/*
 * 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>

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 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);
        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);
        if (!bpage)
                return EVENT_DROPPED;

        ret = ring_buffer_read_page(buffer, &bpage, PAGE_SIZE, cpu, 1);
        if (ret >= 0) {
                rpage = bpage;
                commit = local_read(&rpage->commit);
                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\n");
        do_gettimeofday(&start_tv);
        do {
                struct ring_buffer_event *event;
                int *entry;

                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\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;
                /* 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!\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 (!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\n");
                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;

        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");