tests/unit/test-aio-multithread.c

   1 /*
   2  * AioContext multithreading tests
   3  *
   4  * Copyright Red Hat, Inc. 2016
   5  *
   6  * Authors:
   7  *  Paolo Bonzini    <pbonzini@redhat.com>
   8  *
   9  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  10  * See the COPYING.LIB file in the top-level directory.
  11  */
  12
  13 #include "qemu/osdep.h"
  14 #include "block/aio.h"
  15 #include "qemu/coroutine.h"
  16 #include "qemu/thread.h"
  17 #include "qemu/error-report.h"
  18 #include "iothread.h"
  19
  20 /* AioContext management */
  21
  22 #define NUM_CONTEXTS 5
  23
  24 static IOThread *threads[NUM_CONTEXTS];
  25 static AioContext *ctx[NUM_CONTEXTS];
  26 static __thread int id = -1;
  27
  28 static QemuEvent done_event;
  29
  30 /* Run a function synchronously on a remote iothread. */
  31
  32 typedef struct CtxRunData {
  33     QEMUBHFunc *cb;
  34     void *arg;
  35 } CtxRunData;
  36
  37 static void ctx_run_bh_cb(void *opaque)
  38 {
  39     CtxRunData *data = opaque;
  40
  41     data->cb(data->arg);
  42     qemu_event_set(&done_event);
  43 }
  44
  45 static void ctx_run(int i, QEMUBHFunc *cb, void *opaque)
  46 {
  47     CtxRunData data = {
  48         .cb = cb,
  49         .arg = opaque
  50     };
  51
  52     qemu_event_reset(&done_event);
  53     aio_bh_schedule_oneshot(ctx[i], ctx_run_bh_cb, &data);
  54     qemu_event_wait(&done_event);
  55 }
  56
  57 /* Starting the iothreads. */
  58
  59 static void set_id_cb(void *opaque)
  60 {
  61     int *i = opaque;
  62
  63     id = *i;
  64 }
  65
  66 static void create_aio_contexts(void)
  67 {
  68     int i;
  69
  70     for (i = 0; i < NUM_CONTEXTS; i++) {
  71         threads[i] = iothread_new();
  72         ctx[i] = iothread_get_aio_context(threads[i]);
  73     }
  74
  75     qemu_event_init(&done_event, false);
  76     for (i = 0; i < NUM_CONTEXTS; i++) {
  77         ctx_run(i, set_id_cb, &i);
  78     }
  79 }
  80
  81 /* Stopping the iothreads. */
  82
  83 static void join_aio_contexts(void)
  84 {
  85     int i;
  86
  87     for (i = 0; i < NUM_CONTEXTS; i++) {
  88         aio_context_ref(ctx[i]);
  89     }
  90     for (i = 0; i < NUM_CONTEXTS; i++) {
  91         iothread_join(threads[i]);
  92     }
  93     for (i = 0; i < NUM_CONTEXTS; i++) {
  94         aio_context_unref(ctx[i]);
  95     }
  96     qemu_event_destroy(&done_event);
  97 }
  98
  99 /* Basic test for the stuff above. */
 100
 101 static void test_lifecycle(void)
 102 {
 103     create_aio_contexts();
 104     join_aio_contexts();
 105 }
 106
 107 /* aio_co_schedule test.  */
 108
 109 static Coroutine *to_schedule[NUM_CONTEXTS];
 110
 111 static bool now_stopping;
 112
 113 static int count_retry;
 114 static int count_here;
 115 static int count_other;
 116
 117 static bool schedule_next(int n)
 118 {
 119     Coroutine *co;
 120
 121     co = qatomic_xchg(&to_schedule[n], NULL);
 122     if (!co) {
 123         qatomic_inc(&count_retry);
 124         return false;
 125     }
 126
 127     if (n == id) {
 128         qatomic_inc(&count_here);
 129     } else {
 130         qatomic_inc(&count_other);
 131     }
 132
 133     aio_co_schedule(ctx[n], co);
 134     return true;
 135 }
 136
 137 static void finish_cb(void *opaque)
 138 {
 139     schedule_next(id);
 140 }
 141
 142 static coroutine_fn void test_multi_co_schedule_entry(void *opaque)
 143 {
 144     g_assert(to_schedule[id] == NULL);
 145
 146     while (!qatomic_mb_read(&now_stopping)) {
 147         int n;
 148
 149         n = g_test_rand_int_range(0, NUM_CONTEXTS);
 150         schedule_next(n);
 151
 152         qatomic_mb_set(&to_schedule[id], qemu_coroutine_self());
 153         qemu_coroutine_yield();
 154         g_assert(to_schedule[id] == NULL);
 155     }
 156 }
 157
 158
 159 static void test_multi_co_schedule(int seconds)
 160 {
 161     int i;
 162
 163     count_here = count_other = count_retry = 0;
 164     now_stopping = false;
 165
 166     create_aio_contexts();
 167     for (i = 0; i < NUM_CONTEXTS; i++) {
 168         Coroutine *co1 = qemu_coroutine_create(test_multi_co_schedule_entry, NULL);
 169         aio_co_schedule(ctx[i], co1);
 170     }
 171
 172     g_usleep(seconds * 1000000);
 173
 174     qatomic_mb_set(&now_stopping, true);
 175     for (i = 0; i < NUM_CONTEXTS; i++) {
 176         ctx_run(i, finish_cb, NULL);
 177         to_schedule[i] = NULL;
 178     }
 179
 180     join_aio_contexts();
 181     g_test_message("scheduled %d, queued %d, retry %d, total %d",
 182                   count_other, count_here, count_retry,
 183                   count_here + count_other + count_retry);
 184 }
 185
 186 static void test_multi_co_schedule_1(void)
 187 {
 188     test_multi_co_schedule(1);
 189 }
 190
 191 static void test_multi_co_schedule_10(void)
 192 {
 193     test_multi_co_schedule(10);
 194 }
 195
 196 /* CoMutex thread-safety.  */
 197
 198 static uint32_t atomic_counter;
 199 static uint32_t running;
 200 static uint32_t counter;
 201 static CoMutex comutex;
 202
 203 static void coroutine_fn test_multi_co_mutex_entry(void *opaque)
 204 {
 205     while (!qatomic_mb_read(&now_stopping)) {
 206         qemu_co_mutex_lock(&comutex);
 207         counter++;
 208         qemu_co_mutex_unlock(&comutex);
 209
 210         /* Increase atomic_counter *after* releasing the mutex.  Otherwise
 211          * there is a chance (it happens about 1 in 3 runs) that the iothread
 212          * exits before the coroutine is woken up, causing a spurious
 213          * assertion failure.
 214          */
 215         qatomic_inc(&atomic_counter);
 216     }
 217     qatomic_dec(&running);
 218 }
 219
 220 static void test_multi_co_mutex(int threads, int seconds)
 221 {
 222     int i;
 223
 224     qemu_co_mutex_init(&comutex);
 225     counter = 0;
 226     atomic_counter = 0;
 227     now_stopping = false;
 228
 229     create_aio_contexts();
 230     assert(threads <= NUM_CONTEXTS);
 231     running = threads;
 232     for (i = 0; i < threads; i++) {
 233         Coroutine *co1 = qemu_coroutine_create(test_multi_co_mutex_entry, NULL);
 234         aio_co_schedule(ctx[i], co1);
 235     }
 236
 237     g_usleep(seconds * 1000000);
 238
 239     qatomic_mb_set(&now_stopping, true);
 240     while (running > 0) {
 241         g_usleep(100000);
 242     }
 243
 244     join_aio_contexts();
 245     g_test_message("%d iterations/second", counter / seconds);
 246     g_assert_cmpint(counter, ==, atomic_counter);
 247 }
 248
 249 /* Testing with NUM_CONTEXTS threads focuses on the queue.  The mutex however
 250  * is too contended (and the threads spend too much time in aio_poll)
 251  * to actually stress the handoff protocol.
 252  */
 253 static void test_multi_co_mutex_1(void)
 254 {
 255     test_multi_co_mutex(NUM_CONTEXTS, 1);
 256 }
 257
 258 static void test_multi_co_mutex_10(void)
 259 {
 260     test_multi_co_mutex(NUM_CONTEXTS, 10);
 261 }
 262
 263 /* Testing with fewer threads stresses the handoff protocol too.  Still, the
 264  * case where the locker _can_ pick up a handoff is very rare, happening
 265  * about 10 times in 1 million, so increase the runtime a bit compared to
 266  * other "quick" testcases that only run for 1 second.
 267  */
 268 static void test_multi_co_mutex_2_3(void)
 269 {
 270     test_multi_co_mutex(2, 3);
 271 }
 272
 273 static void test_multi_co_mutex_2_30(void)
 274 {
 275     test_multi_co_mutex(2, 30);
 276 }
 277
 278 /* Same test with fair mutexes, for performance comparison.  */
 279
 280 #ifdef CONFIG_LINUX
 281 #include "qemu/futex.h"
 282
 283 /* The nodes for the mutex reside in this structure (on which we try to avoid
 284  * false sharing).  The head of the mutex is in the "mutex_head" variable.
 285  */
 286 static struct {
 287     int next, locked;
 288     int padding[14];
 289 } nodes[NUM_CONTEXTS] __attribute__((__aligned__(64)));
 290
 291 static int mutex_head = -1;
 292
 293 static void mcs_mutex_lock(void)
 294 {
 295     int prev;
 296
 297     nodes[id].next = -1;
 298     nodes[id].locked = 1;
 299     prev = qatomic_xchg(&mutex_head, id);
 300     if (prev != -1) {
 301         qatomic_set(&nodes[prev].next, id);
 302         qemu_futex_wait(&nodes[id].locked, 1);
 303     }
 304 }
 305
 306 static void mcs_mutex_unlock(void)
 307 {
 308     int next;
 309     if (qatomic_read(&nodes[id].next) == -1) {
 310         if (qatomic_read(&mutex_head) == id &&
 311             qatomic_cmpxchg(&mutex_head, id, -1) == id) {
 312             /* Last item in the list, exit.  */
 313             return;
 314         }
 315         while (qatomic_read(&nodes[id].next) == -1) {
 316             /* mcs_mutex_lock did the xchg, but has not updated
 317              * nodes[prev].next yet.
 318              */
 319         }
 320     }
 321
 322     /* Wake up the next in line.  */
 323     next = qatomic_read(&nodes[id].next);
 324     nodes[next].locked = 0;
 325     qemu_futex_wake(&nodes[next].locked, 1);
 326 }
 327
 328 static void test_multi_fair_mutex_entry(void *opaque)
 329 {
 330     while (!qatomic_mb_read(&now_stopping)) {
 331         mcs_mutex_lock();
 332         counter++;
 333         mcs_mutex_unlock();
 334         qatomic_inc(&atomic_counter);
 335     }
 336     qatomic_dec(&running);
 337 }
 338
 339 static void test_multi_fair_mutex(int threads, int seconds)
 340 {
 341     int i;
 342
 343     assert(mutex_head == -1);
 344     counter = 0;
 345     atomic_counter = 0;
 346     now_stopping = false;
 347
 348     create_aio_contexts();
 349     assert(threads <= NUM_CONTEXTS);
 350     running = threads;
 351     for (i = 0; i < threads; i++) {
 352         Coroutine *co1 = qemu_coroutine_create(test_multi_fair_mutex_entry, NULL);
 353         aio_co_schedule(ctx[i], co1);
 354     }
 355
 356     g_usleep(seconds * 1000000);
 357
 358     qatomic_mb_set(&now_stopping, true);
 359     while (running > 0) {
 360         g_usleep(100000);
 361     }
 362
 363     join_aio_contexts();
 364     g_test_message("%d iterations/second", counter / seconds);
 365     g_assert_cmpint(counter, ==, atomic_counter);
 366 }
 367
 368 static void test_multi_fair_mutex_1(void)
 369 {
 370     test_multi_fair_mutex(NUM_CONTEXTS, 1);
 371 }
 372
 373 static void test_multi_fair_mutex_10(void)
 374 {
 375     test_multi_fair_mutex(NUM_CONTEXTS, 10);
 376 }
 377 #endif
 378
 379 /* Same test with pthread mutexes, for performance comparison and
 380  * portability.  */
 381
 382 static QemuMutex mutex;
 383
 384 static void test_multi_mutex_entry(void *opaque)
 385 {
 386     while (!qatomic_mb_read(&now_stopping)) {
 387         qemu_mutex_lock(&mutex);
 388         counter++;
 389         qemu_mutex_unlock(&mutex);
 390         qatomic_inc(&atomic_counter);
 391     }
 392     qatomic_dec(&running);
 393 }
 394
 395 static void test_multi_mutex(int threads, int seconds)
 396 {
 397     int i;
 398
 399     qemu_mutex_init(&mutex);
 400     counter = 0;
 401     atomic_counter = 0;
 402     now_stopping = false;
 403
 404     create_aio_contexts();
 405     assert(threads <= NUM_CONTEXTS);
 406     running = threads;
 407     for (i = 0; i < threads; i++) {
 408         Coroutine *co1 = qemu_coroutine_create(test_multi_mutex_entry, NULL);
 409         aio_co_schedule(ctx[i], co1);
 410     }
 411
 412     g_usleep(seconds * 1000000);
 413
 414     qatomic_mb_set(&now_stopping, true);
 415     while (running > 0) {
 416         g_usleep(100000);
 417     }
 418
 419     join_aio_contexts();
 420     g_test_message("%d iterations/second", counter / seconds);
 421     g_assert_cmpint(counter, ==, atomic_counter);
 422 }
 423
 424 static void test_multi_mutex_1(void)
 425 {
 426     test_multi_mutex(NUM_CONTEXTS, 1);
 427 }
 428
 429 static void test_multi_mutex_10(void)
 430 {
 431     test_multi_mutex(NUM_CONTEXTS, 10);
 432 }
 433
 434 /* End of tests.  */
 435
 436 int main(int argc, char **argv)
 437 {
 438     init_clocks(NULL);
 439
 440     g_test_init(&argc, &argv, NULL);
 441     g_test_add_func("/aio/multi/lifecycle", test_lifecycle);
 442     if (g_test_quick()) {
 443         g_test_add_func("/aio/multi/schedule", test_multi_co_schedule_1);
 444         g_test_add_func("/aio/multi/mutex/contended", test_multi_co_mutex_1);
 445         g_test_add_func("/aio/multi/mutex/handoff", test_multi_co_mutex_2_3);
 446 #ifdef CONFIG_LINUX
 447         g_test_add_func("/aio/multi/mutex/mcs", test_multi_fair_mutex_1);
 448 #endif
 449         g_test_add_func("/aio/multi/mutex/pthread", test_multi_mutex_1);
 450     } else {
 451         g_test_add_func("/aio/multi/schedule", test_multi_co_schedule_10);
 452         g_test_add_func("/aio/multi/mutex/contended", test_multi_co_mutex_10);
 453         g_test_add_func("/aio/multi/mutex/handoff", test_multi_co_mutex_2_30);
 454 #ifdef CONFIG_LINUX
 455         g_test_add_func("/aio/multi/mutex/mcs", test_multi_fair_mutex_10);
 456 #endif
 457         g_test_add_func("/aio/multi/mutex/pthread", test_multi_mutex_10);
 458     }
 459     return g_test_run();
 460 }