ring_buffer_benchmark.c

Go to the documentation of this file.

/*
 * ring buffer tester and benchmark
 *
 * Copyright (C) 2009 Steven Rostedt <[email protected]>
 */
#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\n");
    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\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");

    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 == 19 && consumer_nice == 19)
        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 (!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;

    /*
     * 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");