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qemu/block-migration.c
Avishay Traeger ff5c52a379 Improve accuracy of block migration bandwidth calculation 
block_mig_state.total_time is currently the sum of the read request
latencies.  This is not very accurate because block migration uses aio and
so several requests can be submitted at once.  Bandwidth should be computed
with wall-clock time, not by adding the latencies.  In this case,
"total_time" has a higher value than it should, and so the computed
bandwidth is lower than it is in reality.  This means that migration can
take longer than it needs to.
However, we don't want to use pure wall-clock time here.  We are computing
bandwidth in the asynchronous phase, where the migration repeatedly wakes
up and sends some aio requests.  The computed bandwidth will be used for
synchronous transfer.

Signed-off-by: Avishay Traeger <avishay@il.ibm.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2011-04-27 14:36:57 +02:00

732 lines
20 KiB
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/*
* QEMU live block migration
*
* Copyright IBM, Corp. 2009
*
* Authors:
* Liran Schour <lirans@il.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
*/
#include "qemu-common.h"
#include "block_int.h"
#include "hw/hw.h"
#include "qemu-queue.h"
#include "qemu-timer.h"
#include "monitor.h"
#include "block-migration.h"
#include "migration.h"
#include "blockdev.h"
#include <assert.h>
#define BLOCK_SIZE (BDRV_SECTORS_PER_DIRTY_CHUNK << BDRV_SECTOR_BITS)
#define BLK_MIG_FLAG_DEVICE_BLOCK 0x01
#define BLK_MIG_FLAG_EOS 0x02
#define BLK_MIG_FLAG_PROGRESS 0x04
#define MAX_IS_ALLOCATED_SEARCH 65536
//#define DEBUG_BLK_MIGRATION
#ifdef DEBUG_BLK_MIGRATION
#define DPRINTF(fmt, ...) \
do { printf("blk_migration: " fmt, ## __VA_ARGS__); } while (0)
#else
#define DPRINTF(fmt, ...) \
do { } while (0)
#endif
typedef struct BlkMigDevState {
BlockDriverState *bs;
int bulk_completed;
int shared_base;
int64_t cur_sector;
int64_t cur_dirty;
int64_t completed_sectors;
int64_t total_sectors;
int64_t dirty;
QSIMPLEQ_ENTRY(BlkMigDevState) entry;
unsigned long *aio_bitmap;
} BlkMigDevState;
typedef struct BlkMigBlock {
uint8_t *buf;
BlkMigDevState *bmds;
int64_t sector;
int nr_sectors;
struct iovec iov;
QEMUIOVector qiov;
BlockDriverAIOCB *aiocb;
int ret;
QSIMPLEQ_ENTRY(BlkMigBlock) entry;
} BlkMigBlock;
typedef struct BlkMigState {
int blk_enable;
int shared_base;
QSIMPLEQ_HEAD(bmds_list, BlkMigDevState) bmds_list;
QSIMPLEQ_HEAD(blk_list, BlkMigBlock) blk_list;
int submitted;
int read_done;
int transferred;
int64_t total_sector_sum;
int prev_progress;
int bulk_completed;
long double total_time;
long double prev_time_offset;
int reads;
} BlkMigState;
static BlkMigState block_mig_state;
static void blk_send(QEMUFile *f, BlkMigBlock * blk)
{
int len;
/* sector number and flags */
qemu_put_be64(f, (blk->sector << BDRV_SECTOR_BITS)
| BLK_MIG_FLAG_DEVICE_BLOCK);
/* device name */
len = strlen(blk->bmds->bs->device_name);
qemu_put_byte(f, len);
qemu_put_buffer(f, (uint8_t *)blk->bmds->bs->device_name, len);
qemu_put_buffer(f, blk->buf, BLOCK_SIZE);
}
int blk_mig_active(void)
{
return !QSIMPLEQ_EMPTY(&block_mig_state.bmds_list);
}
uint64_t blk_mig_bytes_transferred(void)
{
BlkMigDevState *bmds;
uint64_t sum = 0;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
sum += bmds->completed_sectors;
}
return sum << BDRV_SECTOR_BITS;
}
uint64_t blk_mig_bytes_remaining(void)
{
return blk_mig_bytes_total() - blk_mig_bytes_transferred();
}
uint64_t blk_mig_bytes_total(void)
{
BlkMigDevState *bmds;
uint64_t sum = 0;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
sum += bmds->total_sectors;
}
return sum << BDRV_SECTOR_BITS;
}
static inline long double compute_read_bwidth(void)
{
assert(block_mig_state.total_time != 0);
return (block_mig_state.reads / block_mig_state.total_time) * BLOCK_SIZE;
}
static int bmds_aio_inflight(BlkMigDevState *bmds, int64_t sector)
{
int64_t chunk = sector / (int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK;
if ((sector << BDRV_SECTOR_BITS) < bdrv_getlength(bmds->bs)) {
return !!(bmds->aio_bitmap[chunk / (sizeof(unsigned long) * 8)] &
(1UL << (chunk % (sizeof(unsigned long) * 8))));
} else {
return 0;
}
}
static void bmds_set_aio_inflight(BlkMigDevState *bmds, int64_t sector_num,
int nb_sectors, int set)
{
int64_t start, end;
unsigned long val, idx, bit;
start = sector_num / BDRV_SECTORS_PER_DIRTY_CHUNK;
end = (sector_num + nb_sectors - 1) / BDRV_SECTORS_PER_DIRTY_CHUNK;
for (; start <= end; start++) {
idx = start / (sizeof(unsigned long) * 8);
bit = start % (sizeof(unsigned long) * 8);
val = bmds->aio_bitmap[idx];
if (set) {
val |= 1UL << bit;
} else {
val &= ~(1UL << bit);
}
bmds->aio_bitmap[idx] = val;
}
}
static void alloc_aio_bitmap(BlkMigDevState *bmds)
{
BlockDriverState *bs = bmds->bs;
int64_t bitmap_size;
bitmap_size = (bdrv_getlength(bs) >> BDRV_SECTOR_BITS) +
BDRV_SECTORS_PER_DIRTY_CHUNK * 8 - 1;
bitmap_size /= BDRV_SECTORS_PER_DIRTY_CHUNK * 8;
bmds->aio_bitmap = qemu_mallocz(bitmap_size);
}
static void blk_mig_read_cb(void *opaque, int ret)
{
long double curr_time = qemu_get_clock_ns(rt_clock);
BlkMigBlock *blk = opaque;
blk->ret = ret;
block_mig_state.reads++;
block_mig_state.total_time += (curr_time - block_mig_state.prev_time_offset);
block_mig_state.prev_time_offset = curr_time;
QSIMPLEQ_INSERT_TAIL(&block_mig_state.blk_list, blk, entry);
bmds_set_aio_inflight(blk->bmds, blk->sector, blk->nr_sectors, 0);
block_mig_state.submitted--;
block_mig_state.read_done++;
assert(block_mig_state.submitted >= 0);
}
static int mig_save_device_bulk(Monitor *mon, QEMUFile *f,
BlkMigDevState *bmds)
{
int64_t total_sectors = bmds->total_sectors;
int64_t cur_sector = bmds->cur_sector;
BlockDriverState *bs = bmds->bs;
BlkMigBlock *blk;
int nr_sectors;
if (bmds->shared_base) {
while (cur_sector < total_sectors &&
!bdrv_is_allocated(bs, cur_sector, MAX_IS_ALLOCATED_SEARCH,
&nr_sectors)) {
cur_sector += nr_sectors;
}
}
if (cur_sector >= total_sectors) {
bmds->cur_sector = bmds->completed_sectors = total_sectors;
return 1;
}
bmds->completed_sectors = cur_sector;
cur_sector &= ~((int64_t)BDRV_SECTORS_PER_DIRTY_CHUNK - 1);
/* we are going to transfer a full block even if it is not allocated */
nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
if (total_sectors - cur_sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
nr_sectors = total_sectors - cur_sector;
}
blk = qemu_malloc(sizeof(BlkMigBlock));
blk->buf = qemu_malloc(BLOCK_SIZE);
blk->bmds = bmds;
blk->sector = cur_sector;
blk->nr_sectors = nr_sectors;
blk->iov.iov_base = blk->buf;
blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);
if (block_mig_state.submitted == 0) {
block_mig_state.prev_time_offset = qemu_get_clock_ns(rt_clock);
}
blk->aiocb = bdrv_aio_readv(bs, cur_sector, &blk->qiov,
nr_sectors, blk_mig_read_cb, blk);
if (!blk->aiocb) {
goto error;
}
block_mig_state.submitted++;
bdrv_reset_dirty(bs, cur_sector, nr_sectors);
bmds->cur_sector = cur_sector + nr_sectors;
return (bmds->cur_sector >= total_sectors);
error:
monitor_printf(mon, "Error reading sector %" PRId64 "\n", cur_sector);
qemu_file_set_error(f);
qemu_free(blk->buf);
qemu_free(blk);
return 0;
}
static void set_dirty_tracking(int enable)
{
BlkMigDevState *bmds;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
bdrv_set_dirty_tracking(bmds->bs, enable);
}
}
static void init_blk_migration_it(void *opaque, BlockDriverState *bs)
{
Monitor *mon = opaque;
BlkMigDevState *bmds;
int64_t sectors;
if (!bdrv_is_read_only(bs)) {
sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
if (sectors <= 0) {
return;
}
bmds = qemu_mallocz(sizeof(BlkMigDevState));
bmds->bs = bs;
bmds->bulk_completed = 0;
bmds->total_sectors = sectors;
bmds->completed_sectors = 0;
bmds->shared_base = block_mig_state.shared_base;
alloc_aio_bitmap(bmds);
drive_get_ref(drive_get_by_blockdev(bs));
bdrv_set_in_use(bs, 1);
block_mig_state.total_sector_sum += sectors;
if (bmds->shared_base) {
monitor_printf(mon, "Start migration for %s with shared base "
"image\n",
bs->device_name);
} else {
monitor_printf(mon, "Start full migration for %s\n",
bs->device_name);
}
QSIMPLEQ_INSERT_TAIL(&block_mig_state.bmds_list, bmds, entry);
}
}
static void init_blk_migration(Monitor *mon, QEMUFile *f)
{
block_mig_state.submitted = 0;
block_mig_state.read_done = 0;
block_mig_state.transferred = 0;
block_mig_state.total_sector_sum = 0;
block_mig_state.prev_progress = -1;
block_mig_state.bulk_completed = 0;
block_mig_state.total_time = 0;
block_mig_state.reads = 0;
bdrv_iterate(init_blk_migration_it, mon);
}
static int blk_mig_save_bulked_block(Monitor *mon, QEMUFile *f)
{
int64_t completed_sector_sum = 0;
BlkMigDevState *bmds;
int progress;
int ret = 0;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
if (bmds->bulk_completed == 0) {
if (mig_save_device_bulk(mon, f, bmds) == 1) {
/* completed bulk section for this device */
bmds->bulk_completed = 1;
}
completed_sector_sum += bmds->completed_sectors;
ret = 1;
break;
} else {
completed_sector_sum += bmds->completed_sectors;
}
}
if (block_mig_state.total_sector_sum != 0) {
progress = completed_sector_sum * 100 /
block_mig_state.total_sector_sum;
} else {
progress = 100;
}
if (progress != block_mig_state.prev_progress) {
block_mig_state.prev_progress = progress;
qemu_put_be64(f, (progress << BDRV_SECTOR_BITS)
| BLK_MIG_FLAG_PROGRESS);
monitor_printf(mon, "Completed %d %%\r", progress);
monitor_flush(mon);
}
return ret;
}
static void blk_mig_reset_dirty_cursor(void)
{
BlkMigDevState *bmds;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
bmds->cur_dirty = 0;
}
}
static int mig_save_device_dirty(Monitor *mon, QEMUFile *f,
BlkMigDevState *bmds, int is_async)
{
BlkMigBlock *blk;
int64_t total_sectors = bmds->total_sectors;
int64_t sector;
int nr_sectors;
for (sector = bmds->cur_dirty; sector < bmds->total_sectors;) {
if (bmds_aio_inflight(bmds, sector)) {
qemu_aio_flush();
}
if (bdrv_get_dirty(bmds->bs, sector)) {
if (total_sectors - sector < BDRV_SECTORS_PER_DIRTY_CHUNK) {
nr_sectors = total_sectors - sector;
} else {
nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
}
blk = qemu_malloc(sizeof(BlkMigBlock));
blk->buf = qemu_malloc(BLOCK_SIZE);
blk->bmds = bmds;
blk->sector = sector;
blk->nr_sectors = nr_sectors;
if (is_async) {
blk->iov.iov_base = blk->buf;
blk->iov.iov_len = nr_sectors * BDRV_SECTOR_SIZE;
qemu_iovec_init_external(&blk->qiov, &blk->iov, 1);
if (block_mig_state.submitted == 0) {
block_mig_state.prev_time_offset = qemu_get_clock_ns(rt_clock);
}
blk->aiocb = bdrv_aio_readv(bmds->bs, sector, &blk->qiov,
nr_sectors, blk_mig_read_cb, blk);
if (!blk->aiocb) {
goto error;
}
block_mig_state.submitted++;
bmds_set_aio_inflight(bmds, sector, nr_sectors, 1);
} else {
if (bdrv_read(bmds->bs, sector, blk->buf,
nr_sectors) < 0) {
goto error;
}
blk_send(f, blk);
qemu_free(blk->buf);
qemu_free(blk);
}
bdrv_reset_dirty(bmds->bs, sector, nr_sectors);
break;
}
sector += BDRV_SECTORS_PER_DIRTY_CHUNK;
bmds->cur_dirty = sector;
}
return (bmds->cur_dirty >= bmds->total_sectors);
error:
monitor_printf(mon, "Error reading sector %" PRId64 "\n", sector);
qemu_file_set_error(f);
qemu_free(blk->buf);
qemu_free(blk);
return 0;
}
static int blk_mig_save_dirty_block(Monitor *mon, QEMUFile *f, int is_async)
{
BlkMigDevState *bmds;
int ret = 0;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
if (mig_save_device_dirty(mon, f, bmds, is_async) == 0) {
ret = 1;
break;
}
}
return ret;
}
static void flush_blks(QEMUFile* f)
{
BlkMigBlock *blk;
DPRINTF("%s Enter submitted %d read_done %d transferred %d\n",
__FUNCTION__, block_mig_state.submitted, block_mig_state.read_done,
block_mig_state.transferred);
while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
if (qemu_file_rate_limit(f)) {
break;
}
if (blk->ret < 0) {
qemu_file_set_error(f);
break;
}
blk_send(f, blk);
QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);
qemu_free(blk->buf);
qemu_free(blk);
block_mig_state.read_done--;
block_mig_state.transferred++;
assert(block_mig_state.read_done >= 0);
}
DPRINTF("%s Exit submitted %d read_done %d transferred %d\n", __FUNCTION__,
block_mig_state.submitted, block_mig_state.read_done,
block_mig_state.transferred);
}
static int64_t get_remaining_dirty(void)
{
BlkMigDevState *bmds;
int64_t dirty = 0;
QSIMPLEQ_FOREACH(bmds, &block_mig_state.bmds_list, entry) {
dirty += bdrv_get_dirty_count(bmds->bs);
}
return dirty * BLOCK_SIZE;
}
static int is_stage2_completed(void)
{
int64_t remaining_dirty;
long double bwidth;
if (block_mig_state.bulk_completed == 1) {
remaining_dirty = get_remaining_dirty();
if (remaining_dirty == 0) {
return 1;
}
bwidth = compute_read_bwidth();
if ((remaining_dirty / bwidth) <=
migrate_max_downtime()) {
/* finish stage2 because we think that we can finish remaing work
below max_downtime */
return 1;
}
}
return 0;
}
static void blk_mig_cleanup(Monitor *mon)
{
BlkMigDevState *bmds;
BlkMigBlock *blk;
set_dirty_tracking(0);
while ((bmds = QSIMPLEQ_FIRST(&block_mig_state.bmds_list)) != NULL) {
QSIMPLEQ_REMOVE_HEAD(&block_mig_state.bmds_list, entry);
bdrv_set_in_use(bmds->bs, 0);
drive_put_ref(drive_get_by_blockdev(bmds->bs));
qemu_free(bmds->aio_bitmap);
qemu_free(bmds);
}
while ((blk = QSIMPLEQ_FIRST(&block_mig_state.blk_list)) != NULL) {
QSIMPLEQ_REMOVE_HEAD(&block_mig_state.blk_list, entry);
qemu_free(blk->buf);
qemu_free(blk);
}
monitor_printf(mon, "\n");
}
static int block_save_live(Monitor *mon, QEMUFile *f, int stage, void *opaque)
{
DPRINTF("Enter save live stage %d submitted %d transferred %d\n",
stage, block_mig_state.submitted, block_mig_state.transferred);
if (stage < 0) {
blk_mig_cleanup(mon);
return 0;
}
if (block_mig_state.blk_enable != 1) {
/* no need to migrate storage */
qemu_put_be64(f, BLK_MIG_FLAG_EOS);
return 1;
}
if (stage == 1) {
init_blk_migration(mon, f);
/* start track dirty blocks */
set_dirty_tracking(1);
}
flush_blks(f);
if (qemu_file_has_error(f)) {
blk_mig_cleanup(mon);
return 0;
}
blk_mig_reset_dirty_cursor();
if (stage == 2) {
/* control the rate of transfer */
while ((block_mig_state.submitted +
block_mig_state.read_done) * BLOCK_SIZE <
qemu_file_get_rate_limit(f)) {
if (block_mig_state.bulk_completed == 0) {
/* first finish the bulk phase */
if (blk_mig_save_bulked_block(mon, f) == 0) {
/* finished saving bulk on all devices */
block_mig_state.bulk_completed = 1;
}
} else {
if (blk_mig_save_dirty_block(mon, f, 1) == 0) {
/* no more dirty blocks */
break;
}
}
}
flush_blks(f);
if (qemu_file_has_error(f)) {
blk_mig_cleanup(mon);
return 0;
}
}
if (stage == 3) {
/* we know for sure that save bulk is completed and
all async read completed */
assert(block_mig_state.submitted == 0);
while (blk_mig_save_dirty_block(mon, f, 0) != 0);
blk_mig_cleanup(mon);
/* report completion */
qemu_put_be64(f, (100 << BDRV_SECTOR_BITS) | BLK_MIG_FLAG_PROGRESS);
if (qemu_file_has_error(f)) {
return 0;
}
monitor_printf(mon, "Block migration completed\n");
}
qemu_put_be64(f, BLK_MIG_FLAG_EOS);
return ((stage == 2) && is_stage2_completed());
}
static int block_load(QEMUFile *f, void *opaque, int version_id)
{
static int banner_printed;
int len, flags;
char device_name[256];
int64_t addr;
BlockDriverState *bs, *bs_prev = NULL;
uint8_t *buf;
int64_t total_sectors = 0;
int nr_sectors;
do {
addr = qemu_get_be64(f);
flags = addr & ~BDRV_SECTOR_MASK;
addr >>= BDRV_SECTOR_BITS;
if (flags & BLK_MIG_FLAG_DEVICE_BLOCK) {
int ret;
/* get device name */
len = qemu_get_byte(f);
qemu_get_buffer(f, (uint8_t *)device_name, len);
device_name[len] = '\0';
bs = bdrv_find(device_name);
if (!bs) {
fprintf(stderr, "Error unknown block device %s\n",
device_name);
return -EINVAL;
}
if (bs != bs_prev) {
bs_prev = bs;
total_sectors = bdrv_getlength(bs) >> BDRV_SECTOR_BITS;
if (total_sectors <= 0) {
error_report("Error getting length of block device %s\n",
device_name);
return -EINVAL;
}
}
if (total_sectors - addr < BDRV_SECTORS_PER_DIRTY_CHUNK) {
nr_sectors = total_sectors - addr;
} else {
nr_sectors = BDRV_SECTORS_PER_DIRTY_CHUNK;
}
buf = qemu_malloc(BLOCK_SIZE);
qemu_get_buffer(f, buf, BLOCK_SIZE);
ret = bdrv_write(bs, addr, buf, nr_sectors);
qemu_free(buf);
if (ret < 0) {
return ret;
}
} else if (flags & BLK_MIG_FLAG_PROGRESS) {
if (!banner_printed) {
printf("Receiving block device images\n");
banner_printed = 1;
}
printf("Completed %d %%%c", (int)addr,
(addr == 100) ? '\n' : '\r');
fflush(stdout);
} else if (!(flags & BLK_MIG_FLAG_EOS)) {
fprintf(stderr, "Unknown flags\n");
return -EINVAL;
}
if (qemu_file_has_error(f)) {
return -EIO;
}
} while (!(flags & BLK_MIG_FLAG_EOS));
return 0;
}
static void block_set_params(int blk_enable, int shared_base, void *opaque)
{
block_mig_state.blk_enable = blk_enable;
block_mig_state.shared_base = shared_base;
/* shared base means that blk_enable = 1 */
block_mig_state.blk_enable |= shared_base;
}
void blk_mig_init(void)
{
QSIMPLEQ_INIT(&block_mig_state.bmds_list);
QSIMPLEQ_INIT(&block_mig_state.blk_list);
register_savevm_live(NULL, "block", 0, 1, block_set_params,
block_save_live, NULL, block_load, &block_mig_state);
}
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