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 "qmp-commands.h"
  22 #include "qemu/error-report.h"
  23 #include "qemu/rcu.h"
  24 #include "qemu/main-loop.h"
  25
  26 typedef ObjectClass IOThreadClass;
  27
  28 #define IOTHREAD_GET_CLASS(obj) \
  29    OBJECT_GET_CLASS(IOThreadClass, obj, TYPE_IOTHREAD)
  30 #define IOTHREAD_CLASS(klass) \
  31    OBJECT_CLASS_CHECK(IOThreadClass, klass, TYPE_IOTHREAD)
  32
  33 /* Benchmark results from 2016 on NVMe SSD drives show max polling times around
  34  * 16-32 microseconds yield IOPS improvements for both iodepth=1 and iodepth=32
  35  * workloads.
  36  */
  37 #define IOTHREAD_POLL_MAX_NS_DEFAULT 32768ULL
  38
  39 static __thread IOThread *my_iothread;
  40
  41 AioContext *qemu_get_current_aio_context(void)
  42 {
  43     return my_iothread ? my_iothread->ctx : qemu_get_aio_context();
  44 }
  45
  46 static void *iothread_run(void *opaque)
  47 {
  48     IOThread *iothread = opaque;
  49
  50     rcu_register_thread();
  51
  52     my_iothread = iothread;
  53     qemu_mutex_lock(&iothread->init_done_lock);
  54     iothread->thread_id = qemu_get_thread_id();
  55     qemu_cond_signal(&iothread->init_done_cond);
  56     qemu_mutex_unlock(&iothread->init_done_lock);
  57
  58     while (iothread->running) {
  59         aio_poll(iothread->ctx, true);
  60
  61         if (atomic_read(&iothread->worker_context)) {
  62             GMainLoop *loop;
  63
  64             g_main_context_push_thread_default(iothread->worker_context);
  65             iothread->main_loop =
  66                 g_main_loop_new(iothread->worker_context, TRUE);
  67             loop = iothread->main_loop;
  68
  69             g_main_loop_run(iothread->main_loop);
  70             iothread->main_loop = NULL;
  71             g_main_loop_unref(loop);
  72
  73             g_main_context_pop_thread_default(iothread->worker_context);
  74         }
  75     }
  76
  77     rcu_unregister_thread();
  78     return NULL;
  79 }
  80
  81 /* Runs in iothread_run() thread */
  82 static void iothread_stop_bh(void *opaque)
  83 {
  84     IOThread *iothread = opaque;
  85
  86     iothread->running = false; /* stop iothread_run() */
  87
  88     if (iothread->main_loop) {
  89         g_main_loop_quit(iothread->main_loop);
  90     }
  91 }
  92
  93 void iothread_stop(IOThread *iothread)
  94 {
  95     if (!iothread->ctx || iothread->stopping) {
  96         return;
  97     }
  98     iothread->stopping = true;
  99     aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread);
 100     qemu_thread_join(&iothread->thread);
 101 }
 102
 103 static int iothread_stop_iter(Object *object, void *opaque)
 104 {
 105     IOThread *iothread;
 106
 107     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
 108     if (!iothread) {
 109         return 0;
 110     }
 111     iothread_stop(iothread);
 112     return 0;
 113 }
 114
 115 static void iothread_instance_init(Object *obj)
 116 {
 117     IOThread *iothread = IOTHREAD(obj);
 118
 119     iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
 120 }
 121
 122 static void iothread_instance_finalize(Object *obj)
 123 {
 124     IOThread *iothread = IOTHREAD(obj);
 125
 126     iothread_stop(iothread);
 127     if (iothread->worker_context) {
 128         g_main_context_unref(iothread->worker_context);
 129         iothread->worker_context = NULL;
 130     }
 131     qemu_cond_destroy(&iothread->init_done_cond);
 132     qemu_mutex_destroy(&iothread->init_done_lock);
 133     if (!iothread->ctx) {
 134         return;
 135     }
 136     aio_context_unref(iothread->ctx);
 137 }
 138
 139 static void iothread_complete(UserCreatable *obj, Error **errp)
 140 {
 141     Error *local_error = NULL;
 142     IOThread *iothread = IOTHREAD(obj);
 143     char *name, *thread_name;
 144
 145     iothread->stopping = false;
 146     iothread->running = true;
 147     iothread->thread_id = -1;
 148     iothread->ctx = aio_context_new(&local_error);
 149     if (!iothread->ctx) {
 150         error_propagate(errp, local_error);
 151         return;
 152     }
 153
 154     aio_context_set_poll_params(iothread->ctx,
 155                                 iothread->poll_max_ns,
 156                                 iothread->poll_grow,
 157                                 iothread->poll_shrink,
 158                                 &local_error);
 159     if (local_error) {
 160         error_propagate(errp, local_error);
 161         aio_context_unref(iothread->ctx);
 162         iothread->ctx = NULL;
 163         return;
 164     }
 165
 166     qemu_mutex_init(&iothread->init_done_lock);
 167     qemu_cond_init(&iothread->init_done_cond);
 168     iothread->once = (GOnce) G_ONCE_INIT;
 169
 170     /* This assumes we are called from a thread with useful CPU affinity for us
 171      * to inherit.
 172      */
 173     name = object_get_canonical_path_component(OBJECT(obj));
 174     thread_name = g_strdup_printf("IO %s", name);
 175     qemu_thread_create(&iothread->thread, thread_name, iothread_run,
 176                        iothread, QEMU_THREAD_JOINABLE);
 177     g_free(thread_name);
 178     g_free(name);
 179
 180     /* Wait for initialization to complete */
 181     qemu_mutex_lock(&iothread->init_done_lock);
 182     while (iothread->thread_id == -1) {
 183         qemu_cond_wait(&iothread->init_done_cond,
 184                        &iothread->init_done_lock);
 185     }
 186     qemu_mutex_unlock(&iothread->init_done_lock);
 187 }
 188
 189 typedef struct {
 190     const char *name;
 191     ptrdiff_t offset; /* field's byte offset in IOThread struct */
 192 } PollParamInfo;
 193
 194 static PollParamInfo poll_max_ns_info = {
 195     "poll-max-ns", offsetof(IOThread, poll_max_ns),
 196 };
 197 static PollParamInfo poll_grow_info = {
 198     "poll-grow", offsetof(IOThread, poll_grow),
 199 };
 200 static PollParamInfo poll_shrink_info = {
 201     "poll-shrink", offsetof(IOThread, poll_shrink),
 202 };
 203
 204 static void iothread_get_poll_param(Object *obj, Visitor *v,
 205         const char *name, void *opaque, Error **errp)
 206 {
 207     IOThread *iothread = IOTHREAD(obj);
 208     PollParamInfo *info = opaque;
 209     int64_t *field = (void *)iothread + info->offset;
 210
 211     visit_type_int64(v, name, field, errp);
 212 }
 213
 214 static void iothread_set_poll_param(Object *obj, Visitor *v,
 215         const char *name, void *opaque, Error **errp)
 216 {
 217     IOThread *iothread = IOTHREAD(obj);
 218     PollParamInfo *info = opaque;
 219     int64_t *field = (void *)iothread + info->offset;
 220     Error *local_err = NULL;
 221     int64_t value;
 222
 223     visit_type_int64(v, name, &value, &local_err);
 224     if (local_err) {
 225         goto out;
 226     }
 227
 228     if (value < 0) {
 229         error_setg(&local_err, "%s value must be in range [0, %"PRId64"]",
 230                    info->name, INT64_MAX);
 231         goto out;
 232     }
 233
 234     *field = value;
 235
 236     if (iothread->ctx) {
 237         aio_context_set_poll_params(iothread->ctx,
 238                                     iothread->poll_max_ns,
 239                                     iothread->poll_grow,
 240                                     iothread->poll_shrink,
 241                                     &local_err);
 242     }
 243
 244 out:
 245     error_propagate(errp, local_err);
 246 }
 247
 248 static void iothread_class_init(ObjectClass *klass, void *class_data)
 249 {
 250     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
 251     ucc->complete = iothread_complete;
 252
 253     object_class_property_add(klass, "poll-max-ns", "int",
 254                               iothread_get_poll_param,
 255                               iothread_set_poll_param,
 256                               NULL, &poll_max_ns_info, &error_abort);
 257     object_class_property_add(klass, "poll-grow", "int",
 258                               iothread_get_poll_param,
 259                               iothread_set_poll_param,
 260                               NULL, &poll_grow_info, &error_abort);
 261     object_class_property_add(klass, "poll-shrink", "int",
 262                               iothread_get_poll_param,
 263                               iothread_set_poll_param,
 264                               NULL, &poll_shrink_info, &error_abort);
 265 }
 266
 267 static const TypeInfo iothread_info = {
 268     .name = TYPE_IOTHREAD,
 269     .parent = TYPE_OBJECT,
 270     .class_init = iothread_class_init,
 271     .instance_size = sizeof(IOThread),
 272     .instance_init = iothread_instance_init,
 273     .instance_finalize = iothread_instance_finalize,
 274     .interfaces = (InterfaceInfo[]) {
 275         {TYPE_USER_CREATABLE},
 276         {}
 277     },
 278 };
 279
 280 static void iothread_register_types(void)
 281 {
 282     type_register_static(&iothread_info);
 283 }
 284
 285 type_init(iothread_register_types)
 286
 287 char *iothread_get_id(IOThread *iothread)
 288 {
 289     return object_get_canonical_path_component(OBJECT(iothread));
 290 }
 291
 292 AioContext *iothread_get_aio_context(IOThread *iothread)
 293 {
 294     return iothread->ctx;
 295 }
 296
 297 static int query_one_iothread(Object *object, void *opaque)
 298 {
 299     IOThreadInfoList ***prev = opaque;
 300     IOThreadInfoList *elem;
 301     IOThreadInfo *info;
 302     IOThread *iothread;
 303
 304     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
 305     if (!iothread) {
 306         return 0;
 307     }
 308
 309     info = g_new0(IOThreadInfo, 1);
 310     info->id = iothread_get_id(iothread);
 311     info->thread_id = iothread->thread_id;
 312     info->poll_max_ns = iothread->poll_max_ns;
 313     info->poll_grow = iothread->poll_grow;
 314     info->poll_shrink = iothread->poll_shrink;
 315
 316     elem = g_new0(IOThreadInfoList, 1);
 317     elem->value = info;
 318     elem->next = NULL;
 319
 320     **prev = elem;
 321     *prev = &elem->next;
 322     return 0;
 323 }
 324
 325 IOThreadInfoList *qmp_query_iothreads(Error **errp)
 326 {
 327     IOThreadInfoList *head = NULL;
 328     IOThreadInfoList **prev = &head;
 329     Object *container = object_get_objects_root();
 330
 331     object_child_foreach(container, query_one_iothread, &prev);
 332     return head;
 333 }
 334
 335 void iothread_stop_all(void)
 336 {
 337     Object *container = object_get_objects_root();
 338     BlockDriverState *bs;
 339     BdrvNextIterator it;
 340
 341     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 342         AioContext *ctx = bdrv_get_aio_context(bs);
 343         if (ctx == qemu_get_aio_context()) {
 344             continue;
 345         }
 346         aio_context_acquire(ctx);
 347         bdrv_set_aio_context(bs, qemu_get_aio_context());
 348         aio_context_release(ctx);
 349     }
 350
 351     object_child_foreach(container, iothread_stop_iter, NULL);
 352 }
 353
 354 static gpointer iothread_g_main_context_init(gpointer opaque)
 355 {
 356     AioContext *ctx;
 357     IOThread *iothread = opaque;
 358     GSource *source;
 359
 360     iothread->worker_context = g_main_context_new();
 361
 362     ctx = iothread_get_aio_context(iothread);
 363     source = aio_get_g_source(ctx);
 364     g_source_attach(source, iothread->worker_context);
 365     g_source_unref(source);
 366
 367     aio_notify(iothread->ctx);
 368     return NULL;
 369 }
 370
 371 GMainContext *iothread_get_g_main_context(IOThread *iothread)
 372 {
 373     g_once(&iothread->once, iothread_g_main_context_init, iothread);
 374
 375     return iothread->worker_context;
 376 }
 377
 378 IOThread *iothread_create(const char *id, Error **errp)
 379 {
 380     Object *obj;
 381
 382     obj = object_new_with_props(TYPE_IOTHREAD,
 383                                 object_get_internal_root(),
 384                                 id, errp, NULL);
 385
 386     return IOTHREAD(obj);
 387 }
 388
 389 void iothread_destroy(IOThread *iothread)
 390 {
 391     object_unparent(OBJECT(iothread));
 392 }
 393
 394 /* Lookup IOThread by its id.  Only finds user-created objects, not internal
 395  * iothread_create() objects. */
 396 IOThread *iothread_by_id(const char *id)
 397 {
 398     return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL));
 399 }