1 // SPDX-License-Identifier: GPL-2.0
3 * ring buffer tester and benchmark
5 * Copyright (C) 2009 Steven Rostedt <srostedt@redhat.com>
7 #include <linux/ring_buffer.h>
8 #include <linux/completion.h>
9 #include <linux/kthread.h>
10 #include <uapi/linux/sched/types.h>
11 #include <linux/module.h>
12 #include <linux/ktime.h>
13 #include <asm/local.h>
21 /* run time and sleep time in seconds */
22 #define RUN_TIME 10ULL
25 /* number of events for writer to wake up the reader */
26 static int wakeup_interval = 100;
28 static int reader_finish;
29 static DECLARE_COMPLETION(read_start);
30 static DECLARE_COMPLETION(read_done);
32 static struct trace_buffer *buffer;
33 static struct task_struct *producer;
34 static struct task_struct *consumer;
35 static unsigned long read;
37 static unsigned int disable_reader;
38 module_param(disable_reader, uint, 0644);
39 MODULE_PARM_DESC(disable_reader, "only run producer");
41 static unsigned int write_iteration = 50;
42 module_param(write_iteration, uint, 0644);
43 MODULE_PARM_DESC(write_iteration, "# of writes between timestamp readings");
45 static int producer_nice = MAX_NICE;
46 static int consumer_nice = MAX_NICE;
48 static int producer_fifo;
49 static int consumer_fifo;
51 module_param(producer_nice, int, 0644);
52 MODULE_PARM_DESC(producer_nice, "nice prio for producer");
54 module_param(consumer_nice, int, 0644);
55 MODULE_PARM_DESC(consumer_nice, "nice prio for consumer");
57 module_param(producer_fifo, int, 0644);
58 MODULE_PARM_DESC(producer_fifo, "use fifo for producer: 0 - disabled, 1 - low prio, 2 - fifo");
60 module_param(consumer_fifo, int, 0644);
61 MODULE_PARM_DESC(consumer_fifo, "use fifo for consumer: 0 - disabled, 1 - low prio, 2 - fifo");
63 static int read_events;
65 static int test_error;
67 #define TEST_ERROR() \
80 static bool break_test(void)
82 return test_error || kthread_should_stop();
85 static enum event_status read_event(int cpu)
87 struct ring_buffer_event *event;
91 event = ring_buffer_consume(buffer, cpu, &ts, NULL);
95 entry = ring_buffer_event_data(event);
105 static enum event_status read_page(int cpu)
107 struct buffer_data_read_page *bpage;
108 struct ring_buffer_event *event;
109 struct rb_page *rpage;
110 unsigned long commit;
117 bpage = ring_buffer_alloc_read_page(buffer, cpu);
119 return EVENT_DROPPED;
121 page_size = ring_buffer_subbuf_size_get(buffer);
122 ret = ring_buffer_read_page(buffer, bpage, page_size, cpu, 1);
124 rpage = ring_buffer_read_page_data(bpage);
125 /* The commit may have missed event flags set, clear them */
126 commit = local_read(&rpage->commit) & 0xfffff;
127 for (i = 0; i < commit && !test_error ; i += inc) {
129 if (i >= (page_size - offsetof(struct rb_page, data))) {
135 event = (void *)&rpage->data[i];
136 switch (event->type_len) {
137 case RINGBUF_TYPE_PADDING:
138 /* failed writes may be discarded events */
139 if (!event->time_delta)
141 inc = event->array[0] + 4;
143 case RINGBUF_TYPE_TIME_EXTEND:
147 entry = ring_buffer_event_data(event);
153 if (!event->array[0]) {
157 inc = event->array[0] + 4;
160 entry = ring_buffer_event_data(event);
166 inc = ((event->type_len + 1) * 4);
177 ring_buffer_free_read_page(buffer, cpu, bpage);
180 return EVENT_DROPPED;
184 static void ring_buffer_consumer(void)
186 /* toggle between reading pages and events */
191 * Continue running until the producer specifically asks to stop
192 * and is ready for the completion.
194 while (!READ_ONCE(reader_finish)) {
197 while (found && !test_error) {
201 for_each_online_cpu(cpu) {
202 enum event_status stat;
205 stat = read_event(cpu);
207 stat = read_page(cpu);
212 if (stat == EVENT_FOUND)
218 /* Wait till the producer wakes us up when there is more data
219 * available or when the producer wants us to finish reading.
221 set_current_state(TASK_INTERRUPTIBLE);
227 __set_current_state(TASK_RUNNING);
229 complete(&read_done);
232 static void ring_buffer_producer(void)
234 ktime_t start_time, end_time, timeout;
235 unsigned long long time;
236 unsigned long long entries;
237 unsigned long long overruns;
238 unsigned long missed = 0;
239 unsigned long hit = 0;
244 * Hammer the buffer for 10 secs (this may
245 * make the system stall)
247 trace_printk("Starting ring buffer hammer\n");
248 start_time = ktime_get();
249 timeout = ktime_add_ns(start_time, RUN_TIME * NSEC_PER_SEC);
251 struct ring_buffer_event *event;
255 for (i = 0; i < write_iteration; i++) {
256 event = ring_buffer_lock_reserve(buffer, 10);
261 entry = ring_buffer_event_data(event);
262 *entry = smp_processor_id();
263 ring_buffer_unlock_commit(buffer);
266 end_time = ktime_get();
269 if (consumer && !(cnt % wakeup_interval))
270 wake_up_process(consumer);
272 #ifndef CONFIG_PREEMPTION
274 * If we are a non preempt kernel, the 10 seconds run will
275 * stop everything while it runs. Instead, we will call
276 * cond_resched and also add any time that was lost by a
279 * Do a cond resched at the same frequency we would wake up
282 if (cnt % wakeup_interval)
285 } while (ktime_before(end_time, timeout) && !break_test());
286 trace_printk("End ring buffer hammer\n");
289 /* Init both completions here to avoid races */
290 init_completion(&read_start);
291 init_completion(&read_done);
292 /* the completions must be visible before the finish var */
295 wake_up_process(consumer);
296 wait_for_completion(&read_done);
299 time = ktime_us_delta(end_time, start_time);
301 entries = ring_buffer_entries(buffer);
302 overruns = ring_buffer_overruns(buffer);
305 trace_printk("ERROR!\n");
307 if (!disable_reader) {
309 trace_printk("Running Consumer at SCHED_FIFO %s\n",
310 consumer_fifo == 1 ? "low" : "high");
312 trace_printk("Running Consumer at nice: %d\n",
316 trace_printk("Running Producer at SCHED_FIFO %s\n",
317 producer_fifo == 1 ? "low" : "high");
319 trace_printk("Running Producer at nice: %d\n",
322 /* Let the user know that the test is running at low priority */
323 if (!producer_fifo && !consumer_fifo &&
324 producer_nice == MAX_NICE && consumer_nice == MAX_NICE)
325 trace_printk("WARNING!!! This test is running at lowest priority.\n");
327 trace_printk("Time: %lld (usecs)\n", time);
328 trace_printk("Overruns: %lld\n", overruns);
330 trace_printk("Read: (reader disabled)\n");
332 trace_printk("Read: %ld (by %s)\n", read,
333 read_events ? "events" : "pages");
334 trace_printk("Entries: %lld\n", entries);
335 trace_printk("Total: %lld\n", entries + overruns + read);
336 trace_printk("Missed: %ld\n", missed);
337 trace_printk("Hit: %ld\n", hit);
339 /* Convert time from usecs to millisecs */
340 do_div(time, USEC_PER_MSEC);
344 trace_printk("TIME IS ZERO??\n");
346 trace_printk("Entries per millisec: %ld\n", hit);
349 /* Calculate the average time in nanosecs */
350 avg = NSEC_PER_MSEC / hit;
351 trace_printk("%ld ns per entry\n", avg);
356 missed /= (long)time;
358 trace_printk("Total iterations per millisec: %ld\n",
361 /* it is possible that hit + missed will overflow and be zero */
362 if (!(hit + missed)) {
363 trace_printk("hit + missed overflowed and totalled zero!\n");
364 hit--; /* make it non zero */
367 /* Calculate the average time in nanosecs */
368 avg = NSEC_PER_MSEC / (hit + missed);
369 trace_printk("%ld ns per entry\n", avg);
373 static void wait_to_die(void)
375 set_current_state(TASK_INTERRUPTIBLE);
376 while (!kthread_should_stop()) {
378 set_current_state(TASK_INTERRUPTIBLE);
380 __set_current_state(TASK_RUNNING);
383 static int ring_buffer_consumer_thread(void *arg)
385 while (!break_test()) {
386 complete(&read_start);
388 ring_buffer_consumer();
390 set_current_state(TASK_INTERRUPTIBLE);
395 __set_current_state(TASK_RUNNING);
397 if (!kthread_should_stop())
403 static int ring_buffer_producer_thread(void *arg)
405 while (!break_test()) {
406 ring_buffer_reset(buffer);
409 wake_up_process(consumer);
410 wait_for_completion(&read_start);
413 ring_buffer_producer();
417 trace_printk("Sleeping for 10 secs\n");
418 set_current_state(TASK_INTERRUPTIBLE);
421 schedule_timeout(HZ * SLEEP_TIME);
425 __set_current_state(TASK_RUNNING);
426 if (!kthread_should_stop())
432 static int __init ring_buffer_benchmark_init(void)
436 /* make a one meg buffer in overwite mode */
437 buffer = ring_buffer_alloc(1000000, RB_FL_OVERWRITE);
441 if (!disable_reader) {
442 consumer = kthread_create(ring_buffer_consumer_thread,
443 NULL, "rb_consumer");
444 ret = PTR_ERR(consumer);
445 if (IS_ERR(consumer))
449 producer = kthread_run(ring_buffer_producer_thread,
450 NULL, "rb_producer");
451 ret = PTR_ERR(producer);
453 if (IS_ERR(producer))
457 * Run them as low-prio background tasks by default:
459 if (!disable_reader) {
460 if (consumer_fifo >= 2)
461 sched_set_fifo(consumer);
462 else if (consumer_fifo == 1)
463 sched_set_fifo_low(consumer);
465 set_user_nice(consumer, consumer_nice);
468 if (producer_fifo >= 2)
469 sched_set_fifo(producer);
470 else if (producer_fifo == 1)
471 sched_set_fifo_low(producer);
473 set_user_nice(producer, producer_nice);
479 kthread_stop(consumer);
482 ring_buffer_free(buffer);
486 static void __exit ring_buffer_benchmark_exit(void)
488 kthread_stop(producer);
490 kthread_stop(consumer);
491 ring_buffer_free(buffer);
494 module_init(ring_buffer_benchmark_init);
495 module_exit(ring_buffer_benchmark_exit);
497 MODULE_AUTHOR("Steven Rostedt");
498 MODULE_DESCRIPTION("ring_buffer_benchmark");
499 MODULE_LICENSE("GPL");