2 * AioContext multithreading tests
4 * Copyright Red Hat, Inc. 2016
7 * Paolo Bonzini <pbonzini@redhat.com>
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.
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"
20 /* AioContext management */
22 #define NUM_CONTEXTS 5
24 static IOThread *threads[NUM_CONTEXTS];
25 static AioContext *ctx[NUM_CONTEXTS];
26 static __thread int id = -1;
28 static QemuEvent done_event;
30 /* Run a function synchronously on a remote iothread. */
32 typedef struct CtxRunData {
37 static void ctx_run_bh_cb(void *opaque)
39 CtxRunData *data = opaque;
42 qemu_event_set(&done_event);
45 static void ctx_run(int i, QEMUBHFunc *cb, void *opaque)
52 qemu_event_reset(&done_event);
53 aio_bh_schedule_oneshot(ctx[i], ctx_run_bh_cb, &data);
54 qemu_event_wait(&done_event);
57 /* Starting the iothreads. */
59 static void set_id_cb(void *opaque)
66 static void create_aio_contexts(void)
70 for (i = 0; i < NUM_CONTEXTS; i++) {
71 threads[i] = iothread_new();
72 ctx[i] = iothread_get_aio_context(threads[i]);
75 qemu_event_init(&done_event, false);
76 for (i = 0; i < NUM_CONTEXTS; i++) {
77 ctx_run(i, set_id_cb, &i);
81 /* Stopping the iothreads. */
83 static void join_aio_contexts(void)
87 for (i = 0; i < NUM_CONTEXTS; i++) {
88 aio_context_ref(ctx[i]);
90 for (i = 0; i < NUM_CONTEXTS; i++) {
91 iothread_join(threads[i]);
93 for (i = 0; i < NUM_CONTEXTS; i++) {
94 aio_context_unref(ctx[i]);
96 qemu_event_destroy(&done_event);
99 /* Basic test for the stuff above. */
101 static void test_lifecycle(void)
103 create_aio_contexts();
107 /* aio_co_schedule test. */
109 static Coroutine *to_schedule[NUM_CONTEXTS];
110 static bool stop[NUM_CONTEXTS];
112 static int count_retry;
113 static int count_here;
114 static int count_other;
116 static bool schedule_next(int n)
120 co = qatomic_xchg(&to_schedule[n], NULL);
122 qatomic_inc(&count_retry);
127 qatomic_inc(&count_here);
129 qatomic_inc(&count_other);
132 aio_co_schedule(ctx[n], co);
136 static void finish_cb(void *opaque)
142 static coroutine_fn void test_multi_co_schedule_entry(void *opaque)
144 g_assert(to_schedule[id] == NULL);
147 * The next iteration will set to_schedule[id] again, but once finish_cb
148 * is scheduled there is no guarantee that it will actually be woken up,
149 * so at that point it must not go to sleep.
154 n = g_test_rand_int_range(0, NUM_CONTEXTS);
157 qatomic_set_mb(&to_schedule[id], qemu_coroutine_self());
158 /* finish_cb can run here. */
159 qemu_coroutine_yield();
160 g_assert(to_schedule[id] == NULL);
165 static void test_multi_co_schedule(int seconds)
169 count_here = count_other = count_retry = 0;
171 create_aio_contexts();
172 for (i = 0; i < NUM_CONTEXTS; i++) {
173 Coroutine *co1 = qemu_coroutine_create(test_multi_co_schedule_entry, NULL);
174 aio_co_schedule(ctx[i], co1);
177 g_usleep(seconds * 1000000);
179 /* Guarantee that each AioContext is woken up from its last wait. */
180 for (i = 0; i < NUM_CONTEXTS; i++) {
181 ctx_run(i, finish_cb, NULL);
182 g_assert(to_schedule[i] == NULL);
186 g_test_message("scheduled %d, queued %d, retry %d, total %d",
187 count_other, count_here, count_retry,
188 count_here + count_other + count_retry);
191 static void test_multi_co_schedule_1(void)
193 test_multi_co_schedule(1);
196 static void test_multi_co_schedule_10(void)
198 test_multi_co_schedule(10);
201 /* CoMutex thread-safety. */
203 static uint32_t atomic_counter;
204 static uint32_t running;
205 static uint32_t counter;
206 static CoMutex comutex;
207 static bool now_stopping;
209 static void coroutine_fn test_multi_co_mutex_entry(void *opaque)
211 while (!qatomic_read(&now_stopping)) {
212 qemu_co_mutex_lock(&comutex);
214 qemu_co_mutex_unlock(&comutex);
216 /* Increase atomic_counter *after* releasing the mutex. Otherwise
217 * there is a chance (it happens about 1 in 3 runs) that the iothread
218 * exits before the coroutine is woken up, causing a spurious
221 qatomic_inc(&atomic_counter);
223 qatomic_dec(&running);
226 static void test_multi_co_mutex(int threads, int seconds)
230 qemu_co_mutex_init(&comutex);
233 now_stopping = false;
235 create_aio_contexts();
236 assert(threads <= NUM_CONTEXTS);
238 for (i = 0; i < threads; i++) {
239 Coroutine *co1 = qemu_coroutine_create(test_multi_co_mutex_entry, NULL);
240 aio_co_schedule(ctx[i], co1);
243 g_usleep(seconds * 1000000);
245 qatomic_set(&now_stopping, true);
246 while (running > 0) {
251 g_test_message("%d iterations/second", counter / seconds);
252 g_assert_cmpint(counter, ==, atomic_counter);
255 /* Testing with NUM_CONTEXTS threads focuses on the queue. The mutex however
256 * is too contended (and the threads spend too much time in aio_poll)
257 * to actually stress the handoff protocol.
259 static void test_multi_co_mutex_1(void)
261 test_multi_co_mutex(NUM_CONTEXTS, 1);
264 static void test_multi_co_mutex_10(void)
266 test_multi_co_mutex(NUM_CONTEXTS, 10);
269 /* Testing with fewer threads stresses the handoff protocol too. Still, the
270 * case where the locker _can_ pick up a handoff is very rare, happening
271 * about 10 times in 1 million, so increase the runtime a bit compared to
272 * other "quick" testcases that only run for 1 second.
274 static void test_multi_co_mutex_2_3(void)
276 test_multi_co_mutex(2, 3);
279 static void test_multi_co_mutex_2_30(void)
281 test_multi_co_mutex(2, 30);
284 /* Same test with fair mutexes, for performance comparison. */
287 #include "qemu/futex.h"
289 /* The nodes for the mutex reside in this structure (on which we try to avoid
290 * false sharing). The head of the mutex is in the "mutex_head" variable.
295 } nodes[NUM_CONTEXTS] __attribute__((__aligned__(64)));
297 static int mutex_head = -1;
299 static void mcs_mutex_lock(void)
304 nodes[id].locked = 1;
305 prev = qatomic_xchg(&mutex_head, id);
307 qatomic_set(&nodes[prev].next, id);
308 qemu_futex_wait(&nodes[id].locked, 1);
312 static void mcs_mutex_unlock(void)
315 if (qatomic_read(&nodes[id].next) == -1) {
316 if (qatomic_read(&mutex_head) == id &&
317 qatomic_cmpxchg(&mutex_head, id, -1) == id) {
318 /* Last item in the list, exit. */
321 while (qatomic_read(&nodes[id].next) == -1) {
322 /* mcs_mutex_lock did the xchg, but has not updated
323 * nodes[prev].next yet.
328 /* Wake up the next in line. */
329 next = qatomic_read(&nodes[id].next);
330 nodes[next].locked = 0;
331 qemu_futex_wake(&nodes[next].locked, 1);
334 static void test_multi_fair_mutex_entry(void *opaque)
336 while (!qatomic_read(&now_stopping)) {
340 qatomic_inc(&atomic_counter);
342 qatomic_dec(&running);
345 static void test_multi_fair_mutex(int threads, int seconds)
349 assert(mutex_head == -1);
352 now_stopping = false;
354 create_aio_contexts();
355 assert(threads <= NUM_CONTEXTS);
357 for (i = 0; i < threads; i++) {
358 Coroutine *co1 = qemu_coroutine_create(test_multi_fair_mutex_entry, NULL);
359 aio_co_schedule(ctx[i], co1);
362 g_usleep(seconds * 1000000);
364 qatomic_set(&now_stopping, true);
365 while (running > 0) {
370 g_test_message("%d iterations/second", counter / seconds);
371 g_assert_cmpint(counter, ==, atomic_counter);
374 static void test_multi_fair_mutex_1(void)
376 test_multi_fair_mutex(NUM_CONTEXTS, 1);
379 static void test_multi_fair_mutex_10(void)
381 test_multi_fair_mutex(NUM_CONTEXTS, 10);
385 /* Same test with pthread mutexes, for performance comparison and
388 static QemuMutex mutex;
390 static void test_multi_mutex_entry(void *opaque)
392 while (!qatomic_read(&now_stopping)) {
393 qemu_mutex_lock(&mutex);
395 qemu_mutex_unlock(&mutex);
396 qatomic_inc(&atomic_counter);
398 qatomic_dec(&running);
401 static void test_multi_mutex(int threads, int seconds)
405 qemu_mutex_init(&mutex);
408 now_stopping = false;
410 create_aio_contexts();
411 assert(threads <= NUM_CONTEXTS);
413 for (i = 0; i < threads; i++) {
414 Coroutine *co1 = qemu_coroutine_create(test_multi_mutex_entry, NULL);
415 aio_co_schedule(ctx[i], co1);
418 g_usleep(seconds * 1000000);
420 qatomic_set(&now_stopping, true);
421 while (running > 0) {
426 g_test_message("%d iterations/second", counter / seconds);
427 g_assert_cmpint(counter, ==, atomic_counter);
430 static void test_multi_mutex_1(void)
432 test_multi_mutex(NUM_CONTEXTS, 1);
435 static void test_multi_mutex_10(void)
437 test_multi_mutex(NUM_CONTEXTS, 10);
442 int main(int argc, char **argv)
446 g_test_init(&argc, &argv, NULL);
447 g_test_add_func("/aio/multi/lifecycle", test_lifecycle);
448 if (g_test_quick()) {
449 g_test_add_func("/aio/multi/schedule", test_multi_co_schedule_1);
450 g_test_add_func("/aio/multi/mutex/contended", test_multi_co_mutex_1);
451 g_test_add_func("/aio/multi/mutex/handoff", test_multi_co_mutex_2_3);
453 g_test_add_func("/aio/multi/mutex/mcs", test_multi_fair_mutex_1);
455 g_test_add_func("/aio/multi/mutex/pthread", test_multi_mutex_1);
457 g_test_add_func("/aio/multi/schedule", test_multi_co_schedule_10);
458 g_test_add_func("/aio/multi/mutex/contended", test_multi_co_mutex_10);
459 g_test_add_func("/aio/multi/mutex/handoff", test_multi_co_mutex_2_30);
461 g_test_add_func("/aio/multi/mutex/mcs", test_multi_fair_mutex_10);
463 g_test_add_func("/aio/multi/mutex/pthread", test_multi_mutex_10);