1 /*
2  * ring buffer tester and benchmark
3  *
4  * Copyright (C) 2009 Steven Rostedt <srostedt@redhat.com>
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 struct completion read_start;
28 static struct 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 	while (!reader_finish && !kill_test) {
182 		int found;
183 
184 		do {
185 			int cpu;
186 
187 			found = 0;
188 			for_each_online_cpu(cpu) {
189 				enum event_status stat;
190 
191 				if (read_events)
192 					stat = read_event(cpu);
193 				else
194 					stat = read_page(cpu);
195 
196 				if (kill_test)
197 					break;
198 				if (stat == EVENT_FOUND)
199 					found = 1;
200 			}
201 		} while (found && !kill_test);
202 
203 		set_current_state(TASK_INTERRUPTIBLE);
204 		if (reader_finish)
205 			break;
206 
207 		schedule();
208 	}
209 	reader_finish = 0;
210 	complete(&read_done);
211 }
212 
213 static void ring_buffer_producer(void)
214 {
215 	ktime_t start_time, end_time, timeout;
216 	unsigned long long time;
217 	unsigned long long entries;
218 	unsigned long long overruns;
219 	unsigned long missed = 0;
220 	unsigned long hit = 0;
221 	unsigned long avg;
222 	int cnt = 0;
223 
224 	/*
225 	 * Hammer the buffer for 10 secs (this may
226 	 * make the system stall)
227 	 */
228 	trace_printk("Starting ring buffer hammer\n");
229 	start_time = ktime_get();
230 	timeout = ktime_add_ns(start_time, RUN_TIME * NSEC_PER_SEC);
231 	do {
232 		struct ring_buffer_event *event;
233 		int *entry;
234 		int i;
235 
236 		for (i = 0; i < write_iteration; i++) {
237 			event = ring_buffer_lock_reserve(buffer, 10);
238 			if (!event) {
239 				missed++;
240 			} else {
241 				hit++;
242 				entry = ring_buffer_event_data(event);
243 				*entry = smp_processor_id();
244 				ring_buffer_unlock_commit(buffer, event);
245 			}
246 		}
247 		end_time = ktime_get();
248 
249 		cnt++;
250 		if (consumer && !(cnt % wakeup_interval))
251 			wake_up_process(consumer);
252 
253 #ifndef CONFIG_PREEMPT
254 		/*
255 		 * If we are a non preempt kernel, the 10 second run will
256 		 * stop everything while it runs. Instead, we will call
257 		 * cond_resched and also add any time that was lost by a
258 		 * rescedule.
259 		 *
260 		 * Do a cond resched at the same frequency we would wake up
261 		 * the reader.
262 		 */
263 		if (cnt % wakeup_interval)
264 			cond_resched();
265 #endif
266 		if (kthread_should_stop())
267 			kill_test = 1;
268 
269 	} while (ktime_before(end_time, timeout) && !kill_test);
270 	trace_printk("End ring buffer hammer\n");
271 
272 	if (consumer) {
273 		/* Init both completions here to avoid races */
274 		init_completion(&read_start);
275 		init_completion(&read_done);
276 		/* the completions must be visible before the finish var */
277 		smp_wmb();
278 		reader_finish = 1;
279 		/* finish var visible before waking up the consumer */
280 		smp_wmb();
281 		wake_up_process(consumer);
282 		wait_for_completion(&read_done);
283 	}
284 
285 	time = ktime_us_delta(end_time, start_time);
286 
287 	entries = ring_buffer_entries(buffer);
288 	overruns = ring_buffer_overruns(buffer);
289 
290 	if (kill_test && !kthread_should_stop())
291 		trace_printk("ERROR!\n");
292 
293 	if (!disable_reader) {
294 		if (consumer_fifo < 0)
295 			trace_printk("Running Consumer at nice: %d\n",
296 				     consumer_nice);
297 		else
298 			trace_printk("Running Consumer at SCHED_FIFO %d\n",
299 				     consumer_fifo);
300 	}
301 	if (producer_fifo < 0)
302 		trace_printk("Running Producer at nice: %d\n",
303 			     producer_nice);
304 	else
305 		trace_printk("Running Producer at SCHED_FIFO %d\n",
306 			     producer_fifo);
307 
308 	/* Let the user know that the test is running at low priority */
309 	if (producer_fifo < 0 && consumer_fifo < 0 &&
310 	    producer_nice == MAX_NICE && consumer_nice == MAX_NICE)
311 		trace_printk("WARNING!!! This test is running at lowest priority.\n");
312 
313 	trace_printk("Time:     %lld (usecs)\n", time);
314 	trace_printk("Overruns: %lld\n", overruns);
315 	if (disable_reader)
316 		trace_printk("Read:     (reader disabled)\n");
317 	else
318 		trace_printk("Read:     %ld  (by %s)\n", read,
319 			read_events ? "events" : "pages");
320 	trace_printk("Entries:  %lld\n", entries);
321 	trace_printk("Total:    %lld\n", entries + overruns + read);
322 	trace_printk("Missed:   %ld\n", missed);
323 	trace_printk("Hit:      %ld\n", hit);
324 
325 	/* Convert time from usecs to millisecs */
326 	do_div(time, USEC_PER_MSEC);
327 	if (time)
328 		hit /= (long)time;
329 	else
330 		trace_printk("TIME IS ZERO??\n");
331 
332 	trace_printk("Entries per millisec: %ld\n", hit);
333 
334 	if (hit) {
335 		/* Calculate the average time in nanosecs */
336 		avg = NSEC_PER_MSEC / hit;
337 		trace_printk("%ld ns per entry\n", avg);
338 	}
339 
340 	if (missed) {
341 		if (time)
342 			missed /= (long)time;
343 
344 		trace_printk("Total iterations per millisec: %ld\n",
345 			     hit + missed);
346 
347 		/* it is possible that hit + missed will overflow and be zero */
348 		if (!(hit + missed)) {
349 			trace_printk("hit + missed overflowed and totalled zero!\n");
350 			hit--; /* make it non zero */
351 		}
352 
353 		/* Caculate the average time in nanosecs */
354 		avg = NSEC_PER_MSEC / (hit + missed);
355 		trace_printk("%ld ns per entry\n", avg);
356 	}
357 }
358 
359 static void wait_to_die(void)
360 {
361 	set_current_state(TASK_INTERRUPTIBLE);
362 	while (!kthread_should_stop()) {
363 		schedule();
364 		set_current_state(TASK_INTERRUPTIBLE);
365 	}
366 	__set_current_state(TASK_RUNNING);
367 }
368 
369 static int ring_buffer_consumer_thread(void *arg)
370 {
371 	while (!kthread_should_stop() && !kill_test) {
372 		complete(&read_start);
373 
374 		ring_buffer_consumer();
375 
376 		set_current_state(TASK_INTERRUPTIBLE);
377 		if (kthread_should_stop() || kill_test)
378 			break;
379 
380 		schedule();
381 	}
382 	__set_current_state(TASK_RUNNING);
383 
384 	if (!kthread_should_stop())
385 		wait_to_die();
386 
387 	return 0;
388 }
389 
390 static int ring_buffer_producer_thread(void *arg)
391 {
392 	init_completion(&read_start);
393 
394 	while (!kthread_should_stop() && !kill_test) {
395 		ring_buffer_reset(buffer);
396 
397 		if (consumer) {
398 			smp_wmb();
399 			wake_up_process(consumer);
400 			wait_for_completion(&read_start);
401 		}
402 
403 		ring_buffer_producer();
404 		if (kill_test)
405 			goto out_kill;
406 
407 		trace_printk("Sleeping for 10 secs\n");
408 		set_current_state(TASK_INTERRUPTIBLE);
409 		schedule_timeout(HZ * SLEEP_TIME);
410 	}
411 
412 out_kill:
413 	if (!kthread_should_stop())
414 		wait_to_die();
415 
416 	return 0;
417 }
418 
419 static int __init ring_buffer_benchmark_init(void)
420 {
421 	int ret;
422 
423 	/* make a one meg buffer in overwite mode */
424 	buffer = ring_buffer_alloc(1000000, RB_FL_OVERWRITE);
425 	if (!buffer)
426 		return -ENOMEM;
427 
428 	if (!disable_reader) {
429 		consumer = kthread_create(ring_buffer_consumer_thread,
430 					  NULL, "rb_consumer");
431 		ret = PTR_ERR(consumer);
432 		if (IS_ERR(consumer))
433 			goto out_fail;
434 	}
435 
436 	producer = kthread_run(ring_buffer_producer_thread,
437 			       NULL, "rb_producer");
438 	ret = PTR_ERR(producer);
439 
440 	if (IS_ERR(producer))
441 		goto out_kill;
442 
443 	/*
444 	 * Run them as low-prio background tasks by default:
445 	 */
446 	if (!disable_reader) {
447 		if (consumer_fifo >= 0) {
448 			struct sched_param param = {
449 				.sched_priority = consumer_fifo
450 			};
451 			sched_setscheduler(consumer, SCHED_FIFO, &param);
452 		} else
453 			set_user_nice(consumer, consumer_nice);
454 	}
455 
456 	if (producer_fifo >= 0) {
457 		struct sched_param param = {
458 			.sched_priority = producer_fifo
459 		};
460 		sched_setscheduler(producer, SCHED_FIFO, &param);
461 	} else
462 		set_user_nice(producer, producer_nice);
463 
464 	return 0;
465 
466  out_kill:
467 	if (consumer)
468 		kthread_stop(consumer);
469 
470  out_fail:
471 	ring_buffer_free(buffer);
472 	return ret;
473 }
474 
475 static void __exit ring_buffer_benchmark_exit(void)
476 {
477 	kthread_stop(producer);
478 	if (consumer)
479 		kthread_stop(consumer);
480 	ring_buffer_free(buffer);
481 }
482 
483 module_init(ring_buffer_benchmark_init);
484 module_exit(ring_buffer_benchmark_exit);
485 
486 MODULE_AUTHOR("Steven Rostedt");
487 MODULE_DESCRIPTION("ring_buffer_benchmark");
488 MODULE_LICENSE("GPL");
489