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