1 /* 2 * Event loop thread 3 * 4 * Copyright Red Hat Inc., 2013, 2020 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/event-loop-base.h" 21 #include "sysemu/iothread.h" 22 #include "qapi/error.h" 23 #include "qapi/qapi-commands-misc.h" 24 #include "qemu/error-report.h" 25 #include "qemu/rcu.h" 26 #include "qemu/main-loop.h" 27 28 29 #ifdef CONFIG_POSIX 30 /* Benchmark results from 2016 on NVMe SSD drives show max polling times around 31 * 16-32 microseconds yield IOPS improvements for both iodepth=1 and iodepth=32 32 * workloads. 33 */ 34 #define IOTHREAD_POLL_MAX_NS_DEFAULT 32768ULL 35 #else 36 #define IOTHREAD_POLL_MAX_NS_DEFAULT 0ULL 37 #endif 38 39 static void *iothread_run(void *opaque) 40 { 41 IOThread *iothread = opaque; 42 43 rcu_register_thread(); 44 /* 45 * g_main_context_push_thread_default() must be called before anything 46 * in this new thread uses glib. 47 */ 48 g_main_context_push_thread_default(iothread->worker_context); 49 qemu_set_current_aio_context(iothread->ctx); 50 iothread->thread_id = qemu_get_thread_id(); 51 qemu_sem_post(&iothread->init_done_sem); 52 53 while (iothread->running) { 54 /* 55 * Note: from functional-wise the g_main_loop_run() below can 56 * already cover the aio_poll() events, but we can't run the 57 * main loop unconditionally because explicit aio_poll() here 58 * is faster than g_main_loop_run() when we do not need the 59 * gcontext at all (e.g., pure block layer iothreads). In 60 * other words, when we want to run the gcontext with the 61 * iothread we need to pay some performance for functionality. 62 */ 63 aio_poll(iothread->ctx, true); 64 65 /* 66 * We must check the running state again in case it was 67 * changed in previous aio_poll() 68 */ 69 if (iothread->running && qatomic_read(&iothread->run_gcontext)) { 70 g_main_loop_run(iothread->main_loop); 71 } 72 } 73 74 g_main_context_pop_thread_default(iothread->worker_context); 75 rcu_unregister_thread(); 76 return NULL; 77 } 78 79 /* Runs in iothread_run() thread */ 80 static void iothread_stop_bh(void *opaque) 81 { 82 IOThread *iothread = opaque; 83 84 iothread->running = false; /* stop iothread_run() */ 85 86 if (iothread->main_loop) { 87 g_main_loop_quit(iothread->main_loop); 88 } 89 } 90 91 void iothread_stop(IOThread *iothread) 92 { 93 if (!iothread->ctx || iothread->stopping) { 94 return; 95 } 96 iothread->stopping = true; 97 aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread); 98 qemu_thread_join(&iothread->thread); 99 } 100 101 static void iothread_instance_init(Object *obj) 102 { 103 IOThread *iothread = IOTHREAD(obj); 104 105 iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT; 106 iothread->thread_id = -1; 107 qemu_sem_init(&iothread->init_done_sem, 0); 108 /* By default, we don't run gcontext */ 109 qatomic_set(&iothread->run_gcontext, 0); 110 } 111 112 static void iothread_instance_finalize(Object *obj) 113 { 114 IOThread *iothread = IOTHREAD(obj); 115 116 iothread_stop(iothread); 117 118 /* 119 * Before glib2 2.33.10, there is a glib2 bug that GSource context 120 * pointer may not be cleared even if the context has already been 121 * destroyed (while it should). Here let's free the AIO context 122 * earlier to bypass that glib bug. 123 * 124 * We can remove this comment after the minimum supported glib2 125 * version boosts to 2.33.10. Before that, let's free the 126 * GSources first before destroying any GMainContext. 127 */ 128 if (iothread->ctx) { 129 aio_context_unref(iothread->ctx); 130 iothread->ctx = NULL; 131 } 132 if (iothread->worker_context) { 133 g_main_context_unref(iothread->worker_context); 134 iothread->worker_context = NULL; 135 g_main_loop_unref(iothread->main_loop); 136 iothread->main_loop = NULL; 137 } 138 qemu_sem_destroy(&iothread->init_done_sem); 139 } 140 141 static void iothread_init_gcontext(IOThread *iothread, const char *thread_name) 142 { 143 GSource *source; 144 g_autofree char *name = g_strdup_printf("%s aio-context", thread_name); 145 146 iothread->worker_context = g_main_context_new(); 147 source = aio_get_g_source(iothread_get_aio_context(iothread)); 148 g_source_set_name(source, name); 149 g_source_attach(source, iothread->worker_context); 150 g_source_unref(source); 151 iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE); 152 } 153 154 static void iothread_set_aio_context_params(EventLoopBase *base, Error **errp) 155 { 156 ERRP_GUARD(); 157 IOThread *iothread = IOTHREAD(base); 158 159 if (!iothread->ctx) { 160 return; 161 } 162 163 aio_context_set_poll_params(iothread->ctx, 164 iothread->poll_max_ns, 165 iothread->poll_grow, 166 iothread->poll_shrink, 167 errp); 168 if (*errp) { 169 return; 170 } 171 172 aio_context_set_aio_params(iothread->ctx, 173 iothread->parent_obj.aio_max_batch); 174 175 aio_context_set_thread_pool_params(iothread->ctx, base->thread_pool_min, 176 base->thread_pool_max, errp); 177 } 178 179 180 static void iothread_init(EventLoopBase *base, Error **errp) 181 { 182 Error *local_error = NULL; 183 IOThread *iothread = IOTHREAD(base); 184 g_autofree char *thread_name = NULL; 185 186 iothread->stopping = false; 187 iothread->running = true; 188 iothread->ctx = aio_context_new(errp); 189 if (!iothread->ctx) { 190 return; 191 } 192 193 thread_name = g_strdup_printf("IO %s", 194 object_get_canonical_path_component(OBJECT(base))); 195 196 /* 197 * Init one GMainContext for the iothread unconditionally, even if 198 * it's not used 199 */ 200 iothread_init_gcontext(iothread, thread_name); 201 202 iothread_set_aio_context_params(base, &local_error); 203 if (local_error) { 204 error_propagate(errp, local_error); 205 aio_context_unref(iothread->ctx); 206 iothread->ctx = NULL; 207 return; 208 } 209 210 /* This assumes we are called from a thread with useful CPU affinity for us 211 * to inherit. 212 */ 213 qemu_thread_create(&iothread->thread, thread_name, iothread_run, 214 iothread, QEMU_THREAD_JOINABLE); 215 216 /* Wait for initialization to complete */ 217 while (iothread->thread_id == -1) { 218 qemu_sem_wait(&iothread->init_done_sem); 219 } 220 } 221 222 typedef struct { 223 const char *name; 224 ptrdiff_t offset; /* field's byte offset in IOThread struct */ 225 } IOThreadParamInfo; 226 227 static IOThreadParamInfo poll_max_ns_info = { 228 "poll-max-ns", offsetof(IOThread, poll_max_ns), 229 }; 230 static IOThreadParamInfo poll_grow_info = { 231 "poll-grow", offsetof(IOThread, poll_grow), 232 }; 233 static IOThreadParamInfo poll_shrink_info = { 234 "poll-shrink", offsetof(IOThread, poll_shrink), 235 }; 236 237 static void iothread_get_param(Object *obj, Visitor *v, 238 const char *name, IOThreadParamInfo *info, Error **errp) 239 { 240 IOThread *iothread = IOTHREAD(obj); 241 int64_t *field = (void *)iothread + info->offset; 242 243 visit_type_int64(v, name, field, errp); 244 } 245 246 static bool iothread_set_param(Object *obj, Visitor *v, 247 const char *name, IOThreadParamInfo *info, Error **errp) 248 { 249 IOThread *iothread = IOTHREAD(obj); 250 int64_t *field = (void *)iothread + info->offset; 251 int64_t value; 252 253 if (!visit_type_int64(v, name, &value, errp)) { 254 return false; 255 } 256 257 if (value < 0) { 258 error_setg(errp, "%s value must be in range [0, %" PRId64 "]", 259 info->name, INT64_MAX); 260 return false; 261 } 262 263 *field = value; 264 265 return true; 266 } 267 268 static void iothread_get_poll_param(Object *obj, Visitor *v, 269 const char *name, void *opaque, Error **errp) 270 { 271 IOThreadParamInfo *info = opaque; 272 273 iothread_get_param(obj, v, name, info, errp); 274 } 275 276 static void iothread_set_poll_param(Object *obj, Visitor *v, 277 const char *name, void *opaque, Error **errp) 278 { 279 IOThread *iothread = IOTHREAD(obj); 280 IOThreadParamInfo *info = opaque; 281 282 if (!iothread_set_param(obj, v, name, info, errp)) { 283 return; 284 } 285 286 if (iothread->ctx) { 287 aio_context_set_poll_params(iothread->ctx, 288 iothread->poll_max_ns, 289 iothread->poll_grow, 290 iothread->poll_shrink, 291 errp); 292 } 293 } 294 295 static void iothread_class_init(ObjectClass *klass, void *class_data) 296 { 297 EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(klass); 298 299 bc->init = iothread_init; 300 bc->update_params = iothread_set_aio_context_params; 301 302 object_class_property_add(klass, "poll-max-ns", "int", 303 iothread_get_poll_param, 304 iothread_set_poll_param, 305 NULL, &poll_max_ns_info); 306 object_class_property_add(klass, "poll-grow", "int", 307 iothread_get_poll_param, 308 iothread_set_poll_param, 309 NULL, &poll_grow_info); 310 object_class_property_add(klass, "poll-shrink", "int", 311 iothread_get_poll_param, 312 iothread_set_poll_param, 313 NULL, &poll_shrink_info); 314 } 315 316 static const TypeInfo iothread_info = { 317 .name = TYPE_IOTHREAD, 318 .parent = TYPE_EVENT_LOOP_BASE, 319 .class_init = iothread_class_init, 320 .instance_size = sizeof(IOThread), 321 .instance_init = iothread_instance_init, 322 .instance_finalize = iothread_instance_finalize, 323 }; 324 325 static void iothread_register_types(void) 326 { 327 type_register_static(&iothread_info); 328 } 329 330 type_init(iothread_register_types) 331 332 char *iothread_get_id(IOThread *iothread) 333 { 334 return g_strdup(object_get_canonical_path_component(OBJECT(iothread))); 335 } 336 337 AioContext *iothread_get_aio_context(IOThread *iothread) 338 { 339 return iothread->ctx; 340 } 341 342 static int query_one_iothread(Object *object, void *opaque) 343 { 344 IOThreadInfoList ***tail = opaque; 345 IOThreadInfo *info; 346 IOThread *iothread; 347 348 iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD); 349 if (!iothread) { 350 return 0; 351 } 352 353 info = g_new0(IOThreadInfo, 1); 354 info->id = iothread_get_id(iothread); 355 info->thread_id = iothread->thread_id; 356 info->poll_max_ns = iothread->poll_max_ns; 357 info->poll_grow = iothread->poll_grow; 358 info->poll_shrink = iothread->poll_shrink; 359 info->aio_max_batch = iothread->parent_obj.aio_max_batch; 360 361 QAPI_LIST_APPEND(*tail, info); 362 return 0; 363 } 364 365 IOThreadInfoList *qmp_query_iothreads(Error **errp) 366 { 367 IOThreadInfoList *head = NULL; 368 IOThreadInfoList **prev = &head; 369 Object *container = object_get_objects_root(); 370 371 object_child_foreach(container, query_one_iothread, &prev); 372 return head; 373 } 374 375 GMainContext *iothread_get_g_main_context(IOThread *iothread) 376 { 377 qatomic_set(&iothread->run_gcontext, 1); 378 aio_notify(iothread->ctx); 379 return iothread->worker_context; 380 } 381 382 IOThread *iothread_create(const char *id, Error **errp) 383 { 384 Object *obj; 385 386 obj = object_new_with_props(TYPE_IOTHREAD, 387 object_get_internal_root(), 388 id, errp, NULL); 389 390 return IOTHREAD(obj); 391 } 392 393 void iothread_destroy(IOThread *iothread) 394 { 395 object_unparent(OBJECT(iothread)); 396 } 397 398 /* Lookup IOThread by its id. Only finds user-created objects, not internal 399 * iothread_create() objects. */ 400 IOThread *iothread_by_id(const char *id) 401 { 402 return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL)); 403 } 404 405 bool qemu_in_iothread(void) 406 { 407 return qemu_get_current_aio_context() != qemu_get_aio_context(); 408 } 409