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