kernel/trace/ring_buffer_benchmark.c - LeafOS-Devices/android_kernel_samsung_universal7904 - Gitiles

 /*
  * ring buffer tester and benchmark
  *
  * Copyright (C) 2009 Steven Rostedt <srostedt@redhat.com>
  */
 #include <linux/ring_buffer.h>
 #include <linux/completion.h>
 #include <linux/kthread.h>
 #include <linux/module.h>
 #include <linux/ktime.h>
 #include <asm/local.h>

 struct rb_page {
 	u64		ts;
 	local_t		commit;
 	char		data[4080];
 };

 /* run time and sleep time in seconds */
 #define RUN_TIME	10ULL
 #define SLEEP_TIME	10

 /* number of events for writer to wake up the reader */
 static int wakeup_interval = 100;

 static int reader_finish;
 static DECLARE_COMPLETION(read_start);
 static DECLARE_COMPLETION(read_done);

 static struct ring_buffer *buffer;
 static struct task_struct *producer;
 static struct task_struct *consumer;
 static unsigned long read;

 static unsigned int disable_reader;
 module_param(disable_reader, uint, 0644);
 MODULE_PARM_DESC(disable_reader, "only run producer");

 static unsigned int write_iteration = 50;
 module_param(write_iteration, uint, 0644);
 MODULE_PARM_DESC(write_iteration, "# of writes between timestamp readings");

 static int producer_nice = MAX_NICE;
 static int consumer_nice = MAX_NICE;

 static int producer_fifo = -1;
 static int consumer_fifo = -1;

 module_param(producer_nice, int, 0644);
 MODULE_PARM_DESC(producer_nice, "nice prio for producer");

 module_param(consumer_nice, int, 0644);
 MODULE_PARM_DESC(consumer_nice, "nice prio for consumer");

 module_param(producer_fifo, int, 0644);
 MODULE_PARM_DESC(producer_fifo, "fifo prio for producer");

 module_param(consumer_fifo, int, 0644);
 MODULE_PARM_DESC(consumer_fifo, "fifo prio for consumer");

 static int read_events;

 static int test_error;

 #define TEST_ERROR()				\
 	do {					\
 		if (!test_error) {		\
 			test_error = 1;		\
 			WARN_ON(1);		\
 		}				\
 	} while (0)

 enum event_status {
 	EVENT_FOUND,
 	EVENT_DROPPED,
 };

 static bool break_test(void)
 {
 	return test_error || kthread_should_stop();
 }

 static enum event_status read_event(int cpu)
 {
 	struct ring_buffer_event *event;
 	int *entry;
 	u64 ts;

 	event = ring_buffer_consume(buffer, cpu, &ts, NULL);
 	if (!event)
 		return EVENT_DROPPED;

 	entry = ring_buffer_event_data(event);
 	if (*entry != cpu) {
 		TEST_ERROR();
 		return EVENT_DROPPED;
 	}

 	read++;
 	return EVENT_FOUND;
 }

 static enum event_status read_page(int cpu)
 {
 	struct ring_buffer_event *event;
 	struct rb_page *rpage;
 	unsigned long commit;
 	void *bpage;
 	int *entry;
 	int ret;
 	int inc;
 	int i;

 	bpage = ring_buffer_alloc_read_page(buffer, cpu);
 	if (!bpage)
 		return EVENT_DROPPED;

 	ret = ring_buffer_read_page(buffer, &bpage, PAGE_SIZE, cpu, 1);
 	if (ret >= 0) {
 		rpage = bpage;
 		/* The commit may have missed event flags set, clear them */
 		commit = local_read(&rpage->commit) & 0xfffff;
 		for (i = 0; i < commit && !test_error ; i += inc) {

 			if (i >= (PAGE_SIZE - offsetof(struct rb_page, data))) {
 				TEST_ERROR();
 				break;
 			}

 			inc = -1;
 			event = (void *)&rpage->data[i];
 			switch (event->type_len) {
 			case RINGBUF_TYPE_PADDING:
 				/* failed writes may be discarded events */
 				if (!event->time_delta)
 					TEST_ERROR();
 				inc = event->array[0] + 4;
 				break;
 			case RINGBUF_TYPE_TIME_EXTEND:
 				inc = 8;
 				break;
 			case 0:
 				entry = ring_buffer_event_data(event);
 				if (*entry != cpu) {
 					TEST_ERROR();
 					break;
 				}
 				read++;
 				if (!event->array[0]) {
 					TEST_ERROR();
 					break;
 				}
 				inc = event->array[0] + 4;
 				break;
 			default:
 				entry = ring_buffer_event_data(event);
 				if (*entry != cpu) {
 					TEST_ERROR();
 					break;
 				}
 				read++;
 				inc = ((event->type_len + 1) * 4);
 			}
 			if (test_error)
 				break;

 			if (inc <= 0) {
 				TEST_ERROR();
 				break;
 			}
 		}
 	}
 	ring_buffer_free_read_page(buffer, bpage);

 	if (ret < 0)
 		return EVENT_DROPPED;
 	return EVENT_FOUND;
 }

 static void ring_buffer_consumer(void)
 {
 	/* toggle between reading pages and events */
 	read_events ^= 1;

 	read = 0;
 	/*
 	 * Continue running until the producer specifically asks to stop
 	 * and is ready for the completion.
 	 */
 	while (!READ_ONCE(reader_finish)) {
 		int found = 1;

 		while (found && !test_error) {
 			int cpu;

 			found = 0;
 			for_each_online_cpu(cpu) {
 				enum event_status stat;

 				if (read_events)
 					stat = read_event(cpu);
 				else
 					stat = read_page(cpu);

 				if (test_error)
 					break;

 				if (stat == EVENT_FOUND)
 					found = 1;

 			}
 		}

 		/* Wait till the producer wakes us up when there is more data
 		 * available or when the producer wants us to finish reading.
 		 */
 		set_current_state(TASK_INTERRUPTIBLE);
 		if (reader_finish)
 			break;

 		schedule();
 	}
 	__set_current_state(TASK_RUNNING);
 	reader_finish = 0;
 	complete(&read_done);
 }

 static void ring_buffer_producer(void)
 {
 	ktime_t start_time, end_time, timeout;
 	unsigned long long time;
 	unsigned long long entries;
 	unsigned long long overruns;
 	unsigned long missed = 0;
 	unsigned long hit = 0;
 	unsigned long avg;
 	int cnt = 0;

 	/*
 	 * Hammer the buffer for 10 secs (this may
 	 * make the system stall)
 	 */
 	trace_printk("Starting ring buffer hammer\n");
 	start_time = ktime_get();
 	timeout = ktime_add_ns(start_time, RUN_TIME * NSEC_PER_SEC);
 	do {
 		struct ring_buffer_event *event;
 		int *entry;
 		int i;

 		for (i = 0; i < write_iteration; i++) {
 			event = ring_buffer_lock_reserve(buffer, 10);
 			if (!event) {
 				missed++;
 			} else {
 				hit++;
 				entry = ring_buffer_event_data(event);
 				*entry = smp_processor_id();
 				ring_buffer_unlock_commit(buffer, event);
 			}
 		}
 		end_time = ktime_get();

 		cnt++;
 		if (consumer && !(cnt % wakeup_interval))
 			wake_up_process(consumer);

 #ifndef CONFIG_PREEMPT
 		/*
 		 * If we are a non preempt kernel, the 10 second run will
 		 * stop everything while it runs. Instead, we will call
 		 * cond_resched and also add any time that was lost by a
 		 * rescedule.
 		 *
 		 * Do a cond resched at the same frequency we would wake up
 		 * the reader.
 		 */
 		if (cnt % wakeup_interval)
 			cond_resched();
 #endif
 	} while (ktime_before(end_time, timeout) && !break_test());
 	trace_printk("End ring buffer hammer\n");

 	if (consumer) {
 		/* Init both completions here to avoid races */
 		init_completion(&read_start);
 		init_completion(&read_done);
 		/* the completions must be visible before the finish var */
 		smp_wmb();
 		reader_finish = 1;
 		wake_up_process(consumer);
 		wait_for_completion(&read_done);
 	}

 	time = ktime_us_delta(end_time, start_time);

 	entries = ring_buffer_entries(buffer);
 	overruns = ring_buffer_overruns(buffer);

 	if (test_error)
 		trace_printk("ERROR!\n");

 	if (!disable_reader) {
 		if (consumer_fifo < 0)
 			trace_printk("Running Consumer at nice: %d\n",
 				     consumer_nice);
 		else
 			trace_printk("Running Consumer at SCHED_FIFO %d\n",
 				     consumer_fifo);
 	}
 	if (producer_fifo < 0)
 		trace_printk("Running Producer at nice: %d\n",
 			     producer_nice);
 	else
 		trace_printk("Running Producer at SCHED_FIFO %d\n",
 			     producer_fifo);

 	/* Let the user know that the test is running at low priority */
 	if (producer_fifo < 0 && consumer_fifo < 0 &&
 	    producer_nice == MAX_NICE && consumer_nice == MAX_NICE)
 		trace_printk("WARNING!!! This test is running at lowest priority.\n");

 	trace_printk("Time:     %lld (usecs)\n", time);
 	trace_printk("Overruns: %lld\n", overruns);
 	if (disable_reader)
 		trace_printk("Read:     (reader disabled)\n");
 	else
 		trace_printk("Read:     %ld  (by %s)\n", read,
 			read_events ? "events" : "pages");
 	trace_printk("Entries:  %lld\n", entries);
 	trace_printk("Total:    %lld\n", entries + overruns + read);
 	trace_printk("Missed:   %ld\n", missed);
 	trace_printk("Hit:      %ld\n", hit);

 	/* Convert time from usecs to millisecs */
 	do_div(time, USEC_PER_MSEC);
 	if (time)
 		hit /= (long)time;
 	else
 		trace_printk("TIME IS ZERO??\n");

 	trace_printk("Entries per millisec: %ld\n", hit);

 	if (hit) {
 		/* Calculate the average time in nanosecs */
 		avg = NSEC_PER_MSEC / hit;
 		trace_printk("%ld ns per entry\n", avg);
 	}

 	if (missed) {
 		if (time)
 			missed /= (long)time;

 		trace_printk("Total iterations per millisec: %ld\n",
 			     hit + missed);

 		/* it is possible that hit + missed will overflow and be zero */
 		if (!(hit + missed)) {
 			trace_printk("hit + missed overflowed and totalled zero!\n");
 			hit--; /* make it non zero */
 		}

 		/* Caculate the average time in nanosecs */
 		avg = NSEC_PER_MSEC / (hit + missed);
 		trace_printk("%ld ns per entry\n", avg);
 	}
 }

 static void wait_to_die(void)
 {
 	set_current_state(TASK_INTERRUPTIBLE);
 	while (!kthread_should_stop()) {
 		schedule();
 		set_current_state(TASK_INTERRUPTIBLE);
 	}
 	__set_current_state(TASK_RUNNING);
 }

 static int ring_buffer_consumer_thread(void *arg)
 {
 	while (!break_test()) {
 		complete(&read_start);

 		ring_buffer_consumer();

 		set_current_state(TASK_INTERRUPTIBLE);
 		if (break_test())
 			break;
 		schedule();
 	}
 	__set_current_state(TASK_RUNNING);

 	if (!kthread_should_stop())
 		wait_to_die();

 	return 0;
 }

 static int ring_buffer_producer_thread(void *arg)
 {
 	while (!break_test()) {
 		ring_buffer_reset(buffer);

 		if (consumer) {
 			wake_up_process(consumer);
 			wait_for_completion(&read_start);
 		}

 		ring_buffer_producer();
 		if (break_test())
 			goto out_kill;

 		trace_printk("Sleeping for 10 secs\n");
 		set_current_state(TASK_INTERRUPTIBLE);
 		if (break_test())
 			goto out_kill;
 		schedule_timeout(HZ * SLEEP_TIME);
 	}

 out_kill:
 	__set_current_state(TASK_RUNNING);
 	if (!kthread_should_stop())
 		wait_to_die();

 	return 0;
 }

 static int __init ring_buffer_benchmark_init(void)
 {
 	int ret;

 	/* make a one meg buffer in overwite mode */
 	buffer = ring_buffer_alloc(1000000, RB_FL_OVERWRITE);
 	if (!buffer)
 		return -ENOMEM;

 	if (!disable_reader) {
 		consumer = kthread_create(ring_buffer_consumer_thread,
 					  NULL, "rb_consumer");
 		ret = PTR_ERR(consumer);
 		if (IS_ERR(consumer))
 			goto out_fail;
 	}

 	producer = kthread_run(ring_buffer_producer_thread,
 			       NULL, "rb_producer");
 	ret = PTR_ERR(producer);

 	if (IS_ERR(producer))
 		goto out_kill;

 	/*
 	 * Run them as low-prio background tasks by default:
 	 */
 	if (!disable_reader) {
 		if (consumer_fifo >= 0) {
 			struct sched_param param = {
 				.sched_priority = consumer_fifo
 			};
 			sched_setscheduler(consumer, SCHED_FIFO, &param);
 		} else
 			set_user_nice(consumer, consumer_nice);
 	}

 	if (producer_fifo >= 0) {
 		struct sched_param param = {
 			.sched_priority = producer_fifo
 		};
 		sched_setscheduler(producer, SCHED_FIFO, &param);
 	} else
 		set_user_nice(producer, producer_nice);

 	return 0;

  out_kill:
 	if (consumer)
 		kthread_stop(consumer);

  out_fail:
 	ring_buffer_free(buffer);
 	return ret;
 }

 static void __exit ring_buffer_benchmark_exit(void)
 {
 	kthread_stop(producer);
 	if (consumer)
 		kthread_stop(consumer);
 	ring_buffer_free(buffer);
 }

 module_init(ring_buffer_benchmark_init);
 module_exit(ring_buffer_benchmark_exit);

 MODULE_AUTHOR("Steven Rostedt");
 MODULE_DESCRIPTION("ring_buffer_benchmark");
 MODULE_LICENSE("GPL");
	/*
	* ring buffer tester and benchmark
	*
	* Copyright (C) 2009 Steven Rostedt <srostedt@redhat.com>
	*/
	#include <linux/ring_buffer.h>
	#include <linux/completion.h>
	#include <linux/kthread.h>
	#include <linux/module.h>
	#include <linux/ktime.h>
	#include <asm/local.h>

	struct rb_page {
	u64 ts;
	local_t commit;
	char data[4080];
	};

	/* run time and sleep time in seconds */
	#define RUN_TIME 10ULL
	#define SLEEP_TIME 10

	/* number of events for writer to wake up the reader */
	static int wakeup_interval = 100;

	static int reader_finish;
	static DECLARE_COMPLETION(read_start);
	static DECLARE_COMPLETION(read_done);

	static struct ring_buffer *buffer;
	static struct task_struct *producer;
	static struct task_struct *consumer;
	static unsigned long read;

	static unsigned int disable_reader;
	module_param(disable_reader, uint, 0644);
	MODULE_PARM_DESC(disable_reader, "only run producer");

	static unsigned int write_iteration = 50;
	module_param(write_iteration, uint, 0644);
	MODULE_PARM_DESC(write_iteration, "# of writes between timestamp readings");

	static int producer_nice = MAX_NICE;
	static int consumer_nice = MAX_NICE;

	static int producer_fifo = -1;
	static int consumer_fifo = -1;

	module_param(producer_nice, int, 0644);
	MODULE_PARM_DESC(producer_nice, "nice prio for producer");

	module_param(consumer_nice, int, 0644);
	MODULE_PARM_DESC(consumer_nice, "nice prio for consumer");

	module_param(producer_fifo, int, 0644);
	MODULE_PARM_DESC(producer_fifo, "fifo prio for producer");

	module_param(consumer_fifo, int, 0644);
	MODULE_PARM_DESC(consumer_fifo, "fifo prio for consumer");

	static int read_events;

	static int test_error;

	#define TEST_ERROR() \
	do { \
	if (!test_error) { \
	test_error = 1; \
	WARN_ON(1); \
	} \
	} while (0)

	enum event_status {
	EVENT_FOUND,
	EVENT_DROPPED,
	};

	static bool break_test(void)
	{
	return test_error \|\| kthread_should_stop();
	}

	static enum event_status read_event(int cpu)
	{
	struct ring_buffer_event *event;
	int *entry;
	u64 ts;

	event = ring_buffer_consume(buffer, cpu, &ts, NULL);
	if (!event)
	return EVENT_DROPPED;

	entry = ring_buffer_event_data(event);
	if (*entry != cpu) {
	TEST_ERROR();
	return EVENT_DROPPED;
	}

	read++;
	return EVENT_FOUND;
	}

	static enum event_status read_page(int cpu)
	{
	struct ring_buffer_event *event;
	struct rb_page *rpage;
	unsigned long commit;
	void *bpage;
	int *entry;
	int ret;
	int inc;
	int i;

	bpage = ring_buffer_alloc_read_page(buffer, cpu);
	if (!bpage)
	return EVENT_DROPPED;

	ret = ring_buffer_read_page(buffer, &bpage, PAGE_SIZE, cpu, 1);
	if (ret >= 0) {
	rpage = bpage;
	/* The commit may have missed event flags set, clear them */
	commit = local_read(&rpage->commit) & 0xfffff;
	for (i = 0; i < commit && !test_error ; i += inc) {

	if (i >= (PAGE_SIZE - offsetof(struct rb_page, data))) {
	TEST_ERROR();
	break;
	}

	inc = -1;
	event = (void *)&rpage->data[i];
	switch (event->type_len) {
	case RINGBUF_TYPE_PADDING:
	/* failed writes may be discarded events */
	if (!event->time_delta)
	TEST_ERROR();
	inc = event->array[0] + 4;
	break;
	case RINGBUF_TYPE_TIME_EXTEND:
	inc = 8;
	break;
	case 0:
	entry = ring_buffer_event_data(event);
	if (*entry != cpu) {
	TEST_ERROR();
	break;
	}
	read++;
	if (!event->array[0]) {
	TEST_ERROR();
	break;
	}
	inc = event->array[0] + 4;
	break;
	default:
	entry = ring_buffer_event_data(event);
	if (*entry != cpu) {
	TEST_ERROR();
	break;
	}
	read++;
	inc = ((event->type_len + 1) * 4);
	}
	if (test_error)
	break;

	if (inc <= 0) {
	TEST_ERROR();
	break;
	}
	}
	}
	ring_buffer_free_read_page(buffer, bpage);

	if (ret < 0)
	return EVENT_DROPPED;
	return EVENT_FOUND;
	}

	static void ring_buffer_consumer(void)
	{
	/* toggle between reading pages and events */
	read_events ^= 1;

	read = 0;
	/*
	* Continue running until the producer specifically asks to stop
	* and is ready for the completion.
	*/
	while (!READ_ONCE(reader_finish)) {
	int found = 1;

	while (found && !test_error) {
	int cpu;

	found = 0;
	for_each_online_cpu(cpu) {
	enum event_status stat;

	if (read_events)
	stat = read_event(cpu);
	else
	stat = read_page(cpu);

	if (test_error)
	break;

	if (stat == EVENT_FOUND)
	found = 1;

	}
	}

	/* Wait till the producer wakes us up when there is more data
	* available or when the producer wants us to finish reading.
	*/
	set_current_state(TASK_INTERRUPTIBLE);
	if (reader_finish)
	break;

	schedule();
	}
	__set_current_state(TASK_RUNNING);
	reader_finish = 0;
	complete(&read_done);
	}

	static void ring_buffer_producer(void)
	{
	ktime_t start_time, end_time, timeout;
	unsigned long long time;
	unsigned long long entries;
	unsigned long long overruns;
	unsigned long missed = 0;
	unsigned long hit = 0;
	unsigned long avg;
	int cnt = 0;

	/*
	* Hammer the buffer for 10 secs (this may
	* make the system stall)
	*/
	trace_printk("Starting ring buffer hammer\n");
	start_time = ktime_get();
	timeout = ktime_add_ns(start_time, RUN_TIME * NSEC_PER_SEC);
	do {
	struct ring_buffer_event *event;
	int *entry;
	int i;

	for (i = 0; i < write_iteration; i++) {
	event = ring_buffer_lock_reserve(buffer, 10);
	if (!event) {
	missed++;
	} else {
	hit++;
	entry = ring_buffer_event_data(event);
	*entry = smp_processor_id();
	ring_buffer_unlock_commit(buffer, event);
	}
	}
	end_time = ktime_get();

	cnt++;
	if (consumer && !(cnt % wakeup_interval))
	wake_up_process(consumer);

	#ifndef CONFIG_PREEMPT
	/*
	* If we are a non preempt kernel, the 10 second run will
	* stop everything while it runs. Instead, we will call
	* cond_resched and also add any time that was lost by a
	* rescedule.
	*
	* Do a cond resched at the same frequency we would wake up
	* the reader.
	*/
	if (cnt % wakeup_interval)
	cond_resched();
	#endif
	} while (ktime_before(end_time, timeout) && !break_test());
	trace_printk("End ring buffer hammer\n");

	if (consumer) {
	/* Init both completions here to avoid races */
	init_completion(&read_start);
	init_completion(&read_done);
	/* the completions must be visible before the finish var */
	smp_wmb();
	reader_finish = 1;
	wake_up_process(consumer);
	wait_for_completion(&read_done);
	}

	time = ktime_us_delta(end_time, start_time);

	entries = ring_buffer_entries(buffer);
	overruns = ring_buffer_overruns(buffer);

	if (test_error)
	trace_printk("ERROR!\n");

	if (!disable_reader) {
	if (consumer_fifo < 0)
	trace_printk("Running Consumer at nice: %d\n",
	consumer_nice);
	else
	trace_printk("Running Consumer at SCHED_FIFO %d\n",
	consumer_fifo);
	}
	if (producer_fifo < 0)
	trace_printk("Running Producer at nice: %d\n",
	producer_nice);
	else
	trace_printk("Running Producer at SCHED_FIFO %d\n",
	producer_fifo);

	/* Let the user know that the test is running at low priority */
	if (producer_fifo < 0 && consumer_fifo < 0 &&
	producer_nice == MAX_NICE && consumer_nice == MAX_NICE)
	trace_printk("WARNING!!! This test is running at lowest priority.\n");

	trace_printk("Time: %lld (usecs)\n", time);
	trace_printk("Overruns: %lld\n", overruns);
	if (disable_reader)
	trace_printk("Read: (reader disabled)\n");
	else
	trace_printk("Read: %ld (by %s)\n", read,
	read_events ? "events" : "pages");
	trace_printk("Entries: %lld\n", entries);
	trace_printk("Total: %lld\n", entries + overruns + read);
	trace_printk("Missed: %ld\n", missed);
	trace_printk("Hit: %ld\n", hit);

	/* Convert time from usecs to millisecs */
	do_div(time, USEC_PER_MSEC);
	if (time)
	hit /= (long)time;
	else
	trace_printk("TIME IS ZERO??\n");

	trace_printk("Entries per millisec: %ld\n", hit);

	if (hit) {
	/* Calculate the average time in nanosecs */
	avg = NSEC_PER_MSEC / hit;
	trace_printk("%ld ns per entry\n", avg);
	}

	if (missed) {
	if (time)
	missed /= (long)time;

	trace_printk("Total iterations per millisec: %ld\n",
	hit + missed);

	/* it is possible that hit + missed will overflow and be zero */
	if (!(hit + missed)) {
	trace_printk("hit + missed overflowed and totalled zero!\n");
	hit--; /* make it non zero */
	}

	/* Caculate the average time in nanosecs */
	avg = NSEC_PER_MSEC / (hit + missed);
	trace_printk("%ld ns per entry\n", avg);
	}
	}

	static void wait_to_die(void)
	{
	set_current_state(TASK_INTERRUPTIBLE);
	while (!kthread_should_stop()) {
	schedule();
	set_current_state(TASK_INTERRUPTIBLE);
	}
	__set_current_state(TASK_RUNNING);
	}

	static int ring_buffer_consumer_thread(void *arg)
	{
	while (!break_test()) {
	complete(&read_start);

	ring_buffer_consumer();

	set_current_state(TASK_INTERRUPTIBLE);
	if (break_test())
	break;
	schedule();
	}
	__set_current_state(TASK_RUNNING);

	if (!kthread_should_stop())
	wait_to_die();

	return 0;
	}

	static int ring_buffer_producer_thread(void *arg)
	{
	while (!break_test()) {
	ring_buffer_reset(buffer);

	if (consumer) {
	wake_up_process(consumer);
	wait_for_completion(&read_start);
	}

	ring_buffer_producer();
	if (break_test())
	goto out_kill;

	trace_printk("Sleeping for 10 secs\n");
	set_current_state(TASK_INTERRUPTIBLE);
	if (break_test())
	goto out_kill;
	schedule_timeout(HZ * SLEEP_TIME);
	}

	out_kill:
	__set_current_state(TASK_RUNNING);
	if (!kthread_should_stop())
	wait_to_die();

	return 0;
	}

	static int __init ring_buffer_benchmark_init(void)
	{
	int ret;

	/* make a one meg buffer in overwite mode */
	buffer = ring_buffer_alloc(1000000, RB_FL_OVERWRITE);
	if (!buffer)
	return -ENOMEM;

	if (!disable_reader) {
	consumer = kthread_create(ring_buffer_consumer_thread,
	NULL, "rb_consumer");
	ret = PTR_ERR(consumer);
	if (IS_ERR(consumer))
	goto out_fail;
	}

	producer = kthread_run(ring_buffer_producer_thread,
	NULL, "rb_producer");
	ret = PTR_ERR(producer);

	if (IS_ERR(producer))
	goto out_kill;

	/*
	* Run them as low-prio background tasks by default:
	*/
	if (!disable_reader) {
	if (consumer_fifo >= 0) {
	struct sched_param param = {
	.sched_priority = consumer_fifo
	};
	sched_setscheduler(consumer, SCHED_FIFO, &param);
	} else
	set_user_nice(consumer, consumer_nice);
	}

	if (producer_fifo >= 0) {
	struct sched_param param = {
	.sched_priority = producer_fifo
	};
	sched_setscheduler(producer, SCHED_FIFO, &param);
	} else
	set_user_nice(producer, producer_nice);

	return 0;

	out_kill:
	if (consumer)
	kthread_stop(consumer);

	out_fail:
	ring_buffer_free(buffer);
	return ret;
	}

	static void __exit ring_buffer_benchmark_exit(void)
	{
	kthread_stop(producer);
	if (consumer)
	kthread_stop(consumer);
	ring_buffer_free(buffer);
	}

	module_init(ring_buffer_benchmark_init);
	module_exit(ring_buffer_benchmark_exit);

	MODULE_AUTHOR("Steven Rostedt");
	MODULE_DESCRIPTION("ring_buffer_benchmark");
	MODULE_LICENSE("GPL");