iothread.c

   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 int iothread_stop_iter(Object *object, void *opaque)
 105 {
 106     IOThread *iothread;
 107
 108     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
 109     if (!iothread) {
 110         return 0;
 111     }
 112     iothread_stop(iothread);
 113     return 0;
 114 }
 115
 116 static void iothread_instance_init(Object *obj)
 117 {
 118     IOThread *iothread = IOTHREAD(obj);
 119
 120     iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
 121 }
 122
 123 static void iothread_instance_finalize(Object *obj)
 124 {
 125     IOThread *iothread = IOTHREAD(obj);
 126
 127     iothread_stop(iothread);
 128     if (iothread->worker_context) {
 129         g_main_context_unref(iothread->worker_context);
 130         iothread->worker_context = NULL;
 131     }
 132     qemu_cond_destroy(&iothread->init_done_cond);
 133     qemu_mutex_destroy(&iothread->init_done_lock);
 134     if (!iothread->ctx) {
 135         return;
 136     }
 137     aio_context_unref(iothread->ctx);
 138 }
 139
 140 static void iothread_complete(UserCreatable *obj, Error **errp)
 141 {
 142     Error *local_error = NULL;
 143     IOThread *iothread = IOTHREAD(obj);
 144     char *name, *thread_name;
 145
 146     iothread->stopping = false;
 147     iothread->running = true;
 148     iothread->thread_id = -1;
 149     iothread->ctx = aio_context_new(&local_error);
 150     if (!iothread->ctx) {
 151         error_propagate(errp, local_error);
 152         return;
 153     }
 154
 155     aio_context_set_poll_params(iothread->ctx,
 156                                 iothread->poll_max_ns,
 157                                 iothread->poll_grow,
 158                                 iothread->poll_shrink,
 159                                 &local_error);
 160     if (local_error) {
 161         error_propagate(errp, local_error);
 162         aio_context_unref(iothread->ctx);
 163         iothread->ctx = NULL;
 164         return;
 165     }
 166
 167     qemu_mutex_init(&iothread->init_done_lock);
 168     qemu_cond_init(&iothread->init_done_cond);
 169     iothread->once = (GOnce) G_ONCE_INIT;
 170
 171     /* This assumes we are called from a thread with useful CPU affinity for us
 172      * to inherit.
 173      */
 174     name = object_get_canonical_path_component(OBJECT(obj));
 175     thread_name = g_strdup_printf("IO %s", name);
 176     qemu_thread_create(&iothread->thread, thread_name, iothread_run,
 177                        iothread, QEMU_THREAD_JOINABLE);
 178     g_free(thread_name);
 179     g_free(name);
 180
 181     /* Wait for initialization to complete */
 182     qemu_mutex_lock(&iothread->init_done_lock);
 183     while (iothread->thread_id == -1) {
 184         qemu_cond_wait(&iothread->init_done_cond,
 185                        &iothread->init_done_lock);
 186     }
 187     qemu_mutex_unlock(&iothread->init_done_lock);
 188 }
 189
 190 typedef struct {
 191     const char *name;
 192     ptrdiff_t offset; /* field's byte offset in IOThread struct */
 193 } PollParamInfo;
 194
 195 static PollParamInfo poll_max_ns_info = {
 196     "poll-max-ns", offsetof(IOThread, poll_max_ns),
 197 };
 198 static PollParamInfo poll_grow_info = {
 199     "poll-grow", offsetof(IOThread, poll_grow),
 200 };
 201 static PollParamInfo poll_shrink_info = {
 202     "poll-shrink", offsetof(IOThread, poll_shrink),
 203 };
 204
 205 static void iothread_get_poll_param(Object *obj, Visitor *v,
 206         const char *name, void *opaque, Error **errp)
 207 {
 208     IOThread *iothread = IOTHREAD(obj);
 209     PollParamInfo *info = opaque;
 210     int64_t *field = (void *)iothread + info->offset;
 211
 212     visit_type_int64(v, name, field, errp);
 213 }
 214
 215 static void iothread_set_poll_param(Object *obj, Visitor *v,
 216         const char *name, void *opaque, Error **errp)
 217 {
 218     IOThread *iothread = IOTHREAD(obj);
 219     PollParamInfo *info = opaque;
 220     int64_t *field = (void *)iothread + info->offset;
 221     Error *local_err = NULL;
 222     int64_t value;
 223
 224     visit_type_int64(v, name, &value, &local_err);
 225     if (local_err) {
 226         goto out;
 227     }
 228
 229     if (value < 0) {
 230         error_setg(&local_err, "%s value must be in range [0, %"PRId64"]",
 231                    info->name, INT64_MAX);
 232         goto out;
 233     }
 234
 235     *field = value;
 236
 237     if (iothread->ctx) {
 238         aio_context_set_poll_params(iothread->ctx,
 239                                     iothread->poll_max_ns,
 240                                     iothread->poll_grow,
 241                                     iothread->poll_shrink,
 242                                     &local_err);
 243     }
 244
 245 out:
 246     error_propagate(errp, local_err);
 247 }
 248
 249 static void iothread_class_init(ObjectClass *klass, void *class_data)
 250 {
 251     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
 252     ucc->complete = iothread_complete;
 253
 254     object_class_property_add(klass, "poll-max-ns", "int",
 255                               iothread_get_poll_param,
 256                               iothread_set_poll_param,
 257                               NULL, &poll_max_ns_info, &error_abort);
 258     object_class_property_add(klass, "poll-grow", "int",
 259                               iothread_get_poll_param,
 260                               iothread_set_poll_param,
 261                               NULL, &poll_grow_info, &error_abort);
 262     object_class_property_add(klass, "poll-shrink", "int",
 263                               iothread_get_poll_param,
 264                               iothread_set_poll_param,
 265                               NULL, &poll_shrink_info, &error_abort);
 266 }
 267
 268 static const TypeInfo iothread_info = {
 269     .name = TYPE_IOTHREAD,
 270     .parent = TYPE_OBJECT,
 271     .class_init = iothread_class_init,
 272     .instance_size = sizeof(IOThread),
 273     .instance_init = iothread_instance_init,
 274     .instance_finalize = iothread_instance_finalize,
 275     .interfaces = (InterfaceInfo[]) {
 276         {TYPE_USER_CREATABLE},
 277         {}
 278     },
 279 };
 280
 281 static void iothread_register_types(void)
 282 {
 283     type_register_static(&iothread_info);
 284 }
 285
 286 type_init(iothread_register_types)
 287
 288 char *iothread_get_id(IOThread *iothread)
 289 {
 290     return object_get_canonical_path_component(OBJECT(iothread));
 291 }
 292
 293 AioContext *iothread_get_aio_context(IOThread *iothread)
 294 {
 295     return iothread->ctx;
 296 }
 297
 298 static int query_one_iothread(Object *object, void *opaque)
 299 {
 300     IOThreadInfoList ***prev = opaque;
 301     IOThreadInfoList *elem;
 302     IOThreadInfo *info;
 303     IOThread *iothread;
 304
 305     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
 306     if (!iothread) {
 307         return 0;
 308     }
 309
 310     info = g_new0(IOThreadInfo, 1);
 311     info->id = iothread_get_id(iothread);
 312     info->thread_id = iothread->thread_id;
 313     info->poll_max_ns = iothread->poll_max_ns;
 314     info->poll_grow = iothread->poll_grow;
 315     info->poll_shrink = iothread->poll_shrink;
 316
 317     elem = g_new0(IOThreadInfoList, 1);
 318     elem->value = info;
 319     elem->next = NULL;
 320
 321     **prev = elem;
 322     *prev = &elem->next;
 323     return 0;
 324 }
 325
 326 IOThreadInfoList *qmp_query_iothreads(Error **errp)
 327 {
 328     IOThreadInfoList *head = NULL;
 329     IOThreadInfoList **prev = &head;
 330     Object *container = object_get_objects_root();
 331
 332     object_child_foreach(container, query_one_iothread, &prev);
 333     return head;
 334 }
 335
 336 void iothread_stop_all(void)
 337 {
 338     Object *container = object_get_objects_root();
 339     BlockDriverState *bs;
 340     BdrvNextIterator it;
 341
 342     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 343         AioContext *ctx = bdrv_get_aio_context(bs);
 344         if (ctx == qemu_get_aio_context()) {
 345             continue;
 346         }
 347         aio_context_acquire(ctx);
 348         bdrv_set_aio_context(bs, qemu_get_aio_context());
 349         aio_context_release(ctx);
 350     }
 351
 352     object_child_foreach(container, iothread_stop_iter, NULL);
 353 }
 354
 355 static gpointer iothread_g_main_context_init(gpointer opaque)
 356 {
 357     AioContext *ctx;
 358     IOThread *iothread = opaque;
 359     GSource *source;
 360
 361     iothread->worker_context = g_main_context_new();
 362
 363     ctx = iothread_get_aio_context(iothread);
 364     source = aio_get_g_source(ctx);
 365     g_source_attach(source, iothread->worker_context);
 366     g_source_unref(source);
 367
 368     aio_notify(iothread->ctx);
 369     return NULL;
 370 }
 371
 372 GMainContext *iothread_get_g_main_context(IOThread *iothread)
 373 {
 374     g_once(&iothread->once, iothread_g_main_context_init, iothread);
 375
 376     return iothread->worker_context;
 377 }
 378
 379 IOThread *iothread_create(const char *id, Error **errp)
 380 {
 381     Object *obj;
 382
 383     obj = object_new_with_props(TYPE_IOTHREAD,
 384                                 object_get_internal_root(),
 385                                 id, errp, NULL);
 386
 387     return IOTHREAD(obj);
 388 }
 389
 390 void iothread_destroy(IOThread *iothread)
 391 {
 392     object_unparent(OBJECT(iothread));
 393 }
 394
 395 /* Lookup IOThread by its id.  Only finds user-created objects, not internal
 396  * iothread_create() objects. */
 397 IOThread *iothread_by_id(const char *id)
 398 {
 399     return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL));
 400 }