root/kernel/trace/ring_buffer_benchmark.c

DEFINITIONS

1. break_test
2. read_event
3. read_page
4. ring_buffer_consumer
5. ring_buffer_producer
6. wait_to_die
7. ring_buffer_consumer_thread
8. ring_buffer_producer_thread
9. ring_buffer_benchmark_init
10. ring_buffer_benchmark_exit

   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 ring_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 = -1;
  49 static int consumer_fifo = -1;
  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, "fifo prio for producer");
  59 
  60 module_param(consumer_fifo, int, 0644);
  61 MODULE_PARM_DESC(consumer_fifo, "fifo prio for consumer");
  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 
  80 static bool break_test(void)
  81 {
  82         return test_error || kthread_should_stop();
  83 }
  84 
  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 
 105 static 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 
 182 static 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 
 230 static 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_PREEMPTION
 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                 /* Calculate the average time in nanosecs */
 366                 avg = NSEC_PER_MSEC / (hit + missed);
 367                 trace_printk("%ld ns per entry\n", avg);
 368         }
 369 }
 370 
 371 static 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 
 381 static 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 
 401 static 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 
 422 out_kill:
 423         __set_current_state(TASK_RUNNING);
 424         if (!kthread_should_stop())
 425                 wait_to_die();
 426 
 427         return 0;
 428 }
 429 
 430 static 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 
 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");