migration.c

   1 /*
   2  * QEMU live migration
   3  *
   4  * Copyright IBM, Corp. 2008
   5  *
   6  * Authors:
   7  *  Anthony Liguori   <aliguori@us.ibm.com>
   8  *
   9  * This work is licensed under the terms of the GNU GPL, version 2.  See
  10  * the COPYING file in the top-level directory.
  11  *
  12  * Contributions after 2012-01-13 are licensed under the terms of the
  13  * GNU GPL, version 2 or (at your option) any later version.
  14  */
  15
  16 #include "qemu-common.h"
  17 #include "migration/migration.h"
  18 #include "monitor/monitor.h"
  19 #include "migration/qemu-file.h"
  20 #include "sysemu/sysemu.h"
  21 #include "block/block.h"
  22 #include "qemu/sockets.h"
  23 #include "migration/block.h"
  24 #include "qemu/thread.h"
  25 #include "qmp-commands.h"
  26
  27 //#define DEBUG_MIGRATION
  28
  29 #ifdef DEBUG_MIGRATION
  30 #define DPRINTF(fmt, ...) \
  31     do { printf("migration: " fmt, ## __VA_ARGS__); } while (0)
  32 #else
  33 #define DPRINTF(fmt, ...) \
  34     do { } while (0)
  35 #endif
  36
  37 enum {
  38     MIG_STATE_ERROR,
  39     MIG_STATE_SETUP,
  40     MIG_STATE_CANCELLED,
  41     MIG_STATE_ACTIVE,
  42     MIG_STATE_COMPLETED,
  43 };
  44
  45 #define MAX_THROTTLE  (32 << 20)      /* Migration speed throttling */
  46
  47 /* Amount of time to allocate to each "chunk" of bandwidth-throttled
  48  * data. */
  49 #define BUFFER_DELAY     100
  50 #define XFER_LIMIT_RATIO (1000 / BUFFER_DELAY)
  51
  52 /* Migration XBZRLE default cache size */
  53 #define DEFAULT_MIGRATE_CACHE_SIZE (64 * 1024 * 1024)
  54
  55 static NotifierList migration_state_notifiers =
  56     NOTIFIER_LIST_INITIALIZER(migration_state_notifiers);
  57
  58 /* When we add fault tolerance, we could have several
  59    migrations at once.  For now we don't need to add
  60    dynamic creation of migration */
  61
  62 MigrationState *migrate_get_current(void)
  63 {
  64     static MigrationState current_migration = {
  65         .state = MIG_STATE_SETUP,
  66         .bandwidth_limit = MAX_THROTTLE,
  67         .xbzrle_cache_size = DEFAULT_MIGRATE_CACHE_SIZE,
  68     };
  69
  70     return &current_migration;
  71 }
  72
  73 void qemu_start_incoming_migration(const char *uri, Error **errp)
  74 {
  75     const char *p;
  76
  77     if (strstart(uri, "tcp:", &p))
  78         tcp_start_incoming_migration(p, errp);
  79 #if !defined(WIN32)
  80     else if (strstart(uri, "exec:", &p))
  81         exec_start_incoming_migration(p, errp);
  82     else if (strstart(uri, "unix:", &p))
  83         unix_start_incoming_migration(p, errp);
  84     else if (strstart(uri, "fd:", &p))
  85         fd_start_incoming_migration(p, errp);
  86 #endif
  87     else {
  88         error_setg(errp, "unknown migration protocol: %s", uri);
  89     }
  90 }
  91
  92 static void process_incoming_migration_co(void *opaque)
  93 {
  94     QEMUFile *f = opaque;
  95     int ret;
  96
  97     ret = qemu_loadvm_state(f);
  98     qemu_fclose(f);
  99     if (ret < 0) {
 100         fprintf(stderr, "load of migration failed\n");
 101         exit(0);
 102     }
 103     qemu_announce_self();
 104     DPRINTF("successfully loaded vm state\n");
 105
 106     bdrv_clear_incoming_migration_all();
 107     /* Make sure all file formats flush their mutable metadata */
 108     bdrv_invalidate_cache_all();
 109
 110     if (autostart) {
 111         vm_start();
 112     } else {
 113         runstate_set(RUN_STATE_PAUSED);
 114     }
 115 }
 116
 117 void process_incoming_migration(QEMUFile *f)
 118 {
 119     Coroutine *co = qemu_coroutine_create(process_incoming_migration_co);
 120     int fd = qemu_get_fd(f);
 121
 122     assert(fd != -1);
 123     socket_set_nonblock(fd);
 124     qemu_coroutine_enter(co, f);
 125 }
 126
 127 /* amount of nanoseconds we are willing to wait for migration to be down.
 128  * the choice of nanoseconds is because it is the maximum resolution that
 129  * get_clock() can achieve. It is an internal measure. All user-visible
 130  * units must be in seconds */
 131 static uint64_t max_downtime = 30000000;
 132
 133 uint64_t migrate_max_downtime(void)
 134 {
 135     return max_downtime;
 136 }
 137
 138 MigrationCapabilityStatusList *qmp_query_migrate_capabilities(Error **errp)
 139 {
 140     MigrationCapabilityStatusList *head = NULL;
 141     MigrationCapabilityStatusList *caps;
 142     MigrationState *s = migrate_get_current();
 143     int i;
 144
 145     for (i = 0; i < MIGRATION_CAPABILITY_MAX; i++) {
 146         if (head == NULL) {
 147             head = g_malloc0(sizeof(*caps));
 148             caps = head;
 149         } else {
 150             caps->next = g_malloc0(sizeof(*caps));
 151             caps = caps->next;
 152         }
 153         caps->value =
 154             g_malloc(sizeof(*caps->value));
 155         caps->value->capability = i;
 156         caps->value->state = s->enabled_capabilities[i];
 157     }
 158
 159     return head;
 160 }
 161
 162 static void get_xbzrle_cache_stats(MigrationInfo *info)
 163 {
 164     if (migrate_use_xbzrle()) {
 165         info->has_xbzrle_cache = true;
 166         info->xbzrle_cache = g_malloc0(sizeof(*info->xbzrle_cache));
 167         info->xbzrle_cache->cache_size = migrate_xbzrle_cache_size();
 168         info->xbzrle_cache->bytes = xbzrle_mig_bytes_transferred();
 169         info->xbzrle_cache->pages = xbzrle_mig_pages_transferred();
 170         info->xbzrle_cache->cache_miss = xbzrle_mig_pages_cache_miss();
 171         info->xbzrle_cache->overflow = xbzrle_mig_pages_overflow();
 172     }
 173 }
 174
 175 MigrationInfo *qmp_query_migrate(Error **errp)
 176 {
 177     MigrationInfo *info = g_malloc0(sizeof(*info));
 178     MigrationState *s = migrate_get_current();
 179
 180     switch (s->state) {
 181     case MIG_STATE_SETUP:
 182         /* no migration has happened ever */
 183         break;
 184     case MIG_STATE_ACTIVE:
 185         info->has_status = true;
 186         info->status = g_strdup("active");
 187         info->has_total_time = true;
 188         info->total_time = qemu_get_clock_ms(rt_clock)
 189             - s->total_time;
 190         info->has_expected_downtime = true;
 191         info->expected_downtime = s->expected_downtime;
 192
 193         info->has_ram = true;
 194         info->ram = g_malloc0(sizeof(*info->ram));
 195         info->ram->transferred = ram_bytes_transferred();
 196         info->ram->remaining = ram_bytes_remaining();
 197         info->ram->total = ram_bytes_total();
 198         info->ram->duplicate = dup_mig_pages_transferred();
 199         info->ram->normal = norm_mig_pages_transferred();
 200         info->ram->normal_bytes = norm_mig_bytes_transferred();
 201         info->ram->dirty_pages_rate = s->dirty_pages_rate;
 202
 203
 204         if (blk_mig_active()) {
 205             info->has_disk = true;
 206             info->disk = g_malloc0(sizeof(*info->disk));
 207             info->disk->transferred = blk_mig_bytes_transferred();
 208             info->disk->remaining = blk_mig_bytes_remaining();
 209             info->disk->total = blk_mig_bytes_total();
 210         }
 211
 212         get_xbzrle_cache_stats(info);
 213         break;
 214     case MIG_STATE_COMPLETED:
 215         get_xbzrle_cache_stats(info);
 216
 217         info->has_status = true;
 218         info->status = g_strdup("completed");
 219         info->total_time = s->total_time;
 220         info->has_downtime = true;
 221         info->downtime = s->downtime;
 222
 223         info->has_ram = true;
 224         info->ram = g_malloc0(sizeof(*info->ram));
 225         info->ram->transferred = ram_bytes_transferred();
 226         info->ram->remaining = 0;
 227         info->ram->total = ram_bytes_total();
 228         info->ram->duplicate = dup_mig_pages_transferred();
 229         info->ram->normal = norm_mig_pages_transferred();
 230         info->ram->normal_bytes = norm_mig_bytes_transferred();
 231         break;
 232     case MIG_STATE_ERROR:
 233         info->has_status = true;
 234         info->status = g_strdup("failed");
 235         break;
 236     case MIG_STATE_CANCELLED:
 237         info->has_status = true;
 238         info->status = g_strdup("cancelled");
 239         break;
 240     }
 241
 242     return info;
 243 }
 244
 245 void qmp_migrate_set_capabilities(MigrationCapabilityStatusList *params,
 246                                   Error **errp)
 247 {
 248     MigrationState *s = migrate_get_current();
 249     MigrationCapabilityStatusList *cap;
 250
 251     if (s->state == MIG_STATE_ACTIVE) {
 252         error_set(errp, QERR_MIGRATION_ACTIVE);
 253         return;
 254     }
 255
 256     for (cap = params; cap; cap = cap->next) {
 257         s->enabled_capabilities[cap->value->capability] = cap->value->state;
 258     }
 259 }
 260
 261 /* shared migration helpers */
 262
 263 static void migrate_fd_cleanup(MigrationState *s)
 264 {
 265     int ret = 0;
 266
 267     if (s->file) {
 268         DPRINTF("closing file\n");
 269         ret = qemu_fclose(s->file);
 270         s->file = NULL;
 271     }
 272
 273     assert(s->fd == -1);
 274     if (ret < 0 && s->state == MIG_STATE_ACTIVE) {
 275         s->state = MIG_STATE_ERROR;
 276     }
 277
 278     if (s->state != MIG_STATE_ACTIVE) {
 279         qemu_savevm_state_cancel();
 280     }
 281 }
 282
 283 void migrate_fd_error(MigrationState *s)
 284 {
 285     DPRINTF("setting error state\n");
 286     s->state = MIG_STATE_ERROR;
 287     notifier_list_notify(&migration_state_notifiers, s);
 288     migrate_fd_cleanup(s);
 289 }
 290
 291 static void migrate_fd_completed(MigrationState *s)
 292 {
 293     DPRINTF("setting completed state\n");
 294     migrate_fd_cleanup(s);
 295     if (s->state == MIG_STATE_ACTIVE) {
 296         s->state = MIG_STATE_COMPLETED;
 297         runstate_set(RUN_STATE_POSTMIGRATE);
 298     }
 299     notifier_list_notify(&migration_state_notifiers, s);
 300 }
 301
 302 static ssize_t migrate_fd_put_buffer(MigrationState *s, const void *data,
 303                                      size_t size)
 304 {
 305     ssize_t ret;
 306
 307     if (s->state != MIG_STATE_ACTIVE) {
 308         return -EIO;
 309     }
 310
 311     do {
 312         ret = s->write(s, data, size);
 313     } while (ret == -1 && ((s->get_error(s)) == EINTR));
 314
 315     if (ret == -1)
 316         ret = -(s->get_error(s));
 317
 318     return ret;
 319 }
 320
 321 static void migrate_fd_cancel(MigrationState *s)
 322 {
 323     if (s->state != MIG_STATE_ACTIVE)
 324         return;
 325
 326     DPRINTF("cancelling migration\n");
 327
 328     s->state = MIG_STATE_CANCELLED;
 329     notifier_list_notify(&migration_state_notifiers, s);
 330
 331     migrate_fd_cleanup(s);
 332 }
 333
 334 int migrate_fd_close(MigrationState *s)
 335 {
 336     int rc = 0;
 337     if (s->fd != -1) {
 338         rc = s->close(s);
 339         s->fd = -1;
 340     }
 341     return rc;
 342 }
 343
 344 void add_migration_state_change_notifier(Notifier *notify)
 345 {
 346     notifier_list_add(&migration_state_notifiers, notify);
 347 }
 348
 349 void remove_migration_state_change_notifier(Notifier *notify)
 350 {
 351     notifier_remove(notify);
 352 }
 353
 354 bool migration_is_active(MigrationState *s)
 355 {
 356     return s->state == MIG_STATE_ACTIVE;
 357 }
 358
 359 bool migration_has_finished(MigrationState *s)
 360 {
 361     return s->state == MIG_STATE_COMPLETED;
 362 }
 363
 364 bool migration_has_failed(MigrationState *s)
 365 {
 366     return (s->state == MIG_STATE_CANCELLED ||
 367             s->state == MIG_STATE_ERROR);
 368 }
 369
 370 static MigrationState *migrate_init(const MigrationParams *params)
 371 {
 372     MigrationState *s = migrate_get_current();
 373     int64_t bandwidth_limit = s->bandwidth_limit;
 374     bool enabled_capabilities[MIGRATION_CAPABILITY_MAX];
 375     int64_t xbzrle_cache_size = s->xbzrle_cache_size;
 376
 377     memcpy(enabled_capabilities, s->enabled_capabilities,
 378            sizeof(enabled_capabilities));
 379
 380     memset(s, 0, sizeof(*s));
 381     s->bandwidth_limit = bandwidth_limit;
 382     s->params = *params;
 383     memcpy(s->enabled_capabilities, enabled_capabilities,
 384            sizeof(enabled_capabilities));
 385     s->xbzrle_cache_size = xbzrle_cache_size;
 386
 387     s->bandwidth_limit = bandwidth_limit;
 388     s->state = MIG_STATE_SETUP;
 389     s->total_time = qemu_get_clock_ms(rt_clock);
 390
 391     return s;
 392 }
 393
 394 static GSList *migration_blockers;
 395
 396 void migrate_add_blocker(Error *reason)
 397 {
 398     migration_blockers = g_slist_prepend(migration_blockers, reason);
 399 }
 400
 401 void migrate_del_blocker(Error *reason)
 402 {
 403     migration_blockers = g_slist_remove(migration_blockers, reason);
 404 }
 405
 406 void qmp_migrate(const char *uri, bool has_blk, bool blk,
 407                  bool has_inc, bool inc, bool has_detach, bool detach,
 408                  Error **errp)
 409 {
 410     Error *local_err = NULL;
 411     MigrationState *s = migrate_get_current();
 412     MigrationParams params;
 413     const char *p;
 414
 415     params.blk = blk;
 416     params.shared = inc;
 417
 418     if (s->state == MIG_STATE_ACTIVE) {
 419         error_set(errp, QERR_MIGRATION_ACTIVE);
 420         return;
 421     }
 422
 423     if (qemu_savevm_state_blocked(errp)) {
 424         return;
 425     }
 426
 427     if (migration_blockers) {
 428         *errp = error_copy(migration_blockers->data);
 429         return;
 430     }
 431
 432     s = migrate_init(&params);
 433
 434     if (strstart(uri, "tcp:", &p)) {
 435         tcp_start_outgoing_migration(s, p, &local_err);
 436 #if !defined(WIN32)
 437     } else if (strstart(uri, "exec:", &p)) {
 438         exec_start_outgoing_migration(s, p, &local_err);
 439     } else if (strstart(uri, "unix:", &p)) {
 440         unix_start_outgoing_migration(s, p, &local_err);
 441     } else if (strstart(uri, "fd:", &p)) {
 442         fd_start_outgoing_migration(s, p, &local_err);
 443 #endif
 444     } else {
 445         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "uri", "a valid migration protocol");
 446         return;
 447     }
 448
 449     if (local_err) {
 450         migrate_fd_error(s);
 451         error_propagate(errp, local_err);
 452         return;
 453     }
 454 }
 455
 456 void qmp_migrate_cancel(Error **errp)
 457 {
 458     migrate_fd_cancel(migrate_get_current());
 459 }
 460
 461 void qmp_migrate_set_cache_size(int64_t value, Error **errp)
 462 {
 463     MigrationState *s = migrate_get_current();
 464
 465     /* Check for truncation */
 466     if (value != (size_t)value) {
 467         error_set(errp, QERR_INVALID_PARAMETER_VALUE, "cache size",
 468                   "exceeding address space");
 469         return;
 470     }
 471
 472     s->xbzrle_cache_size = xbzrle_cache_resize(value);
 473 }
 474
 475 int64_t qmp_query_migrate_cache_size(Error **errp)
 476 {
 477     return migrate_xbzrle_cache_size();
 478 }
 479
 480 void qmp_migrate_set_speed(int64_t value, Error **errp)
 481 {
 482     MigrationState *s;
 483
 484     if (value < 0) {
 485         value = 0;
 486     }
 487
 488     s = migrate_get_current();
 489     s->bandwidth_limit = value;
 490     qemu_file_set_rate_limit(s->file, s->bandwidth_limit);
 491 }
 492
 493 void qmp_migrate_set_downtime(double value, Error **errp)
 494 {
 495     value *= 1e9;
 496     value = MAX(0, MIN(UINT64_MAX, value));
 497     max_downtime = (uint64_t)value;
 498 }
 499
 500 int migrate_use_xbzrle(void)
 501 {
 502     MigrationState *s;
 503
 504     s = migrate_get_current();
 505
 506     return s->enabled_capabilities[MIGRATION_CAPABILITY_XBZRLE];
 507 }
 508
 509 int64_t migrate_xbzrle_cache_size(void)
 510 {
 511     MigrationState *s;
 512
 513     s = migrate_get_current();
 514
 515     return s->xbzrle_cache_size;
 516 }
 517
 518 /* migration thread support */
 519
 520
 521 static void buffered_flush(MigrationState *s)
 522 {
 523     size_t offset = 0;
 524     ssize_t ret = 0;
 525
 526     DPRINTF("flushing %zu byte(s) of data\n", s->buffer_size);
 527
 528     qemu_fflush(s->file);
 529
 530     while (s->bytes_xfer < s->xfer_limit && offset < s->buffer_size) {
 531         size_t to_send = MIN(s->buffer_size - offset, s->xfer_limit - s->bytes_xfer);
 532         ret = migrate_fd_put_buffer(s, s->buffer + offset, to_send);
 533         if (ret <= 0) {
 534             DPRINTF("error flushing data, %zd\n", ret);
 535             break;
 536         } else {
 537             DPRINTF("flushed %zd byte(s)\n", ret);
 538             offset += ret;
 539             s->bytes_xfer += ret;
 540         }
 541     }
 542
 543     DPRINTF("flushed %zu of %zu byte(s)\n", offset, s->buffer_size);
 544     memmove(s->buffer, s->buffer + offset, s->buffer_size - offset);
 545     s->buffer_size -= offset;
 546
 547     if (ret < 0) {
 548         qemu_file_set_error(s->file, ret);
 549     }
 550 }
 551
 552 static int buffered_put_buffer(void *opaque, const uint8_t *buf,
 553                                int64_t pos, int size)
 554 {
 555     MigrationState *s = opaque;
 556     ssize_t error;
 557
 558     DPRINTF("putting %d bytes at %" PRId64 "\n", size, pos);
 559
 560     error = qemu_file_get_error(s->file);
 561     if (error) {
 562         DPRINTF("flush when error, bailing: %s\n", strerror(-error));
 563         return error;
 564     }
 565
 566     if (size <= 0) {
 567         return size;
 568     }
 569
 570     if (size > (s->buffer_capacity - s->buffer_size)) {
 571         DPRINTF("increasing buffer capacity from %zu by %zu\n",
 572                 s->buffer_capacity, size + 1024);
 573
 574         s->buffer_capacity += size + 1024;
 575
 576         s->buffer = g_realloc(s->buffer, s->buffer_capacity);
 577     }
 578
 579     memcpy(s->buffer + s->buffer_size, buf, size);
 580     s->buffer_size += size;
 581
 582     return size;
 583 }
 584
 585 static int buffered_close(void *opaque)
 586 {
 587     MigrationState *s = opaque;
 588
 589     DPRINTF("closing\n");
 590
 591     s->xfer_limit = INT_MAX;
 592     while (!qemu_file_get_error(s->file) && s->buffer_size) {
 593         buffered_flush(s);
 594     }
 595     s->complete = true;
 596     return migrate_fd_close(s);
 597 }
 598
 599 static int buffered_get_fd(void *opaque)
 600 {
 601     MigrationState *s = opaque;
 602
 603     return s->fd;
 604 }
 605
 606 /*
 607  * The meaning of the return values is:
 608  *   0: We can continue sending
 609  *   1: Time to stop
 610  *   negative: There has been an error
 611  */
 612 static int buffered_rate_limit(void *opaque)
 613 {
 614     MigrationState *s = opaque;
 615     int ret;
 616
 617     ret = qemu_file_get_error(s->file);
 618     if (ret) {
 619         return ret;
 620     }
 621
 622     if (s->bytes_xfer >= s->xfer_limit) {
 623         return 1;
 624     }
 625
 626     return 0;
 627 }
 628
 629 static int64_t buffered_set_rate_limit(void *opaque, int64_t new_rate)
 630 {
 631     MigrationState *s = opaque;
 632     if (qemu_file_get_error(s->file)) {
 633         goto out;
 634     }
 635     if (new_rate > SIZE_MAX) {
 636         new_rate = SIZE_MAX;
 637     }
 638
 639     s->xfer_limit = new_rate / XFER_LIMIT_RATIO;
 640
 641 out:
 642     return s->xfer_limit;
 643 }
 644
 645 static int64_t buffered_get_rate_limit(void *opaque)
 646 {
 647     MigrationState *s = opaque;
 648
 649     return s->xfer_limit;
 650 }
 651
 652 static void *buffered_file_thread(void *opaque)
 653 {
 654     MigrationState *s = opaque;
 655     int64_t initial_time = qemu_get_clock_ms(rt_clock);
 656     int64_t sleep_time = 0;
 657     int64_t max_size = 0;
 658     bool last_round = false;
 659     int ret;
 660
 661     qemu_mutex_lock_iothread();
 662     DPRINTF("beginning savevm\n");
 663     ret = qemu_savevm_state_begin(s->file, &s->params);
 664     qemu_mutex_unlock_iothread();
 665
 666     while (ret >= 0) {
 667         int64_t current_time;
 668         uint64_t pending_size;
 669
 670         qemu_mutex_lock_iothread();
 671         if (s->state != MIG_STATE_ACTIVE) {
 672             DPRINTF("put_ready returning because of non-active state\n");
 673             qemu_mutex_unlock_iothread();
 674             break;
 675         }
 676         if (s->complete) {
 677             qemu_mutex_unlock_iothread();
 678             break;
 679         }
 680         if (s->bytes_xfer < s->xfer_limit) {
 681             DPRINTF("iterate\n");
 682             pending_size = qemu_savevm_state_pending(s->file, max_size);
 683             DPRINTF("pending size %lu max %lu\n", pending_size, max_size);
 684             if (pending_size && pending_size >= max_size) {
 685                 ret = qemu_savevm_state_iterate(s->file);
 686                 if (ret < 0) {
 687                     qemu_mutex_unlock_iothread();
 688                     break;
 689                 }
 690             } else {
 691                 int old_vm_running = runstate_is_running();
 692                 int64_t start_time, end_time;
 693
 694                 DPRINTF("done iterating\n");
 695                 start_time = qemu_get_clock_ms(rt_clock);
 696                 qemu_system_wakeup_request(QEMU_WAKEUP_REASON_OTHER);
 697                 vm_stop_force_state(RUN_STATE_FINISH_MIGRATE);
 698                 ret = qemu_savevm_state_complete(s->file);
 699                 if (ret < 0) {
 700                     qemu_mutex_unlock_iothread();
 701                     break;
 702                 } else {
 703                     migrate_fd_completed(s);
 704                 }
 705                 end_time = qemu_get_clock_ms(rt_clock);
 706                 s->total_time = end_time - s->total_time;
 707                 s->downtime = end_time - start_time;
 708                 if (s->state != MIG_STATE_COMPLETED) {
 709                     if (old_vm_running) {
 710                         vm_start();
 711                     }
 712                 }
 713                 last_round = true;
 714             }
 715         }
 716         qemu_mutex_unlock_iothread();
 717         current_time = qemu_get_clock_ms(rt_clock);
 718         if (current_time >= initial_time + BUFFER_DELAY) {
 719             uint64_t transferred_bytes = s->bytes_xfer;
 720             uint64_t time_spent = current_time - initial_time - sleep_time;
 721             double bandwidth = transferred_bytes / time_spent;
 722             max_size = bandwidth * migrate_max_downtime() / 1000000;
 723
 724             DPRINTF("transferred %" PRIu64 " time_spent %" PRIu64
 725                     " bandwidth %g max_size %" PRId64 "\n",
 726                     transferred_bytes, time_spent, bandwidth, max_size);
 727             /* if we haven't sent anything, we don't want to recalculate
 728                10000 is a small enough number for our purposes */
 729             if (s->dirty_bytes_rate && transferred_bytes > 10000) {
 730                 s->expected_downtime = s->dirty_bytes_rate / bandwidth;
 731             }
 732
 733             s->bytes_xfer = 0;
 734             sleep_time = 0;
 735             initial_time = current_time;
 736         }
 737         if (!last_round && (s->bytes_xfer >= s->xfer_limit)) {
 738             /* usleep expects microseconds */
 739             g_usleep((initial_time + BUFFER_DELAY - current_time)*1000);
 740             sleep_time += qemu_get_clock_ms(rt_clock) - current_time;
 741         }
 742         buffered_flush(s);
 743         ret = qemu_file_get_error(s->file);
 744     }
 745
 746     if (ret < 0) {
 747         migrate_fd_error(s);
 748     }
 749     g_free(s->buffer);
 750     return NULL;
 751 }
 752
 753 static const QEMUFileOps buffered_file_ops = {
 754     .get_fd =         buffered_get_fd,
 755     .put_buffer =     buffered_put_buffer,
 756     .close =          buffered_close,
 757     .rate_limit =     buffered_rate_limit,
 758     .get_rate_limit = buffered_get_rate_limit,
 759     .set_rate_limit = buffered_set_rate_limit,
 760 };
 761
 762 void migrate_fd_connect(MigrationState *s)
 763 {
 764     s->state = MIG_STATE_ACTIVE;
 765     s->bytes_xfer = 0;
 766     s->buffer = NULL;
 767     s->buffer_size = 0;
 768     s->buffer_capacity = 0;
 769     /* This is a best 1st approximation. ns to ms */
 770     s->expected_downtime = max_downtime/1000000;
 771
 772     s->xfer_limit = s->bandwidth_limit / XFER_LIMIT_RATIO;
 773     s->complete = false;
 774
 775     s->file = qemu_fopen_ops(s, &buffered_file_ops);
 776
 777     qemu_thread_create(&s->thread, buffered_file_thread, s,
 778                        QEMU_THREAD_DETACHED);
 779     notifier_list_notify(&migration_state_notifiers, s);
 780 }