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
15 struct 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 */
26 static int wakeup_interval = 100;
27
28 static int reader_finish;
29 static DECLARE_COMPLETION(read_start);
30 static DECLARE_COMPLETION(read_done);
31
32 static struct trace_buffer *buffer;
33 static struct task_struct *producer;
34 static struct task_struct *consumer;
35 static unsigned long read;
36
37 static unsigned int disable_reader;
38 module_param(disable_reader, uint, 0644);
39 MODULE_PARM_DESC(disable_reader, "only run producer");
40
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");
44
45 static int producer_nice = MAX_NICE;
46 static int consumer_nice = MAX_NICE;
47
48 static int producer_fifo;
49 static int consumer_fifo;
50
51 module_param(producer_nice, int, 0644);
52 MODULE_PARM_DESC(producer_nice, "nice prio for producer");
53
54 module_param(consumer_nice, int, 0644);
55 MODULE_PARM_DESC(consumer_nice, "nice prio for consumer");
56
57 module_param(producer_fifo, int, 0644);
58 MODULE_PARM_DESC(producer_fifo, "use fifo for producer: 0 - disabled, 1 - low prio, 2 - fifo");
59
60 module_param(consumer_fifo, int, 0644);
61 MODULE_PARM_DESC(consumer_fifo, "use fifo for consumer: 0 - disabled, 1 - low prio, 2 - fifo");
62
63 static int read_events;
64
65 static 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
75 enum event_status {
76 EVENT_FOUND,
77 EVENT_DROPPED,
78 };
79
break_test(void)80 static bool break_test(void)
81 {
82 return test_error || kthread_should_stop();
83 }
84
read_event(int cpu)85 static 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
read_page(int cpu)105 static enum event_status read_page(int cpu)
106 {
107 struct buffer_data_read_page *bpage;
108 struct ring_buffer_event *event;
109 struct rb_page *rpage;
110 unsigned long commit;
111 int page_size;
112 int *entry;
113 int ret;
114 int inc;
115 int i;
116
117 bpage = ring_buffer_alloc_read_page(buffer, cpu);
118 if (IS_ERR(bpage))
119 return EVENT_DROPPED;
120
121 page_size = ring_buffer_subbuf_size_get(buffer);
122 ret = ring_buffer_read_page(buffer, bpage, page_size, cpu, 1);
123 if (ret >= 0) {
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) {
128
129 if (i >= (page_size - offsetof(struct rb_page, data))) {
130 TEST_ERROR();
131 break;
132 }
133
134 inc = -1;
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)
140 TEST_ERROR();
141 inc = event->array[0] + 4;
142 break;
143 case RINGBUF_TYPE_TIME_EXTEND:
144 inc = 8;
145 break;
146 case 0:
147 entry = ring_buffer_event_data(event);
148 if (*entry != cpu) {
149 TEST_ERROR();
150 break;
151 }
152 read++;
153 if (!event->array[0]) {
154 TEST_ERROR();
155 break;
156 }
157 inc = event->array[0] + 4;
158 break;
159 default:
160 entry = ring_buffer_event_data(event);
161 if (*entry != cpu) {
162 TEST_ERROR();
163 break;
164 }
165 read++;
166 inc = ((event->type_len + 1) * 4);
167 }
168 if (test_error)
169 break;
170
171 if (inc <= 0) {
172 TEST_ERROR();
173 break;
174 }
175 }
176 }
177 ring_buffer_free_read_page(buffer, cpu, bpage);
178
179 if (ret < 0)
180 return EVENT_DROPPED;
181 return EVENT_FOUND;
182 }
183
ring_buffer_consumer(void)184 static void ring_buffer_consumer(void)
185 {
186 /* toggle between reading pages and events */
187 read_events ^= 1;
188
189 read = 0;
190 /*
191 * Continue running until the producer specifically asks to stop
192 * and is ready for the completion.
193 */
194 while (!READ_ONCE(reader_finish)) {
195 int found = 1;
196
197 while (found && !test_error) {
198 int cpu;
199
200 found = 0;
201 for_each_online_cpu(cpu) {
202 enum event_status stat;
203
204 if (read_events)
205 stat = read_event(cpu);
206 else
207 stat = read_page(cpu);
208
209 if (test_error)
210 break;
211
212 if (stat == EVENT_FOUND)
213 found = 1;
214
215 }
216 }
217
218 /* Wait till the producer wakes us up when there is more data
219 * available or when the producer wants us to finish reading.
220 */
221 set_current_state(TASK_INTERRUPTIBLE);
222 if (reader_finish)
223 break;
224
225 schedule();
226 }
227 __set_current_state(TASK_RUNNING);
228 reader_finish = 0;
229 complete(&read_done);
230 }
231
ring_buffer_producer(void)232 static void ring_buffer_producer(void)
233 {
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;
240 unsigned long avg;
241 int cnt = 0;
242
243 /*
244 * Hammer the buffer for 10 secs (this may
245 * make the system stall)
246 */
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);
250 do {
251 struct ring_buffer_event *event;
252 int *entry;
253 int i;
254
255 for (i = 0; i < write_iteration; i++) {
256 event = ring_buffer_lock_reserve(buffer, 10);
257 if (!event) {
258 missed++;
259 } else {
260 hit++;
261 entry = ring_buffer_event_data(event);
262 *entry = smp_processor_id();
263 ring_buffer_unlock_commit(buffer);
264 }
265 }
266 end_time = ktime_get();
267
268 cnt++;
269 if (consumer && !(cnt % wakeup_interval))
270 wake_up_process(consumer);
271
272 #ifndef CONFIG_PREEMPTION
273 /*
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
277 * reschedule.
278 *
279 * Do a cond resched at the same frequency we would wake up
280 * the reader.
281 */
282 if (cnt % wakeup_interval)
283 cond_resched();
284 #endif
285 } while (ktime_before(end_time, timeout) && !break_test());
286 trace_printk("End ring buffer hammer\n");
287
288 if (consumer) {
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 */
293 smp_wmb();
294 reader_finish = 1;
295 wake_up_process(consumer);
296 wait_for_completion(&read_done);
297 }
298
299 time = ktime_us_delta(end_time, start_time);
300
301 entries = ring_buffer_entries(buffer);
302 overruns = ring_buffer_overruns(buffer);
303
304 if (test_error)
305 trace_printk("ERROR!\n");
306
307 if (!disable_reader) {
308 if (consumer_fifo)
309 trace_printk("Running Consumer at SCHED_FIFO %s\n",
310 consumer_fifo == 1 ? "low" : "high");
311 else
312 trace_printk("Running Consumer at nice: %d\n",
313 consumer_nice);
314 }
315 if (producer_fifo)
316 trace_printk("Running Producer at SCHED_FIFO %s\n",
317 producer_fifo == 1 ? "low" : "high");
318 else
319 trace_printk("Running Producer at nice: %d\n",
320 producer_nice);
321
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");
326
327 trace_printk("Time: %lld (usecs)\n", time);
328 trace_printk("Overruns: %lld\n", overruns);
329 if (disable_reader)
330 trace_printk("Read: (reader disabled)\n");
331 else
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);
338
339 /* Convert time from usecs to millisecs */
340 do_div(time, USEC_PER_MSEC);
341 if (time)
342 hit /= (long)time;
343 else
344 trace_printk("TIME IS ZERO??\n");
345
346 trace_printk("Entries per millisec: %ld\n", hit);
347
348 if (hit) {
349 /* Calculate the average time in nanosecs */
350 avg = NSEC_PER_MSEC / hit;
351 trace_printk("%ld ns per entry\n", avg);
352 }
353
354 if (missed) {
355 if (time)
356 missed /= (long)time;
357
358 trace_printk("Total iterations per millisec: %ld\n",
359 hit + missed);
360
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 */
365 }
366
367 /* Calculate the average time in nanosecs */
368 avg = NSEC_PER_MSEC / (hit + missed);
369 trace_printk("%ld ns per entry\n", avg);
370 }
371 }
372
wait_to_die(void)373 static void wait_to_die(void)
374 {
375 set_current_state(TASK_INTERRUPTIBLE);
376 while (!kthread_should_stop()) {
377 schedule();
378 set_current_state(TASK_INTERRUPTIBLE);
379 }
380 __set_current_state(TASK_RUNNING);
381 }
382
ring_buffer_consumer_thread(void * arg)383 static int ring_buffer_consumer_thread(void *arg)
384 {
385 while (!break_test()) {
386 complete(&read_start);
387
388 ring_buffer_consumer();
389
390 set_current_state(TASK_INTERRUPTIBLE);
391 if (break_test())
392 break;
393 schedule();
394 }
395 __set_current_state(TASK_RUNNING);
396
397 if (!kthread_should_stop())
398 wait_to_die();
399
400 return 0;
401 }
402
ring_buffer_producer_thread(void * arg)403 static int ring_buffer_producer_thread(void *arg)
404 {
405 while (!break_test()) {
406 ring_buffer_reset(buffer);
407
408 if (consumer) {
409 wake_up_process(consumer);
410 wait_for_completion(&read_start);
411 }
412
413 ring_buffer_producer();
414 if (break_test())
415 goto out_kill;
416
417 trace_printk("Sleeping for 10 secs\n");
418 set_current_state(TASK_INTERRUPTIBLE);
419 if (break_test())
420 goto out_kill;
421 schedule_timeout(HZ * SLEEP_TIME);
422 }
423
424 out_kill:
425 __set_current_state(TASK_RUNNING);
426 if (!kthread_should_stop())
427 wait_to_die();
428
429 return 0;
430 }
431
ring_buffer_benchmark_init(void)432 static int __init ring_buffer_benchmark_init(void)
433 {
434 int ret;
435
436 /* make a one meg buffer in overwite mode */
437 buffer = ring_buffer_alloc(1000000, RB_FL_OVERWRITE);
438 if (!buffer)
439 return -ENOMEM;
440
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))
446 goto out_fail;
447 }
448
449 producer = kthread_run(ring_buffer_producer_thread,
450 NULL, "rb_producer");
451 ret = PTR_ERR(producer);
452
453 if (IS_ERR(producer))
454 goto out_kill;
455
456 /*
457 * Run them as low-prio background tasks by default:
458 */
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);
464 else
465 set_user_nice(consumer, consumer_nice);
466 }
467
468 if (producer_fifo >= 2)
469 sched_set_fifo(producer);
470 else if (producer_fifo == 1)
471 sched_set_fifo_low(producer);
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
ring_buffer_benchmark_exit(void)486 static 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
494 module_init(ring_buffer_benchmark_init);
495 module_exit(ring_buffer_benchmark_exit);
496
497 MODULE_AUTHOR("Steven Rostedt");
498 MODULE_DESCRIPTION("ring_buffer_benchmark");
499 MODULE_LICENSE("GPL");
500