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block: add I/O throttling algorithm 

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Zhi Yong Wu 2011-11-08 13:00:14 +08:00 committed by Kevin Wolf
parent e9e6295b28
commit 98f90dba5e
3 changed files with 236 additions and 0 deletions
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234
block.c
View File

@ -74,6 +74,13 @@ static BlockDriverAIOCB *bdrv_co_aio_rw_vector(BlockDriverState *bs,
bool is_write);
static void coroutine_fn bdrv_co_do_rw(void *opaque);
static bool bdrv_exceed_bps_limits(BlockDriverState *bs, int nb_sectors,
bool is_write, double elapsed_time, uint64_t *wait);
static bool bdrv_exceed_iops_limits(BlockDriverState *bs, bool is_write,
double elapsed_time, uint64_t *wait);
static bool bdrv_exceed_io_limits(BlockDriverState *bs, int nb_sectors,
bool is_write, int64_t *wait);
static QTAILQ_HEAD(, BlockDriverState) bdrv_states =
QTAILQ_HEAD_INITIALIZER(bdrv_states);
@ -107,6 +114,24 @@ int is_windows_drive(const char *filename)
#endif
/* throttling disk I/O limits */
void bdrv_io_limits_disable(BlockDriverState *bs)
{
bs->io_limits_enabled = false;
while (qemu_co_queue_next(&bs->throttled_reqs));
if (bs->block_timer) {
qemu_del_timer(bs->block_timer);
qemu_free_timer(bs->block_timer);
bs->block_timer = NULL;
}
bs->slice_start = 0;
bs->slice_end = 0;
bs->slice_time = 0;
memset(&bs->io_base, 0, sizeof(bs->io_base));
}
static void bdrv_block_timer(void *opaque)
{
BlockDriverState *bs = opaque;
@ -136,6 +161,31 @@ bool bdrv_io_limits_enabled(BlockDriverState *bs)
|| io_limits->iops[BLOCK_IO_LIMIT_TOTAL];
}
static void bdrv_io_limits_intercept(BlockDriverState *bs,
bool is_write, int nb_sectors)
{
int64_t wait_time = -1;
if (!qemu_co_queue_empty(&bs->throttled_reqs)) {
qemu_co_queue_wait(&bs->throttled_reqs);
}
/* In fact, we hope to keep each request's timing, in FIFO mode. The next
* throttled requests will not be dequeued until the current request is
* allowed to be serviced. So if the current request still exceeds the
* limits, it will be inserted to the head. All requests followed it will
* be still in throttled_reqs queue.
*/
while (bdrv_exceed_io_limits(bs, nb_sectors, is_write, &wait_time)) {
qemu_mod_timer(bs->block_timer,
wait_time + qemu_get_clock_ns(vm_clock));
qemu_co_queue_wait_insert_head(&bs->throttled_reqs);
}
qemu_co_queue_next(&bs->throttled_reqs);
}
/* check if the path starts with "<protocol>:" */
static int path_has_protocol(const char *path)
{
@ -718,6 +768,11 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
bdrv_dev_change_media_cb(bs, true);
}
/* throttling disk I/O limits */
if (bs->io_limits_enabled) {
bdrv_io_limits_enable(bs);
}
return 0;
unlink_and_fail:
@ -753,6 +808,11 @@ void bdrv_close(BlockDriverState *bs)
bdrv_dev_change_media_cb(bs, false);
}
/*throttling disk I/O limits*/
if (bs->io_limits_enabled) {
bdrv_io_limits_disable(bs);
}
}
void bdrv_close_all(void)
@ -1298,6 +1358,11 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
return -EIO;
}
/* throttling disk read I/O */
if (bs->io_limits_enabled) {
bdrv_io_limits_intercept(bs, false, nb_sectors);
}
return drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
}
@ -1328,6 +1393,11 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
return -EIO;
}
/* throttling disk write I/O */
if (bs->io_limits_enabled) {
bdrv_io_limits_intercept(bs, true, nb_sectors);
}
ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov);
if (bs->dirty_bitmap) {
@ -2519,6 +2589,170 @@ void bdrv_aio_cancel(BlockDriverAIOCB *acb)
acb->pool->cancel(acb);
}
/* block I/O throttling */
static bool bdrv_exceed_bps_limits(BlockDriverState *bs, int nb_sectors,
bool is_write, double elapsed_time, uint64_t *wait)
{
uint64_t bps_limit = 0;
double bytes_limit, bytes_base, bytes_res;
double slice_time, wait_time;
if (bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL]) {
bps_limit = bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL];
} else if (bs->io_limits.bps[is_write]) {
bps_limit = bs->io_limits.bps[is_write];
} else {
if (wait) {
*wait = 0;
}
return false;
}
slice_time = bs->slice_end - bs->slice_start;
slice_time /= (NANOSECONDS_PER_SECOND);
bytes_limit = bps_limit * slice_time;
bytes_base = bs->nr_bytes[is_write] - bs->io_base.bytes[is_write];
if (bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL]) {
bytes_base += bs->nr_bytes[!is_write] - bs->io_base.bytes[!is_write];
}
/* bytes_base: the bytes of data which have been read/written; and
* it is obtained from the history statistic info.
* bytes_res: the remaining bytes of data which need to be read/written.
* (bytes_base + bytes_res) / bps_limit: used to calcuate
* the total time for completing reading/writting all data.
*/
bytes_res = (unsigned) nb_sectors * BDRV_SECTOR_SIZE;
if (bytes_base + bytes_res <= bytes_limit) {
if (wait) {
*wait = 0;
}
return false;
}
/* Calc approx time to dispatch */
wait_time = (bytes_base + bytes_res) / bps_limit - elapsed_time;
/* When the I/O rate at runtime exceeds the limits,
* bs->slice_end need to be extended in order that the current statistic
* info can be kept until the timer fire, so it is increased and tuned
* based on the result of experiment.
*/
bs->slice_time = wait_time * BLOCK_IO_SLICE_TIME * 10;
bs->slice_end += bs->slice_time - 3 * BLOCK_IO_SLICE_TIME;
if (wait) {
*wait = wait_time * BLOCK_IO_SLICE_TIME * 10;
}
return true;
}
static bool bdrv_exceed_iops_limits(BlockDriverState *bs, bool is_write,
double elapsed_time, uint64_t *wait)
{
uint64_t iops_limit = 0;
double ios_limit, ios_base;
double slice_time, wait_time;
if (bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL]) {
iops_limit = bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL];
} else if (bs->io_limits.iops[is_write]) {
iops_limit = bs->io_limits.iops[is_write];
} else {
if (wait) {
*wait = 0;
}
return false;
}
slice_time = bs->slice_end - bs->slice_start;
slice_time /= (NANOSECONDS_PER_SECOND);
ios_limit = iops_limit * slice_time;
ios_base = bs->nr_ops[is_write] - bs->io_base.ios[is_write];
if (bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL]) {
ios_base += bs->nr_ops[!is_write] - bs->io_base.ios[!is_write];
}
if (ios_base + 1 <= ios_limit) {
if (wait) {
*wait = 0;
}
return false;
}
/* Calc approx time to dispatch */
wait_time = (ios_base + 1) / iops_limit;
if (wait_time > elapsed_time) {
wait_time = wait_time - elapsed_time;
} else {
wait_time = 0;
}
bs->slice_time = wait_time * BLOCK_IO_SLICE_TIME * 10;
bs->slice_end += bs->slice_time - 3 * BLOCK_IO_SLICE_TIME;
if (wait) {
*wait = wait_time * BLOCK_IO_SLICE_TIME * 10;
}
return true;
}
static bool bdrv_exceed_io_limits(BlockDriverState *bs, int nb_sectors,
bool is_write, int64_t *wait)
{
int64_t now, max_wait;
uint64_t bps_wait = 0, iops_wait = 0;
double elapsed_time;
int bps_ret, iops_ret;
now = qemu_get_clock_ns(vm_clock);
if ((bs->slice_start < now)
&& (bs->slice_end > now)) {
bs->slice_end = now + bs->slice_time;
} else {
bs->slice_time = 5 * BLOCK_IO_SLICE_TIME;
bs->slice_start = now;
bs->slice_end = now + bs->slice_time;
bs->io_base.bytes[is_write] = bs->nr_bytes[is_write];
bs->io_base.bytes[!is_write] = bs->nr_bytes[!is_write];
bs->io_base.ios[is_write] = bs->nr_ops[is_write];
bs->io_base.ios[!is_write] = bs->nr_ops[!is_write];
}
elapsed_time = now - bs->slice_start;
elapsed_time /= (NANOSECONDS_PER_SECOND);
bps_ret = bdrv_exceed_bps_limits(bs, nb_sectors,
is_write, elapsed_time, &bps_wait);
iops_ret = bdrv_exceed_iops_limits(bs, is_write,
elapsed_time, &iops_wait);
if (bps_ret || iops_ret) {
max_wait = bps_wait > iops_wait ? bps_wait : iops_wait;
if (wait) {
*wait = max_wait;
}
now = qemu_get_clock_ns(vm_clock);
if (bs->slice_end < now + max_wait) {
bs->slice_end = now + max_wait;
}
return true;
}
if (wait) {
*wait = 0;
}
return false;
}
/**************************************************************/
/* async block device emulation */

1
block.h
View File

@ -100,6 +100,7 @@ void bdrv_info_stats(Monitor *mon, QObject **ret_data);
/* disk I/O throttling */
void bdrv_io_limits_enable(BlockDriverState *bs);
void bdrv_io_limits_disable(BlockDriverState *bs);
bool bdrv_io_limits_enabled(BlockDriverState *bs);
void bdrv_init(void);

1
block_int.h
View File

@ -39,6 +39,7 @@
#define BLOCK_IO_LIMIT_TOTAL 2
#define BLOCK_IO_SLICE_TIME 100000000
#define NANOSECONDS_PER_SECOND 1000000000.0
#define BLOCK_OPT_SIZE "size"
#define BLOCK_OPT_ENCRYPT "encryption"