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 errp); 175 176 aio_context_set_thread_pool_params(iothread->ctx, base->thread_pool_min, 177 base->thread_pool_max, errp); 178 } 179 180 181 static void iothread_init(EventLoopBase *base, Error **errp) 182 { 183 Error *local_error = NULL; 184 IOThread *iothread = IOTHREAD(base); 185 g_autofree char *thread_name = NULL; 186 187 iothread->stopping = false; 188 iothread->running = true; 189 iothread->ctx = aio_context_new(errp); 190 if (!iothread->ctx) { 191 return; 192 } 193 194 thread_name = g_strdup_printf("IO %s", 195 object_get_canonical_path_component(OBJECT(base))); 196 197 /* 198 * Init one GMainContext for the iothread unconditionally, even if 199 * it's not used 200 */ 201 iothread_init_gcontext(iothread, thread_name); 202 203 iothread_set_aio_context_params(base, &local_error); 204 if (local_error) { 205 error_propagate(errp, local_error); 206 aio_context_unref(iothread->ctx); 207 iothread->ctx = NULL; 208 return; 209 } 210 211 /* This assumes we are called from a thread with useful CPU affinity for us 212 * to inherit. 213 */ 214 qemu_thread_create(&iothread->thread, thread_name, iothread_run, 215 iothread, QEMU_THREAD_JOINABLE); 216 217 /* Wait for initialization to complete */ 218 while (iothread->thread_id == -1) { 219 qemu_sem_wait(&iothread->init_done_sem); 220 } 221 } 222 223 typedef struct { 224 const char *name; 225 ptrdiff_t offset; /* field's byte offset in IOThread struct */ 226 } IOThreadParamInfo; 227 228 static IOThreadParamInfo poll_max_ns_info = { 229 "poll-max-ns", offsetof(IOThread, poll_max_ns), 230 }; 231 static IOThreadParamInfo poll_grow_info = { 232 "poll-grow", offsetof(IOThread, poll_grow), 233 }; 234 static IOThreadParamInfo poll_shrink_info = { 235 "poll-shrink", offsetof(IOThread, poll_shrink), 236 }; 237 238 static void iothread_get_param(Object *obj, Visitor *v, 239 const char *name, IOThreadParamInfo *info, Error **errp) 240 { 241 IOThread *iothread = IOTHREAD(obj); 242 int64_t *field = (void *)iothread + info->offset; 243 244 visit_type_int64(v, name, field, errp); 245 } 246 247 static bool iothread_set_param(Object *obj, Visitor *v, 248 const char *name, IOThreadParamInfo *info, Error **errp) 249 { 250 IOThread *iothread = IOTHREAD(obj); 251 int64_t *field = (void *)iothread + info->offset; 252 int64_t value; 253 254 if (!visit_type_int64(v, name, &value, errp)) { 255 return false; 256 } 257 258 if (value < 0) { 259 error_setg(errp, "%s value must be in range [0, %" PRId64 "]", 260 info->name, INT64_MAX); 261 return false; 262 } 263 264 *field = value; 265 266 return true; 267 } 268 269 static void iothread_get_poll_param(Object *obj, Visitor *v, 270 const char *name, void *opaque, Error **errp) 271 { 272 IOThreadParamInfo *info = opaque; 273 274 iothread_get_param(obj, v, name, info, errp); 275 } 276 277 static void iothread_set_poll_param(Object *obj, Visitor *v, 278 const char *name, void *opaque, Error **errp) 279 { 280 IOThread *iothread = IOTHREAD(obj); 281 IOThreadParamInfo *info = opaque; 282 283 if (!iothread_set_param(obj, v, name, info, errp)) { 284 return; 285 } 286 287 if (iothread->ctx) { 288 aio_context_set_poll_params(iothread->ctx, 289 iothread->poll_max_ns, 290 iothread->poll_grow, 291 iothread->poll_shrink, 292 errp); 293 } 294 } 295 296 static void iothread_class_init(ObjectClass *klass, void *class_data) 297 { 298 EventLoopBaseClass *bc = EVENT_LOOP_BASE_CLASS(klass); 299 300 bc->init = iothread_init; 301 bc->update_params = iothread_set_aio_context_params; 302 303 object_class_property_add(klass, "poll-max-ns", "int", 304 iothread_get_poll_param, 305 iothread_set_poll_param, 306 NULL, &poll_max_ns_info); 307 object_class_property_add(klass, "poll-grow", "int", 308 iothread_get_poll_param, 309 iothread_set_poll_param, 310 NULL, &poll_grow_info); 311 object_class_property_add(klass, "poll-shrink", "int", 312 iothread_get_poll_param, 313 iothread_set_poll_param, 314 NULL, &poll_shrink_info); 315 } 316 317 static const TypeInfo iothread_info = { 318 .name = TYPE_IOTHREAD, 319 .parent = TYPE_EVENT_LOOP_BASE, 320 .class_init = iothread_class_init, 321 .instance_size = sizeof(IOThread), 322 .instance_init = iothread_instance_init, 323 .instance_finalize = iothread_instance_finalize, 324 }; 325 326 static void iothread_register_types(void) 327 { 328 type_register_static(&iothread_info); 329 } 330 331 type_init(iothread_register_types) 332 333 char *iothread_get_id(IOThread *iothread) 334 { 335 return g_strdup(object_get_canonical_path_component(OBJECT(iothread))); 336 } 337 338 AioContext *iothread_get_aio_context(IOThread *iothread) 339 { 340 return iothread->ctx; 341 } 342 343 static int query_one_iothread(Object *object, void *opaque) 344 { 345 IOThreadInfoList ***tail = opaque; 346 IOThreadInfo *info; 347 IOThread *iothread; 348 349 iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD); 350 if (!iothread) { 351 return 0; 352 } 353 354 info = g_new0(IOThreadInfo, 1); 355 info->id = iothread_get_id(iothread); 356 info->thread_id = iothread->thread_id; 357 info->poll_max_ns = iothread->poll_max_ns; 358 info->poll_grow = iothread->poll_grow; 359 info->poll_shrink = iothread->poll_shrink; 360 info->aio_max_batch = iothread->parent_obj.aio_max_batch; 361 362 QAPI_LIST_APPEND(*tail, info); 363 return 0; 364 } 365 366 IOThreadInfoList *qmp_query_iothreads(Error **errp) 367 { 368 IOThreadInfoList *head = NULL; 369 IOThreadInfoList **prev = &head; 370 Object *container = object_get_objects_root(); 371 372 object_child_foreach(container, query_one_iothread, &prev); 373 return head; 374 } 375 376 GMainContext *iothread_get_g_main_context(IOThread *iothread) 377 { 378 qatomic_set(&iothread->run_gcontext, 1); 379 aio_notify(iothread->ctx); 380 return iothread->worker_context; 381 } 382 383 IOThread *iothread_create(const char *id, Error **errp) 384 { 385 Object *obj; 386 387 obj = object_new_with_props(TYPE_IOTHREAD, 388 object_get_internal_root(), 389 id, errp, NULL); 390 391 return IOTHREAD(obj); 392 } 393 394 void iothread_destroy(IOThread *iothread) 395 { 396 object_unparent(OBJECT(iothread)); 397 } 398 399 /* Lookup IOThread by its id. Only finds user-created objects, not internal 400 * iothread_create() objects. */ 401 IOThread *iothread_by_id(const char *id) 402 { 403 return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL)); 404 } 405 406 bool qemu_in_iothread(void) 407 { 408 return qemu_get_current_aio_context() == qemu_get_aio_context() ? 409 false : true; 410 } 411