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     /*
 121      * Before glib2 2.33.10, there is a glib2 bug that GSource context
 122      * pointer may not be cleared even if the context has already been
 123      * destroyed (while it should).  Here let's free the AIO context
 124      * earlier to bypass that glib bug.
 125      *
 126      * We can remove this comment after the minimum supported glib2
 127      * version boosts to 2.33.10.  Before that, let's free the
 128      * GSources first before destroying any GMainContext.
 129      */
 130     if (iothread->ctx) {
 131         aio_context_unref(iothread->ctx);
 132         iothread->ctx = NULL;
 133     }
 134     if (iothread->worker_context) {
 135         g_main_context_unref(iothread->worker_context);
 136         iothread->worker_context = NULL;
 137     }
 138     qemu_cond_destroy(&iothread->init_done_cond);
 139     qemu_mutex_destroy(&iothread->init_done_lock);
 140 }
 141
 142 static void iothread_complete(UserCreatable *obj, Error **errp)
 143 {
 144     Error *local_error = NULL;
 145     IOThread *iothread = IOTHREAD(obj);
 146     char *name, *thread_name;
 147
 148     iothread->stopping = false;
 149     iothread->running = true;
 150     iothread->thread_id = -1;
 151     iothread->ctx = aio_context_new(&local_error);
 152     if (!iothread->ctx) {
 153         error_propagate(errp, local_error);
 154         return;
 155     }
 156
 157     aio_context_set_poll_params(iothread->ctx,
 158                                 iothread->poll_max_ns,
 159                                 iothread->poll_grow,
 160                                 iothread->poll_shrink,
 161                                 &local_error);
 162     if (local_error) {
 163         error_propagate(errp, local_error);
 164         aio_context_unref(iothread->ctx);
 165         iothread->ctx = NULL;
 166         return;
 167     }
 168
 169     qemu_mutex_init(&iothread->init_done_lock);
 170     qemu_cond_init(&iothread->init_done_cond);
 171     iothread->once = (GOnce) G_ONCE_INIT;
 172
 173     /* This assumes we are called from a thread with useful CPU affinity for us
 174      * to inherit.
 175      */
 176     name = object_get_canonical_path_component(OBJECT(obj));
 177     thread_name = g_strdup_printf("IO %s", name);
 178     qemu_thread_create(&iothread->thread, thread_name, iothread_run,
 179                        iothread, QEMU_THREAD_JOINABLE);
 180     g_free(thread_name);
 181     g_free(name);
 182
 183     /* Wait for initialization to complete */
 184     qemu_mutex_lock(&iothread->init_done_lock);
 185     while (iothread->thread_id == -1) {
 186         qemu_cond_wait(&iothread->init_done_cond,
 187                        &iothread->init_done_lock);
 188     }
 189     qemu_mutex_unlock(&iothread->init_done_lock);
 190 }
 191
 192 typedef struct {
 193     const char *name;
 194     ptrdiff_t offset; /* field's byte offset in IOThread struct */
 195 } PollParamInfo;
 196
 197 static PollParamInfo poll_max_ns_info = {
 198     "poll-max-ns", offsetof(IOThread, poll_max_ns),
 199 };
 200 static PollParamInfo poll_grow_info = {
 201     "poll-grow", offsetof(IOThread, poll_grow),
 202 };
 203 static PollParamInfo poll_shrink_info = {
 204     "poll-shrink", offsetof(IOThread, poll_shrink),
 205 };
 206
 207 static void iothread_get_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
 214     visit_type_int64(v, name, field, errp);
 215 }
 216
 217 static void iothread_set_poll_param(Object *obj, Visitor *v,
 218         const char *name, void *opaque, Error **errp)
 219 {
 220     IOThread *iothread = IOTHREAD(obj);
 221     PollParamInfo *info = opaque;
 222     int64_t *field = (void *)iothread + info->offset;
 223     Error *local_err = NULL;
 224     int64_t value;
 225
 226     visit_type_int64(v, name, &value, &local_err);
 227     if (local_err) {
 228         goto out;
 229     }
 230
 231     if (value < 0) {
 232         error_setg(&local_err, "%s value must be in range [0, %"PRId64"]",
 233                    info->name, INT64_MAX);
 234         goto out;
 235     }
 236
 237     *field = value;
 238
 239     if (iothread->ctx) {
 240         aio_context_set_poll_params(iothread->ctx,
 241                                     iothread->poll_max_ns,
 242                                     iothread->poll_grow,
 243                                     iothread->poll_shrink,
 244                                     &local_err);
 245     }
 246
 247 out:
 248     error_propagate(errp, local_err);
 249 }
 250
 251 static void iothread_class_init(ObjectClass *klass, void *class_data)
 252 {
 253     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
 254     ucc->complete = iothread_complete;
 255
 256     object_class_property_add(klass, "poll-max-ns", "int",
 257                               iothread_get_poll_param,
 258                               iothread_set_poll_param,
 259                               NULL, &poll_max_ns_info, &error_abort);
 260     object_class_property_add(klass, "poll-grow", "int",
 261                               iothread_get_poll_param,
 262                               iothread_set_poll_param,
 263                               NULL, &poll_grow_info, &error_abort);
 264     object_class_property_add(klass, "poll-shrink", "int",
 265                               iothread_get_poll_param,
 266                               iothread_set_poll_param,
 267                               NULL, &poll_shrink_info, &error_abort);
 268 }
 269
 270 static const TypeInfo iothread_info = {
 271     .name = TYPE_IOTHREAD,
 272     .parent = TYPE_OBJECT,
 273     .class_init = iothread_class_init,
 274     .instance_size = sizeof(IOThread),
 275     .instance_init = iothread_instance_init,
 276     .instance_finalize = iothread_instance_finalize,
 277     .interfaces = (InterfaceInfo[]) {
 278         {TYPE_USER_CREATABLE},
 279         {}
 280     },
 281 };
 282
 283 static void iothread_register_types(void)
 284 {
 285     type_register_static(&iothread_info);
 286 }
 287
 288 type_init(iothread_register_types)
 289
 290 char *iothread_get_id(IOThread *iothread)
 291 {
 292     return object_get_canonical_path_component(OBJECT(iothread));
 293 }
 294
 295 AioContext *iothread_get_aio_context(IOThread *iothread)
 296 {
 297     return iothread->ctx;
 298 }
 299
 300 static int query_one_iothread(Object *object, void *opaque)
 301 {
 302     IOThreadInfoList ***prev = opaque;
 303     IOThreadInfoList *elem;
 304     IOThreadInfo *info;
 305     IOThread *iothread;
 306
 307     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
 308     if (!iothread) {
 309         return 0;
 310     }
 311
 312     info = g_new0(IOThreadInfo, 1);
 313     info->id = iothread_get_id(iothread);
 314     info->thread_id = iothread->thread_id;
 315     info->poll_max_ns = iothread->poll_max_ns;
 316     info->poll_grow = iothread->poll_grow;
 317     info->poll_shrink = iothread->poll_shrink;
 318
 319     elem = g_new0(IOThreadInfoList, 1);
 320     elem->value = info;
 321     elem->next = NULL;
 322
 323     **prev = elem;
 324     *prev = &elem->next;
 325     return 0;
 326 }
 327
 328 IOThreadInfoList *qmp_query_iothreads(Error **errp)
 329 {
 330     IOThreadInfoList *head = NULL;
 331     IOThreadInfoList **prev = &head;
 332     Object *container = object_get_objects_root();
 333
 334     object_child_foreach(container, query_one_iothread, &prev);
 335     return head;
 336 }
 337
 338 static gpointer iothread_g_main_context_init(gpointer opaque)
 339 {
 340     AioContext *ctx;
 341     IOThread *iothread = opaque;
 342     GSource *source;
 343
 344     iothread->worker_context = g_main_context_new();
 345
 346     ctx = iothread_get_aio_context(iothread);
 347     source = aio_get_g_source(ctx);
 348     g_source_attach(source, iothread->worker_context);
 349     g_source_unref(source);
 350
 351     aio_notify(iothread->ctx);
 352     return NULL;
 353 }
 354
 355 GMainContext *iothread_get_g_main_context(IOThread *iothread)
 356 {
 357     g_once(&iothread->once, iothread_g_main_context_init, iothread);
 358
 359     return iothread->worker_context;
 360 }
 361
 362 IOThread *iothread_create(const char *id, Error **errp)
 363 {
 364     Object *obj;
 365
 366     obj = object_new_with_props(TYPE_IOTHREAD,
 367                                 object_get_internal_root(),
 368                                 id, errp, NULL);
 369
 370     return IOTHREAD(obj);
 371 }
 372
 373 void iothread_destroy(IOThread *iothread)
 374 {
 375     object_unparent(OBJECT(iothread));
 376 }
 377
 378 /* Lookup IOThread by its id.  Only finds user-created objects, not internal
 379  * iothread_create() objects. */
 380 IOThread *iothread_by_id(const char *id)
 381 {
 382     return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL));
 383 }