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