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