migration/dirtyrate.c

   1 /*
   2  * Dirtyrate implement code
   3  *
   4  * Copyright (c) 2020 HUAWEI TECHNOLOGIES CO.,LTD.
   5  *
   6  * Authors:
   7  *  Chuan Zheng <zhengchuan@huawei.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 #include "qemu/osdep.h"
  14 #include <zlib.h>
  15 #include "qapi/error.h"
  16 #include "cpu.h"
  17 #include "exec/ramblock.h"
  18 #include "qemu/rcu_queue.h"
  19 #include "qemu/main-loop.h"
  20 #include "qapi/qapi-commands-migration.h"
  21 #include "ram.h"
  22 #include "trace.h"
  23 #include "dirtyrate.h"
  24 #include "monitor/hmp.h"
  25 #include "monitor/monitor.h"
  26 #include "qapi/qmp/qdict.h"
  27 #include "sysemu/kvm.h"
  28 #include "sysemu/runstate.h"
  29 #include "exec/memory.h"
  30
  31 typedef struct DirtyPageRecord {
  32     uint64_t start_pages;
  33     uint64_t end_pages;
  34 } DirtyPageRecord;
  35
  36 static int CalculatingState = DIRTY_RATE_STATUS_UNSTARTED;
  37 static struct DirtyRateStat DirtyStat;
  38 static DirtyRateMeasureMode dirtyrate_mode =
  39                 DIRTY_RATE_MEASURE_MODE_PAGE_SAMPLING;
  40
  41 static int64_t set_sample_page_period(int64_t msec, int64_t initial_time)
  42 {
  43     int64_t current_time;
  44
  45     current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
  46     if ((current_time - initial_time) >= msec) {
  47         msec = current_time - initial_time;
  48     } else {
  49         g_usleep((msec + initial_time - current_time) * 1000);
  50     }
  51
  52     return msec;
  53 }
  54
  55 static bool is_sample_period_valid(int64_t sec)
  56 {
  57     if (sec < MIN_FETCH_DIRTYRATE_TIME_SEC ||
  58         sec > MAX_FETCH_DIRTYRATE_TIME_SEC) {
  59         return false;
  60     }
  61
  62     return true;
  63 }
  64
  65 static bool is_sample_pages_valid(int64_t pages)
  66 {
  67     return pages >= MIN_SAMPLE_PAGE_COUNT &&
  68            pages <= MAX_SAMPLE_PAGE_COUNT;
  69 }
  70
  71 static int dirtyrate_set_state(int *state, int old_state, int new_state)
  72 {
  73     assert(new_state < DIRTY_RATE_STATUS__MAX);
  74     trace_dirtyrate_set_state(DirtyRateStatus_str(new_state));
  75     if (qatomic_cmpxchg(state, old_state, new_state) == old_state) {
  76         return 0;
  77     } else {
  78         return -1;
  79     }
  80 }
  81
  82 static struct DirtyRateInfo *query_dirty_rate_info(void)
  83 {
  84     int i;
  85     int64_t dirty_rate = DirtyStat.dirty_rate;
  86     struct DirtyRateInfo *info = g_malloc0(sizeof(DirtyRateInfo));
  87     DirtyRateVcpuList *head = NULL, **tail = &head;
  88
  89     info->status = CalculatingState;
  90     info->start_time = DirtyStat.start_time;
  91     info->calc_time = DirtyStat.calc_time;
  92     info->sample_pages = DirtyStat.sample_pages;
  93     info->mode = dirtyrate_mode;
  94
  95     if (qatomic_read(&CalculatingState) == DIRTY_RATE_STATUS_MEASURED) {
  96         info->has_dirty_rate = true;
  97         info->dirty_rate = dirty_rate;
  98
  99         if (dirtyrate_mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) {
 100             /*
 101              * set sample_pages with 0 to indicate page sampling
 102              * isn't enabled
 103              **/
 104             info->sample_pages = 0;
 105             info->has_vcpu_dirty_rate = true;
 106             for (i = 0; i < DirtyStat.dirty_ring.nvcpu; i++) {
 107                 DirtyRateVcpu *rate = g_malloc0(sizeof(DirtyRateVcpu));
 108                 rate->id = DirtyStat.dirty_ring.rates[i].id;
 109                 rate->dirty_rate = DirtyStat.dirty_ring.rates[i].dirty_rate;
 110                 QAPI_LIST_APPEND(tail, rate);
 111             }
 112             info->vcpu_dirty_rate = head;
 113         }
 114     }
 115
 116     trace_query_dirty_rate_info(DirtyRateStatus_str(CalculatingState));
 117
 118     return info;
 119 }
 120
 121 static void init_dirtyrate_stat(int64_t start_time,
 122                                 struct DirtyRateConfig config)
 123 {
 124     DirtyStat.dirty_rate = -1;
 125     DirtyStat.start_time = start_time;
 126     DirtyStat.calc_time = config.sample_period_seconds;
 127     DirtyStat.sample_pages = config.sample_pages_per_gigabytes;
 128
 129     switch (config.mode) {
 130     case DIRTY_RATE_MEASURE_MODE_PAGE_SAMPLING:
 131         DirtyStat.page_sampling.total_dirty_samples = 0;
 132         DirtyStat.page_sampling.total_sample_count = 0;
 133         DirtyStat.page_sampling.total_block_mem_MB = 0;
 134         break;
 135     case DIRTY_RATE_MEASURE_MODE_DIRTY_RING:
 136         DirtyStat.dirty_ring.nvcpu = -1;
 137         DirtyStat.dirty_ring.rates = NULL;
 138         break;
 139     default:
 140         break;
 141     }
 142 }
 143
 144 static void cleanup_dirtyrate_stat(struct DirtyRateConfig config)
 145 {
 146     /* last calc-dirty-rate qmp use dirty ring mode */
 147     if (dirtyrate_mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) {
 148         free(DirtyStat.dirty_ring.rates);
 149         DirtyStat.dirty_ring.rates = NULL;
 150     }
 151 }
 152
 153 static void update_dirtyrate_stat(struct RamblockDirtyInfo *info)
 154 {
 155     DirtyStat.page_sampling.total_dirty_samples += info->sample_dirty_count;
 156     DirtyStat.page_sampling.total_sample_count += info->sample_pages_count;
 157     /* size of total pages in MB */
 158     DirtyStat.page_sampling.total_block_mem_MB += (info->ramblock_pages *
 159                                                    TARGET_PAGE_SIZE) >> 20;
 160 }
 161
 162 static void update_dirtyrate(uint64_t msec)
 163 {
 164     uint64_t dirtyrate;
 165     uint64_t total_dirty_samples = DirtyStat.page_sampling.total_dirty_samples;
 166     uint64_t total_sample_count = DirtyStat.page_sampling.total_sample_count;
 167     uint64_t total_block_mem_MB = DirtyStat.page_sampling.total_block_mem_MB;
 168
 169     dirtyrate = total_dirty_samples * total_block_mem_MB *
 170                 1000 / (total_sample_count * msec);
 171
 172     DirtyStat.dirty_rate = dirtyrate;
 173 }
 174
 175 /*
 176  * get hash result for the sampled memory with length of TARGET_PAGE_SIZE
 177  * in ramblock, which starts from ramblock base address.
 178  */
 179 static uint32_t get_ramblock_vfn_hash(struct RamblockDirtyInfo *info,
 180                                       uint64_t vfn)
 181 {
 182     uint32_t crc;
 183
 184     crc = crc32(0, (info->ramblock_addr +
 185                 vfn * TARGET_PAGE_SIZE), TARGET_PAGE_SIZE);
 186
 187     trace_get_ramblock_vfn_hash(info->idstr, vfn, crc);
 188     return crc;
 189 }
 190
 191 static bool save_ramblock_hash(struct RamblockDirtyInfo *info)
 192 {
 193     unsigned int sample_pages_count;
 194     int i;
 195     GRand *rand;
 196
 197     sample_pages_count = info->sample_pages_count;
 198
 199     /* ramblock size less than one page, return success to skip this ramblock */
 200     if (unlikely(info->ramblock_pages == 0 || sample_pages_count == 0)) {
 201         return true;
 202     }
 203
 204     info->hash_result = g_try_malloc0_n(sample_pages_count,
 205                                         sizeof(uint32_t));
 206     if (!info->hash_result) {
 207         return false;
 208     }
 209
 210     info->sample_page_vfn = g_try_malloc0_n(sample_pages_count,
 211                                             sizeof(uint64_t));
 212     if (!info->sample_page_vfn) {
 213         g_free(info->hash_result);
 214         return false;
 215     }
 216
 217     rand  = g_rand_new();
 218     for (i = 0; i < sample_pages_count; i++) {
 219         info->sample_page_vfn[i] = g_rand_int_range(rand, 0,
 220                                                     info->ramblock_pages - 1);
 221         info->hash_result[i] = get_ramblock_vfn_hash(info,
 222                                                      info->sample_page_vfn[i]);
 223     }
 224     g_rand_free(rand);
 225
 226     return true;
 227 }
 228
 229 static void get_ramblock_dirty_info(RAMBlock *block,
 230                                     struct RamblockDirtyInfo *info,
 231                                     struct DirtyRateConfig *config)
 232 {
 233     uint64_t sample_pages_per_gigabytes = config->sample_pages_per_gigabytes;
 234
 235     /* Right shift 30 bits to calc ramblock size in GB */
 236     info->sample_pages_count = (qemu_ram_get_used_length(block) *
 237                                 sample_pages_per_gigabytes) >> 30;
 238     /* Right shift TARGET_PAGE_BITS to calc page count */
 239     info->ramblock_pages = qemu_ram_get_used_length(block) >>
 240                            TARGET_PAGE_BITS;
 241     info->ramblock_addr = qemu_ram_get_host_addr(block);
 242     strcpy(info->idstr, qemu_ram_get_idstr(block));
 243 }
 244
 245 static void free_ramblock_dirty_info(struct RamblockDirtyInfo *infos, int count)
 246 {
 247     int i;
 248
 249     if (!infos) {
 250         return;
 251     }
 252
 253     for (i = 0; i < count; i++) {
 254         g_free(infos[i].sample_page_vfn);
 255         g_free(infos[i].hash_result);
 256     }
 257     g_free(infos);
 258 }
 259
 260 static bool skip_sample_ramblock(RAMBlock *block)
 261 {
 262     /*
 263      * Sample only blocks larger than MIN_RAMBLOCK_SIZE.
 264      */
 265     if (qemu_ram_get_used_length(block) < (MIN_RAMBLOCK_SIZE << 10)) {
 266         trace_skip_sample_ramblock(block->idstr,
 267                                    qemu_ram_get_used_length(block));
 268         return true;
 269     }
 270
 271     return false;
 272 }
 273
 274 static bool record_ramblock_hash_info(struct RamblockDirtyInfo **block_dinfo,
 275                                       struct DirtyRateConfig config,
 276                                       int *block_count)
 277 {
 278     struct RamblockDirtyInfo *info = NULL;
 279     struct RamblockDirtyInfo *dinfo = NULL;
 280     RAMBlock *block = NULL;
 281     int total_count = 0;
 282     int index = 0;
 283     bool ret = false;
 284
 285     RAMBLOCK_FOREACH_MIGRATABLE(block) {
 286         if (skip_sample_ramblock(block)) {
 287             continue;
 288         }
 289         total_count++;
 290     }
 291
 292     dinfo = g_try_malloc0_n(total_count, sizeof(struct RamblockDirtyInfo));
 293     if (dinfo == NULL) {
 294         goto out;
 295     }
 296
 297     RAMBLOCK_FOREACH_MIGRATABLE(block) {
 298         if (skip_sample_ramblock(block)) {
 299             continue;
 300         }
 301         if (index >= total_count) {
 302             break;
 303         }
 304         info = &dinfo[index];
 305         get_ramblock_dirty_info(block, info, &config);
 306         if (!save_ramblock_hash(info)) {
 307             goto out;
 308         }
 309         index++;
 310     }
 311     ret = true;
 312
 313 out:
 314     *block_count = index;
 315     *block_dinfo = dinfo;
 316     return ret;
 317 }
 318
 319 static void calc_page_dirty_rate(struct RamblockDirtyInfo *info)
 320 {
 321     uint32_t crc;
 322     int i;
 323
 324     for (i = 0; i < info->sample_pages_count; i++) {
 325         crc = get_ramblock_vfn_hash(info, info->sample_page_vfn[i]);
 326         if (crc != info->hash_result[i]) {
 327             trace_calc_page_dirty_rate(info->idstr, crc, info->hash_result[i]);
 328             info->sample_dirty_count++;
 329         }
 330     }
 331 }
 332
 333 static struct RamblockDirtyInfo *
 334 find_block_matched(RAMBlock *block, int count,
 335                   struct RamblockDirtyInfo *infos)
 336 {
 337     int i;
 338     struct RamblockDirtyInfo *matched;
 339
 340     for (i = 0; i < count; i++) {
 341         if (!strcmp(infos[i].idstr, qemu_ram_get_idstr(block))) {
 342             break;
 343         }
 344     }
 345
 346     if (i == count) {
 347         return NULL;
 348     }
 349
 350     if (infos[i].ramblock_addr != qemu_ram_get_host_addr(block) ||
 351         infos[i].ramblock_pages !=
 352             (qemu_ram_get_used_length(block) >> TARGET_PAGE_BITS)) {
 353         trace_find_page_matched(block->idstr);
 354         return NULL;
 355     }
 356
 357     matched = &infos[i];
 358
 359     return matched;
 360 }
 361
 362 static bool compare_page_hash_info(struct RamblockDirtyInfo *info,
 363                                   int block_count)
 364 {
 365     struct RamblockDirtyInfo *block_dinfo = NULL;
 366     RAMBlock *block = NULL;
 367
 368     RAMBLOCK_FOREACH_MIGRATABLE(block) {
 369         if (skip_sample_ramblock(block)) {
 370             continue;
 371         }
 372         block_dinfo = find_block_matched(block, block_count, info);
 373         if (block_dinfo == NULL) {
 374             continue;
 375         }
 376         calc_page_dirty_rate(block_dinfo);
 377         update_dirtyrate_stat(block_dinfo);
 378     }
 379
 380     if (DirtyStat.page_sampling.total_sample_count == 0) {
 381         return false;
 382     }
 383
 384     return true;
 385 }
 386
 387 static inline void record_dirtypages(DirtyPageRecord *dirty_pages,
 388                                      CPUState *cpu, bool start)
 389 {
 390     if (start) {
 391         dirty_pages[cpu->cpu_index].start_pages = cpu->dirty_pages;
 392     } else {
 393         dirty_pages[cpu->cpu_index].end_pages = cpu->dirty_pages;
 394     }
 395 }
 396
 397 static void dirtyrate_global_dirty_log_start(void)
 398 {
 399     qemu_mutex_lock_iothread();
 400     memory_global_dirty_log_start(GLOBAL_DIRTY_DIRTY_RATE);
 401     qemu_mutex_unlock_iothread();
 402 }
 403
 404 static void dirtyrate_global_dirty_log_stop(void)
 405 {
 406     qemu_mutex_lock_iothread();
 407     memory_global_dirty_log_sync();
 408     memory_global_dirty_log_stop(GLOBAL_DIRTY_DIRTY_RATE);
 409     qemu_mutex_unlock_iothread();
 410 }
 411
 412 static int64_t do_calculate_dirtyrate_vcpu(DirtyPageRecord dirty_pages)
 413 {
 414     uint64_t memory_size_MB;
 415     int64_t time_s;
 416     uint64_t increased_dirty_pages =
 417         dirty_pages.end_pages - dirty_pages.start_pages;
 418
 419     memory_size_MB = (increased_dirty_pages * TARGET_PAGE_SIZE) >> 20;
 420     time_s = DirtyStat.calc_time;
 421
 422     return memory_size_MB / time_s;
 423 }
 424
 425 static void calculate_dirtyrate_dirty_ring(struct DirtyRateConfig config)
 426 {
 427     CPUState *cpu;
 428     int64_t msec = 0;
 429     int64_t start_time;
 430     uint64_t dirtyrate = 0;
 431     uint64_t dirtyrate_sum = 0;
 432     DirtyPageRecord *dirty_pages;
 433     int nvcpu = 0;
 434     int i = 0;
 435
 436     CPU_FOREACH(cpu) {
 437         nvcpu++;
 438     }
 439
 440     dirty_pages = malloc(sizeof(*dirty_pages) * nvcpu);
 441
 442     DirtyStat.dirty_ring.nvcpu = nvcpu;
 443     DirtyStat.dirty_ring.rates = malloc(sizeof(DirtyRateVcpu) * nvcpu);
 444
 445     dirtyrate_global_dirty_log_start();
 446
 447     CPU_FOREACH(cpu) {
 448         record_dirtypages(dirty_pages, cpu, true);
 449     }
 450
 451     start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
 452     DirtyStat.start_time = start_time / 1000;
 453
 454     msec = config.sample_period_seconds * 1000;
 455     msec = set_sample_page_period(msec, start_time);
 456     DirtyStat.calc_time = msec / 1000;
 457
 458     dirtyrate_global_dirty_log_stop();
 459
 460     CPU_FOREACH(cpu) {
 461         record_dirtypages(dirty_pages, cpu, false);
 462     }
 463
 464     for (i = 0; i < DirtyStat.dirty_ring.nvcpu; i++) {
 465         dirtyrate = do_calculate_dirtyrate_vcpu(dirty_pages[i]);
 466         trace_dirtyrate_do_calculate_vcpu(i, dirtyrate);
 467
 468         DirtyStat.dirty_ring.rates[i].id = i;
 469         DirtyStat.dirty_ring.rates[i].dirty_rate = dirtyrate;
 470         dirtyrate_sum += dirtyrate;
 471     }
 472
 473     DirtyStat.dirty_rate = dirtyrate_sum;
 474     free(dirty_pages);
 475 }
 476
 477 static void calculate_dirtyrate_sample_vm(struct DirtyRateConfig config)
 478 {
 479     struct RamblockDirtyInfo *block_dinfo = NULL;
 480     int block_count = 0;
 481     int64_t msec = 0;
 482     int64_t initial_time;
 483
 484     rcu_read_lock();
 485     initial_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
 486     if (!record_ramblock_hash_info(&block_dinfo, config, &block_count)) {
 487         goto out;
 488     }
 489     rcu_read_unlock();
 490
 491     msec = config.sample_period_seconds * 1000;
 492     msec = set_sample_page_period(msec, initial_time);
 493     DirtyStat.start_time = initial_time / 1000;
 494     DirtyStat.calc_time = msec / 1000;
 495
 496     rcu_read_lock();
 497     if (!compare_page_hash_info(block_dinfo, block_count)) {
 498         goto out;
 499     }
 500
 501     update_dirtyrate(msec);
 502
 503 out:
 504     rcu_read_unlock();
 505     free_ramblock_dirty_info(block_dinfo, block_count);
 506 }
 507
 508 static void calculate_dirtyrate(struct DirtyRateConfig config)
 509 {
 510     if (config.mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) {
 511         calculate_dirtyrate_dirty_ring(config);
 512     } else {
 513         calculate_dirtyrate_sample_vm(config);
 514     }
 515
 516     trace_dirtyrate_calculate(DirtyStat.dirty_rate);
 517 }
 518
 519 void *get_dirtyrate_thread(void *arg)
 520 {
 521     struct DirtyRateConfig config = *(struct DirtyRateConfig *)arg;
 522     int ret;
 523     rcu_register_thread();
 524
 525     ret = dirtyrate_set_state(&CalculatingState, DIRTY_RATE_STATUS_UNSTARTED,
 526                               DIRTY_RATE_STATUS_MEASURING);
 527     if (ret == -1) {
 528         error_report("change dirtyrate state failed.");
 529         return NULL;
 530     }
 531
 532     calculate_dirtyrate(config);
 533
 534     ret = dirtyrate_set_state(&CalculatingState, DIRTY_RATE_STATUS_MEASURING,
 535                               DIRTY_RATE_STATUS_MEASURED);
 536     if (ret == -1) {
 537         error_report("change dirtyrate state failed.");
 538     }
 539
 540     rcu_unregister_thread();
 541     return NULL;
 542 }
 543
 544 void qmp_calc_dirty_rate(int64_t calc_time,
 545                          bool has_sample_pages,
 546                          int64_t sample_pages,
 547                          bool has_mode,
 548                          DirtyRateMeasureMode mode,
 549                          Error **errp)
 550 {
 551     static struct DirtyRateConfig config;
 552     QemuThread thread;
 553     int ret;
 554     int64_t start_time;
 555
 556     /*
 557      * If the dirty rate is already being measured, don't attempt to start.
 558      */
 559     if (qatomic_read(&CalculatingState) == DIRTY_RATE_STATUS_MEASURING) {
 560         error_setg(errp, "the dirty rate is already being measured.");
 561         return;
 562     }
 563
 564     if (!is_sample_period_valid(calc_time)) {
 565         error_setg(errp, "calc-time is out of range[%d, %d].",
 566                          MIN_FETCH_DIRTYRATE_TIME_SEC,
 567                          MAX_FETCH_DIRTYRATE_TIME_SEC);
 568         return;
 569     }
 570
 571     if (!has_mode) {
 572         mode =  DIRTY_RATE_MEASURE_MODE_PAGE_SAMPLING;
 573     }
 574
 575     if (has_sample_pages && mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) {
 576         error_setg(errp, "either sample-pages or dirty-ring can be specified.");
 577         return;
 578     }
 579
 580     if (has_sample_pages) {
 581         if (!is_sample_pages_valid(sample_pages)) {
 582             error_setg(errp, "sample-pages is out of range[%d, %d].",
 583                             MIN_SAMPLE_PAGE_COUNT,
 584                             MAX_SAMPLE_PAGE_COUNT);
 585             return;
 586         }
 587     } else {
 588         sample_pages = DIRTYRATE_DEFAULT_SAMPLE_PAGES;
 589     }
 590
 591     /*
 592      * dirty ring mode only works when kvm dirty ring is enabled.
 593      */
 594     if ((mode == DIRTY_RATE_MEASURE_MODE_DIRTY_RING) &&
 595         !kvm_dirty_ring_enabled()) {
 596         error_setg(errp, "dirty ring is disabled, use sample-pages method "
 597                          "or remeasure later.");
 598         return;
 599     }
 600
 601     /*
 602      * Init calculation state as unstarted.
 603      */
 604     ret = dirtyrate_set_state(&CalculatingState, CalculatingState,
 605                               DIRTY_RATE_STATUS_UNSTARTED);
 606     if (ret == -1) {
 607         error_setg(errp, "init dirty rate calculation state failed.");
 608         return;
 609     }
 610
 611     config.sample_period_seconds = calc_time;
 612     config.sample_pages_per_gigabytes = sample_pages;
 613     config.mode = mode;
 614
 615     cleanup_dirtyrate_stat(config);
 616
 617     /*
 618      * update dirty rate mode so that we can figure out what mode has
 619      * been used in last calculation
 620      **/
 621     dirtyrate_mode = mode;
 622
 623     start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) / 1000;
 624     init_dirtyrate_stat(start_time, config);
 625
 626     qemu_thread_create(&thread, "get_dirtyrate", get_dirtyrate_thread,
 627                        (void *)&config, QEMU_THREAD_DETACHED);
 628 }
 629
 630 struct DirtyRateInfo *qmp_query_dirty_rate(Error **errp)
 631 {
 632     return query_dirty_rate_info();
 633 }
 634
 635 void hmp_info_dirty_rate(Monitor *mon, const QDict *qdict)
 636 {
 637     DirtyRateInfo *info = query_dirty_rate_info();
 638
 639     monitor_printf(mon, "Status: %s\n",
 640                    DirtyRateStatus_str(info->status));
 641     monitor_printf(mon, "Start Time: %"PRIi64" (ms)\n",
 642                    info->start_time);
 643     monitor_printf(mon, "Sample Pages: %"PRIu64" (per GB)\n",
 644                    info->sample_pages);
 645     monitor_printf(mon, "Period: %"PRIi64" (sec)\n",
 646                    info->calc_time);
 647     monitor_printf(mon, "Mode: %s\n",
 648                    DirtyRateMeasureMode_str(info->mode));
 649     monitor_printf(mon, "Dirty rate: ");
 650     if (info->has_dirty_rate) {
 651         monitor_printf(mon, "%"PRIi64" (MB/s)\n", info->dirty_rate);
 652         if (info->has_vcpu_dirty_rate) {
 653             DirtyRateVcpuList *rate, *head = info->vcpu_dirty_rate;
 654             for (rate = head; rate != NULL; rate = rate->next) {
 655                 monitor_printf(mon, "vcpu[%"PRIi64"], Dirty rate: %"PRIi64
 656                                " (MB/s)\n", rate->value->id,
 657                                rate->value->dirty_rate);
 658             }
 659         }
 660     } else {
 661         monitor_printf(mon, "(not ready)\n");
 662     }
 663
 664     qapi_free_DirtyRateVcpuList(info->vcpu_dirty_rate);
 665     g_free(info);
 666 }
 667
 668 void hmp_calc_dirty_rate(Monitor *mon, const QDict *qdict)
 669 {
 670     int64_t sec = qdict_get_try_int(qdict, "second", 0);
 671     int64_t sample_pages = qdict_get_try_int(qdict, "sample_pages_per_GB", -1);
 672     bool has_sample_pages = (sample_pages != -1);
 673     bool dirty_ring = qdict_get_try_bool(qdict, "dirty_ring", false);
 674     DirtyRateMeasureMode mode =
 675         (dirty_ring ? DIRTY_RATE_MEASURE_MODE_DIRTY_RING :
 676          DIRTY_RATE_MEASURE_MODE_PAGE_SAMPLING);
 677     Error *err = NULL;
 678
 679     if (!sec) {
 680         monitor_printf(mon, "Incorrect period length specified!\n");
 681         return;
 682     }
 683
 684     qmp_calc_dirty_rate(sec, has_sample_pages, sample_pages, true,
 685                         mode, &err);
 686     if (err) {
 687         hmp_handle_error(mon, err);
 688         return;
 689     }
 690
 691     monitor_printf(mon, "Starting dirty rate measurement with period %"PRIi64
 692                    " seconds\n", sec);
 693     monitor_printf(mon, "[Please use 'info dirty_rate' to check results]\n");
 694 }