work, __entry->function, __entry->worker)
+);
+
+/**
+ * sched_kthread_work_execute_start - called immediately before the work callback
+ * @work: pointer to struct kthread_work
+ *
+ * Allows to track kthread work execution.
+ */
+TRACE_EVENT(sched_kthread_work_execute_start,
+
+ TP_PROTO(struct kthread_work *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 %ps", __entry->work, __entry->function)
+);
+
+/**
+ * sched_kthread_work_execute_end - called immediately after the work callback
+ * @work: pointer to struct work_struct
+ * @function: pointer to worker function
+ *
+ * Allows to track workqueue execution.
+ */
+TRACE_EVENT(sched_kthread_work_execute_end,
+
+ TP_PROTO(struct kthread_work *work, kthread_work_func_t function),
+
+ TP_ARGS(work, function),
+
+ TP_STRUCT__entry(
+ __field( void *, work )
+ __field( void *, function)
+ ),
+
+ TP_fast_assign(
+ __entry->work = work;
+ __entry->function = function;
+ ),
+
+ TP_printk("work struct %p: function %ps", __entry->work, __entry->function)
+);
+
/*
* Tracepoint for waking up a task:
*/
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 3edaa380dc7b..c1e59d6bf802 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -704,8 +704,15 @@ int kthread_worker_fn(void *worker_ptr)
raw_spin_unlock_irq(&worker->lock);
if (work) {
+ kthread_work_func_t func = work->func;
__set_current_state(TASK_RUNNING);
+ trace_sched_kthread_work_execute_start(work);
work->func(work);
+ /*
+ * Avoid dereferencing work after this point. The trace
+ * event only cares about the address.
+ */
+ trace_sched_kthread_work_execute_end(work, func);
} else if (!freezing(current))
schedule();
@@ -834,6 +841,8 @@ static void kthread_insert_work(struct kthread_worker *worker,
{
kthread_insert_work_sanity_check(worker, work);
+ trace_sched_kthread_work_queue_work(worker, work);
+
list_add_tail(&work->node, pos);
work->worker = worker;
if (!worker->current_work && likely(worker->task))
--
2.26.2
On Sat, 10 Oct 2020 11:03:22 -0700
Rob Clark <[email protected]> wrote:
> /**
> + * sched_kthread_work_execute_start - called immediately before the work callback
> + * @work: pointer to struct kthread_work
> + *
> + * Allows to track kthread work execution.
> + */
> +TRACE_EVENT(sched_kthread_work_execute_start,
> +
> + TP_PROTO(struct kthread_work *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 %ps", __entry->work, __entry->function)
> +);
> +
> +/**
> + * sched_kthread_work_execute_end - called immediately after the work callback
> + * @work: pointer to struct work_struct
> + * @function: pointer to worker function
> + *
> + * Allows to track workqueue execution.
> + */
> +TRACE_EVENT(sched_kthread_work_execute_end,
> +
> + TP_PROTO(struct kthread_work *work, kthread_work_func_t function),
> +
> + TP_ARGS(work, function),
> +
> + TP_STRUCT__entry(
> + __field( void *, work )
> + __field( void *, function)
> + ),
> +
> + TP_fast_assign(
> + __entry->work = work;
> + __entry->function = function;
> + ),
> +
> + TP_printk("work struct %p: function %ps", __entry->work, __entry->function)
> +);
> +
Please combine the above into:
DECLARE_EVENT_CLASS(sched_kthread_work_execute_template,
TP_PROTO(struct kthread_work *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 %ps", __entry->work, __entry->function)
);
DEFINE_EVENT(sched_kthread_work_execute_template, sched_kthread_work_execute_start,
TP_PROTO(struct kthread_work *work),
TP_ARGS(work));
DEFINE_EVENT(sched_kthread_work_execute_template, sched_kthread_work_execute_end,
TP_PROTO(struct kthread_work *work),
TP_ARGS(work));
As events are cheap, classes are expensive (size wise), and a TRACE_EVENT()
is really just a CLASS and EVENT for a single instance.
-- Steve
On Mon, Oct 12, 2020 at 6:59 AM Steven Rostedt <[email protected]> wrote:
>
> On Sat, 10 Oct 2020 11:03:22 -0700
> Rob Clark <[email protected]> wrote:
>
> > /**
> > + * sched_kthread_work_execute_start - called immediately before the work callback
> > + * @work: pointer to struct kthread_work
> > + *
> > + * Allows to track kthread work execution.
> > + */
> > +TRACE_EVENT(sched_kthread_work_execute_start,
> > +
> > + TP_PROTO(struct kthread_work *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 %ps", __entry->work, __entry->function)
> > +);
> > +
> > +/**
> > + * sched_kthread_work_execute_end - called immediately after the work callback
> > + * @work: pointer to struct work_struct
> > + * @function: pointer to worker function
> > + *
> > + * Allows to track workqueue execution.
> > + */
> > +TRACE_EVENT(sched_kthread_work_execute_end,
> > +
> > + TP_PROTO(struct kthread_work *work, kthread_work_func_t function),
> > +
> > + TP_ARGS(work, function),
> > +
> > + TP_STRUCT__entry(
> > + __field( void *, work )
> > + __field( void *, function)
> > + ),
> > +
> > + TP_fast_assign(
> > + __entry->work = work;
> > + __entry->function = function;
> > + ),
> > +
> > + TP_printk("work struct %p: function %ps", __entry->work, __entry->function)
> > +);
> > +
>
>
> Please combine the above into:
>
> DECLARE_EVENT_CLASS(sched_kthread_work_execute_template,
>
> TP_PROTO(struct kthread_work *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 %ps", __entry->work, __entry->function)
> );
>
> DEFINE_EVENT(sched_kthread_work_execute_template, sched_kthread_work_execute_start,
> TP_PROTO(struct kthread_work *work),
> TP_ARGS(work));
>
> DEFINE_EVENT(sched_kthread_work_execute_template, sched_kthread_work_execute_end,
> TP_PROTO(struct kthread_work *work),
> TP_ARGS(work));
>
> As events are cheap, classes are expensive (size wise), and a TRACE_EVENT()
> is really just a CLASS and EVENT for a single instance.
I think we cannot quite do this, because we should not rely on being
able to dereference work after it finishes. Although I suppose I
could just define it to explicitly pass the fxn ptr to both
tracepoints..
BR,
-R
On Mon, 12 Oct 2020 08:14:50 -0700
Rob Clark <[email protected]> wrote:
> > DEFINE_EVENT(sched_kthread_work_execute_template, sched_kthread_work_execute_start,
> > TP_PROTO(struct kthread_work *work),
> > TP_ARGS(work));
> >
> > DEFINE_EVENT(sched_kthread_work_execute_template, sched_kthread_work_execute_end,
> > TP_PROTO(struct kthread_work *work),
> > TP_ARGS(work));
> >
> > As events are cheap, classes are expensive (size wise), and a TRACE_EVENT()
> > is really just a CLASS and EVENT for a single instance.
>
> I think we cannot quite do this, because we should not rely on being
Ah I missed seeing that one used work->func and the other passed in the
function.
> able to dereference work after it finishes. Although I suppose I
> could just define it to explicitly pass the fxn ptr to both
> tracepoints..
But yes, I would rather see that. It could save up to 5K in text and data.
-- Steve