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