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