1 /*
2  * ring buffer tester and benchmark
3  *
4  * Copyright (C) 2009 Steven Rostedt <[email protected]>
5  */
6 #include <linux/ring_buffer.h>
7 #include <linux/completion.h>
8 #include <linux/kthread.h>
9 #include <linux/module.h>
10 #include <linux/ktime.h>
11 #include <asm/local.h>
12 
13 struct rb_page {
14 	u64		ts;
15 	local_t		commit;
16 	char		data[4080];
17 };
18 
19 /* run time and sleep time in seconds */
20 #define RUN_TIME	10ULL
21 #define SLEEP_TIME	10
22 
23 /* number of events for writer to wake up the reader */
24 static int wakeup_interval = 100;
25 
26 static int reader_finish;
27 static DECLARE_COMPLETION(read_start);
28 static DECLARE_COMPLETION(read_done);
29 
30 static struct ring_buffer *buffer;
31 static struct task_struct *producer;
32 static struct task_struct *consumer;
33 static unsigned long read;
34 
35 static unsigned int disable_reader;
36 module_param(disable_reader, uint, 0644);
37 MODULE_PARM_DESC(disable_reader, "only run producer");
38 
39 static unsigned int write_iteration = 50;
40 module_param(write_iteration, uint, 0644);
41 MODULE_PARM_DESC(write_iteration, "# of writes between timestamp readings");
42 
43 static int producer_nice = MAX_NICE;
44 static int consumer_nice = MAX_NICE;
45 
46 static int producer_fifo = -1;
47 static int consumer_fifo = -1;
48 
49 module_param(producer_nice, int, 0644);
50 MODULE_PARM_DESC(producer_nice, "nice prio for producer");
51 
52 module_param(consumer_nice, int, 0644);
53 MODULE_PARM_DESC(consumer_nice, "nice prio for consumer");
54 
55 module_param(producer_fifo, int, 0644);
56 MODULE_PARM_DESC(producer_fifo, "fifo prio for producer");
57 
58 module_param(consumer_fifo, int, 0644);
59 MODULE_PARM_DESC(consumer_fifo, "fifo prio for consumer");
60 
61 static int read_events;
62 
63 static int kill_test;
64 
65 #define KILL_TEST()				\
66 	do {					\
67 		if (!kill_test) {		\
68 			kill_test = 1;		\
69 			WARN_ON(1);		\
70 		}				\
71 	} while (0)
72 
73 enum event_status {
74 	EVENT_FOUND,
75 	EVENT_DROPPED,
76 };
77 
78 static enum event_status read_event(int cpu)
79 {
80 	struct ring_buffer_event *event;
81 	int *entry;
82 	u64 ts;
83 
84 	event = ring_buffer_consume(buffer, cpu, &ts, NULL);
85 	if (!event)
86 		return EVENT_DROPPED;
87 
88 	entry = ring_buffer_event_data(event);
89 	if (*entry != cpu) {
90 		KILL_TEST();
91 		return EVENT_DROPPED;
92 	}
93 
94 	read++;
95 	return EVENT_FOUND;
96 }
97 
98 static enum event_status read_page(int cpu)
99 {
100 	struct ring_buffer_event *event;
101 	struct rb_page *rpage;
102 	unsigned long commit;
103 	void *bpage;
104 	int *entry;
105 	int ret;
106 	int inc;
107 	int i;
108 
109 	bpage = ring_buffer_alloc_read_page(buffer, cpu);
110 	if (!bpage)
111 		return EVENT_DROPPED;
112 
113 	ret = ring_buffer_read_page(buffer, &bpage, PAGE_SIZE, cpu, 1);
114 	if (ret >= 0) {
115 		rpage = bpage;
116 		/* The commit may have missed event flags set, clear them */
117 		commit = local_read(&rpage->commit) & 0xfffff;
118 		for (i = 0; i < commit && !kill_test; i += inc) {
119 
120 			if (i >= (PAGE_SIZE - offsetof(struct rb_page, data))) {
121 				KILL_TEST();
122 				break;
123 			}
124 
125 			inc = -1;
126 			event = (void *)&rpage->data[i];
127 			switch (event->type_len) {
128 			case RINGBUF_TYPE_PADDING:
129 				/* failed writes may be discarded events */
130 				if (!event->time_delta)
131 					KILL_TEST();
132 				inc = event->array[0] + 4;
133 				break;
134 			case RINGBUF_TYPE_TIME_EXTEND:
135 				inc = 8;
136 				break;
137 			case 0:
138 				entry = ring_buffer_event_data(event);
139 				if (*entry != cpu) {
140 					KILL_TEST();
141 					break;
142 				}
143 				read++;
144 				if (!event->array[0]) {
145 					KILL_TEST();
146 					break;
147 				}
148 				inc = event->array[0] + 4;
149 				break;
150 			default:
151 				entry = ring_buffer_event_data(event);
152 				if (*entry != cpu) {
153 					KILL_TEST();
154 					break;
155 				}
156 				read++;
157 				inc = ((event->type_len + 1) * 4);
158 			}
159 			if (kill_test)
160 				break;
161 
162 			if (inc <= 0) {
163 				KILL_TEST();
164 				break;
165 			}
166 		}
167 	}
168 	ring_buffer_free_read_page(buffer, bpage);
169 
170 	if (ret < 0)
171 		return EVENT_DROPPED;
172 	return EVENT_FOUND;
173 }
174 
175 static void ring_buffer_consumer(void)
176 {
177 	/* toggle between reading pages and events */
178 	read_events ^= 1;
179 
180 	read = 0;
181 	/*
182 	 * Continue running until the producer specifically asks to stop
183 	 * and is ready for the completion.
184 	 */
185 	while (!READ_ONCE(reader_finish)) {
186 		int found = 1;
187 
188 		while (found && !kill_test) {
189 			int cpu;
190 
191 			found = 0;
192 			for_each_online_cpu(cpu) {
193 				enum event_status stat;
194 
195 				if (read_events)
196 					stat = read_event(cpu);
197 				else
198 					stat = read_page(cpu);
199 
200 				if (kill_test)
201 					break;
202 
203 				if (stat == EVENT_FOUND)
204 					found = 1;
205 
206 			}
207 		}
208 
209 		/* Wait till the producer wakes us up when there is more data
210 		 * available or when the producer wants us to finish reading.
211 		 */
212 		set_current_state(TASK_INTERRUPTIBLE);
213 		if (reader_finish)
214 			break;
215 
216 		schedule();
217 	}
218 	__set_current_state(TASK_RUNNING);
219 	reader_finish = 0;
220 	complete(&read_done);
221 }
222 
223 static void ring_buffer_producer(void)
224 {
225 	ktime_t start_time, end_time, timeout;
226 	unsigned long long time;
227 	unsigned long long entries;
228 	unsigned long long overruns;
229 	unsigned long missed = 0;
230 	unsigned long hit = 0;
231 	unsigned long avg;
232 	int cnt = 0;
233 
234 	/*
235 	 * Hammer the buffer for 10 secs (this may
236 	 * make the system stall)
237 	 */
238 	trace_printk("Starting ring buffer hammer\n");
239 	start_time = ktime_get();
240 	timeout = ktime_add_ns(start_time, RUN_TIME * NSEC_PER_SEC);
241 	do {
242 		struct ring_buffer_event *event;
243 		int *entry;
244 		int i;
245 
246 		for (i = 0; i < write_iteration; i++) {
247 			event = ring_buffer_lock_reserve(buffer, 10);
248 			if (!event) {
249 				missed++;
250 			} else {
251 				hit++;
252 				entry = ring_buffer_event_data(event);
253 				*entry = smp_processor_id();
254 				ring_buffer_unlock_commit(buffer, event);
255 			}
256 		}
257 		end_time = ktime_get();
258 
259 		cnt++;
260 		if (consumer && !(cnt % wakeup_interval))
261 			wake_up_process(consumer);
262 
263 #ifndef CONFIG_PREEMPT
264 		/*
265 		 * If we are a non preempt kernel, the 10 second run will
266 		 * stop everything while it runs. Instead, we will call
267 		 * cond_resched and also add any time that was lost by a
268 		 * rescedule.
269 		 *
270 		 * Do a cond resched at the same frequency we would wake up
271 		 * the reader.
272 		 */
273 		if (cnt % wakeup_interval)
274 			cond_resched();
275 #endif
276 		if (kthread_should_stop())
277 			kill_test = 1;
278 
279 	} while (ktime_before(end_time, timeout) && !kill_test);
280 	trace_printk("End ring buffer hammer\n");
281 
282 	if (consumer) {
283 		/* Init both completions here to avoid races */
284 		init_completion(&read_start);
285 		init_completion(&read_done);
286 		/* the completions must be visible before the finish var */
287 		smp_wmb();
288 		reader_finish = 1;
289 		/* finish var visible before waking up the consumer */
290 		smp_wmb();
291 		wake_up_process(consumer);
292 		wait_for_completion(&read_done);
293 	}
294 
295 	time = ktime_us_delta(end_time, start_time);
296 
297 	entries = ring_buffer_entries(buffer);
298 	overruns = ring_buffer_overruns(buffer);
299 
300 	if (kill_test && !kthread_should_stop())
301 		trace_printk("ERROR!\n");
302 
303 	if (!disable_reader) {
304 		if (consumer_fifo < 0)
305 			trace_printk("Running Consumer at nice: %d\n",
306 				     consumer_nice);
307 		else
308 			trace_printk("Running Consumer at SCHED_FIFO %d\n",
309 				     consumer_fifo);
310 	}
311 	if (producer_fifo < 0)
312 		trace_printk("Running Producer at nice: %d\n",
313 			     producer_nice);
314 	else
315 		trace_printk("Running Producer at SCHED_FIFO %d\n",
316 			     producer_fifo);
317 
318 	/* Let the user know that the test is running at low priority */
319 	if (producer_fifo < 0 && consumer_fifo < 0 &&
320 	    producer_nice == MAX_NICE && consumer_nice == MAX_NICE)
321 		trace_printk("WARNING!!! This test is running at lowest priority.\n");
322 
323 	trace_printk("Time:     %lld (usecs)\n", time);
324 	trace_printk("Overruns: %lld\n", overruns);
325 	if (disable_reader)
326 		trace_printk("Read:     (reader disabled)\n");
327 	else
328 		trace_printk("Read:     %ld  (by %s)\n", read,
329 			read_events ? "events" : "pages");
330 	trace_printk("Entries:  %lld\n", entries);
331 	trace_printk("Total:    %lld\n", entries + overruns + read);
332 	trace_printk("Missed:   %ld\n", missed);
333 	trace_printk("Hit:      %ld\n", hit);
334 
335 	/* Convert time from usecs to millisecs */
336 	do_div(time, USEC_PER_MSEC);
337 	if (time)
338 		hit /= (long)time;
339 	else
340 		trace_printk("TIME IS ZERO??\n");
341 
342 	trace_printk("Entries per millisec: %ld\n", hit);
343 
344 	if (hit) {
345 		/* Calculate the average time in nanosecs */
346 		avg = NSEC_PER_MSEC / hit;
347 		trace_printk("%ld ns per entry\n", avg);
348 	}
349 
350 	if (missed) {
351 		if (time)
352 			missed /= (long)time;
353 
354 		trace_printk("Total iterations per millisec: %ld\n",
355 			     hit + missed);
356 
357 		/* it is possible that hit + missed will overflow and be zero */
358 		if (!(hit + missed)) {
359 			trace_printk("hit + missed overflowed and totalled zero!\n");
360 			hit--; /* make it non zero */
361 		}
362 
363 		/* Caculate the average time in nanosecs */
364 		avg = NSEC_PER_MSEC / (hit + missed);
365 		trace_printk("%ld ns per entry\n", avg);
366 	}
367 }
368 
369 static void wait_to_die(void)
370 {
371 	set_current_state(TASK_INTERRUPTIBLE);
372 	while (!kthread_should_stop()) {
373 		schedule();
374 		set_current_state(TASK_INTERRUPTIBLE);
375 	}
376 	__set_current_state(TASK_RUNNING);
377 }
378 
379 static int ring_buffer_consumer_thread(void *arg)
380 {
381 	while (!kthread_should_stop() && !kill_test) {
382 		complete(&read_start);
383 
384 		ring_buffer_consumer();
385 
386 		set_current_state(TASK_INTERRUPTIBLE);
387 		if (kthread_should_stop() || kill_test)
388 			break;
389 
390 		schedule();
391 	}
392 	__set_current_state(TASK_RUNNING);
393 
394 	if (!kthread_should_stop())
395 		wait_to_die();
396 
397 	return 0;
398 }
399 
400 static int ring_buffer_producer_thread(void *arg)
401 {
402 	while (!kthread_should_stop() && !kill_test) {
403 		ring_buffer_reset(buffer);
404 
405 		if (consumer) {
406 			wake_up_process(consumer);
407 			wait_for_completion(&read_start);
408 		}
409 
410 		ring_buffer_producer();
411 		if (kill_test)
412 			goto out_kill;
413 
414 		trace_printk("Sleeping for 10 secs\n");
415 		set_current_state(TASK_INTERRUPTIBLE);
416 		schedule_timeout(HZ * SLEEP_TIME);
417 	}
418 
419 out_kill:
420 	if (!kthread_should_stop())
421 		wait_to_die();
422 
423 	return 0;
424 }
425 
426 static int __init ring_buffer_benchmark_init(void)
427 {
428 	int ret;
429 
430 	/* make a one meg buffer in overwite mode */
431 	buffer = ring_buffer_alloc(1000000, RB_FL_OVERWRITE);
432 	if (!buffer)
433 		return -ENOMEM;
434 
435 	if (!disable_reader) {
436 		consumer = kthread_create(ring_buffer_consumer_thread,
437 					  NULL, "rb_consumer");
438 		ret = PTR_ERR(consumer);
439 		if (IS_ERR(consumer))
440 			goto out_fail;
441 	}
442 
443 	producer = kthread_run(ring_buffer_producer_thread,
444 			       NULL, "rb_producer");
445 	ret = PTR_ERR(producer);
446 
447 	if (IS_ERR(producer))
448 		goto out_kill;
449 
450 	/*
451 	 * Run them as low-prio background tasks by default:
452 	 */
453 	if (!disable_reader) {
454 		if (consumer_fifo >= 0) {
455 			struct sched_param param = {
456 				.sched_priority = consumer_fifo
457 			};
458 			sched_setscheduler(consumer, SCHED_FIFO, &param);
459 		} else
460 			set_user_nice(consumer, consumer_nice);
461 	}
462 
463 	if (producer_fifo >= 0) {
464 		struct sched_param param = {
465 			.sched_priority = producer_fifo
466 		};
467 		sched_setscheduler(producer, SCHED_FIFO, &param);
468 	} else
469 		set_user_nice(producer, producer_nice);
470 
471 	return 0;
472 
473  out_kill:
474 	if (consumer)
475 		kthread_stop(consumer);
476 
477  out_fail:
478 	ring_buffer_free(buffer);
479 	return ret;
480 }
481 
482 static void __exit ring_buffer_benchmark_exit(void)
483 {
484 	kthread_stop(producer);
485 	if (consumer)
486 		kthread_stop(consumer);
487 	ring_buffer_free(buffer);
488 }
489 
490 module_init(ring_buffer_benchmark_init);
491 module_exit(ring_buffer_benchmark_exit);
492 
493 MODULE_AUTHOR("Steven Rostedt");
494 MODULE_DESCRIPTION("ring_buffer_benchmark");
495 MODULE_LICENSE("GPL");
496