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Commit a4be7c27 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf_counter: Allow sharing of output channels 



Provide the ability to configure a counter to send its output
to another (already existing) counter's output stream.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: stephane eranian <eranian@googlemail.com>
Cc: Paul Mackerras <paulus@samba.org>
LKML-Reference: <20090819092023.980284148@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent fa289bec

include/linux/perf_counter.h

+5 −0
Original line number Diff line number Diff line
@@ -216,6 +216,7 @@ struct perf_counter_attr { 
#define PERF_COUNTER_IOC_REFRESH	_IO ('$', 2)

#define PERF_COUNTER_IOC_RESET		_IO ('$', 3)

#define PERF_COUNTER_IOC_PERIOD		_IOW('$', 4, u64)

#define PERF_COUNTER_IOC_SET_OUTPUT	_IO ('$', 5)



enum perf_counter_ioc_flags {

	PERF_IOC_FLAG_GROUP		= 1U << 0,
@@ -415,6 +416,9 @@ enum perf_callchain_context { 
	PERF_CONTEXT_MAX		= (__u64)-4095,

};



#define PERF_FLAG_FD_NO_GROUP	(1U << 0)

#define PERF_FLAG_FD_OUTPUT	(1U << 1)



#ifdef __KERNEL__

/*

 * Kernel-internal data types and definitions:
@@ -536,6 +540,7 @@ struct perf_counter { 
	struct list_head		sibling_list;

	int				nr_siblings;

	struct perf_counter		*group_leader;

	struct perf_counter		*output;

	const struct pmu		*pmu;



	enum perf_counter_active_state	state;

kernel/perf_counter.c

+80 −3
Original line number Diff line number Diff line
@@ -1692,6 +1692,11 @@ static void free_counter(struct perf_counter *counter) 
			atomic_dec(&nr_task_counters);

	}



	if (counter->output) {

		fput(counter->output->filp);

		counter->output = NULL;

	}



	if (counter->destroy)

		counter->destroy(counter);
@@ -1977,6 +1982,8 @@ static int perf_counter_period(struct perf_counter *counter, u64 __user *arg) 
	return ret;

}



int perf_counter_set_output(struct perf_counter *counter, int output_fd);



static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg)

{

	struct perf_counter *counter = file->private_data;
@@ -2000,6 +2007,9 @@ static long perf_ioctl(struct file *file, unsigned int cmd, unsigned long arg) 
	case PERF_COUNTER_IOC_PERIOD:

		return perf_counter_period(counter, (u64 __user *)arg);



	case PERF_COUNTER_IOC_SET_OUTPUT:

		return perf_counter_set_output(counter, arg);



	default:

		return -ENOTTY;

	}
@@ -2270,6 +2280,11 @@ static int perf_mmap(struct file *file, struct vm_area_struct *vma) 


	WARN_ON_ONCE(counter->ctx->parent_ctx);

	mutex_lock(&counter->mmap_mutex);

	if (counter->output) {

		ret = -EINVAL;

		goto unlock;

	}



	if (atomic_inc_not_zero(&counter->mmap_count)) {

		if (nr_pages != counter->data->nr_pages)

			ret = -EINVAL;
@@ -2655,6 +2670,7 @@ static int perf_output_begin(struct perf_output_handle *handle, 
			     struct perf_counter *counter, unsigned int size,

			     int nmi, int sample)

{

	struct perf_counter *output_counter;

	struct perf_mmap_data *data;

	unsigned int offset, head;

	int have_lost;
@@ -2664,13 +2680,17 @@ static int perf_output_begin(struct perf_output_handle *handle, 
		u64			 lost;

	} lost_event;



	rcu_read_lock();

	/*

	 * For inherited counters we send all the output towards the parent.

	 */

	if (counter->parent)

		counter = counter->parent;



	rcu_read_lock();

	output_counter = rcu_dereference(counter->output);

	if (output_counter)

		counter = output_counter;



	data = rcu_dereference(counter->data);

	if (!data)

		goto out;
@@ -4218,6 +4238,57 @@ static int perf_copy_attr(struct perf_counter_attr __user *uattr, 
	goto out;

}



int perf_counter_set_output(struct perf_counter *counter, int output_fd)

{

	struct perf_counter *output_counter = NULL;

	struct file *output_file = NULL;

	struct perf_counter *old_output;

	int fput_needed = 0;

	int ret = -EINVAL;



	if (!output_fd)

		goto set;



	output_file = fget_light(output_fd, &fput_needed);

	if (!output_file)

		return -EBADF;



	if (output_file->f_op != &perf_fops)

		goto out;



	output_counter = output_file->private_data;



	/* Don't chain output fds */

	if (output_counter->output)

		goto out;



	/* Don't set an output fd when we already have an output channel */

	if (counter->data)

		goto out;



	atomic_long_inc(&output_file->f_count);



set:

	mutex_lock(&counter->mmap_mutex);

	old_output = counter->output;

	rcu_assign_pointer(counter->output, output_counter);

	mutex_unlock(&counter->mmap_mutex);



	if (old_output) {

		/*

		 * we need to make sure no existing perf_output_*()

		 * is still referencing this counter.

		 */

		synchronize_rcu();

		fput(old_output->filp);

	}



	ret = 0;

out:

	fput_light(output_file, fput_needed);

	return ret;

}



/**

 * sys_perf_counter_open - open a performance counter, associate it to a task/cpu

 *
@@ -4240,7 +4311,7 @@ SYSCALL_DEFINE5(perf_counter_open, 
	int ret;



	/* for future expandability... */

	if (flags)

	if (flags & ~(PERF_FLAG_FD_NO_GROUP | PERF_FLAG_FD_OUTPUT))

		return -EINVAL;



	ret = perf_copy_attr(attr_uptr, &attr);
@@ -4268,7 +4339,7 @@ SYSCALL_DEFINE5(perf_counter_open, 
	 * Look up the group leader (we will attach this counter to it):

	 */

	group_leader = NULL;

	if (group_fd != -1) {

	if (group_fd != -1 && !(flags & PERF_FLAG_FD_NO_GROUP)) {

		ret = -EINVAL;

		group_file = fget_light(group_fd, &fput_needed);

		if (!group_file)
@@ -4310,6 +4381,12 @@ SYSCALL_DEFINE5(perf_counter_open, 
	if (!counter_file)

		goto err_free_put_context;



	if (flags & PERF_FLAG_FD_OUTPUT) {

		ret = perf_counter_set_output(counter, group_fd);

		if (ret)

			goto err_free_put_context;

	}



	counter->filp = counter_file;

	WARN_ON_ONCE(ctx->parent_ctx);

	mutex_lock(&ctx->mutex);