Commit 9f498cc5 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf_counter: Full task tracing 



In order to be able to distinguish between no samples due to
inactivity and no samples due to task ended, Arjan asked for
PERF_EVENT_EXIT events. This is useful to the boot delay
instrumentation (bootchart) app.

This patch changes the PERF_EVENT_FORK to be emitted on every
clone, and adds PERF_EVENT_EXIT to be emitted on task exit,
after the task's counters have been closed.

This task tracing is controlled through: attr.comm || attr.mmap
and through the new attr.task field.

Suggested-by: default avatarArjan van de Ven <arjan@linux.intel.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Anton Blanchard <anton@samba.org>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
[ cleaned up perf_counter.h a bit ]
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent e53c0994

include/linux/perf_counter.h

+12 −1
Original line number Diff line number Diff line
@@ -181,8 +181,9 @@ struct perf_counter_attr { 
				freq           :  1, /* use freq, not period  */

				inherit_stat   :  1, /* per task counts       */

				enable_on_exec :  1, /* next exec enables     */

				task           :  1, /* trace fork/exit       */



				__reserved_1   : 51;

				__reserved_1   : 50;



	__u32			wakeup_events;	/* wakeup every n events */

	__u32			__reserved_2;
@@ -308,6 +309,15 @@ enum perf_event_type { 
	 */

	PERF_EVENT_COMM			= 3,



	/*

	 * struct {

	 *	struct perf_event_header	header;

	 *	u32				pid, ppid;

	 *	u32				tid, ptid;

	 * };

	 */

	PERF_EVENT_EXIT			= 4,



	/*

	 * struct {

	 *	struct perf_event_header	header;
@@ -323,6 +333,7 @@ enum perf_event_type { 
	 * struct {

	 *	struct perf_event_header	header;

	 *	u32				pid, ppid;

	 *	u32				tid, ptid;

	 * };

	 */

	PERF_EVENT_FORK			= 7,

kernel/fork.c

+1 −3
Original line number Diff line number Diff line
@@ -1269,6 +1269,7 @@ static struct task_struct *copy_process(unsigned long clone_flags, 
	write_unlock_irq(&tasklist_lock);

	proc_fork_connector(p);

	cgroup_post_fork(p);

	perf_counter_fork(p);

	return p;



bad_fork_free_pid:
@@ -1410,9 +1411,6 @@ long do_fork(unsigned long clone_flags, 
			init_completion(&vfork);

		}



		if (!(clone_flags & CLONE_THREAD))

			perf_counter_fork(p);



		audit_finish_fork(p);

		tracehook_report_clone(regs, clone_flags, nr, p);

kernel/perf_counter.c

+58 −29
Original line number Diff line number Diff line
@@ -42,6 +42,7 @@ static int perf_overcommit __read_mostly = 1; 
static atomic_t nr_counters __read_mostly;

static atomic_t nr_mmap_counters __read_mostly;

static atomic_t nr_comm_counters __read_mostly;

static atomic_t nr_task_counters __read_mostly;



/*

 * perf counter paranoia level:
@@ -1654,6 +1655,8 @@ static void free_counter(struct perf_counter *counter) 
			atomic_dec(&nr_mmap_counters);

		if (counter->attr.comm)

			atomic_dec(&nr_comm_counters);

		if (counter->attr.task)

			atomic_dec(&nr_task_counters);

	}



	if (counter->destroy)
@@ -2831,10 +2834,12 @@ perf_counter_read_event(struct perf_counter *counter, 
}



/*

 * fork tracking

 * task tracking -- fork/exit

 *

 * enabled by: attr.comm | attr.mmap | attr.task

 */



struct perf_fork_event {

struct perf_task_event {

	struct task_struct	*task;



	struct {
@@ -2842,37 +2847,42 @@ struct perf_fork_event { 


		u32				pid;

		u32				ppid;

		u32				tid;

		u32				ptid;

	} event;

};



static void perf_counter_fork_output(struct perf_counter *counter,

				     struct perf_fork_event *fork_event)

static void perf_counter_task_output(struct perf_counter *counter,

				     struct perf_task_event *task_event)

{

	struct perf_output_handle handle;

	int size = fork_event->event.header.size;

	struct task_struct *task = fork_event->task;

	int size = task_event->event.header.size;

	struct task_struct *task = task_event->task;

	int ret = perf_output_begin(&handle, counter, size, 0, 0);



	if (ret)

		return;



	fork_event->event.pid = perf_counter_pid(counter, task);

	fork_event->event.ppid = perf_counter_pid(counter, task->real_parent);

	task_event->event.pid = perf_counter_pid(counter, task);

	task_event->event.ppid = perf_counter_pid(counter, task->real_parent);



	task_event->event.tid = perf_counter_tid(counter, task);

	task_event->event.ptid = perf_counter_tid(counter, task->real_parent);



	perf_output_put(&handle, fork_event->event);

	perf_output_put(&handle, task_event->event);

	perf_output_end(&handle);

}



static int perf_counter_fork_match(struct perf_counter *counter)

static int perf_counter_task_match(struct perf_counter *counter)

{

	if (counter->attr.comm || counter->attr.mmap)

	if (counter->attr.comm || counter->attr.mmap || counter->attr.task)

		return 1;



	return 0;

}



static void perf_counter_fork_ctx(struct perf_counter_context *ctx,

				  struct perf_fork_event *fork_event)

static void perf_counter_task_ctx(struct perf_counter_context *ctx,

				  struct perf_task_event *task_event)

{

	struct perf_counter *counter;
@@ -2881,19 +2891,19 @@ static void perf_counter_fork_ctx(struct perf_counter_context *ctx, 


	rcu_read_lock();

	list_for_each_entry_rcu(counter, &ctx->event_list, event_entry) {

		if (perf_counter_fork_match(counter))

			perf_counter_fork_output(counter, fork_event);

		if (perf_counter_task_match(counter))

			perf_counter_task_output(counter, task_event);

	}

	rcu_read_unlock();

}



static void perf_counter_fork_event(struct perf_fork_event *fork_event)

static void perf_counter_task_event(struct perf_task_event *task_event)

{

	struct perf_cpu_context *cpuctx;

	struct perf_counter_context *ctx;



	cpuctx = &get_cpu_var(perf_cpu_context);

	perf_counter_fork_ctx(&cpuctx->ctx, fork_event);

	perf_counter_task_ctx(&cpuctx->ctx, task_event);

	put_cpu_var(perf_cpu_context);



	rcu_read_lock();
@@ -2903,32 +2913,40 @@ static void perf_counter_fork_event(struct perf_fork_event *fork_event) 
	 */

	ctx = rcu_dereference(current->perf_counter_ctxp);

	if (ctx)

		perf_counter_fork_ctx(ctx, fork_event);

		perf_counter_task_ctx(ctx, task_event);

	rcu_read_unlock();

}



void perf_counter_fork(struct task_struct *task)

static void perf_counter_task(struct task_struct *task, int new)

{

	struct perf_fork_event fork_event;

	struct perf_task_event task_event;



	if (!atomic_read(&nr_comm_counters) &&

	    !atomic_read(&nr_mmap_counters))

	    !atomic_read(&nr_mmap_counters) &&

	    !atomic_read(&nr_task_counters))

		return;



	fork_event = (struct perf_fork_event){

	task_event = (struct perf_task_event){

		.task	= task,

		.event  = {

			.header = {

				.type = PERF_EVENT_FORK,

				.type = new ? PERF_EVENT_FORK : PERF_EVENT_EXIT,

				.misc = 0,

				.size = sizeof(fork_event.event),

				.size = sizeof(task_event.event),

			},

			/* .pid  */

			/* .ppid */

			/* .tid  */

			/* .ptid */

		},

	};



	perf_counter_fork_event(&fork_event);

	perf_counter_task_event(&task_event);

}



void perf_counter_fork(struct task_struct *task)

{

	perf_counter_task(task, 1);

}



/*
@@ -3887,6 +3905,8 @@ done: 
			atomic_inc(&nr_mmap_counters);

		if (counter->attr.comm)

			atomic_inc(&nr_comm_counters);

		if (counter->attr.task)

			atomic_inc(&nr_task_counters);

	}



	return counter;
@@ -4248,8 +4268,10 @@ void perf_counter_exit_task(struct task_struct *child) 
	struct perf_counter_context *child_ctx;

	unsigned long flags;



	if (likely(!child->perf_counter_ctxp))

	if (likely(!child->perf_counter_ctxp)) {

		perf_counter_task(child, 0);

		return;

	}



	local_irq_save(flags);

	/*
@@ -4267,15 +4289,22 @@ void perf_counter_exit_task(struct task_struct *child) 
	 * incremented the context's refcount before we do put_ctx below.

	 */

	spin_lock(&child_ctx->lock);

	child->perf_counter_ctxp = NULL;

	/*

	 * If this context is a clone; unclone it so it can't get

	 * swapped to another process while we're removing all

	 * the counters from it.

	 */

	unclone_ctx(child_ctx);

	spin_unlock(&child_ctx->lock);

	local_irq_restore(flags);

	spin_unlock_irqrestore(&child_ctx->lock, flags);



	/*

	 * Report the task dead after unscheduling the counters so that we

	 * won't get any samples after PERF_EVENT_EXIT. We can however still

	 * get a few PERF_EVENT_READ events.

	 */

	perf_counter_task(child, 0);



	child->perf_counter_ctxp = NULL;



	/*

	 * We can recurse on the same lock type through:

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