migration/dirtyrate.c - third_party/qemu - Git at Google

 /*
  * Dirtyrate implement code
  *
  * Copyright (c) 2020 HUAWEI TECHNOLOGIES CO.,LTD.
  *
  * Authors:
  *  Chuan Zheng <zhengchuan@huawei.com>
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
  */

 #include "qemu/osdep.h"
 #include <zlib.h>
 #include "qapi/error.h"
 #include "cpu.h"
 #include "exec/ramblock.h"
 #include "qemu/rcu_queue.h"
 #include "qapi/qapi-commands-migration.h"
 #include "ram.h"
 #include "trace.h"
 #include "dirtyrate.h"
 #include "monitor/hmp.h"
 #include "monitor/monitor.h"
 #include "qapi/qmp/qdict.h"

 static int CalculatingState = DIRTY_RATE_STATUS_UNSTARTED;
 static struct DirtyRateStat DirtyStat;

 static int64_t set_sample_page_period(int64_t msec, int64_t initial_time)
 {
     int64_t current_time;

     current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     if ((current_time - initial_time) >= msec) {
         msec = current_time - initial_time;
     } else {
         g_usleep((msec + initial_time - current_time) * 1000);
     }

     return msec;
 }

 static bool is_sample_period_valid(int64_t sec)
 {
     if (sec < MIN_FETCH_DIRTYRATE_TIME_SEC ||
         sec > MAX_FETCH_DIRTYRATE_TIME_SEC) {
         return false;
     }

     return true;
 }

 static bool is_sample_pages_valid(int64_t pages)
 {
     return pages >= MIN_SAMPLE_PAGE_COUNT &&
            pages <= MAX_SAMPLE_PAGE_COUNT;
 }

 static int dirtyrate_set_state(int *state, int old_state, int new_state)
 {
     assert(new_state < DIRTY_RATE_STATUS__MAX);
     trace_dirtyrate_set_state(DirtyRateStatus_str(new_state));
     if (qatomic_cmpxchg(state, old_state, new_state) == old_state) {
         return 0;
     } else {
         return -1;
     }
 }

 static struct DirtyRateInfo *query_dirty_rate_info(void)
 {
     int64_t dirty_rate = DirtyStat.dirty_rate;
     struct DirtyRateInfo *info = g_malloc0(sizeof(DirtyRateInfo));

     if (qatomic_read(&CalculatingState) == DIRTY_RATE_STATUS_MEASURED) {
         info->has_dirty_rate = true;
         info->dirty_rate = dirty_rate;
     }

     info->status = CalculatingState;
     info->start_time = DirtyStat.start_time;
     info->calc_time = DirtyStat.calc_time;
     info->sample_pages = DirtyStat.sample_pages;

     trace_query_dirty_rate_info(DirtyRateStatus_str(CalculatingState));

     return info;
 }

 static void init_dirtyrate_stat(int64_t start_time, int64_t calc_time,
                                 uint64_t sample_pages)
 {
     DirtyStat.total_dirty_samples = 0;
     DirtyStat.total_sample_count = 0;
     DirtyStat.total_block_mem_MB = 0;
     DirtyStat.dirty_rate = -1;
     DirtyStat.start_time = start_time;
     DirtyStat.calc_time = calc_time;
     DirtyStat.sample_pages = sample_pages;
 }

 static void update_dirtyrate_stat(struct RamblockDirtyInfo *info)
 {
     DirtyStat.total_dirty_samples += info->sample_dirty_count;
     DirtyStat.total_sample_count += info->sample_pages_count;
     /* size of total pages in MB */
     DirtyStat.total_block_mem_MB += (info->ramblock_pages *
                                      TARGET_PAGE_SIZE) >> 20;
 }

 static void update_dirtyrate(uint64_t msec)
 {
     uint64_t dirtyrate;
     uint64_t total_dirty_samples = DirtyStat.total_dirty_samples;
     uint64_t total_sample_count = DirtyStat.total_sample_count;
     uint64_t total_block_mem_MB = DirtyStat.total_block_mem_MB;

     dirtyrate = total_dirty_samples * total_block_mem_MB *
                 1000 / (total_sample_count * msec);

     DirtyStat.dirty_rate = dirtyrate;
 }

 /*
  * get hash result for the sampled memory with length of TARGET_PAGE_SIZE
  * in ramblock, which starts from ramblock base address.
  */
 static uint32_t get_ramblock_vfn_hash(struct RamblockDirtyInfo *info,
                                       uint64_t vfn)
 {
     uint32_t crc;

     crc = crc32(0, (info->ramblock_addr +
                 vfn * TARGET_PAGE_SIZE), TARGET_PAGE_SIZE);

     trace_get_ramblock_vfn_hash(info->idstr, vfn, crc);
     return crc;
 }

 static bool save_ramblock_hash(struct RamblockDirtyInfo *info)
 {
     unsigned int sample_pages_count;
     int i;
     GRand *rand;

     sample_pages_count = info->sample_pages_count;

     /* ramblock size less than one page, return success to skip this ramblock */
     if (unlikely(info->ramblock_pages == 0 || sample_pages_count == 0)) {
         return true;
     }

     info->hash_result = g_try_malloc0_n(sample_pages_count,
                                         sizeof(uint32_t));
     if (!info->hash_result) {
         return false;
     }

     info->sample_page_vfn = g_try_malloc0_n(sample_pages_count,
                                             sizeof(uint64_t));
     if (!info->sample_page_vfn) {
         g_free(info->hash_result);
         return false;
     }

     rand  = g_rand_new();
     for (i = 0; i < sample_pages_count; i++) {
         info->sample_page_vfn[i] = g_rand_int_range(rand, 0,
                                                     info->ramblock_pages - 1);
         info->hash_result[i] = get_ramblock_vfn_hash(info,
                                                      info->sample_page_vfn[i]);
     }
     g_rand_free(rand);

     return true;
 }

 static void get_ramblock_dirty_info(RAMBlock *block,
                                     struct RamblockDirtyInfo *info,
                                     struct DirtyRateConfig *config)
 {
     uint64_t sample_pages_per_gigabytes = config->sample_pages_per_gigabytes;

     /* Right shift 30 bits to calc ramblock size in GB */
     info->sample_pages_count = (qemu_ram_get_used_length(block) *
                                 sample_pages_per_gigabytes) >> 30;
     /* Right shift TARGET_PAGE_BITS to calc page count */
     info->ramblock_pages = qemu_ram_get_used_length(block) >>
                            TARGET_PAGE_BITS;
     info->ramblock_addr = qemu_ram_get_host_addr(block);
     strcpy(info->idstr, qemu_ram_get_idstr(block));
 }

 static void free_ramblock_dirty_info(struct RamblockDirtyInfo *infos, int count)
 {
     int i;

     if (!infos) {
         return;
     }

     for (i = 0; i < count; i++) {
         g_free(infos[i].sample_page_vfn);
         g_free(infos[i].hash_result);
     }
     g_free(infos);
 }

 static bool skip_sample_ramblock(RAMBlock *block)
 {
     /*
      * Sample only blocks larger than MIN_RAMBLOCK_SIZE.
      */
     if (qemu_ram_get_used_length(block) < (MIN_RAMBLOCK_SIZE << 10)) {
         trace_skip_sample_ramblock(block->idstr,
                                    qemu_ram_get_used_length(block));
         return true;
     }

     return false;
 }

 static bool record_ramblock_hash_info(struct RamblockDirtyInfo **block_dinfo,
                                       struct DirtyRateConfig config,
                                       int *block_count)
 {
     struct RamblockDirtyInfo *info = NULL;
     struct RamblockDirtyInfo *dinfo = NULL;
     RAMBlock *block = NULL;
     int total_count = 0;
     int index = 0;
     bool ret = false;

     RAMBLOCK_FOREACH_MIGRATABLE(block) {
         if (skip_sample_ramblock(block)) {
             continue;
         }
         total_count++;
     }

     dinfo = g_try_malloc0_n(total_count, sizeof(struct RamblockDirtyInfo));
     if (dinfo == NULL) {
         goto out;
     }

     RAMBLOCK_FOREACH_MIGRATABLE(block) {
         if (skip_sample_ramblock(block)) {
             continue;
         }
         if (index >= total_count) {
             break;
         }
         info = &dinfo[index];
         get_ramblock_dirty_info(block, info, &config);
         if (!save_ramblock_hash(info)) {
             goto out;
         }
         index++;
     }
     ret = true;

 out:
     *block_count = index;
     *block_dinfo = dinfo;
     return ret;
 }

 static void calc_page_dirty_rate(struct RamblockDirtyInfo *info)
 {
     uint32_t crc;
     int i;

     for (i = 0; i < info->sample_pages_count; i++) {
         crc = get_ramblock_vfn_hash(info, info->sample_page_vfn[i]);
         if (crc != info->hash_result[i]) {
             trace_calc_page_dirty_rate(info->idstr, crc, info->hash_result[i]);
             info->sample_dirty_count++;
         }
     }
 }

 static struct RamblockDirtyInfo *
 find_block_matched(RAMBlock *block, int count,
                   struct RamblockDirtyInfo *infos)
 {
     int i;
     struct RamblockDirtyInfo *matched;

     for (i = 0; i < count; i++) {
         if (!strcmp(infos[i].idstr, qemu_ram_get_idstr(block))) {
             break;
         }
     }

     if (i == count) {
         return NULL;
     }

     if (infos[i].ramblock_addr != qemu_ram_get_host_addr(block) ||
         infos[i].ramblock_pages !=
             (qemu_ram_get_used_length(block) >> TARGET_PAGE_BITS)) {
         trace_find_page_matched(block->idstr);
         return NULL;
     }

     matched = &infos[i];

     return matched;
 }

 static bool compare_page_hash_info(struct RamblockDirtyInfo *info,
                                   int block_count)
 {
     struct RamblockDirtyInfo *block_dinfo = NULL;
     RAMBlock *block = NULL;

     RAMBLOCK_FOREACH_MIGRATABLE(block) {
         if (skip_sample_ramblock(block)) {
             continue;
         }
         block_dinfo = find_block_matched(block, block_count, info);
         if (block_dinfo == NULL) {
             continue;
         }
         calc_page_dirty_rate(block_dinfo);
         update_dirtyrate_stat(block_dinfo);
     }

     if (DirtyStat.total_sample_count == 0) {
         return false;
     }

     return true;
 }

 static void calculate_dirtyrate(struct DirtyRateConfig config)
 {
     struct RamblockDirtyInfo *block_dinfo = NULL;
     int block_count = 0;
     int64_t msec = 0;
     int64_t initial_time;

     rcu_register_thread();
     rcu_read_lock();
     initial_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
     if (!record_ramblock_hash_info(&block_dinfo, config, &block_count)) {
         goto out;
     }
     rcu_read_unlock();

     msec = config.sample_period_seconds * 1000;
     msec = set_sample_page_period(msec, initial_time);
     DirtyStat.start_time = initial_time / 1000;
     DirtyStat.calc_time = msec / 1000;

     rcu_read_lock();
     if (!compare_page_hash_info(block_dinfo, block_count)) {
         goto out;
     }

     update_dirtyrate(msec);

 out:
     rcu_read_unlock();
     free_ramblock_dirty_info(block_dinfo, block_count);
     rcu_unregister_thread();
 }

 void *get_dirtyrate_thread(void *arg)
 {
     struct DirtyRateConfig config = *(struct DirtyRateConfig *)arg;
     int ret;
     int64_t start_time;
     int64_t calc_time;
     uint64_t sample_pages;

     ret = dirtyrate_set_state(&CalculatingState, DIRTY_RATE_STATUS_UNSTARTED,
                               DIRTY_RATE_STATUS_MEASURING);
     if (ret == -1) {
         error_report("change dirtyrate state failed.");
         return NULL;
     }

     start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) / 1000;
     calc_time = config.sample_period_seconds;
     sample_pages = config.sample_pages_per_gigabytes;
     init_dirtyrate_stat(start_time, calc_time, sample_pages);

     calculate_dirtyrate(config);

     ret = dirtyrate_set_state(&CalculatingState, DIRTY_RATE_STATUS_MEASURING,
                               DIRTY_RATE_STATUS_MEASURED);
     if (ret == -1) {
         error_report("change dirtyrate state failed.");
     }
     return NULL;
 }

 void qmp_calc_dirty_rate(int64_t calc_time, bool has_sample_pages,
                          int64_t sample_pages, Error **errp)
 {
     static struct DirtyRateConfig config;
     QemuThread thread;
     int ret;

     /*
      * If the dirty rate is already being measured, don't attempt to start.
      */
     if (qatomic_read(&CalculatingState) == DIRTY_RATE_STATUS_MEASURING) {
         error_setg(errp, "the dirty rate is already being measured.");
         return;
     }

     if (!is_sample_period_valid(calc_time)) {
         error_setg(errp, "calc-time is out of range[%d, %d].",
                          MIN_FETCH_DIRTYRATE_TIME_SEC,
                          MAX_FETCH_DIRTYRATE_TIME_SEC);
         return;
     }

     if (has_sample_pages) {
         if (!is_sample_pages_valid(sample_pages)) {
             error_setg(errp, "sample-pages is out of range[%d, %d].",
                             MIN_SAMPLE_PAGE_COUNT,
                             MAX_SAMPLE_PAGE_COUNT);
             return;
         }
     } else {
         sample_pages = DIRTYRATE_DEFAULT_SAMPLE_PAGES;
     }

     /*
      * Init calculation state as unstarted.
      */
     ret = dirtyrate_set_state(&CalculatingState, CalculatingState,
                               DIRTY_RATE_STATUS_UNSTARTED);
     if (ret == -1) {
         error_setg(errp, "init dirty rate calculation state failed.");
         return;
     }

     config.sample_period_seconds = calc_time;
     config.sample_pages_per_gigabytes = sample_pages;
     qemu_thread_create(&thread, "get_dirtyrate", get_dirtyrate_thread,
                        (void *)&config, QEMU_THREAD_DETACHED);
 }

 struct DirtyRateInfo *qmp_query_dirty_rate(Error **errp)
 {
     return query_dirty_rate_info();
 }

 void hmp_info_dirty_rate(Monitor *mon, const QDict *qdict)
 {
     DirtyRateInfo *info = query_dirty_rate_info();

     monitor_printf(mon, "Status: %s\n",
                    DirtyRateStatus_str(info->status));
     monitor_printf(mon, "Start Time: %"PRIi64" (ms)\n",
                    info->start_time);
     monitor_printf(mon, "Sample Pages: %"PRIu64" (per GB)\n",
                    info->sample_pages);
     monitor_printf(mon, "Period: %"PRIi64" (sec)\n",
                    info->calc_time);
     monitor_printf(mon, "Dirty rate: ");
     if (info->has_dirty_rate) {
         monitor_printf(mon, "%"PRIi64" (MB/s)\n", info->dirty_rate);
     } else {
         monitor_printf(mon, "(not ready)\n");
     }
     g_free(info);
 }

 void hmp_calc_dirty_rate(Monitor *mon, const QDict *qdict)
 {
     int64_t sec = qdict_get_try_int(qdict, "second", 0);
     int64_t sample_pages = qdict_get_try_int(qdict, "sample_pages_per_GB", -1);
     bool has_sample_pages = (sample_pages != -1);
     Error *err = NULL;

     if (!sec) {
         monitor_printf(mon, "Incorrect period length specified!\n");
         return;
     }

     qmp_calc_dirty_rate(sec, has_sample_pages, sample_pages, &err);
     if (err) {
         hmp_handle_error(mon, err);
         return;
     }

     monitor_printf(mon, "Starting dirty rate measurement with period %"PRIi64
                    " seconds\n", sec);
     monitor_printf(mon, "[Please use 'info dirty_rate' to check results]\n");
 }
	/*
	* Dirtyrate implement code
	*
	* Copyright (c) 2020 HUAWEI TECHNOLOGIES CO.,LTD.
	*
	* Authors:
	* Chuan Zheng <zhengchuan@huawei.com>
	*
	* This work is licensed under the terms of the GNU GPL, version 2 or later.
	* See the COPYING file in the top-level directory.
	*/

	#include "qemu/osdep.h"
	#include <zlib.h>
	#include "qapi/error.h"
	#include "cpu.h"
	#include "exec/ramblock.h"
	#include "qemu/rcu_queue.h"
	#include "qapi/qapi-commands-migration.h"
	#include "ram.h"
	#include "trace.h"
	#include "dirtyrate.h"
	#include "monitor/hmp.h"
	#include "monitor/monitor.h"
	#include "qapi/qmp/qdict.h"

	static int CalculatingState = DIRTY_RATE_STATUS_UNSTARTED;
	static struct DirtyRateStat DirtyStat;

	static int64_t set_sample_page_period(int64_t msec, int64_t initial_time)
	{
	int64_t current_time;

	current_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
	if ((current_time - initial_time) >= msec) {
	msec = current_time - initial_time;
	} else {
	g_usleep((msec + initial_time - current_time) * 1000);
	}

	return msec;
	}

	static bool is_sample_period_valid(int64_t sec)
	{
	if (sec < MIN_FETCH_DIRTYRATE_TIME_SEC \|\|
	sec > MAX_FETCH_DIRTYRATE_TIME_SEC) {
	return false;
	}

	return true;
	}

	static bool is_sample_pages_valid(int64_t pages)
	{
	return pages >= MIN_SAMPLE_PAGE_COUNT &&
	pages <= MAX_SAMPLE_PAGE_COUNT;
	}

	static int dirtyrate_set_state(int *state, int old_state, int new_state)
	{
	assert(new_state < DIRTY_RATE_STATUS__MAX);
	trace_dirtyrate_set_state(DirtyRateStatus_str(new_state));
	if (qatomic_cmpxchg(state, old_state, new_state) == old_state) {
	return 0;
	} else {
	return -1;
	}
	}

	static struct DirtyRateInfo *query_dirty_rate_info(void)
	{
	int64_t dirty_rate = DirtyStat.dirty_rate;
	struct DirtyRateInfo *info = g_malloc0(sizeof(DirtyRateInfo));

	if (qatomic_read(&CalculatingState) == DIRTY_RATE_STATUS_MEASURED) {
	info->has_dirty_rate = true;
	info->dirty_rate = dirty_rate;
	}

	info->status = CalculatingState;
	info->start_time = DirtyStat.start_time;
	info->calc_time = DirtyStat.calc_time;
	info->sample_pages = DirtyStat.sample_pages;

	trace_query_dirty_rate_info(DirtyRateStatus_str(CalculatingState));

	return info;
	}

	static void init_dirtyrate_stat(int64_t start_time, int64_t calc_time,
	uint64_t sample_pages)
	{
	DirtyStat.total_dirty_samples = 0;
	DirtyStat.total_sample_count = 0;
	DirtyStat.total_block_mem_MB = 0;
	DirtyStat.dirty_rate = -1;
	DirtyStat.start_time = start_time;
	DirtyStat.calc_time = calc_time;
	DirtyStat.sample_pages = sample_pages;
	}

	static void update_dirtyrate_stat(struct RamblockDirtyInfo *info)
	{
	DirtyStat.total_dirty_samples += info->sample_dirty_count;
	DirtyStat.total_sample_count += info->sample_pages_count;
	/* size of total pages in MB */
	DirtyStat.total_block_mem_MB += (info->ramblock_pages *
	TARGET_PAGE_SIZE) >> 20;
	}

	static void update_dirtyrate(uint64_t msec)
	{
	uint64_t dirtyrate;
	uint64_t total_dirty_samples = DirtyStat.total_dirty_samples;
	uint64_t total_sample_count = DirtyStat.total_sample_count;
	uint64_t total_block_mem_MB = DirtyStat.total_block_mem_MB;

	dirtyrate = total_dirty_samples * total_block_mem_MB *
	1000 / (total_sample_count * msec);

	DirtyStat.dirty_rate = dirtyrate;
	}

	/*
	* get hash result for the sampled memory with length of TARGET_PAGE_SIZE
	* in ramblock, which starts from ramblock base address.
	*/
	static uint32_t get_ramblock_vfn_hash(struct RamblockDirtyInfo *info,
	uint64_t vfn)
	{
	uint32_t crc;

	crc = crc32(0, (info->ramblock_addr +
	vfn * TARGET_PAGE_SIZE), TARGET_PAGE_SIZE);

	trace_get_ramblock_vfn_hash(info->idstr, vfn, crc);
	return crc;
	}

	static bool save_ramblock_hash(struct RamblockDirtyInfo *info)
	{
	unsigned int sample_pages_count;
	int i;
	GRand *rand;

	sample_pages_count = info->sample_pages_count;

	/* ramblock size less than one page, return success to skip this ramblock */
	if (unlikely(info->ramblock_pages == 0 \|\| sample_pages_count == 0)) {
	return true;
	}

	info->hash_result = g_try_malloc0_n(sample_pages_count,
	sizeof(uint32_t));
	if (!info->hash_result) {
	return false;
	}

	info->sample_page_vfn = g_try_malloc0_n(sample_pages_count,
	sizeof(uint64_t));
	if (!info->sample_page_vfn) {
	g_free(info->hash_result);
	return false;
	}

	rand = g_rand_new();
	for (i = 0; i < sample_pages_count; i++) {
	info->sample_page_vfn[i] = g_rand_int_range(rand, 0,
	info->ramblock_pages - 1);
	info->hash_result[i] = get_ramblock_vfn_hash(info,
	info->sample_page_vfn[i]);
	}
	g_rand_free(rand);

	return true;
	}

	static void get_ramblock_dirty_info(RAMBlock *block,
	struct RamblockDirtyInfo *info,
	struct DirtyRateConfig *config)
	{
	uint64_t sample_pages_per_gigabytes = config->sample_pages_per_gigabytes;

	/* Right shift 30 bits to calc ramblock size in GB */
	info->sample_pages_count = (qemu_ram_get_used_length(block) *
	sample_pages_per_gigabytes) >> 30;
	/* Right shift TARGET_PAGE_BITS to calc page count */
	info->ramblock_pages = qemu_ram_get_used_length(block) >>
	TARGET_PAGE_BITS;
	info->ramblock_addr = qemu_ram_get_host_addr(block);
	strcpy(info->idstr, qemu_ram_get_idstr(block));
	}

	static void free_ramblock_dirty_info(struct RamblockDirtyInfo *infos, int count)
	{
	int i;

	if (!infos) {
	return;
	}

	for (i = 0; i < count; i++) {
	g_free(infos[i].sample_page_vfn);
	g_free(infos[i].hash_result);
	}
	g_free(infos);
	}

	static bool skip_sample_ramblock(RAMBlock *block)
	{
	/*
	* Sample only blocks larger than MIN_RAMBLOCK_SIZE.
	*/
	if (qemu_ram_get_used_length(block) < (MIN_RAMBLOCK_SIZE << 10)) {
	trace_skip_sample_ramblock(block->idstr,
	qemu_ram_get_used_length(block));
	return true;
	}

	return false;
	}

	static bool record_ramblock_hash_info(struct RamblockDirtyInfo **block_dinfo,
	struct DirtyRateConfig config,
	int *block_count)
	{
	struct RamblockDirtyInfo *info = NULL;
	struct RamblockDirtyInfo *dinfo = NULL;
	RAMBlock *block = NULL;
	int total_count = 0;
	int index = 0;
	bool ret = false;

	RAMBLOCK_FOREACH_MIGRATABLE(block) {
	if (skip_sample_ramblock(block)) {
	continue;
	}
	total_count++;
	}

	dinfo = g_try_malloc0_n(total_count, sizeof(struct RamblockDirtyInfo));
	if (dinfo == NULL) {
	goto out;
	}

	RAMBLOCK_FOREACH_MIGRATABLE(block) {
	if (skip_sample_ramblock(block)) {
	continue;
	}
	if (index >= total_count) {
	break;
	}
	info = &dinfo[index];
	get_ramblock_dirty_info(block, info, &config);
	if (!save_ramblock_hash(info)) {
	goto out;
	}
	index++;
	}
	ret = true;

	out:
	*block_count = index;
	*block_dinfo = dinfo;
	return ret;
	}

	static void calc_page_dirty_rate(struct RamblockDirtyInfo *info)
	{
	uint32_t crc;
	int i;

	for (i = 0; i < info->sample_pages_count; i++) {
	crc = get_ramblock_vfn_hash(info, info->sample_page_vfn[i]);
	if (crc != info->hash_result[i]) {
	trace_calc_page_dirty_rate(info->idstr, crc, info->hash_result[i]);
	info->sample_dirty_count++;
	}
	}
	}

	static struct RamblockDirtyInfo *
	find_block_matched(RAMBlock *block, int count,
	struct RamblockDirtyInfo *infos)
	{
	int i;
	struct RamblockDirtyInfo *matched;

	for (i = 0; i < count; i++) {
	if (!strcmp(infos[i].idstr, qemu_ram_get_idstr(block))) {
	break;
	}
	}

	if (i == count) {
	return NULL;
	}

	if (infos[i].ramblock_addr != qemu_ram_get_host_addr(block) \|\|
	infos[i].ramblock_pages !=
	(qemu_ram_get_used_length(block) >> TARGET_PAGE_BITS)) {
	trace_find_page_matched(block->idstr);
	return NULL;
	}

	matched = &infos[i];

	return matched;
	}

	static bool compare_page_hash_info(struct RamblockDirtyInfo *info,
	int block_count)
	{
	struct RamblockDirtyInfo *block_dinfo = NULL;
	RAMBlock *block = NULL;

	RAMBLOCK_FOREACH_MIGRATABLE(block) {
	if (skip_sample_ramblock(block)) {
	continue;
	}
	block_dinfo = find_block_matched(block, block_count, info);
	if (block_dinfo == NULL) {
	continue;
	}
	calc_page_dirty_rate(block_dinfo);
	update_dirtyrate_stat(block_dinfo);
	}

	if (DirtyStat.total_sample_count == 0) {
	return false;
	}

	return true;
	}

	static void calculate_dirtyrate(struct DirtyRateConfig config)
	{
	struct RamblockDirtyInfo *block_dinfo = NULL;
	int block_count = 0;
	int64_t msec = 0;
	int64_t initial_time;

	rcu_register_thread();
	rcu_read_lock();
	initial_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
	if (!record_ramblock_hash_info(&block_dinfo, config, &block_count)) {
	goto out;
	}
	rcu_read_unlock();

	msec = config.sample_period_seconds * 1000;
	msec = set_sample_page_period(msec, initial_time);
	DirtyStat.start_time = initial_time / 1000;
	DirtyStat.calc_time = msec / 1000;

	rcu_read_lock();
	if (!compare_page_hash_info(block_dinfo, block_count)) {
	goto out;
	}

	update_dirtyrate(msec);

	out:
	rcu_read_unlock();
	free_ramblock_dirty_info(block_dinfo, block_count);
	rcu_unregister_thread();
	}

	void get_dirtyrate_thread(void arg)
	{
	struct DirtyRateConfig config = (struct DirtyRateConfig )arg;
	int ret;
	int64_t start_time;
	int64_t calc_time;
	uint64_t sample_pages;

	ret = dirtyrate_set_state(&CalculatingState, DIRTY_RATE_STATUS_UNSTARTED,
	DIRTY_RATE_STATUS_MEASURING);
	if (ret == -1) {
	error_report("change dirtyrate state failed.");
	return NULL;
	}

	start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) / 1000;
	calc_time = config.sample_period_seconds;
	sample_pages = config.sample_pages_per_gigabytes;
	init_dirtyrate_stat(start_time, calc_time, sample_pages);

	calculate_dirtyrate(config);

	ret = dirtyrate_set_state(&CalculatingState, DIRTY_RATE_STATUS_MEASURING,
	DIRTY_RATE_STATUS_MEASURED);
	if (ret == -1) {
	error_report("change dirtyrate state failed.");
	}
	return NULL;
	}

	void qmp_calc_dirty_rate(int64_t calc_time, bool has_sample_pages,
	int64_t sample_pages, Error **errp)
	{
	static struct DirtyRateConfig config;
	QemuThread thread;
	int ret;

	/*
	* If the dirty rate is already being measured, don't attempt to start.
	*/
	if (qatomic_read(&CalculatingState) == DIRTY_RATE_STATUS_MEASURING) {
	error_setg(errp, "the dirty rate is already being measured.");
	return;
	}

	if (!is_sample_period_valid(calc_time)) {
	error_setg(errp, "calc-time is out of range[%d, %d].",
	MIN_FETCH_DIRTYRATE_TIME_SEC,
	MAX_FETCH_DIRTYRATE_TIME_SEC);
	return;
	}

	if (has_sample_pages) {
	if (!is_sample_pages_valid(sample_pages)) {
	error_setg(errp, "sample-pages is out of range[%d, %d].",
	MIN_SAMPLE_PAGE_COUNT,
	MAX_SAMPLE_PAGE_COUNT);
	return;
	}
	} else {
	sample_pages = DIRTYRATE_DEFAULT_SAMPLE_PAGES;
	}

	/*
	* Init calculation state as unstarted.
	*/
	ret = dirtyrate_set_state(&CalculatingState, CalculatingState,
	DIRTY_RATE_STATUS_UNSTARTED);
	if (ret == -1) {
	error_setg(errp, "init dirty rate calculation state failed.");
	return;
	}

	config.sample_period_seconds = calc_time;
	config.sample_pages_per_gigabytes = sample_pages;
	qemu_thread_create(&thread, "get_dirtyrate", get_dirtyrate_thread,
	(void *)&config, QEMU_THREAD_DETACHED);
	}

	struct DirtyRateInfo qmp_query_dirty_rate(Error *errp)
	{
	return query_dirty_rate_info();
	}

	void hmp_info_dirty_rate(Monitor mon, const QDict qdict)
	{
	DirtyRateInfo *info = query_dirty_rate_info();

	monitor_printf(mon, "Status: %s\n",
	DirtyRateStatus_str(info->status));
	monitor_printf(mon, "Start Time: %"PRIi64" (ms)\n",
	info->start_time);
	monitor_printf(mon, "Sample Pages: %"PRIu64" (per GB)\n",
	info->sample_pages);
	monitor_printf(mon, "Period: %"PRIi64" (sec)\n",
	info->calc_time);
	monitor_printf(mon, "Dirty rate: ");
	if (info->has_dirty_rate) {
	monitor_printf(mon, "%"PRIi64" (MB/s)\n", info->dirty_rate);
	} else {
	monitor_printf(mon, "(not ready)\n");
	}
	g_free(info);
	}

	void hmp_calc_dirty_rate(Monitor mon, const QDict qdict)
	{
	int64_t sec = qdict_get_try_int(qdict, "second", 0);
	int64_t sample_pages = qdict_get_try_int(qdict, "sample_pages_per_GB", -1);
	bool has_sample_pages = (sample_pages != -1);
	Error *err = NULL;

	if (!sec) {
	monitor_printf(mon, "Incorrect period length specified!\n");
	return;
	}

	qmp_calc_dirty_rate(sec, has_sample_pages, sample_pages, &err);
	if (err) {
	hmp_handle_error(mon, err);
	return;
	}

	monitor_printf(mon, "Starting dirty rate measurement with period %"PRIi64
	" seconds\n", sec);
	monitor_printf(mon, "[Please use 'info dirty_rate' to check results]\n");
	}