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     iothread->thread_id = qemu_get_thread_id();
  59     qemu_sem_post(&iothread->init_done_sem);
  60
  61     while (iothread->running) {
  62         aio_poll(iothread->ctx, true);
  63
  64         /*
  65          * We must check the running state again in case it was
  66          * changed in previous aio_poll()
  67          */
  68         if (iothread->running && atomic_read(&iothread->worker_context)) {
  69             GMainLoop *loop;
  70
  71             g_main_context_push_thread_default(iothread->worker_context);
  72             iothread->main_loop =
  73                 g_main_loop_new(iothread->worker_context, TRUE);
  74             loop = iothread->main_loop;
  75
  76             g_main_loop_run(iothread->main_loop);
  77             iothread->main_loop = NULL;
  78             g_main_loop_unref(loop);
  79
  80             g_main_context_pop_thread_default(iothread->worker_context);
  81         }
  82     }
  83
  84     rcu_unregister_thread();
  85     return NULL;
  86 }
  87
  88 /* Runs in iothread_run() thread */
  89 static void iothread_stop_bh(void *opaque)
  90 {
  91     IOThread *iothread = opaque;
  92
  93     iothread->running = false; /* stop iothread_run() */
  94
  95     if (iothread->main_loop) {
  96         g_main_loop_quit(iothread->main_loop);
  97     }
  98 }
  99
 100 void iothread_stop(IOThread *iothread)
 101 {
 102     if (!iothread->ctx || iothread->stopping) {
 103         return;
 104     }
 105     iothread->stopping = true;
 106     aio_bh_schedule_oneshot(iothread->ctx, iothread_stop_bh, iothread);
 107     qemu_thread_join(&iothread->thread);
 108 }
 109
 110 static void iothread_instance_init(Object *obj)
 111 {
 112     IOThread *iothread = IOTHREAD(obj);
 113
 114     iothread->poll_max_ns = IOTHREAD_POLL_MAX_NS_DEFAULT;
 115     iothread->thread_id = -1;
 116     qemu_sem_init(&iothread->init_done_sem, 0);
 117 }
 118
 119 static void iothread_instance_finalize(Object *obj)
 120 {
 121     IOThread *iothread = IOTHREAD(obj);
 122
 123     iothread_stop(iothread);
 124
 125     /*
 126      * Before glib2 2.33.10, there is a glib2 bug that GSource context
 127      * pointer may not be cleared even if the context has already been
 128      * destroyed (while it should).  Here let's free the AIO context
 129      * earlier to bypass that glib bug.
 130      *
 131      * We can remove this comment after the minimum supported glib2
 132      * version boosts to 2.33.10.  Before that, let's free the
 133      * GSources first before destroying any GMainContext.
 134      */
 135     if (iothread->ctx) {
 136         aio_context_unref(iothread->ctx);
 137         iothread->ctx = NULL;
 138     }
 139     if (iothread->worker_context) {
 140         g_main_context_unref(iothread->worker_context);
 141         iothread->worker_context = NULL;
 142     }
 143     qemu_sem_destroy(&iothread->init_done_sem);
 144 }
 145
 146 static void iothread_complete(UserCreatable *obj, Error **errp)
 147 {
 148     Error *local_error = NULL;
 149     IOThread *iothread = IOTHREAD(obj);
 150     char *name, *thread_name;
 151
 152     iothread->stopping = false;
 153     iothread->running = true;
 154     iothread->ctx = aio_context_new(&local_error);
 155     if (!iothread->ctx) {
 156         error_propagate(errp, local_error);
 157         return;
 158     }
 159
 160     aio_context_set_poll_params(iothread->ctx,
 161                                 iothread->poll_max_ns,
 162                                 iothread->poll_grow,
 163                                 iothread->poll_shrink,
 164                                 &local_error);
 165     if (local_error) {
 166         error_propagate(errp, local_error);
 167         aio_context_unref(iothread->ctx);
 168         iothread->ctx = NULL;
 169         return;
 170     }
 171
 172     iothread->once = (GOnce) G_ONCE_INIT;
 173
 174     /* This assumes we are called from a thread with useful CPU affinity for us
 175      * to inherit.
 176      */
 177     name = object_get_canonical_path_component(OBJECT(obj));
 178     thread_name = g_strdup_printf("IO %s", name);
 179     qemu_thread_create(&iothread->thread, thread_name, iothread_run,
 180                        iothread, QEMU_THREAD_JOINABLE);
 181     g_free(thread_name);
 182     g_free(name);
 183
 184     /* Wait for initialization to complete */
 185     while (iothread->thread_id == -1) {
 186         qemu_sem_wait(&iothread->init_done_sem);
 187     }
 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 static gpointer iothread_g_main_context_init(gpointer opaque)
 337 {
 338     AioContext *ctx;
 339     IOThread *iothread = opaque;
 340     GSource *source;
 341
 342     iothread->worker_context = g_main_context_new();
 343
 344     ctx = iothread_get_aio_context(iothread);
 345     source = aio_get_g_source(ctx);
 346     g_source_attach(source, iothread->worker_context);
 347     g_source_unref(source);
 348
 349     aio_notify(iothread->ctx);
 350     return NULL;
 351 }
 352
 353 GMainContext *iothread_get_g_main_context(IOThread *iothread)
 354 {
 355     g_once(&iothread->once, iothread_g_main_context_init, iothread);
 356
 357     return iothread->worker_context;
 358 }
 359
 360 IOThread *iothread_create(const char *id, Error **errp)
 361 {
 362     Object *obj;
 363
 364     obj = object_new_with_props(TYPE_IOTHREAD,
 365                                 object_get_internal_root(),
 366                                 id, errp, NULL);
 367
 368     return IOTHREAD(obj);
 369 }
 370
 371 void iothread_destroy(IOThread *iothread)
 372 {
 373     object_unparent(OBJECT(iothread));
 374 }
 375
 376 /* Lookup IOThread by its id.  Only finds user-created objects, not internal
 377  * iothread_create() objects. */
 378 IOThread *iothread_by_id(const char *id)
 379 {
 380     return IOTHREAD(object_resolve_path_type(id, TYPE_IOTHREAD, NULL));
 381 }