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FRET-qemu/migration/ram.c
Liang Li 9f5f380b54 migration: reduce the count of strlen call 
'strlen' is called three times in 'save_page_header', it's
inefficient.

Signed-off-by: Liang Li <liang.z.li@intel.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
2015-07-15 12:21:28 +02:00

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/*
* QEMU System Emulator
*
* Copyright (c) 2003-2008 Fabrice Bellard
* Copyright (c) 2011-2015 Red Hat Inc
*
* Authors:
* Juan Quintela <quintela@redhat.com>
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include <stdint.h>
#include <zlib.h>
#include "qemu/bitops.h"
#include "qemu/bitmap.h"
#include "qemu/timer.h"
#include "qemu/main-loop.h"
#include "migration/migration.h"
#include "exec/address-spaces.h"
#include "migration/page_cache.h"
#include "qemu/error-report.h"
#include "trace.h"
#include "exec/ram_addr.h"
#include "qemu/rcu_queue.h"
#ifdef DEBUG_MIGRATION_RAM
#define DPRINTF(fmt, ...) \
do { fprintf(stdout, "migration_ram: " fmt, ## __VA_ARGS__); } while (0)
#else
#define DPRINTF(fmt, ...) \
do { } while (0)
#endif
static bool mig_throttle_on;
static int dirty_rate_high_cnt;
static void check_guest_throttling(void);
static uint64_t bitmap_sync_count;
/***********************************************************/
/* ram save/restore */
#define RAM_SAVE_FLAG_FULL 0x01 /* Obsolete, not used anymore */
#define RAM_SAVE_FLAG_COMPRESS 0x02
#define RAM_SAVE_FLAG_MEM_SIZE 0x04
#define RAM_SAVE_FLAG_PAGE 0x08
#define RAM_SAVE_FLAG_EOS 0x10
#define RAM_SAVE_FLAG_CONTINUE 0x20
#define RAM_SAVE_FLAG_XBZRLE 0x40
/* 0x80 is reserved in migration.h start with 0x100 next */
#define RAM_SAVE_FLAG_COMPRESS_PAGE 0x100
static const uint8_t ZERO_TARGET_PAGE[TARGET_PAGE_SIZE];
static inline bool is_zero_range(uint8_t *p, uint64_t size)
{
return buffer_find_nonzero_offset(p, size) == size;
}
/* struct contains XBZRLE cache and a static page
used by the compression */
static struct {
/* buffer used for XBZRLE encoding */
uint8_t *encoded_buf;
/* buffer for storing page content */
uint8_t *current_buf;
/* Cache for XBZRLE, Protected by lock. */
PageCache *cache;
QemuMutex lock;
} XBZRLE;
/* buffer used for XBZRLE decoding */
static uint8_t *xbzrle_decoded_buf;
static void XBZRLE_cache_lock(void)
{
if (migrate_use_xbzrle())
qemu_mutex_lock(&XBZRLE.lock);
}
static void XBZRLE_cache_unlock(void)
{
if (migrate_use_xbzrle())
qemu_mutex_unlock(&XBZRLE.lock);
}
/*
* called from qmp_migrate_set_cache_size in main thread, possibly while
* a migration is in progress.
* A running migration maybe using the cache and might finish during this
* call, hence changes to the cache are protected by XBZRLE.lock().
*/
int64_t xbzrle_cache_resize(int64_t new_size)
{
PageCache *new_cache;
int64_t ret;
if (new_size < TARGET_PAGE_SIZE) {
return -1;
}
XBZRLE_cache_lock();
if (XBZRLE.cache != NULL) {
if (pow2floor(new_size) == migrate_xbzrle_cache_size()) {
goto out_new_size;
}
new_cache = cache_init(new_size / TARGET_PAGE_SIZE,
TARGET_PAGE_SIZE);
if (!new_cache) {
error_report("Error creating cache");
ret = -1;
goto out;
}
cache_fini(XBZRLE.cache);
XBZRLE.cache = new_cache;
}
out_new_size:
ret = pow2floor(new_size);
out:
XBZRLE_cache_unlock();
return ret;
}
/* accounting for migration statistics */
typedef struct AccountingInfo {
uint64_t dup_pages;
uint64_t skipped_pages;
uint64_t norm_pages;
uint64_t iterations;
uint64_t xbzrle_bytes;
uint64_t xbzrle_pages;
uint64_t xbzrle_cache_miss;
double xbzrle_cache_miss_rate;
uint64_t xbzrle_overflows;
} AccountingInfo;
static AccountingInfo acct_info;
static void acct_clear(void)
{
memset(&acct_info, 0, sizeof(acct_info));
}
uint64_t dup_mig_bytes_transferred(void)
{
return acct_info.dup_pages * TARGET_PAGE_SIZE;
}
uint64_t dup_mig_pages_transferred(void)
{
return acct_info.dup_pages;
}
uint64_t skipped_mig_bytes_transferred(void)
{
return acct_info.skipped_pages * TARGET_PAGE_SIZE;
}
uint64_t skipped_mig_pages_transferred(void)
{
return acct_info.skipped_pages;
}
uint64_t norm_mig_bytes_transferred(void)
{
return acct_info.norm_pages * TARGET_PAGE_SIZE;
}
uint64_t norm_mig_pages_transferred(void)
{
return acct_info.norm_pages;
}
uint64_t xbzrle_mig_bytes_transferred(void)
{
return acct_info.xbzrle_bytes;
}
uint64_t xbzrle_mig_pages_transferred(void)
{
return acct_info.xbzrle_pages;
}
uint64_t xbzrle_mig_pages_cache_miss(void)
{
return acct_info.xbzrle_cache_miss;
}
double xbzrle_mig_cache_miss_rate(void)
{
return acct_info.xbzrle_cache_miss_rate;
}
uint64_t xbzrle_mig_pages_overflow(void)
{
return acct_info.xbzrle_overflows;
}
/* This is the last block that we have visited serching for dirty pages
*/
static RAMBlock *last_seen_block;
/* This is the last block from where we have sent data */
static RAMBlock *last_sent_block;
static ram_addr_t last_offset;
static unsigned long *migration_bitmap;
static QemuMutex migration_bitmap_mutex;
static uint64_t migration_dirty_pages;
static uint32_t last_version;
static bool ram_bulk_stage;
struct CompressParam {
bool start;
bool done;
QEMUFile *file;
QemuMutex mutex;
QemuCond cond;
RAMBlock *block;
ram_addr_t offset;
};
typedef struct CompressParam CompressParam;
struct DecompressParam {
bool start;
QemuMutex mutex;
QemuCond cond;
void *des;
uint8 *compbuf;
int len;
};
typedef struct DecompressParam DecompressParam;
static CompressParam *comp_param;
static QemuThread *compress_threads;
/* comp_done_cond is used to wake up the migration thread when
* one of the compression threads has finished the compression.
* comp_done_lock is used to co-work with comp_done_cond.
*/
static QemuMutex *comp_done_lock;
static QemuCond *comp_done_cond;
/* The empty QEMUFileOps will be used by file in CompressParam */
static const QEMUFileOps empty_ops = { };
static bool compression_switch;
static bool quit_comp_thread;
static bool quit_decomp_thread;
static DecompressParam *decomp_param;
static QemuThread *decompress_threads;
static uint8_t *compressed_data_buf;
static int do_compress_ram_page(CompressParam *param);
static void *do_data_compress(void *opaque)
{
CompressParam *param = opaque;
while (!quit_comp_thread) {
qemu_mutex_lock(&param->mutex);
/* Re-check the quit_comp_thread in case of
* terminate_compression_threads is called just before
* qemu_mutex_lock(&param->mutex) and after
* while(!quit_comp_thread), re-check it here can make
* sure the compression thread terminate as expected.
*/
while (!param->start && !quit_comp_thread) {
qemu_cond_wait(&param->cond, &param->mutex);
}
if (!quit_comp_thread) {
do_compress_ram_page(param);
}
param->start = false;
qemu_mutex_unlock(&param->mutex);
qemu_mutex_lock(comp_done_lock);
param->done = true;
qemu_cond_signal(comp_done_cond);
qemu_mutex_unlock(comp_done_lock);
}
return NULL;
}
static inline void terminate_compression_threads(void)
{
int idx, thread_count;
thread_count = migrate_compress_threads();
quit_comp_thread = true;
for (idx = 0; idx < thread_count; idx++) {
qemu_mutex_lock(&comp_param[idx].mutex);
qemu_cond_signal(&comp_param[idx].cond);
qemu_mutex_unlock(&comp_param[idx].mutex);
}
}
void migrate_compress_threads_join(void)
{
int i, thread_count;
if (!migrate_use_compression()) {
return;
}
terminate_compression_threads();
thread_count = migrate_compress_threads();
for (i = 0; i < thread_count; i++) {
qemu_thread_join(compress_threads + i);
qemu_fclose(comp_param[i].file);
qemu_mutex_destroy(&comp_param[i].mutex);
qemu_cond_destroy(&comp_param[i].cond);
}
qemu_mutex_destroy(comp_done_lock);
qemu_cond_destroy(comp_done_cond);
g_free(compress_threads);
g_free(comp_param);
g_free(comp_done_cond);
g_free(comp_done_lock);
compress_threads = NULL;
comp_param = NULL;
comp_done_cond = NULL;
comp_done_lock = NULL;
}
void migrate_compress_threads_create(void)
{
int i, thread_count;
if (!migrate_use_compression()) {
return;
}
quit_comp_thread = false;
compression_switch = true;
thread_count = migrate_compress_threads();
compress_threads = g_new0(QemuThread, thread_count);
comp_param = g_new0(CompressParam, thread_count);
comp_done_cond = g_new0(QemuCond, 1);
comp_done_lock = g_new0(QemuMutex, 1);
qemu_cond_init(comp_done_cond);
qemu_mutex_init(comp_done_lock);
for (i = 0; i < thread_count; i++) {
/* com_param[i].file is just used as a dummy buffer to save data, set
* it's ops to empty.
*/
comp_param[i].file = qemu_fopen_ops(NULL, &empty_ops);
comp_param[i].done = true;
qemu_mutex_init(&comp_param[i].mutex);
qemu_cond_init(&comp_param[i].cond);
qemu_thread_create(compress_threads + i, "compress",
do_data_compress, comp_param + i,
QEMU_THREAD_JOINABLE);
}
}
/**
* save_page_header: Write page header to wire
*
* If this is the 1st block, it also writes the block identification
*
* Returns: Number of bytes written
*
* @f: QEMUFile where to send the data
* @block: block that contains the page we want to send
* @offset: offset inside the block for the page
* in the lower bits, it contains flags
*/
static size_t save_page_header(QEMUFile *f, RAMBlock *block, ram_addr_t offset)
{
size_t size, len;
qemu_put_be64(f, offset);
size = 8;
if (!(offset & RAM_SAVE_FLAG_CONTINUE)) {
len = strlen(block->idstr);
qemu_put_byte(f, len);
qemu_put_buffer(f, (uint8_t *)block->idstr, len);
size += 1 + len;
}
return size;
}
/* Update the xbzrle cache to reflect a page that's been sent as all 0.
* The important thing is that a stale (not-yet-0'd) page be replaced
* by the new data.
* As a bonus, if the page wasn't in the cache it gets added so that
* when a small write is made into the 0'd page it gets XBZRLE sent
*/
static void xbzrle_cache_zero_page(ram_addr_t current_addr)
{
if (ram_bulk_stage || !migrate_use_xbzrle()) {
return;
}
/* We don't care if this fails to allocate a new cache page
* as long as it updated an old one */
cache_insert(XBZRLE.cache, current_addr, ZERO_TARGET_PAGE,
bitmap_sync_count);
}
#define ENCODING_FLAG_XBZRLE 0x1
/**
* save_xbzrle_page: compress and send current page
*
* Returns: 1 means that we wrote the page
* 0 means that page is identical to the one already sent
* -1 means that xbzrle would be longer than normal
*
* @f: QEMUFile where to send the data
* @current_data:
* @current_addr:
* @block: block that contains the page we want to send
* @offset: offset inside the block for the page
* @last_stage: if we are at the completion stage
* @bytes_transferred: increase it with the number of transferred bytes
*/
static int save_xbzrle_page(QEMUFile *f, uint8_t **current_data,
ram_addr_t current_addr, RAMBlock *block,
ram_addr_t offset, bool last_stage,
uint64_t *bytes_transferred)
{
int encoded_len = 0, bytes_xbzrle;
uint8_t *prev_cached_page;
if (!cache_is_cached(XBZRLE.cache, current_addr, bitmap_sync_count)) {
acct_info.xbzrle_cache_miss++;
if (!last_stage) {
if (cache_insert(XBZRLE.cache, current_addr, *current_data,
bitmap_sync_count) == -1) {
return -1;
} else {
/* update *current_data when the page has been
inserted into cache */
*current_data = get_cached_data(XBZRLE.cache, current_addr);
}
}
return -1;
}
prev_cached_page = get_cached_data(XBZRLE.cache, current_addr);
/* save current buffer into memory */
memcpy(XBZRLE.current_buf, *current_data, TARGET_PAGE_SIZE);
/* XBZRLE encoding (if there is no overflow) */
encoded_len = xbzrle_encode_buffer(prev_cached_page, XBZRLE.current_buf,
TARGET_PAGE_SIZE, XBZRLE.encoded_buf,
TARGET_PAGE_SIZE);
if (encoded_len == 0) {
DPRINTF("Skipping unmodified page\n");
return 0;
} else if (encoded_len == -1) {
DPRINTF("Overflow\n");
acct_info.xbzrle_overflows++;
/* update data in the cache */
if (!last_stage) {
memcpy(prev_cached_page, *current_data, TARGET_PAGE_SIZE);
*current_data = prev_cached_page;
}
return -1;
}
/* we need to update the data in the cache, in order to get the same data */
if (!last_stage) {
memcpy(prev_cached_page, XBZRLE.current_buf, TARGET_PAGE_SIZE);
}
/* Send XBZRLE based compressed page */
bytes_xbzrle = save_page_header(f, block, offset | RAM_SAVE_FLAG_XBZRLE);
qemu_put_byte(f, ENCODING_FLAG_XBZRLE);
qemu_put_be16(f, encoded_len);
qemu_put_buffer(f, XBZRLE.encoded_buf, encoded_len);
bytes_xbzrle += encoded_len + 1 + 2;
acct_info.xbzrle_pages++;
acct_info.xbzrle_bytes += bytes_xbzrle;
*bytes_transferred += bytes_xbzrle;
return 1;
}
/* Called with rcu_read_lock() to protect migration_bitmap */
static inline
ram_addr_t migration_bitmap_find_and_reset_dirty(MemoryRegion *mr,
ram_addr_t start)
{
unsigned long base = mr->ram_addr >> TARGET_PAGE_BITS;
unsigned long nr = base + (start >> TARGET_PAGE_BITS);
uint64_t mr_size = TARGET_PAGE_ALIGN(memory_region_size(mr));
unsigned long size = base + (mr_size >> TARGET_PAGE_BITS);
unsigned long *bitmap;
unsigned long next;
bitmap = atomic_rcu_read(&migration_bitmap);
if (ram_bulk_stage && nr > base) {
next = nr + 1;
} else {
next = find_next_bit(bitmap, size, nr);
}
if (next < size) {
clear_bit(next, bitmap);
migration_dirty_pages--;
}
return (next - base) << TARGET_PAGE_BITS;
}
/* Called with rcu_read_lock() to protect migration_bitmap */
static void migration_bitmap_sync_range(ram_addr_t start, ram_addr_t length)
{
unsigned long *bitmap;
bitmap = atomic_rcu_read(&migration_bitmap);
migration_dirty_pages +=
cpu_physical_memory_sync_dirty_bitmap(bitmap, start, length);
}
/* Fix me: there are too many global variables used in migration process. */
static int64_t start_time;
static int64_t bytes_xfer_prev;
static int64_t num_dirty_pages_period;
static uint64_t xbzrle_cache_miss_prev;
static uint64_t iterations_prev;
static void migration_bitmap_sync_init(void)
{
start_time = 0;
bytes_xfer_prev = 0;
num_dirty_pages_period = 0;
xbzrle_cache_miss_prev = 0;
iterations_prev = 0;
}
/* Called with iothread lock held, to protect ram_list.dirty_memory[] */
static void migration_bitmap_sync(void)
{
RAMBlock *block;
uint64_t num_dirty_pages_init = migration_dirty_pages;
MigrationState *s = migrate_get_current();
int64_t end_time;
int64_t bytes_xfer_now;
bitmap_sync_count++;
if (!bytes_xfer_prev) {
bytes_xfer_prev = ram_bytes_transferred();
}
if (!start_time) {
start_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
}
trace_migration_bitmap_sync_start();
address_space_sync_dirty_bitmap(&address_space_memory);
qemu_mutex_lock(&migration_bitmap_mutex);
rcu_read_lock();
QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
migration_bitmap_sync_range(block->mr->ram_addr, block->used_length);
}
rcu_read_unlock();
qemu_mutex_unlock(&migration_bitmap_mutex);
trace_migration_bitmap_sync_end(migration_dirty_pages
- num_dirty_pages_init);
num_dirty_pages_period += migration_dirty_pages - num_dirty_pages_init;
end_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
/* more than 1 second = 1000 millisecons */
if (end_time > start_time + 1000) {
if (migrate_auto_converge()) {
/* The following detection logic can be refined later. For now:
Check to see if the dirtied bytes is 50% more than the approx.
amount of bytes that just got transferred since the last time we
were in this routine. If that happens >N times (for now N==4)
we turn on the throttle down logic */
bytes_xfer_now = ram_bytes_transferred();
if (s->dirty_pages_rate &&
(num_dirty_pages_period * TARGET_PAGE_SIZE >
(bytes_xfer_now - bytes_xfer_prev)/2) &&
(dirty_rate_high_cnt++ > 4)) {
trace_migration_throttle();
mig_throttle_on = true;
dirty_rate_high_cnt = 0;
}
bytes_xfer_prev = bytes_xfer_now;
} else {
mig_throttle_on = false;
}
if (migrate_use_xbzrle()) {
if (iterations_prev != acct_info.iterations) {
acct_info.xbzrle_cache_miss_rate =
(double)(acct_info.xbzrle_cache_miss -
xbzrle_cache_miss_prev) /
(acct_info.iterations - iterations_prev);
}
iterations_prev = acct_info.iterations;
xbzrle_cache_miss_prev = acct_info.xbzrle_cache_miss;
}
s->dirty_pages_rate = num_dirty_pages_period * 1000
/ (end_time - start_time);
s->dirty_bytes_rate = s->dirty_pages_rate * TARGET_PAGE_SIZE;
start_time = end_time;
num_dirty_pages_period = 0;
}
s->dirty_sync_count = bitmap_sync_count;
}
/**
* save_zero_page: Send the zero page to the stream
*
* Returns: Number of pages written.
*
* @f: QEMUFile where to send the data
* @block: block that contains the page we want to send
* @offset: offset inside the block for the page
* @p: pointer to the page
* @bytes_transferred: increase it with the number of transferred bytes
*/
static int save_zero_page(QEMUFile *f, RAMBlock *block, ram_addr_t offset,
uint8_t *p, uint64_t *bytes_transferred)
{
int pages = -1;
if (is_zero_range(p, TARGET_PAGE_SIZE)) {
acct_info.dup_pages++;
*bytes_transferred += save_page_header(f, block,
offset | RAM_SAVE_FLAG_COMPRESS);
qemu_put_byte(f, 0);
*bytes_transferred += 1;
pages = 1;
}
return pages;
}
/**
* ram_save_page: Send the given page to the stream
*
* Returns: Number of pages written.
*
* @f: QEMUFile where to send the data
* @block: block that contains the page we want to send
* @offset: offset inside the block for the page
* @last_stage: if we are at the completion stage
* @bytes_transferred: increase it with the number of transferred bytes
*/
static int ram_save_page(QEMUFile *f, RAMBlock* block, ram_addr_t offset,
bool last_stage, uint64_t *bytes_transferred)
{
int pages = -1;
uint64_t bytes_xmit;
ram_addr_t current_addr;
MemoryRegion *mr = block->mr;
uint8_t *p;
int ret;
bool send_async = true;
p = memory_region_get_ram_ptr(mr) + offset;
/* In doubt sent page as normal */
bytes_xmit = 0;
ret = ram_control_save_page(f, block->offset,
offset, TARGET_PAGE_SIZE, &bytes_xmit);
if (bytes_xmit) {
*bytes_transferred += bytes_xmit;
pages = 1;
}
XBZRLE_cache_lock();
current_addr = block->offset + offset;
if (block == last_sent_block) {
offset |= RAM_SAVE_FLAG_CONTINUE;
}
if (ret != RAM_SAVE_CONTROL_NOT_SUPP) {
if (ret != RAM_SAVE_CONTROL_DELAYED) {
if (bytes_xmit > 0) {
acct_info.norm_pages++;
} else if (bytes_xmit == 0) {
acct_info.dup_pages++;
}
}
} else {
pages = save_zero_page(f, block, offset, p, bytes_transferred);
if (pages > 0) {
/* Must let xbzrle know, otherwise a previous (now 0'd) cached
* page would be stale
*/
xbzrle_cache_zero_page(current_addr);
} else if (!ram_bulk_stage && migrate_use_xbzrle()) {
pages = save_xbzrle_page(f, &p, current_addr, block,
offset, last_stage, bytes_transferred);
if (!last_stage) {
/* Can't send this cached data async, since the cache page
* might get updated before it gets to the wire
*/
send_async = false;
}
}
}
/* XBZRLE overflow or normal page */
if (pages == -1) {
*bytes_transferred += save_page_header(f, block,
offset | RAM_SAVE_FLAG_PAGE);
if (send_async) {
qemu_put_buffer_async(f, p, TARGET_PAGE_SIZE);
} else {
qemu_put_buffer(f, p, TARGET_PAGE_SIZE);
}
*bytes_transferred += TARGET_PAGE_SIZE;
pages = 1;
acct_info.norm_pages++;
}
XBZRLE_cache_unlock();
return pages;
}
static int do_compress_ram_page(CompressParam *param)
{
int bytes_sent, blen;
uint8_t *p;
RAMBlock *block = param->block;
ram_addr_t offset = param->offset;
p = memory_region_get_ram_ptr(block->mr) + (offset & TARGET_PAGE_MASK);
bytes_sent = save_page_header(param->file, block, offset |
RAM_SAVE_FLAG_COMPRESS_PAGE);
blen = qemu_put_compression_data(param->file, p, TARGET_PAGE_SIZE,
migrate_compress_level());
bytes_sent += blen;
return bytes_sent;
}
static inline void start_compression(CompressParam *param)
{
param->done = false;
qemu_mutex_lock(&param->mutex);
param->start = true;
qemu_cond_signal(&param->cond);
qemu_mutex_unlock(&param->mutex);
}
static inline void start_decompression(DecompressParam *param)
{
qemu_mutex_lock(&param->mutex);
param->start = true;
qemu_cond_signal(&param->cond);
qemu_mutex_unlock(&param->mutex);
}
static uint64_t bytes_transferred;
static void flush_compressed_data(QEMUFile *f)
{
int idx, len, thread_count;
if (!migrate_use_compression()) {
return;
}
thread_count = migrate_compress_threads();
for (idx = 0; idx < thread_count; idx++) {
if (!comp_param[idx].done) {
qemu_mutex_lock(comp_done_lock);
while (!comp_param[idx].done && !quit_comp_thread) {
qemu_cond_wait(comp_done_cond, comp_done_lock);
}
qemu_mutex_unlock(comp_done_lock);
}
if (!quit_comp_thread) {
len = qemu_put_qemu_file(f, comp_param[idx].file);
bytes_transferred += len;
}
}
}
static inline void set_compress_params(CompressParam *param, RAMBlock *block,
ram_addr_t offset)
{
param->block = block;
param->offset = offset;
}
static int compress_page_with_multi_thread(QEMUFile *f, RAMBlock *block,
ram_addr_t offset,
uint64_t *bytes_transferred)
{
int idx, thread_count, bytes_xmit = -1, pages = -1;
thread_count = migrate_compress_threads();
qemu_mutex_lock(comp_done_lock);
while (true) {
for (idx = 0; idx < thread_count; idx++) {
if (comp_param[idx].done) {
bytes_xmit = qemu_put_qemu_file(f, comp_param[idx].file);
set_compress_params(&comp_param[idx], block, offset);
start_compression(&comp_param[idx]);
pages = 1;
acct_info.norm_pages++;
*bytes_transferred += bytes_xmit;
break;
}
}
if (pages > 0) {
break;
} else {
qemu_cond_wait(comp_done_cond, comp_done_lock);
}
}
qemu_mutex_unlock(comp_done_lock);
return pages;
}
/**
* ram_save_compressed_page: compress the given page and send it to the stream
*
* Returns: Number of pages written.
*
* @f: QEMUFile where to send the data
* @block: block that contains the page we want to send
* @offset: offset inside the block for the page
* @last_stage: if we are at the completion stage
* @bytes_transferred: increase it with the number of transferred bytes
*/
static int ram_save_compressed_page(QEMUFile *f, RAMBlock *block,
ram_addr_t offset, bool last_stage,
uint64_t *bytes_transferred)
{
int pages = -1;
uint64_t bytes_xmit;
MemoryRegion *mr = block->mr;
uint8_t *p;
int ret;
p = memory_region_get_ram_ptr(mr) + offset;
bytes_xmit = 0;
ret = ram_control_save_page(f, block->offset,
offset, TARGET_PAGE_SIZE, &bytes_xmit);
if (bytes_xmit) {
*bytes_transferred += bytes_xmit;
pages = 1;
}
if (block == last_sent_block) {
offset |= RAM_SAVE_FLAG_CONTINUE;
}
if (ret != RAM_SAVE_CONTROL_NOT_SUPP) {
if (ret != RAM_SAVE_CONTROL_DELAYED) {
if (bytes_xmit > 0) {
acct_info.norm_pages++;
} else if (bytes_xmit == 0) {
acct_info.dup_pages++;
}
}
} else {
/* When starting the process of a new block, the first page of
* the block should be sent out before other pages in the same
* block, and all the pages in last block should have been sent
* out, keeping this order is important, because the 'cont' flag
* is used to avoid resending the block name.
*/
if (block != last_sent_block) {
flush_compressed_data(f);
pages = save_zero_page(f, block, offset, p, bytes_transferred);
if (pages == -1) {
set_compress_params(&comp_param[0], block, offset);
/* Use the qemu thread to compress the data to make sure the
* first page is sent out before other pages
*/
bytes_xmit = do_compress_ram_page(&comp_param[0]);
acct_info.norm_pages++;
qemu_put_qemu_file(f, comp_param[0].file);
*bytes_transferred += bytes_xmit;
pages = 1;
}
} else {
pages = save_zero_page(f, block, offset, p, bytes_transferred);
if (pages == -1) {
pages = compress_page_with_multi_thread(f, block, offset,
bytes_transferred);
}
}
}
return pages;
}
/**
* ram_find_and_save_block: Finds a dirty page and sends it to f
*
* Called within an RCU critical section.
*
* Returns: The number of pages written
* 0 means no dirty pages
*
* @f: QEMUFile where to send the data
* @last_stage: if we are at the completion stage
* @bytes_transferred: increase it with the number of transferred bytes
*/
static int ram_find_and_save_block(QEMUFile *f, bool last_stage,
uint64_t *bytes_transferred)
{
RAMBlock *block = last_seen_block;
ram_addr_t offset = last_offset;
bool complete_round = false;
int pages = 0;
MemoryRegion *mr;
if (!block)
block = QLIST_FIRST_RCU(&ram_list.blocks);
while (true) {
mr = block->mr;
offset = migration_bitmap_find_and_reset_dirty(mr, offset);
if (complete_round && block == last_seen_block &&
offset >= last_offset) {
break;
}
if (offset >= block->used_length) {
offset = 0;
block = QLIST_NEXT_RCU(block, next);
if (!block) {
block = QLIST_FIRST_RCU(&ram_list.blocks);
complete_round = true;
ram_bulk_stage = false;
if (migrate_use_xbzrle()) {
/* If xbzrle is on, stop using the data compression at this
* point. In theory, xbzrle can do better than compression.
*/
flush_compressed_data(f);
compression_switch = false;
}
}
} else {
if (compression_switch && migrate_use_compression()) {
pages = ram_save_compressed_page(f, block, offset, last_stage,
bytes_transferred);
} else {
pages = ram_save_page(f, block, offset, last_stage,
bytes_transferred);
}
/* if page is unmodified, continue to the next */
if (pages > 0) {
last_sent_block = block;
break;
}
}
}
last_seen_block = block;
last_offset = offset;
return pages;
}
void acct_update_position(QEMUFile *f, size_t size, bool zero)
{
uint64_t pages = size / TARGET_PAGE_SIZE;
if (zero) {
acct_info.dup_pages += pages;
} else {
acct_info.norm_pages += pages;
bytes_transferred += size;
qemu_update_position(f, size);
}
}
static ram_addr_t ram_save_remaining(void)
{
return migration_dirty_pages;
}
uint64_t ram_bytes_remaining(void)
{
return ram_save_remaining() * TARGET_PAGE_SIZE;
}
uint64_t ram_bytes_transferred(void)
{
return bytes_transferred;
}
uint64_t ram_bytes_total(void)
{
RAMBlock *block;
uint64_t total = 0;
rcu_read_lock();
QLIST_FOREACH_RCU(block, &ram_list.blocks, next)
total += block->used_length;
rcu_read_unlock();
return total;
}
void free_xbzrle_decoded_buf(void)
{
g_free(xbzrle_decoded_buf);
xbzrle_decoded_buf = NULL;
}
static void migration_end(void)
{
/* caller have hold iothread lock or is in a bh, so there is
* no writing race against this migration_bitmap
*/
unsigned long *bitmap = migration_bitmap;
atomic_rcu_set(&migration_bitmap, NULL);
if (bitmap) {
memory_global_dirty_log_stop();
synchronize_rcu();
g_free(bitmap);
}
XBZRLE_cache_lock();
if (XBZRLE.cache) {
cache_fini(XBZRLE.cache);
g_free(XBZRLE.encoded_buf);
g_free(XBZRLE.current_buf);
XBZRLE.cache = NULL;
XBZRLE.encoded_buf = NULL;
XBZRLE.current_buf = NULL;
}
XBZRLE_cache_unlock();
}
static void ram_migration_cancel(void *opaque)
{
migration_end();
}
static void reset_ram_globals(void)
{
last_seen_block = NULL;
last_sent_block = NULL;
last_offset = 0;
last_version = ram_list.version;
ram_bulk_stage = true;
}
#define MAX_WAIT 50 /* ms, half buffered_file limit */
void migration_bitmap_extend(ram_addr_t old, ram_addr_t new)
{
/* called in qemu main thread, so there is
* no writing race against this migration_bitmap
*/
if (migration_bitmap) {
unsigned long *old_bitmap = migration_bitmap, *bitmap;
bitmap = bitmap_new(new);
/* prevent migration_bitmap content from being set bit
* by migration_bitmap_sync_range() at the same time.
* it is safe to migration if migration_bitmap is cleared bit
* at the same time.
*/
qemu_mutex_lock(&migration_bitmap_mutex);
bitmap_copy(bitmap, old_bitmap, old);
bitmap_set(bitmap, old, new - old);
atomic_rcu_set(&migration_bitmap, bitmap);
qemu_mutex_unlock(&migration_bitmap_mutex);
migration_dirty_pages += new - old;
synchronize_rcu();
g_free(old_bitmap);
}
}
/* Each of ram_save_setup, ram_save_iterate and ram_save_complete has
* long-running RCU critical section. When rcu-reclaims in the code
* start to become numerous it will be necessary to reduce the
* granularity of these critical sections.
*/
static int ram_save_setup(QEMUFile *f, void *opaque)
{
RAMBlock *block;
int64_t ram_bitmap_pages; /* Size of bitmap in pages, including gaps */
mig_throttle_on = false;
dirty_rate_high_cnt = 0;
bitmap_sync_count = 0;
migration_bitmap_sync_init();
qemu_mutex_init(&migration_bitmap_mutex);
if (migrate_use_xbzrle()) {
XBZRLE_cache_lock();
XBZRLE.cache = cache_init(migrate_xbzrle_cache_size() /
TARGET_PAGE_SIZE,
TARGET_PAGE_SIZE);
if (!XBZRLE.cache) {
XBZRLE_cache_unlock();
error_report("Error creating cache");
return -1;
}
XBZRLE_cache_unlock();
/* We prefer not to abort if there is no memory */
XBZRLE.encoded_buf = g_try_malloc0(TARGET_PAGE_SIZE);
if (!XBZRLE.encoded_buf) {
error_report("Error allocating encoded_buf");
return -1;
}
XBZRLE.current_buf = g_try_malloc(TARGET_PAGE_SIZE);
if (!XBZRLE.current_buf) {
error_report("Error allocating current_buf");
g_free(XBZRLE.encoded_buf);
XBZRLE.encoded_buf = NULL;
return -1;
}
acct_clear();
}
/* iothread lock needed for ram_list.dirty_memory[] */
qemu_mutex_lock_iothread();
qemu_mutex_lock_ramlist();
rcu_read_lock();
bytes_transferred = 0;
reset_ram_globals();
ram_bitmap_pages = last_ram_offset() >> TARGET_PAGE_BITS;
migration_bitmap = bitmap_new(ram_bitmap_pages);
bitmap_set(migration_bitmap, 0, ram_bitmap_pages);
/*
* Count the total number of pages used by ram blocks not including any
* gaps due to alignment or unplugs.
*/
migration_dirty_pages = ram_bytes_total() >> TARGET_PAGE_BITS;
memory_global_dirty_log_start();
migration_bitmap_sync();
qemu_mutex_unlock_ramlist();
qemu_mutex_unlock_iothread();
qemu_put_be64(f, ram_bytes_total() | RAM_SAVE_FLAG_MEM_SIZE);
QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
qemu_put_byte(f, strlen(block->idstr));
qemu_put_buffer(f, (uint8_t *)block->idstr, strlen(block->idstr));
qemu_put_be64(f, block->used_length);
}
rcu_read_unlock();
ram_control_before_iterate(f, RAM_CONTROL_SETUP);
ram_control_after_iterate(f, RAM_CONTROL_SETUP);
qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
return 0;
}
static int ram_save_iterate(QEMUFile *f, void *opaque)
{
int ret;
int i;
int64_t t0;
int pages_sent = 0;
rcu_read_lock();
if (ram_list.version != last_version) {
reset_ram_globals();
}
/* Read version before ram_list.blocks */
smp_rmb();
ram_control_before_iterate(f, RAM_CONTROL_ROUND);
t0 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
i = 0;
while ((ret = qemu_file_rate_limit(f)) == 0) {
int pages;
pages = ram_find_and_save_block(f, false, &bytes_transferred);
/* no more pages to sent */
if (pages == 0) {
break;
}
pages_sent += pages;
acct_info.iterations++;
check_guest_throttling();
/* we want to check in the 1st loop, just in case it was the 1st time
and we had to sync the dirty bitmap.
qemu_get_clock_ns() is a bit expensive, so we only check each some
iterations
*/
if ((i & 63) == 0) {
uint64_t t1 = (qemu_clock_get_ns(QEMU_CLOCK_REALTIME) - t0) / 1000000;
if (t1 > MAX_WAIT) {
DPRINTF("big wait: %" PRIu64 " milliseconds, %d iterations\n",
t1, i);
break;
}
}
i++;
}
flush_compressed_data(f);
rcu_read_unlock();
/*
* Must occur before EOS (or any QEMUFile operation)
* because of RDMA protocol.
*/
ram_control_after_iterate(f, RAM_CONTROL_ROUND);
qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
bytes_transferred += 8;
ret = qemu_file_get_error(f);
if (ret < 0) {
return ret;
}
return pages_sent;
}
/* Called with iothread lock */
static int ram_save_complete(QEMUFile *f, void *opaque)
{
rcu_read_lock();
migration_bitmap_sync();
ram_control_before_iterate(f, RAM_CONTROL_FINISH);
/* try transferring iterative blocks of memory */
/* flush all remaining blocks regardless of rate limiting */
while (true) {
int pages;
pages = ram_find_and_save_block(f, true, &bytes_transferred);
/* no more blocks to sent */
if (pages == 0) {
break;
}
}
flush_compressed_data(f);
ram_control_after_iterate(f, RAM_CONTROL_FINISH);
rcu_read_unlock();
migration_end();
qemu_put_be64(f, RAM_SAVE_FLAG_EOS);
return 0;
}
static uint64_t ram_save_pending(QEMUFile *f, void *opaque, uint64_t max_size)
{
uint64_t remaining_size;
remaining_size = ram_save_remaining() * TARGET_PAGE_SIZE;
if (remaining_size < max_size) {
qemu_mutex_lock_iothread();
rcu_read_lock();
migration_bitmap_sync();
rcu_read_unlock();
qemu_mutex_unlock_iothread();
remaining_size = ram_save_remaining() * TARGET_PAGE_SIZE;
}
return remaining_size;
}
static int load_xbzrle(QEMUFile *f, ram_addr_t addr, void *host)
{
unsigned int xh_len;
int xh_flags;
if (!xbzrle_decoded_buf) {
xbzrle_decoded_buf = g_malloc(TARGET_PAGE_SIZE);
}
/* extract RLE header */
xh_flags = qemu_get_byte(f);
xh_len = qemu_get_be16(f);
if (xh_flags != ENCODING_FLAG_XBZRLE) {
error_report("Failed to load XBZRLE page - wrong compression!");
return -1;
}
if (xh_len > TARGET_PAGE_SIZE) {
error_report("Failed to load XBZRLE page - len overflow!");
return -1;
}
/* load data and decode */
qemu_get_buffer(f, xbzrle_decoded_buf, xh_len);
/* decode RLE */
if (xbzrle_decode_buffer(xbzrle_decoded_buf, xh_len, host,
TARGET_PAGE_SIZE) == -1) {
error_report("Failed to load XBZRLE page - decode error!");
return -1;
}
return 0;
}
/* Must be called from within a rcu critical section.
* Returns a pointer from within the RCU-protected ram_list.
*/
static inline void *host_from_stream_offset(QEMUFile *f,
ram_addr_t offset,
int flags)
{
static RAMBlock *block = NULL;
char id[256];
uint8_t len;
if (flags & RAM_SAVE_FLAG_CONTINUE) {
if (!block || block->max_length <= offset) {
error_report("Ack, bad migration stream!");
return NULL;
}
return memory_region_get_ram_ptr(block->mr) + offset;
}
len = qemu_get_byte(f);
qemu_get_buffer(f, (uint8_t *)id, len);
id[len] = 0;
QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
if (!strncmp(id, block->idstr, sizeof(id)) &&
block->max_length > offset) {
return memory_region_get_ram_ptr(block->mr) + offset;
}
}
error_report("Can't find block %s!", id);
return NULL;
}
/*
* If a page (or a whole RDMA chunk) has been
* determined to be zero, then zap it.
*/
void ram_handle_compressed(void *host, uint8_t ch, uint64_t size)
{
if (ch != 0 || !is_zero_range(host, size)) {
memset(host, ch, size);
}
}
static void *do_data_decompress(void *opaque)
{
DecompressParam *param = opaque;
unsigned long pagesize;
while (!quit_decomp_thread) {
qemu_mutex_lock(&param->mutex);
while (!param->start && !quit_decomp_thread) {
qemu_cond_wait(&param->cond, &param->mutex);
pagesize = TARGET_PAGE_SIZE;
if (!quit_decomp_thread) {
/* uncompress() will return failed in some case, especially
* when the page is dirted when doing the compression, it's
* not a problem because the dirty page will be retransferred
* and uncompress() won't break the data in other pages.
*/
uncompress((Bytef *)param->des, &pagesize,
(const Bytef *)param->compbuf, param->len);
}
param->start = false;
}
qemu_mutex_unlock(&param->mutex);
}
return NULL;
}
void migrate_decompress_threads_create(void)
{
int i, thread_count;
thread_count = migrate_decompress_threads();
decompress_threads = g_new0(QemuThread, thread_count);
decomp_param = g_new0(DecompressParam, thread_count);
compressed_data_buf = g_malloc0(compressBound(TARGET_PAGE_SIZE));
quit_decomp_thread = false;
for (i = 0; i < thread_count; i++) {
qemu_mutex_init(&decomp_param[i].mutex);
qemu_cond_init(&decomp_param[i].cond);
decomp_param[i].compbuf = g_malloc0(compressBound(TARGET_PAGE_SIZE));
qemu_thread_create(decompress_threads + i, "decompress",
do_data_decompress, decomp_param + i,
QEMU_THREAD_JOINABLE);
}
}
void migrate_decompress_threads_join(void)
{
int i, thread_count;
quit_decomp_thread = true;
thread_count = migrate_decompress_threads();
for (i = 0; i < thread_count; i++) {
qemu_mutex_lock(&decomp_param[i].mutex);
qemu_cond_signal(&decomp_param[i].cond);
qemu_mutex_unlock(&decomp_param[i].mutex);
}
for (i = 0; i < thread_count; i++) {
qemu_thread_join(decompress_threads + i);
qemu_mutex_destroy(&decomp_param[i].mutex);
qemu_cond_destroy(&decomp_param[i].cond);
g_free(decomp_param[i].compbuf);
}
g_free(decompress_threads);
g_free(decomp_param);
g_free(compressed_data_buf);
decompress_threads = NULL;
decomp_param = NULL;
compressed_data_buf = NULL;
}
static void decompress_data_with_multi_threads(uint8_t *compbuf,
void *host, int len)
{
int idx, thread_count;
thread_count = migrate_decompress_threads();
while (true) {
for (idx = 0; idx < thread_count; idx++) {
if (!decomp_param[idx].start) {
memcpy(decomp_param[idx].compbuf, compbuf, len);
decomp_param[idx].des = host;
decomp_param[idx].len = len;
start_decompression(&decomp_param[idx]);
break;
}
}
if (idx < thread_count) {
break;
}
}
}
static int ram_load(QEMUFile *f, void *opaque, int version_id)
{
int flags = 0, ret = 0;
static uint64_t seq_iter;
int len = 0;
seq_iter++;
if (version_id != 4) {
ret = -EINVAL;
}
/* This RCU critical section can be very long running.
* When RCU reclaims in the code start to become numerous,
* it will be necessary to reduce the granularity of this
* critical section.
*/
rcu_read_lock();
while (!ret && !(flags & RAM_SAVE_FLAG_EOS)) {
ram_addr_t addr, total_ram_bytes;
void *host;
uint8_t ch;
addr = qemu_get_be64(f);
flags = addr & ~TARGET_PAGE_MASK;
addr &= TARGET_PAGE_MASK;
switch (flags & ~RAM_SAVE_FLAG_CONTINUE) {
case RAM_SAVE_FLAG_MEM_SIZE:
/* Synchronize RAM block list */
total_ram_bytes = addr;
while (!ret && total_ram_bytes) {
RAMBlock *block;
char id[256];
ram_addr_t length;
len = qemu_get_byte(f);
qemu_get_buffer(f, (uint8_t *)id, len);
id[len] = 0;
length = qemu_get_be64(f);
QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
if (!strncmp(id, block->idstr, sizeof(id))) {
if (length != block->used_length) {
Error *local_err = NULL;
ret = qemu_ram_resize(block->offset, length, &local_err);
if (local_err) {
error_report_err(local_err);
}
}
ram_control_load_hook(f, RAM_CONTROL_BLOCK_REG,
block->idstr);
break;
}
}
if (!block) {
error_report("Unknown ramblock \"%s\", cannot "
"accept migration", id);
ret = -EINVAL;
}
total_ram_bytes -= length;
}
break;
case RAM_SAVE_FLAG_COMPRESS:
host = host_from_stream_offset(f, addr, flags);
if (!host) {
error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
ret = -EINVAL;
break;
}
ch = qemu_get_byte(f);
ram_handle_compressed(host, ch, TARGET_PAGE_SIZE);
break;
case RAM_SAVE_FLAG_PAGE:
host = host_from_stream_offset(f, addr, flags);
if (!host) {
error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
ret = -EINVAL;
break;
}
qemu_get_buffer(f, host, TARGET_PAGE_SIZE);
break;
case RAM_SAVE_FLAG_COMPRESS_PAGE:
host = host_from_stream_offset(f, addr, flags);
if (!host) {
error_report("Invalid RAM offset " RAM_ADDR_FMT, addr);
ret = -EINVAL;
break;
}
len = qemu_get_be32(f);
if (len < 0 || len > compressBound(TARGET_PAGE_SIZE)) {
error_report("Invalid compressed data length: %d", len);
ret = -EINVAL;
break;
}
qemu_get_buffer(f, compressed_data_buf, len);
decompress_data_with_multi_threads(compressed_data_buf, host, len);
break;
case RAM_SAVE_FLAG_XBZRLE:
host = host_from_stream_offset(f, addr, flags);
if (!host) {
error_report("Illegal RAM offset " RAM_ADDR_FMT, addr);
ret = -EINVAL;
break;
}
if (load_xbzrle(f, addr, host) < 0) {
error_report("Failed to decompress XBZRLE page at "
RAM_ADDR_FMT, addr);
ret = -EINVAL;
break;
}
break;
case RAM_SAVE_FLAG_EOS:
/* normal exit */
break;
default:
if (flags & RAM_SAVE_FLAG_HOOK) {
ram_control_load_hook(f, RAM_CONTROL_HOOK, NULL);
} else {
error_report("Unknown combination of migration flags: %#x",
flags);
ret = -EINVAL;
}
}
if (!ret) {
ret = qemu_file_get_error(f);
}
}
rcu_read_unlock();
DPRINTF("Completed load of VM with exit code %d seq iteration "
"%" PRIu64 "\n", ret, seq_iter);
return ret;
}
static SaveVMHandlers savevm_ram_handlers = {
.save_live_setup = ram_save_setup,
.save_live_iterate = ram_save_iterate,
.save_live_complete = ram_save_complete,
.save_live_pending = ram_save_pending,
.load_state = ram_load,
.cancel = ram_migration_cancel,
};
void ram_mig_init(void)
{
qemu_mutex_init(&XBZRLE.lock);
register_savevm_live(NULL, "ram", 0, 4, &savevm_ram_handlers, NULL);
}
/* Stub function that's gets run on the vcpu when its brought out of the
VM to run inside qemu via async_run_on_cpu()*/
static void mig_sleep_cpu(void *opq)
{
qemu_mutex_unlock_iothread();
g_usleep(30*1000);
qemu_mutex_lock_iothread();
}
/* To reduce the dirty rate explicitly disallow the VCPUs from spending
much time in the VM. The migration thread will try to catchup.
Workload will experience a performance drop.
*/
static void mig_throttle_guest_down(void)
{
CPUState *cpu;
qemu_mutex_lock_iothread();
CPU_FOREACH(cpu) {
async_run_on_cpu(cpu, mig_sleep_cpu, NULL);
}
qemu_mutex_unlock_iothread();
}
static void check_guest_throttling(void)
{
static int64_t t0;
int64_t t1;
if (!mig_throttle_on) {
return;
}
if (!t0) {
t0 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
return;
}
t1 = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
/* If it has been more than 40 ms since the last time the guest
* was throttled then do it again.
*/
if (40 < (t1-t0)/1000000) {
mig_throttle_guest_down();
t0 = t1;
}
}
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