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 (!atomic_read(&iothread->stopping)) {
  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 void iothread_stop(IOThread *iothread)
  82 {
  83     if (!iothread->ctx || iothread->stopping) {
  84         return;
  85     }
  86     iothread->stopping = true;
  87     aio_notify(iothread->ctx);
  88     if (atomic_read(&iothread->main_loop)) {
  89         g_main_loop_quit(iothread->main_loop);
  90     }
  91     qemu_thread_join(&iothread->thread);
  92 }
  93
  94 static int iothread_stop_iter(Object *object, void *opaque)
  95 {
  96     IOThread *iothread;
  97
  98     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
  99     if (!iothread) {
 100         return 0;
 101     }
 102     iothread_stop(iothread);
 103     return 0;
 104 }
 105
 106 static void iothread_instance_init(Object *obj)
 107 {
 108     IOThread *iothread = IOTHREAD(obj);
 109
 110     iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
 111 }
 112
 113 static void iothread_instance_finalize(Object *obj)
 114 {
 115     IOThread *iothread = IOTHREAD(obj);
 116
 117     iothread_stop(iothread);
 118     if (iothread->worker_context) {
 119         g_main_context_unref(iothread->worker_context);
 120         iothread->worker_context = NULL;
 121     }
 122     qemu_cond_destroy(&iothread->init_done_cond);
 123     qemu_mutex_destroy(&iothread->init_done_lock);
 124     if (!iothread->ctx) {
 125         return;
 126     }
 127     aio_context_unref(iothread->ctx);
 128 }
 129
 130 static void iothread_complete(UserCreatable *obj, Error **errp)
 131 {
 132     Error *local_error = NULL;
 133     IOThread *iothread = IOTHREAD(obj);
 134     char *name, *thread_name;
 135
 136     iothread->stopping = false;
 137     iothread->thread_id = -1;
 138     iothread->ctx = aio_context_new(&local_error);
 139     if (!iothread->ctx) {
 140         error_propagate(errp, local_error);
 141         return;
 142     }
 143
 144     aio_context_set_poll_params(iothread->ctx,
 145                                 iothread->poll_max_ns,
 146                                 iothread->poll_grow,
 147                                 iothread->poll_shrink,
 148                                 &local_error);
 149     if (local_error) {
 150         error_propagate(errp, local_error);
 151         aio_context_unref(iothread->ctx);
 152         iothread->ctx = NULL;
 153         return;
 154     }
 155
 156     qemu_mutex_init(&iothread->init_done_lock);
 157     qemu_cond_init(&iothread->init_done_cond);
 158     iothread->once = (GOnce) G_ONCE_INIT;
 159
 160     /* This assumes we are called from a thread with useful CPU affinity for us
 161      * to inherit.
 162      */
 163     name = object_get_canonical_path_component(OBJECT(obj));
 164     thread_name = g_strdup_printf("IO %s", name);
 165     qemu_thread_create(&iothread->thread, thread_name, iothread_run,
 166                        iothread, QEMU_THREAD_JOINABLE);
 167     g_free(thread_name);
 168     g_free(name);
 169
 170     /* Wait for initialization to complete */
 171     qemu_mutex_lock(&iothread->init_done_lock);
 172     while (iothread->thread_id == -1) {
 173         qemu_cond_wait(&iothread->init_done_cond,
 174                        &iothread->init_done_lock);
 175     }
 176     qemu_mutex_unlock(&iothread->init_done_lock);
 177 }
 178
 179 typedef struct {
 180     const char *name;
 181     ptrdiff_t offset; /* field's byte offset in IOThread struct */
 182 } PollParamInfo;
 183
 184 static PollParamInfo poll_max_ns_info = {
 185     "poll-max-ns", offsetof(IOThread, poll_max_ns),
 186 };
 187 static PollParamInfo poll_grow_info = {
 188     "poll-grow", offsetof(IOThread, poll_grow),
 189 };
 190 static PollParamInfo poll_shrink_info = {
 191     "poll-shrink", offsetof(IOThread, poll_shrink),
 192 };
 193
 194 static void iothread_get_poll_param(Object *obj, Visitor *v,
 195         const char *name, void *opaque, Error **errp)
 196 {
 197     IOThread *iothread = IOTHREAD(obj);
 198     PollParamInfo *info = opaque;
 199     int64_t *field = (void *)iothread + info->offset;
 200
 201     visit_type_int64(v, name, field, errp);
 202 }
 203
 204 static void iothread_set_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     Error *local_err = NULL;
 211     int64_t value;
 212
 213     visit_type_int64(v, name, &value, &local_err);
 214     if (local_err) {
 215         goto out;
 216     }
 217
 218     if (value < 0) {
 219         error_setg(&local_err, "%s value must be in range [0, %"PRId64"]",
 220                    info->name, INT64_MAX);
 221         goto out;
 222     }
 223
 224     *field = value;
 225
 226     if (iothread->ctx) {
 227         aio_context_set_poll_params(iothread->ctx,
 228                                     iothread->poll_max_ns,
 229                                     iothread->poll_grow,
 230                                     iothread->poll_shrink,
 231                                     &local_err);
 232     }
 233
 234 out:
 235     error_propagate(errp, local_err);
 236 }
 237
 238 static void iothread_class_init(ObjectClass *klass, void *class_data)
 239 {
 240     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);
 241     ucc->complete = iothread_complete;
 242
 243     object_class_property_add(klass, "poll-max-ns", "int",
 244                               iothread_get_poll_param,
 245                               iothread_set_poll_param,
 246                               NULL, &poll_max_ns_info, &error_abort);
 247     object_class_property_add(klass, "poll-grow", "int",
 248                               iothread_get_poll_param,
 249                               iothread_set_poll_param,
 250                               NULL, &poll_grow_info, &error_abort);
 251     object_class_property_add(klass, "poll-shrink", "int",
 252                               iothread_get_poll_param,
 253                               iothread_set_poll_param,
 254                               NULL, &poll_shrink_info, &error_abort);
 255 }
 256
 257 static const TypeInfo iothread_info = {
 258     .name = TYPE_IOTHREAD,
 259     .parent = TYPE_OBJECT,
 260     .class_init = iothread_class_init,
 261     .instance_size = sizeof(IOThread),
 262     .instance_init = iothread_instance_init,
 263     .instance_finalize = iothread_instance_finalize,
 264     .interfaces = (InterfaceInfo[]) {
 265         {TYPE_USER_CREATABLE},
 266         {}
 267     },
 268 };
 269
 270 static void iothread_register_types(void)
 271 {
 272     type_register_static(&iothread_info);
 273 }
 274
 275 type_init(iothread_register_types)
 276
 277 char *iothread_get_id(IOThread *iothread)
 278 {
 279     return object_get_canonical_path_component(OBJECT(iothread));
 280 }
 281
 282 AioContext *iothread_get_aio_context(IOThread *iothread)
 283 {
 284     return iothread->ctx;
 285 }
 286
 287 static int query_one_iothread(Object *object, void *opaque)
 288 {
 289     IOThreadInfoList ***prev = opaque;
 290     IOThreadInfoList *elem;
 291     IOThreadInfo *info;
 292     IOThread *iothread;
 293
 294     iothread = (IOThread *)object_dynamic_cast(object, TYPE_IOTHREAD);
 295     if (!iothread) {
 296         return 0;
 297     }
 298
 299     info = g_new0(IOThreadInfo, 1);
 300     info->id = iothread_get_id(iothread);
 301     info->thread_id = iothread->thread_id;
 302     info->poll_max_ns = iothread->poll_max_ns;
 303     info->poll_grow = iothread->poll_grow;
 304     info->poll_shrink = iothread->poll_shrink;
 305
 306     elem = g_new0(IOThreadInfoList, 1);
 307     elem->value = info;
 308     elem->next = NULL;
 309
 310     **prev = elem;
 311     *prev = &elem->next;
 312     return 0;
 313 }
 314
 315 IOThreadInfoList *qmp_query_iothreads(Error **errp)
 316 {
 317     IOThreadInfoList *head = NULL;
 318     IOThreadInfoList **prev = &head;
 319     Object *container = object_get_objects_root();
 320
 321     object_child_foreach(container, query_one_iothread, &prev);
 322     return head;
 323 }
 324
 325 void iothread_stop_all(void)
 326 {
 327     Object *container = object_get_objects_root();
 328     BlockDriverState *bs;
 329     BdrvNextIterator it;
 330
 331     for (bs = bdrv_first(&it); bs; bs = bdrv_next(&it)) {
 332         AioContext *ctx = bdrv_get_aio_context(bs);
 333         if (ctx == qemu_get_aio_context()) {
 334             continue;
 335         }
 336         aio_context_acquire(ctx);
 337         bdrv_set_aio_context(bs, qemu_get_aio_context());
 338         aio_context_release(ctx);
 339     }
 340
 341     object_child_foreach(container, iothread_stop_iter, NULL);
 342 }
 343
 344 static gpointer iothread_g_main_context_init(gpointer opaque)
 345 {
 346     AioContext *ctx;
 347     IOThread *iothread = opaque;
 348     GSource *source;
 349
 350     iothread->worker_context = g_main_context_new();
 351
 352     ctx = iothread_get_aio_context(iothread);
 353     source = aio_get_g_source(ctx);
 354     g_source_attach(source, iothread->worker_context);
 355     g_source_unref(source);
 356
 357     aio_notify(iothread->ctx);
 358     return NULL;
 359 }
 360
 361 GMainContext *iothread_get_g_main_context(IOThread *iothread)
 362 {
 363     g_once(&iothread->once, iothread_g_main_context_init, iothread);
 364
 365     return iothread->worker_context;
 366 }
 367
 368 IOThread *iothread_create(const char *id, Error **errp)
 369 {
 370     Object *obj;
 371
 372     obj = object_new_with_props(TYPE_IOTHREAD,
 373                                 object_get_internal_root(),
 374                                 id, errp, NULL);
 375
 376     return IOTHREAD(obj);
 377 }
 378
 379 void iothread_destroy(IOThread *iothread)
 380 {
 381     object_unparent(OBJECT(iothread));
 382 }