/*
   * 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/time.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	10
  #define SLEEP_TIME	10
  
  /* number of events for writer to wake up the reader */
  static int wakeup_interval = 100;
  
  static int reader_finish;
  static struct completion read_start;
  static struct completion read_done;
  
  static struct ring_buffer *buffer;
  static struct task_struct *producer;
  static struct task_struct *consumer;
  static unsigned long read;
  
  static int disable_reader;
  module_param(disable_reader, uint, 0644);
  MODULE_PARM_DESC(disable_reader, "only run producer");

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

  static int producer_nice = 19;
  static int consumer_nice = 19;
  
  static int producer_fifo = -1;
  static int consumer_fifo = -1;
  
  module_param(producer_nice, uint, 0644);
  MODULE_PARM_DESC(producer_nice, "nice prio for producer");
  
  module_param(consumer_nice, uint, 0644);
  MODULE_PARM_DESC(consumer_nice, "nice prio for consumer");
  
  module_param(producer_fifo, uint, 0644);
  MODULE_PARM_DESC(producer_fifo, "fifo prio for producer");
  
  module_param(consumer_fifo, uint, 0644);
  MODULE_PARM_DESC(consumer_fifo, "fifo prio for consumer");

  static int read_events;
  
  static int kill_test;
  
  #define KILL_TEST()				\
  	do {					\
  		if (!kill_test) {		\
  			kill_test = 1;		\
  			WARN_ON(1);		\
  		}				\
  	} while (0)
  
  enum event_status {
  	EVENT_FOUND,
  	EVENT_DROPPED,
  };
  
  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) {
  		KILL_TEST();
  		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 && !kill_test; i += inc) {
  
  			if (i >= (PAGE_SIZE - offsetof(struct rb_page, data))) {
  				KILL_TEST();
  				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)
  					KILL_TEST();
  				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) {
  					KILL_TEST();
  					break;
  				}
  				read++;
  				if (!event->array[0]) {
  					KILL_TEST();
  					break;
  				}

  				inc = event->array[0] + 4;

  				break;
  			default:
  				entry = ring_buffer_event_data(event);
  				if (*entry != cpu) {
  					KILL_TEST();
  					break;
  				}
  				read++;
  				inc = ((event->type_len + 1) * 4);
  			}
  			if (kill_test)
  				break;
  
  			if (inc <= 0) {
  				KILL_TEST();
  				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;
  	while (!reader_finish && !kill_test) {
  		int found;
  
  		do {
  			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 (kill_test)
  					break;
  				if (stat == EVENT_FOUND)
  					found = 1;
  			}
  		} while (found && !kill_test);
  
  		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)
  {
  	struct timeval start_tv;
  	struct timeval end_tv;
  	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
  ");

  	do_gettimeofday(&start_tv);
  	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);
  			}

  		}
  		do_gettimeofday(&end_tv);

  		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 (end_tv.tv_sec < (start_tv.tv_sec + RUN_TIME) && !kill_test);

  	trace_printk("End ring buffer hammer
  ");

  
  	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;
  		/* finish var visible before waking up the consumer */
  		smp_wmb();
  		wake_up_process(consumer);
  		wait_for_completion(&read_done);
  	}
  
  	time = end_tv.tv_sec - start_tv.tv_sec;

  	time *= USEC_PER_SEC;

  	time += (long long)((long)end_tv.tv_usec - (long)start_tv.tv_usec);
  
  	entries = ring_buffer_entries(buffer);
  	overruns = ring_buffer_overruns(buffer);
  
  	if (kill_test)

  		trace_printk("ERROR!
  ");

  
  	if (!disable_reader) {
  		if (consumer_fifo < 0)
  			trace_printk("Running Consumer at nice: %d
  ",
  				     consumer_nice);
  		else
  			trace_printk("Running Consumer at SCHED_FIFO %d
  ",
  				     consumer_fifo);
  	}
  	if (producer_fifo < 0)
  		trace_printk("Running Producer at nice: %d
  ",
  			     producer_nice);
  	else
  		trace_printk("Running Producer at SCHED_FIFO %d
  ",
  			     producer_fifo);
  
  	/* Let the user know that the test is running at low priority */
  	if (producer_fifo < 0 && consumer_fifo < 0 &&
  	    producer_nice == 19 && consumer_nice == 19)
  		trace_printk("WARNING!!! This test is running at lowest priority.
  ");

  	trace_printk("Time:     %lld (usecs)
  ", time);
  	trace_printk("Overruns: %lld
  ", overruns);

  	if (disable_reader)

  		trace_printk("Read:     (reader disabled)
  ");

  	else

  		trace_printk("Read:     %ld  (by %s)
  ", read,

  			read_events ? "events" : "pages");

  	trace_printk("Entries:  %lld
  ", entries);
  	trace_printk("Total:    %lld
  ", entries + overruns + read);
  	trace_printk("Missed:   %ld
  ", missed);
  	trace_printk("Hit:      %ld
  ", hit);

  	/* Convert time from usecs to millisecs */
  	do_div(time, USEC_PER_MSEC);

  	if (time)
  		hit /= (long)time;
  	else

  		trace_printk("TIME IS ZERO??
  ");

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

  
  	if (hit) {

  		/* Calculate the average time in nanosecs */
  		avg = NSEC_PER_MSEC / hit;

  		trace_printk("%ld ns per entry
  ", avg);

  	}

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

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

  		/* it is possible that hit + missed will overflow and be zero */
  		if (!(hit + missed)) {

  			trace_printk("hit + missed overflowed and totalled zero!
  ");

  			hit--; /* make it non zero */
  		}

  		/* Caculate the average time in nanosecs */
  		avg = NSEC_PER_MSEC / (hit + missed);

  		trace_printk("%ld ns per entry
  ", 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 (!kthread_should_stop() && !kill_test) {
  		complete(&read_start);
  
  		ring_buffer_consumer();
  
  		set_current_state(TASK_INTERRUPTIBLE);
  		if (kthread_should_stop() || kill_test)
  			break;
  
  		schedule();
  		__set_current_state(TASK_RUNNING);
  	}
  	__set_current_state(TASK_RUNNING);
  
  	if (kill_test)
  		wait_to_die();
  
  	return 0;
  }
  
  static int ring_buffer_producer_thread(void *arg)
  {
  	init_completion(&read_start);
  
  	while (!kthread_should_stop() && !kill_test) {
  		ring_buffer_reset(buffer);
  
  		if (consumer) {
  			smp_wmb();
  			wake_up_process(consumer);
  			wait_for_completion(&read_start);
  		}
  
  		ring_buffer_producer();

  		trace_printk("Sleeping for 10 secs
  ");

  		set_current_state(TASK_INTERRUPTIBLE);
  		schedule_timeout(HZ * SLEEP_TIME);
  		__set_current_state(TASK_RUNNING);
  	}
  
  	if (kill_test)
  		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 = consumer_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");