// SPDX-License-Identifier: GPL-2.0
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/*
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* ring buffer tester and benchmark
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*
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* Copyright (C) 2009 Steven Rostedt <srostedt@redhat.com>
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*/
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#include <linux/ring_buffer.h>
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#include <linux/completion.h>
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#include <linux/kthread.h>
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#include <uapi/linux/sched/types.h>
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#include <linux/module.h>
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#include <linux/ktime.h>
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#include <asm/local.h>
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struct rb_page {
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u64 ts;
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local_t commit;
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char data[4080];
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};
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/* run time and sleep time in seconds */
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#define RUN_TIME 10ULL
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#define SLEEP_TIME 10
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/* number of events for writer to wake up the reader */
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static int wakeup_interval = 100;
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static int reader_finish;
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static DECLARE_COMPLETION(read_start);
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static DECLARE_COMPLETION(read_done);
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static struct trace_buffer *buffer;
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static struct task_struct *producer;
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static struct task_struct *consumer;
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static unsigned long read;
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static unsigned int disable_reader;
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module_param(disable_reader, uint, 0644);
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MODULE_PARM_DESC(disable_reader, "only run producer");
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static unsigned int write_iteration = 50;
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module_param(write_iteration, uint, 0644);
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MODULE_PARM_DESC(write_iteration, "# of writes between timestamp readings");
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static int producer_nice = MAX_NICE;
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static int consumer_nice = MAX_NICE;
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static int producer_fifo;
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static int consumer_fifo;
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module_param(producer_nice, int, 0644);
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MODULE_PARM_DESC(producer_nice, "nice prio for producer");
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module_param(consumer_nice, int, 0644);
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MODULE_PARM_DESC(consumer_nice, "nice prio for consumer");
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module_param(producer_fifo, int, 0644);
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MODULE_PARM_DESC(producer_fifo, "use fifo for producer: 0 - disabled, 1 - low prio, 2 - fifo");
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module_param(consumer_fifo, int, 0644);
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MODULE_PARM_DESC(consumer_fifo, "use fifo for consumer: 0 - disabled, 1 - low prio, 2 - fifo");
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static int read_events;
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static int test_error;
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#define TEST_ERROR() \
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do { \
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if (!test_error) { \
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test_error = 1; \
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WARN_ON(1); \
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} \
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} while (0)
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enum event_status {
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EVENT_FOUND,
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EVENT_DROPPED,
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};
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static bool break_test(void)
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{
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return test_error || kthread_should_stop();
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}
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static enum event_status read_event(int cpu)
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{
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struct ring_buffer_event *event;
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int *entry;
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u64 ts;
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event = ring_buffer_consume(buffer, cpu, &ts, NULL);
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if (!event)
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return EVENT_DROPPED;
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entry = ring_buffer_event_data(event);
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if (*entry != cpu) {
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TEST_ERROR();
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return EVENT_DROPPED;
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}
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read++;
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return EVENT_FOUND;
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}
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static enum event_status read_page(int cpu)
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{
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struct ring_buffer_event *event;
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struct rb_page *rpage;
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unsigned long commit;
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void *bpage;
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int *entry;
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int ret;
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int inc;
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int i;
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bpage = ring_buffer_alloc_read_page(buffer, cpu);
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if (IS_ERR(bpage))
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return EVENT_DROPPED;
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ret = ring_buffer_read_page(buffer, &bpage, PAGE_SIZE, cpu, 1);
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if (ret >= 0) {
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rpage = bpage;
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/* The commit may have missed event flags set, clear them */
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commit = local_read(&rpage->commit) & 0xfffff;
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for (i = 0; i < commit && !test_error ; i += inc) {
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if (i >= (PAGE_SIZE - offsetof(struct rb_page, data))) {
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TEST_ERROR();
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break;
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}
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inc = -1;
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event = (void *)&rpage->data[i];
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switch (event->type_len) {
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case RINGBUF_TYPE_PADDING:
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/* failed writes may be discarded events */
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if (!event->time_delta)
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TEST_ERROR();
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inc = event->array[0] + 4;
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break;
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case RINGBUF_TYPE_TIME_EXTEND:
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inc = 8;
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break;
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case 0:
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entry = ring_buffer_event_data(event);
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if (*entry != cpu) {
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TEST_ERROR();
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break;
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}
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read++;
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if (!event->array[0]) {
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TEST_ERROR();
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break;
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}
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inc = event->array[0] + 4;
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break;
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default:
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entry = ring_buffer_event_data(event);
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if (*entry != cpu) {
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TEST_ERROR();
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break;
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}
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read++;
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inc = ((event->type_len + 1) * 4);
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}
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if (test_error)
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break;
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if (inc <= 0) {
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TEST_ERROR();
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break;
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}
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}
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}
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ring_buffer_free_read_page(buffer, cpu, bpage);
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if (ret < 0)
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return EVENT_DROPPED;
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return EVENT_FOUND;
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}
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static void ring_buffer_consumer(void)
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{
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/* toggle between reading pages and events */
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read_events ^= 1;
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read = 0;
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/*
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* Continue running until the producer specifically asks to stop
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* and is ready for the completion.
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*/
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while (!READ_ONCE(reader_finish)) {
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int found = 1;
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while (found && !test_error) {
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int cpu;
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found = 0;
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for_each_online_cpu(cpu) {
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enum event_status stat;
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if (read_events)
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stat = read_event(cpu);
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else
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stat = read_page(cpu);
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if (test_error)
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break;
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if (stat == EVENT_FOUND)
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found = 1;
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}
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}
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/* Wait till the producer wakes us up when there is more data
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* available or when the producer wants us to finish reading.
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*/
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set_current_state(TASK_INTERRUPTIBLE);
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if (reader_finish)
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break;
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schedule();
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}
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__set_current_state(TASK_RUNNING);
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reader_finish = 0;
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complete(&read_done);
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}
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static void ring_buffer_producer(void)
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{
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ktime_t start_time, end_time, timeout;
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unsigned long long time;
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unsigned long long entries;
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unsigned long long overruns;
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unsigned long missed = 0;
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unsigned long hit = 0;
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unsigned long avg;
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int cnt = 0;
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/*
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* Hammer the buffer for 10 secs (this may
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* make the system stall)
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*/
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trace_printk("Starting ring buffer hammer\n");
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start_time = ktime_get();
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timeout = ktime_add_ns(start_time, RUN_TIME * NSEC_PER_SEC);
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do {
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struct ring_buffer_event *event;
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int *entry;
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int i;
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for (i = 0; i < write_iteration; i++) {
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event = ring_buffer_lock_reserve(buffer, 10);
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if (!event) {
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missed++;
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} else {
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hit++;
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entry = ring_buffer_event_data(event);
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*entry = smp_processor_id();
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ring_buffer_unlock_commit(buffer, event);
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}
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}
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end_time = ktime_get();
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cnt++;
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if (consumer && !(cnt % wakeup_interval))
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wake_up_process(consumer);
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#ifndef CONFIG_PREEMPTION
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/*
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* If we are a non preempt kernel, the 10 seconds run will
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* stop everything while it runs. Instead, we will call
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* cond_resched and also add any time that was lost by a
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* reschedule.
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*
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* Do a cond resched at the same frequency we would wake up
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* the reader.
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*/
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if (cnt % wakeup_interval)
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cond_resched();
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#endif
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} while (ktime_before(end_time, timeout) && !break_test());
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trace_printk("End ring buffer hammer\n");
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if (consumer) {
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/* Init both completions here to avoid races */
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init_completion(&read_start);
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init_completion(&read_done);
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/* the completions must be visible before the finish var */
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smp_wmb();
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reader_finish = 1;
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wake_up_process(consumer);
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wait_for_completion(&read_done);
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}
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time = ktime_us_delta(end_time, start_time);
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entries = ring_buffer_entries(buffer);
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overruns = ring_buffer_overruns(buffer);
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if (test_error)
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trace_printk("ERROR!\n");
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if (!disable_reader) {
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if (consumer_fifo)
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trace_printk("Running Consumer at SCHED_FIFO %s\n",
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consumer_fifo == 1 ? "low" : "high");
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else
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trace_printk("Running Consumer at nice: %d\n",
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consumer_nice);
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}
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if (producer_fifo)
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trace_printk("Running Producer at SCHED_FIFO %s\n",
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producer_fifo == 1 ? "low" : "high");
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else
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trace_printk("Running Producer at nice: %d\n",
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producer_nice);
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/* Let the user know that the test is running at low priority */
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if (!producer_fifo && !consumer_fifo &&
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producer_nice == MAX_NICE && consumer_nice == MAX_NICE)
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trace_printk("WARNING!!! This test is running at lowest priority.\n");
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trace_printk("Time: %lld (usecs)\n", time);
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trace_printk("Overruns: %lld\n", overruns);
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if (disable_reader)
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trace_printk("Read: (reader disabled)\n");
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else
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trace_printk("Read: %ld (by %s)\n", read,
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read_events ? "events" : "pages");
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trace_printk("Entries: %lld\n", entries);
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trace_printk("Total: %lld\n", entries + overruns + read);
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trace_printk("Missed: %ld\n", missed);
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trace_printk("Hit: %ld\n", hit);
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/* Convert time from usecs to millisecs */
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do_div(time, USEC_PER_MSEC);
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if (time)
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hit /= (long)time;
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else
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trace_printk("TIME IS ZERO??\n");
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trace_printk("Entries per millisec: %ld\n", hit);
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if (hit) {
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/* Calculate the average time in nanosecs */
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avg = NSEC_PER_MSEC / hit;
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trace_printk("%ld ns per entry\n", avg);
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}
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if (missed) {
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if (time)
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missed /= (long)time;
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trace_printk("Total iterations per millisec: %ld\n",
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hit + missed);
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/* it is possible that hit + missed will overflow and be zero */
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if (!(hit + missed)) {
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trace_printk("hit + missed overflowed and totalled zero!\n");
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hit--; /* make it non zero */
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}
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/* Calculate the average time in nanosecs */
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avg = NSEC_PER_MSEC / (hit + missed);
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trace_printk("%ld ns per entry\n", avg);
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}
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}
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static void wait_to_die(void)
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{
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set_current_state(TASK_INTERRUPTIBLE);
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while (!kthread_should_stop()) {
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schedule();
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set_current_state(TASK_INTERRUPTIBLE);
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}
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__set_current_state(TASK_RUNNING);
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}
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static int ring_buffer_consumer_thread(void *arg)
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{
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while (!break_test()) {
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complete(&read_start);
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ring_buffer_consumer();
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set_current_state(TASK_INTERRUPTIBLE);
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if (break_test())
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break;
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schedule();
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}
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__set_current_state(TASK_RUNNING);
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if (!kthread_should_stop())
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wait_to_die();
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return 0;
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}
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static int ring_buffer_producer_thread(void *arg)
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{
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while (!break_test()) {
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ring_buffer_reset(buffer);
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if (consumer) {
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wake_up_process(consumer);
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wait_for_completion(&read_start);
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}
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ring_buffer_producer();
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if (break_test())
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goto out_kill;
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trace_printk("Sleeping for 10 secs\n");
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set_current_state(TASK_INTERRUPTIBLE);
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if (break_test())
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goto out_kill;
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schedule_timeout(HZ * SLEEP_TIME);
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}
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out_kill:
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__set_current_state(TASK_RUNNING);
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if (!kthread_should_stop())
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wait_to_die();
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return 0;
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}
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static int __init ring_buffer_benchmark_init(void)
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{
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int ret;
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/* make a one meg buffer in overwite mode */
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buffer = ring_buffer_alloc(1000000, RB_FL_OVERWRITE);
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if (!buffer)
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return -ENOMEM;
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if (!disable_reader) {
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consumer = kthread_create(ring_buffer_consumer_thread,
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NULL, "rb_consumer");
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ret = PTR_ERR(consumer);
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if (IS_ERR(consumer))
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goto out_fail;
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}
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producer = kthread_run(ring_buffer_producer_thread,
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NULL, "rb_producer");
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ret = PTR_ERR(producer);
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if (IS_ERR(producer))
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goto out_kill;
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/*
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* Run them as low-prio background tasks by default:
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*/
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if (!disable_reader) {
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if (consumer_fifo >= 2)
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sched_set_fifo(consumer);
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else if (consumer_fifo == 1)
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sched_set_fifo_low(consumer);
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else
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set_user_nice(consumer, consumer_nice);
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}
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if (producer_fifo >= 2)
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sched_set_fifo(producer);
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else if (producer_fifo == 1)
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sched_set_fifo_low(producer);
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else
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set_user_nice(producer, producer_nice);
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return 0;
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out_kill:
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if (consumer)
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kthread_stop(consumer);
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out_fail:
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ring_buffer_free(buffer);
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return ret;
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}
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static void __exit ring_buffer_benchmark_exit(void)
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{
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kthread_stop(producer);
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if (consumer)
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kthread_stop(consumer);
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ring_buffer_free(buffer);
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}
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module_init(ring_buffer_benchmark_init);
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module_exit(ring_buffer_benchmark_exit);
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MODULE_AUTHOR("Steven Rostedt");
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MODULE_DESCRIPTION("ring_buffer_benchmark");
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MODULE_LICENSE("GPL");
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