1 /* 2 * Event loop thread 3 * 4 * Copyright Red Hat Inc., 2013 5 * 6 * Authors: 7 * Stefan Hajnoczi <stefanha@redhat.com> 8 * 9 * This work is licensed under the terms of the GNU GPL, version 2 or later. 10 * See the COPYING file in the top-level directory. 11 * 12 */ 13 14 #include "qemu/osdep.h" 15 #include "qom/object.h" 16 #include "qom/object_interfaces.h" 17 #include "qemu/module.h" 18 #include "block/aio.h" 19 #include "block/block.h" 20 #include "sysemu/iothread.h" 21 #include "qapi/error.h" 22 #include "qapi/qapi-commands-misc.h" 23 #include "qemu/error-report.h" 24 #include "qemu/rcu.h" 25 #include "qemu/main-loop.h" 26 27 typedef ObjectClass IOThreadClass; 28 29 #define IOTHREAD_GET_CLASS(obj) \ 30 OBJECT_GET_CLASS(IOThreadClass, obj, TYPE_IOTHREAD) 31 #define IOTHREAD_CLASS(klass) \ 32 OBJECT_CLASS_CHECK(IOThreadClass, klass, TYPE_IOTHREAD) 33 34 /* Benchmark results from 2016 on NVMe SSD drives show max polling times around 35 * 16-32 microseconds yield IOPS improvements for both iodepth=1 and iodepth=32 36 * workloads. 37 */ 38 #define IOTHREAD_POLL_MAX_NS_DEFAULT 32768ULL 39 40 static __thread IOThread *my_iothread; 41 42 AioContext *qemu_get_current_aio_context(void) 43 { 44 return my_iothread ? my_iothread->ctx : qemu_get_aio_context(); 45 } 46 47 static void *iothread_run(void *opaque) 48 { 49 IOThread *iothread = opaque; 50 51 rcu_register_thread(); 52 53 my_iothread = iothread; 54 qemu_mutex_lock(&iothread->init_done_lock); 55 iothread->thread_id = qemu_get_thread_id(); 56 qemu_cond_signal(&iothread->init_done_cond); 57 qemu_mutex_unlock(&iothread->init_done_lock); 58 59 while (iothread->running) { 60 aio_poll(iothread->ctx, true); 61 62 if (atomic_read(&iothread->worker_context)) { 63 GMainLoop *loop; 64 65 g_main_context_push_thread_default(iothread->worker_context); 66 iothread->main_loop = 67 g_main_loop_new(iothread->worker_context, TRUE); 68 loop = iothread->main_loop; 69 70 g_main_loop_run(iothread->main_loop); 71 iothread->main_loop = NULL; 72 g_main_loop_unref(loop); 73 74 g_main_context_pop_thread_default(iothread->worker_context); 75 } 76 } 77 78 rcu_unregister_thread(); 79 return NULL; 80 } 81 82 /* Runs in iothread_run() thread */ 83 static void iothread_stop_bh(void *opaque) 84 { 85 IOThread *iothread = opaque; 86 87 iothread->running = false; /* stop iothread_run() */ 88 89 if (iothread->main_loop) { 90 g_main_loop_quit(iothread->main_loop); 91 } 92 } 93 94 void iothread_stop(IOThread *iothread) 95 { 96 if (!iothread->ctx || iothread->stopping) { 97 return; 98 } 99 iothread->stopping = true; 100 aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread); 101 qemu_thread_join(&iothread->thread); 102 } 103 104 static int iothread_stop_iter(Object *object, void *opaque) 105 { 106 IOThread *iothread; 107 108 iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD); 109 if (!iothread) { 110 return 0; 111 } 112 iothread_stop(iothread); 113 return 0; 114 } 115 116 static void iothread_instance_init(Object *obj) 117 { 118 IOThread *iothread = IOTHREAD(obj); 119 120 iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT; 121 } 122 123 static void iothread_instance_finalize(Object *obj) 124 { 125 IOThread *iothread = IOTHREAD(obj); 126 127 iothread_stop(iothread); 128 if (iothread->worker_context) { 129 g_main_context_unref(iothread->worker_context); 130 iothread->worker_context = NULL; 131 } 132 qemu_cond_destroy(&iothread->init_done_cond); 133 qemu_mutex_destroy(&iothread->init_done_lock); 134 if (!iothread->ctx) { 135 return; 136 } 137 aio_context_unref(iothread->ctx); 138 } 139 140 static void iothread_complete(UserCreatable *obj, Error **errp) 141 { 142 Error *local_error = NULL; 143 IOThread *iothread = IOTHREAD(obj); 144 char *name, *thread_name; 145 146 iothread->stopping = false; 147 iothread->running = true; 148 iothread->thread_id = -1; 149 iothread->ctx = aio_context_new(&local_error); 150 if (!iothread->ctx) { 151 error_propagate(errp, local_error); 152 return; 153 } 154 155 aio_context_set_poll_params(iothread->ctx, 156 iothread->poll_max_ns, 157 iothread->poll_grow, 158 iothread->poll_shrink, 159 &local_error); 160 if (local_error) { 161 error_propagate(errp, local_error); 162 aio_context_unref(iothread->ctx); 163 iothread->ctx = NULL; 164 return; 165 } 166 167 qemu_mutex_init(&iothread->init_done_lock); 168 qemu_cond_init(&iothread->init_done_cond); 169 iothread->once = (GOnce) G_ONCE_INIT; 170 171 /* This assumes we are called from a thread with useful CPU affinity for us 172 * to inherit. 173 */ 174 name = object_get_canonical_path_component(OBJECT(obj)); 175 thread_name = g_strdup_printf("IO %s", name); 176 qemu_thread_create(&iothread->thread, thread_name, iothread_run, 177 iothread, QEMU_THREAD_JOINABLE); 178 g_free(thread_name); 179 g_free(name); 180 181 /* Wait for initialization to complete */ 182 qemu_mutex_lock(&iothread->init_done_lock); 183 while (iothread->thread_id == -1) { 184 qemu_cond_wait(&iothread->init_done_cond, 185 &iothread->init_done_lock); 186 } 187 qemu_mutex_unlock(&iothread->init_done_lock); 188 } 189 190 typedef struct { 191 const char *name; 192 ptrdiff_t offset; /* field's byte offset in IOThread struct */ 193 } PollParamInfo; 194 195 static PollParamInfo poll_max_ns_info = { 196 "poll-max-ns", offsetof(IOThread, poll_max_ns), 197 }; 198 static PollParamInfo poll_grow_info = { 199 "poll-grow", offsetof(IOThread, poll_grow), 200 }; 201 static PollParamInfo poll_shrink_info = { 202 "poll-shrink", offsetof(IOThread, poll_shrink), 203 }; 204 205 static void iothread_get_poll_param(Object *obj, Visitor *v, 206 const char *name, void *opaque, Error **errp) 207 { 208 IOThread *iothread = IOTHREAD(obj); 209 PollParamInfo *info = opaque; 210 int64_t *field = (void *)iothread + info->offset; 211 212 visit_type_int64(v, name, field, errp); 213 } 214 215 static void iothread_set_poll_param(Object *obj, Visitor *v, 216 const char *name, void *opaque, Error **errp) 217 { 218 IOThread *iothread = IOTHREAD(obj); 219 PollParamInfo *info = opaque; 220 int64_t *field = (void *)iothread + info->offset; 221 Error *local_err = NULL; 222 int64_t value; 223 224 visit_type_int64(v, name, &value, &local_err); 225 if (local_err) { 226 goto out; 227 } 228 229 if (value < 0) { 230 error_setg(&local_err, "%s value must be in range [0, %"PRId64"]", 231 info->name, INT64_MAX); 232 goto out; 233 } 234 235 *field = value; 236 237 if (iothread->ctx) { 238 aio_context_set_poll_params(iothread->ctx, 239 iothread->poll_max_ns, 240 iothread->poll_grow, 241 iothread->poll_shrink, 242 &local_err); 243 } 244 245 out: 246 error_propagate(errp, local_err); 247 } 248 249 static void iothread_class_init(ObjectClass *klass, void *class_data) 250 { 251 UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass); 252 ucc->complete = iothread_complete; 253 254 object_class_property_add(klass, "poll-max-ns", "int", 255 iothread_get_poll_param, 256 iothread_set_poll_param, 257 NULL, &poll_max_ns_info, &error_abort); 258 object_class_property_add(klass, "poll-grow", "int", 259 iothread_get_poll_param, 260 iothread_set_poll_param, 261 NULL, &poll_grow_info, &error_abort); 262 object_class_property_add(klass, "poll-shrink", "int", 263 iothread_get_poll_param, 264 iothread_set_poll_param, 265 NULL, &poll_shrink_info, &error_abort); 266 } 267 268 static const TypeInfo iothread_info = { 269 .name = TYPE_IOTHREAD, 270 .parent = TYPE_OBJECT, 271 .class_init = iothread_class_init, 272 .instance_size = sizeof(IOThread), 273 .instance_init = iothread_instance_init, 274 .instance_finalize = iothread_instance_finalize, 275 .interfaces = (InterfaceInfo[]) { 276 {TYPE_USER_CREATABLE}, 277 {} 278 }, 279 }; 280 281 static void iothread_register_types(void) 282 { 283 type_register_static(&iothread_info); 284 } 285 286 type_init(iothread_register_types) 287 288 char *iothread_get_id(IOThread *iothread) 289 { 290 return object_get_canonical_path_component(OBJECT(iothread)); 291 } 292 293 AioContext *iothread_get_aio_context(IOThread *iothread) 294 { 295 return iothread->ctx; 296 } 297 298 static int query_one_iothread(Object *object, void *opaque) 299 { 300 IOThreadInfoList ***prev = opaque; 301 IOThreadInfoList *elem; 302 IOThreadInfo *info; 303 IOThread *iothread; 304 305 iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD); 306 if (!iothread) { 307 return 0; 308 } 309 310 info = g_new0(IOThreadInfo, 1); 311 info->id = iothread_get_id(iothread); 312 info->thread_id = iothread->thread_id; 313 info->poll_max_ns = iothread->poll_max_ns; 314 info->poll_grow = iothread->poll_grow; 315 info->poll_shrink = iothread->poll_shrink; 316 317 elem = g_new0(IOThreadInfoList, 1); 318 elem->value = info; 319 elem->next = NULL; 320 321 **prev = elem; 322 *prev = &elem->next; 323 return 0; 324 } 325 326 IOThreadInfoList *qmp_query_iothreads(Error **errp) 327 { 328 IOThreadInfoList *head = NULL; 329 IOThreadInfoList **prev = &head; 330 Object *container = object_get_objects_root(); 331 332 object_child_foreach(container, query_one_iothread, &prev); 333 return head; 334 } 335 336 void iothread_stop_all(void) 337 { 338 Object *container = object_get_objects_root(); 339 BlockDriverState *bs; 340 BdrvNextIterator it; 341 342 for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) { 343 AioContext *ctx = bdrv_get_aio_context(bs); 344 if (ctx == qemu_get_aio_context()) { 345 continue; 346 } 347 aio_context_acquire(ctx); 348 bdrv_set_aio_context(bs, qemu_get_aio_context()); 349 aio_context_release(ctx); 350 } 351 352 object_child_foreach(container, iothread_stop_iter, NULL); 353 } 354 355 static gpointer iothread_g_main_context_init(gpointer opaque) 356 { 357 AioContext *ctx; 358 IOThread *iothread = opaque; 359 GSource *source; 360 361 iothread->worker_context = g_main_context_new(); 362 363 ctx = iothread_get_aio_context(iothread); 364 source = aio_get_g_source(ctx); 365 g_source_attach(source, iothread->worker_context); 366 g_source_unref(source); 367 368 aio_notify(iothread->ctx); 369 return NULL; 370 } 371 372 GMainContext *iothread_get_g_main_context(IOThread *iothread) 373 { 374 g_once(&iothread->once, iothread_g_main_context_init, iothread); 375 376 return iothread->worker_context; 377 } 378 379 IOThread *iothread_create(const char *id, Error **errp) 380 { 381 Object *obj; 382 383 obj = object_new_with_props(TYPE_IOTHREAD, 384 object_get_internal_root(), 385 id, errp, NULL); 386 387 return IOTHREAD(obj); 388 } 389 390 void iothread_destroy(IOThread *iothread) 391 { 392 object_unparent(OBJECT(iothread)); 393 } 394 395 /* Lookup IOThread by its id. Only finds user-created objects, not internal 396 * iothread_create() objects. */ 397 IOThread *iothread_by_id(const char *id) 398 { 399 return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL)); 400 } 401