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Commit cdce9d73 authored by Frederic Weisbecker's avatar Frederic Weisbecker Committed by Ingo Molnar
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perf sched: Add sched latency profiling 



Add the -l --latency option that reports statistics about the
scheduler latencies.

For now, the latencies are measured in the following sequence
scope:

- task A is sleeping (D or S state)
- task B wakes up A
         ^
         |
         |

   latency timeframe

         |
         |
         v
- task A is scheduled in

Start by recording every scheduler events:

	perf record -e sched:*

and then fetch the results:

	perf sched -l

 Tasks                     count          total              avg            max

migration/0                  2             39849            19924           28826
ksoftirqd/0                  7            756383           108054          373014
migration/1                  5             45391             9078           10452
ksoftirqd/1                  2            399055           199527          359130
events/0                     8           4780110           597513         4500250
events/1                     9           6353057           705895         2986012
kblockd/0                   42          37805097           900121         5077684

The snapshot are in nanoseconds.

- Count: number of snapshots taken for the given task
- Total: total latencies in nanosec
- Avg  : average of latency between wake up and sched in
- Max  : max snapshot latency

Signed-off-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 419ab0d6

tools/perf/builtin-sched.c

+285 −11
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ static struct perf_header *header; 
static u64			sample_type;



static int			replay_mode;

static int			lat_mode;





/*
@@ -847,6 +848,269 @@ static struct trace_sched_handler replay_ops = { 
	.fork_event = replay_fork_event,

};



#define TASK_STATE_TO_CHAR_STR "RSDTtZX"



enum thread_state {

	THREAD_SLEEPING,

	THREAD_WAKED_UP,

	THREAD_SCHED_IN,

	THREAD_IGNORE

};



struct lat_snapshot {

	struct list_head	list;

	enum thread_state	state;

	u64			wake_up_time;

	u64			sched_in_time;

};



struct thread_latency {

	struct list_head	snapshot_list;

	struct thread		*thread;

	struct rb_node		node;

};



static struct rb_root lat_snapshot_root;



static struct thread_latency *

thread_latency_search(struct rb_root *root, struct thread *thread)

{

	struct rb_node *node = root->rb_node;



	while (node) {

		struct thread_latency *lat;



		lat = container_of(node, struct thread_latency, node);

		if (thread->pid < lat->thread->pid)

			node = node->rb_left;

		else if (thread->pid > lat->thread->pid)

			node = node->rb_right;

		else {

			return lat;

		}

	}

	return NULL;

}



static void

__thread_latency_insert(struct rb_root *root, struct thread_latency *data)

{

	struct rb_node **new = &(root->rb_node), *parent = NULL;



	while (*new) {

		struct thread_latency *this;



		this = container_of(*new, struct thread_latency, node);

		parent = *new;

		if (data->thread->pid < this->thread->pid)

			new = &((*new)->rb_left);

		else if (data->thread->pid > this->thread->pid)

			new = &((*new)->rb_right);

		else

			die("Double thread insertion\n");

	}



	rb_link_node(&data->node, parent, new);

	rb_insert_color(&data->node, root);

}



static void thread_latency_insert(struct thread *thread)

{

	struct thread_latency *lat;

	lat = calloc(sizeof(*lat), 1);

	if (!lat)

		die("No memory");



	lat->thread = thread;

	INIT_LIST_HEAD(&lat->snapshot_list);

	__thread_latency_insert(&lat_snapshot_root, lat);

}



static void

latency_fork_event(struct trace_fork_event *fork_event __used,

		   struct event *event __used,

		   int cpu __used,

		   u64 timestamp __used,

		   struct thread *thread __used)

{

	/* should insert the newcomer */

}



static char sched_out_state(struct trace_switch_event *switch_event)

{

	const char *str = TASK_STATE_TO_CHAR_STR;



	return str[switch_event->prev_state];

}



static void

lat_sched_out(struct thread_latency *lat,

	     struct trace_switch_event *switch_event)

{

	struct lat_snapshot *snapshot;



	if (sched_out_state(switch_event) == 'R')

		return;



	snapshot = calloc(sizeof(*snapshot), 1);

	if (!snapshot)

		die("Non memory");



	list_add_tail(&snapshot->list, &lat->snapshot_list);

}



static void

lat_sched_in(struct thread_latency *lat, u64 timestamp)

{

	struct lat_snapshot *snapshot;



	if (list_empty(&lat->snapshot_list))

		return;



	snapshot = list_entry(lat->snapshot_list.prev, struct lat_snapshot,

			      list);



	if (snapshot->state != THREAD_WAKED_UP)

		return;



	if (timestamp < snapshot->wake_up_time) {

		snapshot->state = THREAD_IGNORE;

		return;

	}



	snapshot->state = THREAD_SCHED_IN;

	snapshot->sched_in_time = timestamp;

}





static void

latency_switch_event(struct trace_switch_event *switch_event,

		     struct event *event __used,

		     int cpu __used,

		     u64 timestamp,

		     struct thread *thread __used)

{

	struct thread_latency *out_lat, *in_lat;

	struct thread *sched_out, *sched_in;



	sched_out = threads__findnew(switch_event->prev_pid, &threads, &last_match);

	sched_in = threads__findnew(switch_event->next_pid, &threads, &last_match);



	in_lat = thread_latency_search(&lat_snapshot_root, sched_in);

	if (!in_lat) {

		thread_latency_insert(sched_in);

		in_lat = thread_latency_search(&lat_snapshot_root, sched_in);

		if (!in_lat)

			die("Internal latency tree error");

	}



	out_lat = thread_latency_search(&lat_snapshot_root, sched_out);

	if (!out_lat) {

		thread_latency_insert(sched_out);

		out_lat = thread_latency_search(&lat_snapshot_root, sched_out);

		if (!out_lat)

			die("Internal latency tree error");

	}



	lat_sched_in(in_lat, timestamp);

	lat_sched_out(out_lat, switch_event);

}



static void

latency_wakeup_event(struct trace_wakeup_event *wakeup_event,

		     struct event *event __used,

		     int cpu __used,

		     u64 timestamp,

		     struct thread *thread __used)

{

	struct thread_latency *lat;

	struct lat_snapshot *snapshot;

	struct thread *wakee;



	/* Note for later, it may be interesting to observe the failing cases */

	if (!wakeup_event->success)

		return;



	wakee = threads__findnew(wakeup_event->pid, &threads, &last_match);

	lat = thread_latency_search(&lat_snapshot_root, wakee);

	if (!lat) {

		thread_latency_insert(wakee);

		return;

	}



	if (list_empty(&lat->snapshot_list))

		return;



	snapshot = list_entry(lat->snapshot_list.prev, struct lat_snapshot,

			      list);



	if (snapshot->state != THREAD_SLEEPING)

		return;



	snapshot->state = THREAD_WAKED_UP;

	snapshot->wake_up_time = timestamp;

}



static struct trace_sched_handler lat_ops  = {

	.wakeup_event = latency_wakeup_event,

	.switch_event = latency_switch_event,

	.fork_event = latency_fork_event,

};



static void output_lat_thread(struct thread_latency *lat)

{

	struct lat_snapshot *shot;

	int count = 0;

	int i;

	int ret;

	u64 max = 0, avg;

	u64 total = 0, delta;



	list_for_each_entry(shot, &lat->snapshot_list, list) {

		if (shot->state != THREAD_SCHED_IN)

			continue;



		count++;



		delta = shot->sched_in_time - shot->wake_up_time;

		if (delta > max)

			max = delta;

		total += delta;

	}



	if (!count)

		return;



	ret = printf("%s", lat->thread->comm);



	for (i = 0; i < 25 - ret; i++)

		printf(" ");



	avg = total / count;



	printf("%5d        %10llu       %10llu      %10llu\n", count, total, avg, max);

}



static void output_lat_results(void)

{

	struct rb_node *next;



	printf(" Tasks");

	printf("                     count");

	printf("          total");

	printf("              avg");

	printf("            max\n\n");



	next = rb_first(&lat_snapshot_root);



	while (next) {

		struct thread_latency *lat;



		lat = rb_entry(next, struct thread_latency, node);

		output_lat_thread(lat);

		next = rb_next(next);

	}

}



static struct trace_sched_handler *trace_handler;
@@ -1154,6 +1418,8 @@ static const struct option options[] = { 
		    "dump raw trace in ASCII"),

	OPT_BOOLEAN('r', "replay", &replay_mode,

		    "replay sched behaviour from traces"),

	OPT_BOOLEAN('l', "latency", &lat_mode,

		    "measure various latencies"),

	OPT_BOOLEAN('v', "verbose", &verbose,

		    "be more verbose (show symbol address, etc)"),

	OPT_END()
@@ -1180,9 +1446,12 @@ int cmd_sched(int argc, const char **argv, const char *prefix __used) 


	if (replay_mode)

		trace_handler = &replay_ops;

	else /* We may need a default subcommand */

	else if (lat_mode)

		trace_handler = &lat_ops;

	else /* We may need a default subcommand (perf trace?) */

		die("Please select a sub command (-r)\n");



	if (replay_mode) {

		calibrate_run_measurement_overhead();

		calibrate_sleep_measurement_overhead();
@@ -1196,6 +1465,11 @@ int cmd_sched(int argc, const char **argv, const char *prefix __used) 
		printf("------------------------------------------------------------\n");

		for (i = 0; i < nr_iterations; i++)

			run_one_test();

	} else if (lat_mode) {

		setup_pager();

		__cmd_sched();

		output_lat_results();

	}



	return 0;

}