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 trace_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;
49static int consumer_fifo;
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, "use fifo for producer: 0 - disabled, 1 - low prio, 2 - fifo");
59
60module_param(consumer_fifo, int, 0644);
61MODULE_PARM_DESC(consumer_fifo, "use fifo for consumer: 0 - disabled, 1 - low prio, 2 - fifo");
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 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
184static 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
232static 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
373static 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
383static 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
403static 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
424out_kill:
425	__set_current_state(TASK_RUNNING);
426	if (!kthread_should_stop())
427		wait_to_die();
428
429	return 0;
430}
431
432static 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
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