1// SPDX-License-Identifier: GPL-2.0
2/*
3 * ring buffer tester and benchmark
4 *
5 * Copyright (C) 2009 Steven Rostedt <srostedt@redhat.com>
6 */
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>
14
15struct rb_page {
16 u64 ts;
17 local_t commit;
18 char data[4080];
19};
20
21/* run time and sleep time in seconds */
22#define RUN_TIME 10ULL
23#define SLEEP_TIME 10
24
25/* number of events for writer to wake up the reader */
26static int wakeup_interval = 100;
27
28static int reader_finish;
29static DECLARE_COMPLETION(read_start);
30static DECLARE_COMPLETION(read_done);
31
32static struct ring_buffer *buffer;
33static struct task_struct *producer;
34static struct task_struct *consumer;
35static unsigned long read;
36
37static unsigned int disable_reader;
38module_param(disable_reader, uint, 0644);
39MODULE_PARM_DESC(disable_reader, "only run producer");
40
41static unsigned int write_iteration = 50;
42module_param(write_iteration, uint, 0644);
43MODULE_PARM_DESC(write_iteration, "# of writes between timestamp readings");
44
45static int producer_nice = MAX_NICE;
46static int consumer_nice = MAX_NICE;
47
48static int producer_fifo = -1;
49static int consumer_fifo = -1;
50
51module_param(producer_nice, int, 0644);
52MODULE_PARM_DESC(producer_nice, "nice prio for producer");
53
54module_param(consumer_nice, int, 0644);
55MODULE_PARM_DESC(consumer_nice, "nice prio for consumer");
56
57module_param(producer_fifo, int, 0644);
58MODULE_PARM_DESC(producer_fifo, "fifo prio for producer");
59
60module_param(consumer_fifo, int, 0644);
61MODULE_PARM_DESC(consumer_fifo, "fifo prio for consumer");
62
63static int read_events;
64
65static int test_error;
66
67#define TEST_ERROR() \
68 do { \
69 if (!test_error) { \
70 test_error = 1; \
71 WARN_ON(1); \
72 } \
73 } while (0)
74
75enum event_status {
76 EVENT_FOUND,
77 EVENT_DROPPED,
78};
79
80static bool break_test(void)
81{
82 return test_error || kthread_should_stop();
83}
84
85static enum event_status read_event(int cpu)
86{
87 struct ring_buffer_event *event;
88 int *entry;
89 u64 ts;
90
91 event = ring_buffer_consume(buffer, cpu, &ts, NULL);
92 if (!event)
93 return EVENT_DROPPED;
94
95 entry = ring_buffer_event_data(event);
96 if (*entry != cpu) {
97 TEST_ERROR();
98 return EVENT_DROPPED;
99 }
100
101 read++;
102 return EVENT_FOUND;
103}
104
105static enum event_status read_page(int cpu)
106{
107 struct ring_buffer_event *event;
108 struct rb_page *rpage;
109 unsigned long commit;
110 void *bpage;
111 int *entry;
112 int ret;
113 int inc;
114 int i;
115
116 bpage = ring_buffer_alloc_read_page(buffer, cpu);
117 if (IS_ERR(bpage))
118 return EVENT_DROPPED;
119
120 ret = ring_buffer_read_page(buffer, &bpage, PAGE_SIZE, cpu, 1);
121 if (ret >= 0) {
122 rpage = bpage;
123 /* The commit may have missed event flags set, clear them */
124 commit = local_read(&rpage->commit) & 0xfffff;
125 for (i = 0; i < commit && !test_error ; i += inc) {
126
127 if (i >= (PAGE_SIZE - offsetof(struct rb_page, data))) {
128 TEST_ERROR();
129 break;
130 }
131
132 inc = -1;
133 event = (void *)&rpage->data[i];
134 switch (event->type_len) {
135 case RINGBUF_TYPE_PADDING:
136 /* failed writes may be discarded events */
137 if (!event->time_delta)
138 TEST_ERROR();
139 inc = event->array[0] + 4;
140 break;
141 case RINGBUF_TYPE_TIME_EXTEND:
142 inc = 8;
143 break;
144 case 0:
145 entry = ring_buffer_event_data(event);
146 if (*entry != cpu) {
147 TEST_ERROR();
148 break;
149 }
150 read++;
151 if (!event->array[0]) {
152 TEST_ERROR();
153 break;
154 }
155 inc = event->array[0] + 4;
156 break;
157 default:
158 entry = ring_buffer_event_data(event);
159 if (*entry != cpu) {
160 TEST_ERROR();
161 break;
162 }
163 read++;
164 inc = ((event->type_len + 1) * 4);
165 }
166 if (test_error)
167 break;
168
169 if (inc <= 0) {
170 TEST_ERROR();
171 break;
172 }
173 }
174 }
175 ring_buffer_free_read_page(buffer, cpu, bpage);
176
177 if (ret < 0)
178 return EVENT_DROPPED;
179 return EVENT_FOUND;
180}
181
182static void ring_buffer_consumer(void)
183{
184 /* toggle between reading pages and events */
185 read_events ^= 1;
186
187 read = 0;
188 /*
189 * Continue running until the producer specifically asks to stop
190 * and is ready for the completion.
191 */
192 while (!READ_ONCE(reader_finish)) {
193 int found = 1;
194
195 while (found && !test_error) {
196 int cpu;
197
198 found = 0;
199 for_each_online_cpu(cpu) {
200 enum event_status stat;
201
202 if (read_events)
203 stat = read_event(cpu);
204 else
205 stat = read_page(cpu);
206
207 if (test_error)
208 break;
209
210 if (stat == EVENT_FOUND)
211 found = 1;
212
213 }
214 }
215
216 /* Wait till the producer wakes us up when there is more data
217 * available or when the producer wants us to finish reading.
218 */
219 set_current_state(TASK_INTERRUPTIBLE);
220 if (reader_finish)
221 break;
222
223 schedule();
224 }
225 __set_current_state(TASK_RUNNING);
226 reader_finish = 0;
227 complete(&read_done);
228}
229
230static void ring_buffer_producer(void)
231{
232 ktime_t start_time, end_time, timeout;
233 unsigned long long time;
234 unsigned long long entries;
235 unsigned long long overruns;
236 unsigned long missed = 0;
237 unsigned long hit = 0;
238 unsigned long avg;
239 int cnt = 0;
240
241 /*
242 * Hammer the buffer for 10 secs (this may
243 * make the system stall)
244 */
245 trace_printk("Starting ring buffer hammer\n");
246 start_time = ktime_get();
247 timeout = ktime_add_ns(start_time, RUN_TIME * NSEC_PER_SEC);
248 do {
249 struct ring_buffer_event *event;
250 int *entry;
251 int i;
252
253 for (i = 0; i < write_iteration; i++) {
254 event = ring_buffer_lock_reserve(buffer, 10);
255 if (!event) {
256 missed++;
257 } else {
258 hit++;
259 entry = ring_buffer_event_data(event);
260 *entry = smp_processor_id();
261 ring_buffer_unlock_commit(buffer, event);
262 }
263 }
264 end_time = ktime_get();
265
266 cnt++;
267 if (consumer && !(cnt % wakeup_interval))
268 wake_up_process(consumer);
269
270#ifndef CONFIG_PREEMPT
271 /*
272 * If we are a non preempt kernel, the 10 second run will
273 * stop everything while it runs. Instead, we will call
274 * cond_resched and also add any time that was lost by a
275 * rescedule.
276 *
277 * Do a cond resched at the same frequency we would wake up
278 * the reader.
279 */
280 if (cnt % wakeup_interval)
281 cond_resched();
282#endif
283 } while (ktime_before(end_time, timeout) && !break_test());
284 trace_printk("End ring buffer hammer\n");
285
286 if (consumer) {
287 /* Init both completions here to avoid races */
288 init_completion(&read_start);
289 init_completion(&read_done);
290 /* the completions must be visible before the finish var */
291 smp_wmb();
292 reader_finish = 1;
293 wake_up_process(consumer);
294 wait_for_completion(&read_done);
295 }
296
297 time = ktime_us_delta(end_time, start_time);
298
299 entries = ring_buffer_entries(buffer);
300 overruns = ring_buffer_overruns(buffer);
301
302 if (test_error)
303 trace_printk("ERROR!\n");
304
305 if (!disable_reader) {
306 if (consumer_fifo < 0)
307 trace_printk("Running Consumer at nice: %d\n",
308 consumer_nice);
309 else
310 trace_printk("Running Consumer at SCHED_FIFO %d\n",
311 consumer_fifo);
312 }
313 if (producer_fifo < 0)
314 trace_printk("Running Producer at nice: %d\n",
315 producer_nice);
316 else
317 trace_printk("Running Producer at SCHED_FIFO %d\n",
318 producer_fifo);
319
320 /* Let the user know that the test is running at low priority */
321 if (producer_fifo < 0 && consumer_fifo < 0 &&
322 producer_nice == MAX_NICE && consumer_nice == MAX_NICE)
323 trace_printk("WARNING!!! This test is running at lowest priority.\n");
324
325 trace_printk("Time: %lld (usecs)\n", time);
326 trace_printk("Overruns: %lld\n", overruns);
327 if (disable_reader)
328 trace_printk("Read: (reader disabled)\n");
329 else
330 trace_printk("Read: %ld (by %s)\n", read,
331 read_events ? "events" : "pages");
332 trace_printk("Entries: %lld\n", entries);
333 trace_printk("Total: %lld\n", entries + overruns + read);
334 trace_printk("Missed: %ld\n", missed);
335 trace_printk("Hit: %ld\n", hit);
336
337 /* Convert time from usecs to millisecs */
338 do_div(time, USEC_PER_MSEC);
339 if (time)
340 hit /= (long)time;
341 else
342 trace_printk("TIME IS ZERO??\n");
343
344 trace_printk("Entries per millisec: %ld\n", hit);
345
346 if (hit) {
347 /* Calculate the average time in nanosecs */
348 avg = NSEC_PER_MSEC / hit;
349 trace_printk("%ld ns per entry\n", avg);
350 }
351
352 if (missed) {
353 if (time)
354 missed /= (long)time;
355
356 trace_printk("Total iterations per millisec: %ld\n",
357 hit + missed);
358
359 /* it is possible that hit + missed will overflow and be zero */
360 if (!(hit + missed)) {
361 trace_printk("hit + missed overflowed and totalled zero!\n");
362 hit--; /* make it non zero */
363 }
364
365 /* Caculate the average time in nanosecs */
366 avg = NSEC_PER_MSEC / (hit + missed);
367 trace_printk("%ld ns per entry\n", avg);
368 }
369}
370
371static void wait_to_die(void)
372{
373 set_current_state(TASK_INTERRUPTIBLE);
374 while (!kthread_should_stop()) {
375 schedule();
376 set_current_state(TASK_INTERRUPTIBLE);
377 }
378 __set_current_state(TASK_RUNNING);
379}
380
381static int ring_buffer_consumer_thread(void *arg)
382{
383 while (!break_test()) {
384 complete(&read_start);
385
386 ring_buffer_consumer();
387
388 set_current_state(TASK_INTERRUPTIBLE);
389 if (break_test())
390 break;
391 schedule();
392 }
393 __set_current_state(TASK_RUNNING);
394
395 if (!kthread_should_stop())
396 wait_to_die();
397
398 return 0;
399}
400
401static int ring_buffer_producer_thread(void *arg)
402{
403 while (!break_test()) {
404 ring_buffer_reset(buffer);
405
406 if (consumer) {
407 wake_up_process(consumer);
408 wait_for_completion(&read_start);
409 }
410
411 ring_buffer_producer();
412 if (break_test())
413 goto out_kill;
414
415 trace_printk("Sleeping for 10 secs\n");
416 set_current_state(TASK_INTERRUPTIBLE);
417 if (break_test())
418 goto out_kill;
419 schedule_timeout(HZ * SLEEP_TIME);
420 }
421
422out_kill:
423 __set_current_state(TASK_RUNNING);
424 if (!kthread_should_stop())
425 wait_to_die();
426
427 return 0;
428}
429
430static int __init ring_buffer_benchmark_init(void)
431{
432 int ret;
433
434 /* make a one meg buffer in overwite mode */
435 buffer = ring_buffer_alloc(1000000, RB_FL_OVERWRITE);
436 if (!buffer)
437 return -ENOMEM;
438
439 if (!disable_reader) {
440 consumer = kthread_create(ring_buffer_consumer_thread,
441 NULL, "rb_consumer");
442 ret = PTR_ERR(consumer);
443 if (IS_ERR(consumer))
444 goto out_fail;
445 }
446
447 producer = kthread_run(ring_buffer_producer_thread,
448 NULL, "rb_producer");
449 ret = PTR_ERR(producer);
450
451 if (IS_ERR(producer))
452 goto out_kill;
453
454 /*
455 * Run them as low-prio background tasks by default:
456 */
457 if (!disable_reader) {
458 if (consumer_fifo >= 0) {
459 struct sched_param param = {
460 .sched_priority = consumer_fifo
461 };
462 sched_setscheduler(consumer, SCHED_FIFO, &param);
463 } else
464 set_user_nice(consumer, consumer_nice);
465 }
466
467 if (producer_fifo >= 0) {
468 struct sched_param param = {
469 .sched_priority = producer_fifo
470 };
471 sched_setscheduler(producer, SCHED_FIFO, &param);
472 } else
473 set_user_nice(producer, producer_nice);
474
475 return 0;
476
477 out_kill:
478 if (consumer)
479 kthread_stop(consumer);
480
481 out_fail:
482 ring_buffer_free(buffer);
483 return ret;
484}
485
486static void __exit ring_buffer_benchmark_exit(void)
487{
488 kthread_stop(producer);
489 if (consumer)
490 kthread_stop(consumer);
491 ring_buffer_free(buffer);
492}
493
494module_init(ring_buffer_benchmark_init);
495module_exit(ring_buffer_benchmark_exit);
496
497MODULE_AUTHOR("Steven Rostedt");
498MODULE_DESCRIPTION("ring_buffer_benchmark");
499MODULE_LICENSE("GPL");
500