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 #ifdef CONFIG_POSIX 35 /* Benchmark results from 2016 on NVMe SSD drives show max polling times around 36 * 16-32 microseconds yield IOPS improvements for both iodepth=1 and iodepth=32 37 * workloads. 38 */ 39 #define IOTHREAD_POLL_MAX_NS_DEFAULT 32768ULL 40 #else 41 #define IOTHREAD_POLL_MAX_NS_DEFAULT 0ULL 42 #endif 43 44 static __thread IOThread *my_iothread; 45 46 AioContext *qemu_get_current_aio_context(void) 47 { 48 return my_iothread ? my_iothread->ctx : qemu_get_aio_context(); 49 } 50 51 static void *iothread_run(void *opaque) 52 { 53 IOThread *iothread = opaque; 54 55 rcu_register_thread(); 56 57 my_iothread = iothread; 58 qemu_mutex_lock(&iothread->init_done_lock); 59 iothread->thread_id = qemu_get_thread_id(); 60 qemu_cond_signal(&iothread->init_done_cond); 61 qemu_mutex_unlock(&iothread->init_done_lock); 62 63 while (iothread->running) { 64 aio_poll(iothread->ctx, true); 65 66 /* 67 * We must check the running state again in case it was 68 * changed in previous aio_poll() 69 */ 70 if (iothread->running && atomic_read(&iothread->worker_context)) { 71 GMainLoop *loop; 72 73 g_main_context_push_thread_default(iothread->worker_context); 74 iothread->main_loop = 75 g_main_loop_new(iothread->worker_context, TRUE); 76 loop = iothread->main_loop; 77 78 g_main_loop_run(iothread->main_loop); 79 iothread->main_loop = NULL; 80 g_main_loop_unref(loop); 81 82 g_main_context_pop_thread_default(iothread->worker_context); 83 } 84 } 85 86 rcu_unregister_thread(); 87 return NULL; 88 } 89 90 /* Runs in iothread_run() thread */ 91 static void iothread_stop_bh(void *opaque) 92 { 93 IOThread *iothread = opaque; 94 95 iothread->running = false; /* stop iothread_run() */ 96 97 if (iothread->main_loop) { 98 g_main_loop_quit(iothread->main_loop); 99 } 100 } 101 102 void iothread_stop(IOThread *iothread) 103 { 104 if (!iothread->ctx || iothread->stopping) { 105 return; 106 } 107 iothread->stopping = true; 108 aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread); 109 qemu_thread_join(&iothread->thread); 110 } 111 112 static void iothread_instance_init(Object *obj) 113 { 114 IOThread *iothread = IOTHREAD(obj); 115 116 iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT; 117 iothread->thread_id = -1; 118 } 119 120 static void iothread_instance_finalize(Object *obj) 121 { 122 IOThread *iothread = IOTHREAD(obj); 123 124 iothread_stop(iothread); 125 126 if (iothread->thread_id != -1) { 127 qemu_cond_destroy(&iothread->init_done_cond); 128 qemu_mutex_destroy(&iothread->init_done_lock); 129 } 130 /* 131 * Before glib2 2.33.10, there is a glib2 bug that GSource context 132 * pointer may not be cleared even if the context has already been 133 * destroyed (while it should). Here let's free the AIO context 134 * earlier to bypass that glib bug. 135 * 136 * We can remove this comment after the minimum supported glib2 137 * version boosts to 2.33.10. Before that, let's free the 138 * GSources first before destroying any GMainContext. 139 */ 140 if (iothread->ctx) { 141 aio_context_unref(iothread->ctx); 142 iothread->ctx = NULL; 143 } 144 if (iothread->worker_context) { 145 g_main_context_unref(iothread->worker_context); 146 iothread->worker_context = NULL; 147 } 148 } 149 150 static void iothread_complete(UserCreatable *obj, Error **errp) 151 { 152 Error *local_error = NULL; 153 IOThread *iothread = IOTHREAD(obj); 154 char *name, *thread_name; 155 156 iothread->stopping = false; 157 iothread->running = true; 158 iothread->ctx = aio_context_new(&local_error); 159 if (!iothread->ctx) { 160 error_propagate(errp, local_error); 161 return; 162 } 163 164 aio_context_set_poll_params(iothread->ctx, 165 iothread->poll_max_ns, 166 iothread->poll_grow, 167 iothread->poll_shrink, 168 &local_error); 169 if (local_error) { 170 error_propagate(errp, local_error); 171 aio_context_unref(iothread->ctx); 172 iothread->ctx = NULL; 173 return; 174 } 175 176 qemu_mutex_init(&iothread->init_done_lock); 177 qemu_cond_init(&iothread->init_done_cond); 178 iothread->once = (GOnce) G_ONCE_INIT; 179 180 /* This assumes we are called from a thread with useful CPU affinity for us 181 * to inherit. 182 */ 183 name = object_get_canonical_path_component(OBJECT(obj)); 184 thread_name = g_strdup_printf("IO %s", name); 185 qemu_thread_create(&iothread->thread, thread_name, iothread_run, 186 iothread, QEMU_THREAD_JOINABLE); 187 g_free(thread_name); 188 g_free(name); 189 190 /* Wait for initialization to complete */ 191 qemu_mutex_lock(&iothread->init_done_lock); 192 while (iothread->thread_id == -1) { 193 qemu_cond_wait(&iothread->init_done_cond, 194 &iothread->init_done_lock); 195 } 196 qemu_mutex_unlock(&iothread->init_done_lock); 197 } 198 199 typedef struct { 200 const char *name; 201 ptrdiff_t offset; /* field's byte offset in IOThread struct */ 202 } PollParamInfo; 203 204 static PollParamInfo poll_max_ns_info = { 205 "poll-max-ns", offsetof(IOThread, poll_max_ns), 206 }; 207 static PollParamInfo poll_grow_info = { 208 "poll-grow", offsetof(IOThread, poll_grow), 209 }; 210 static PollParamInfo poll_shrink_info = { 211 "poll-shrink", offsetof(IOThread, poll_shrink), 212 }; 213 214 static void iothread_get_poll_param(Object *obj, Visitor *v, 215 const char *name, void *opaque, Error **errp) 216 { 217 IOThread *iothread = IOTHREAD(obj); 218 PollParamInfo *info = opaque; 219 int64_t *field = (void *)iothread + info->offset; 220 221 visit_type_int64(v, name, field, errp); 222 } 223 224 static void iothread_set_poll_param(Object *obj, Visitor *v, 225 const char *name, void *opaque, Error **errp) 226 { 227 IOThread *iothread = IOTHREAD(obj); 228 PollParamInfo *info = opaque; 229 int64_t *field = (void *)iothread + info->offset; 230 Error *local_err = NULL; 231 int64_t value; 232 233 visit_type_int64(v, name, &value, &local_err); 234 if (local_err) { 235 goto out; 236 } 237 238 if (value < 0) { 239 error_setg(&local_err, "%s value must be in range [0, %"PRId64"]", 240 info->name, INT64_MAX); 241 goto out; 242 } 243 244 *field = value; 245 246 if (iothread->ctx) { 247 aio_context_set_poll_params(iothread->ctx, 248 iothread->poll_max_ns, 249 iothread->poll_grow, 250 iothread->poll_shrink, 251 &local_err); 252 } 253 254 out: 255 error_propagate(errp, local_err); 256 } 257 258 static void iothread_class_init(ObjectClass *klass, void *class_data) 259 { 260 UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass); 261 ucc->complete = iothread_complete; 262 263 object_class_property_add(klass, "poll-max-ns", "int", 264 iothread_get_poll_param, 265 iothread_set_poll_param, 266 NULL, &poll_max_ns_info, &error_abort); 267 object_class_property_add(klass, "poll-grow", "int", 268 iothread_get_poll_param, 269 iothread_set_poll_param, 270 NULL, &poll_grow_info, &error_abort); 271 object_class_property_add(klass, "poll-shrink", "int", 272 iothread_get_poll_param, 273 iothread_set_poll_param, 274 NULL, &poll_shrink_info, &error_abort); 275 } 276 277 static const TypeInfo iothread_info = { 278 .name = TYPE_IOTHREAD, 279 .parent = TYPE_OBJECT, 280 .class_init = iothread_class_init, 281 .instance_size = sizeof(IOThread), 282 .instance_init = iothread_instance_init, 283 .instance_finalize = iothread_instance_finalize, 284 .interfaces = (InterfaceInfo[]) { 285 {TYPE_USER_CREATABLE}, 286 {} 287 }, 288 }; 289 290 static void iothread_register_types(void) 291 { 292 type_register_static(&iothread_info); 293 } 294 295 type_init(iothread_register_types) 296 297 char *iothread_get_id(IOThread *iothread) 298 { 299 return object_get_canonical_path_component(OBJECT(iothread)); 300 } 301 302 AioContext *iothread_get_aio_context(IOThread *iothread) 303 { 304 return iothread->ctx; 305 } 306 307 static int query_one_iothread(Object *object, void *opaque) 308 { 309 IOThreadInfoList ***prev = opaque; 310 IOThreadInfoList *elem; 311 IOThreadInfo *info; 312 IOThread *iothread; 313 314 iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD); 315 if (!iothread) { 316 return 0; 317 } 318 319 info = g_new0(IOThreadInfo, 1); 320 info->id = iothread_get_id(iothread); 321 info->thread_id = iothread->thread_id; 322 info->poll_max_ns = iothread->poll_max_ns; 323 info->poll_grow = iothread->poll_grow; 324 info->poll_shrink = iothread->poll_shrink; 325 326 elem = g_new0(IOThreadInfoList, 1); 327 elem->value = info; 328 elem->next = NULL; 329 330 **prev = elem; 331 *prev = &elem->next; 332 return 0; 333 } 334 335 IOThreadInfoList *qmp_query_iothreads(Error **errp) 336 { 337 IOThreadInfoList *head = NULL; 338 IOThreadInfoList **prev = &head; 339 Object *container = object_get_objects_root(); 340 341 object_child_foreach(container, query_one_iothread, &prev); 342 return head; 343 } 344 345 static gpointer iothread_g_main_context_init(gpointer opaque) 346 { 347 AioContext *ctx; 348 IOThread *iothread = opaque; 349 GSource *source; 350 351 iothread->worker_context = g_main_context_new(); 352 353 ctx = iothread_get_aio_context(iothread); 354 source = aio_get_g_source(ctx); 355 g_source_attach(source, iothread->worker_context); 356 g_source_unref(source); 357 358 aio_notify(iothread->ctx); 359 return NULL; 360 } 361 362 GMainContext *iothread_get_g_main_context(IOThread *iothread) 363 { 364 g_once(&iothread->once, iothread_g_main_context_init, iothread); 365 366 return iothread->worker_context; 367 } 368 369 IOThread *iothread_create(const char *id, Error **errp) 370 { 371 Object *obj; 372 373 obj = object_new_with_props(TYPE_IOTHREAD, 374 object_get_internal_root(), 375 id, errp, NULL); 376 377 return IOTHREAD(obj); 378 } 379 380 void iothread_destroy(IOThread *iothread) 381 { 382 object_unparent(OBJECT(iothread)); 383 } 384 385 /* Lookup IOThread by its id. Only finds user-created objects, not internal 386 * iothread_create() objects. */ 387 IOThread *iothread_by_id(const char *id) 388 { 389 return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL)); 390 } 391