Commit f4bf3ca2 authored Apr 07, 2023 by Lingutla Chandrasekhar Committed by Thomas Gleixner Apr 15, 2023

softirq: Add trace points for tasklet entry/exit



Tasklets are supposed to finish their work quickly and should not block the
current running process, but it is not guaranteed that they do so.

Currently softirq_entry/exit can be used to analyse the total tasklets
execution time, but that's not helpful to track individual tasklets
execution time. That makes it hard to identify tasklet functions, which
take more time than expected.

Add tasklet_entry/exit trace point support to track individual tasklet
execution.

Trivial usage example:
   # echo 1 > /sys/kernel/debug/tracing/events/irq/tasklet_entry/enable
   # echo 1 > /sys/kernel/debug/tracing/events/irq/tasklet_exit/enable
   # cat /sys/kernel/debug/tracing/trace
 # tracer: nop
 #
 # entries-in-buffer/entries-written: 4/4   #P:4
 #
 #                                _-----=> irqs-off/BH-disabled
 #                               / _----=> need-resched
 #                              | / _---=> hardirq/softirq
 #                              || / _--=> preempt-depth
 #                              ||| / _-=> migrate-disable
 #                              |||| /     delay
 #           TASK-PID     CPU#  |||||  TIMESTAMP  FUNCTION
 #              | |         |   |||||     |         |
           <idle>-0       [003] ..s1.   314.011428: tasklet_entry: tasklet=0xffffa01ef8db2740 function=tcp_tasklet_func
           <idle>-0       [003] ..s1.   314.011432: tasklet_exit: tasklet=0xffffa01ef8db2740 function=tcp_tasklet_func
           <idle>-0       [003] ..s1.   314.017369: tasklet_entry: tasklet=0xffffa01ef8db2740 function=tcp_tasklet_func
           <idle>-0       [003] ..s1.   314.017371: tasklet_exit: tasklet=0xffffa01ef8db2740 function=tcp_tasklet_func

Signed-off-by: Lingutla Chandrasekhar <clingutla@codeaurora.org>
Signed-off-by: J. Avila <elavila@google.com>
Signed-off-by: John Stultz <jstultz@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Link: https://lore.kernel.org/r/20230407230526.1685443-1-jstultz@google.com

[elavila: Port to android-mainline]
[jstultz: Rebased to upstream, cut unused trace points, added
 comments for the tracepoints, reworded commit]

parent 7e364e56

include/trace/events/irq.h

+47 −0

Original line number	Diff line number	Diff line
		@@ -160,6 +160,53 @@ DEFINE_EVENT(softirq, softirq_raise,
		TP_ARGS(vec_nr)
		);

		DECLARE_EVENT_CLASS(tasklet,

		TP_PROTO(struct tasklet_struct t, void func),

		TP_ARGS(t, func),

		TP_STRUCT__entry(
		__field( void *, tasklet)
		__field( void *, func)
		),

		TP_fast_assign(
		__entry->tasklet = t;
		__entry->func = func;
		),

		TP_printk("tasklet=%ps function=%ps", __entry->tasklet, __entry->func)
		);

		/**
		* tasklet_entry - called immediately before the tasklet is run
		* @t: tasklet pointer
		* @func: tasklet callback or function being run
		*
		* Used to find individual tasklet execution time
		*/
		DEFINE_EVENT(tasklet, tasklet_entry,

		TP_PROTO(struct tasklet_struct t, void func),

		TP_ARGS(t, func)
		);

		/**
		* tasklet_exit - called immediately after the tasklet is run
		* @t: tasklet pointer
		* @func: tasklet callback or function being run
		*
		* Used to find individual tasklet execution time
		*/
		DEFINE_EVENT(tasklet, tasklet_exit,

		TP_PROTO(struct tasklet_struct t, void func),

		TP_ARGS(t, func)
		);

		#endif /* _TRACE_IRQ_H */

		/* This part must be outside protection */

kernel/softirq.c

+7 −2

Original line number	Diff line number	Diff line
		@@ -793,10 +793,15 @@ static void tasklet_action_common(struct softirq_action *a,
		if (tasklet_trylock(t)) {
		if (!atomic_read(&t->count)) {
		if (tasklet_clear_sched(t)) {
		if (t->use_callback)
		if (t->use_callback) {
		trace_tasklet_entry(t, t->callback);
		t->callback(t);
		else
		trace_tasklet_exit(t, t->callback);
		} else {
		trace_tasklet_entry(t, t->func);
		t->func(t->data);
		trace_tasklet_exit(t, t->func);
		}
		}
		tasklet_unlock(t);
		continue;