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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
Kevin Wolf
parent
e9e6295b28
commit
98f90dba5e
234
block.c
234
block.c
@ -74,6 +74,13 @@ static BlockDriverAIOCB *bdrv_co_aio_rw_vector(BlockDriverState *bs,
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bool is_write);
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static void coroutine_fn bdrv_co_do_rw(void *opaque);
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static bool bdrv_exceed_bps_limits(BlockDriverState *bs, int nb_sectors,
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bool is_write, double elapsed_time, uint64_t *wait);
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static bool bdrv_exceed_iops_limits(BlockDriverState *bs, bool is_write,
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double elapsed_time, uint64_t *wait);
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static bool bdrv_exceed_io_limits(BlockDriverState *bs, int nb_sectors,
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bool is_write, int64_t *wait);
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static QTAILQ_HEAD(, BlockDriverState) bdrv_states =
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QTAILQ_HEAD_INITIALIZER(bdrv_states);
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@ -107,6 +114,24 @@ int is_windows_drive(const char *filename)
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#endif
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/* throttling disk I/O limits */
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void bdrv_io_limits_disable(BlockDriverState *bs)
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{
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bs->io_limits_enabled = false;
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while (qemu_co_queue_next(&bs->throttled_reqs));
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if (bs->block_timer) {
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qemu_del_timer(bs->block_timer);
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qemu_free_timer(bs->block_timer);
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bs->block_timer = NULL;
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}
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bs->slice_start = 0;
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bs->slice_end = 0;
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bs->slice_time = 0;
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memset(&bs->io_base, 0, sizeof(bs->io_base));
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}
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static void bdrv_block_timer(void *opaque)
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{
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BlockDriverState *bs = opaque;
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@ -136,6 +161,31 @@ bool bdrv_io_limits_enabled(BlockDriverState *bs)
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|| io_limits->iops[BLOCK_IO_LIMIT_TOTAL];
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}
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static void bdrv_io_limits_intercept(BlockDriverState *bs,
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bool is_write, int nb_sectors)
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{
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int64_t wait_time = -1;
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if (!qemu_co_queue_empty(&bs->throttled_reqs)) {
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qemu_co_queue_wait(&bs->throttled_reqs);
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}
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/* In fact, we hope to keep each request's timing, in FIFO mode. The next
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* throttled requests will not be dequeued until the current request is
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* allowed to be serviced. So if the current request still exceeds the
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* limits, it will be inserted to the head. All requests followed it will
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* be still in throttled_reqs queue.
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*/
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while (bdrv_exceed_io_limits(bs, nb_sectors, is_write, &wait_time)) {
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qemu_mod_timer(bs->block_timer,
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wait_time + qemu_get_clock_ns(vm_clock));
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qemu_co_queue_wait_insert_head(&bs->throttled_reqs);
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}
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qemu_co_queue_next(&bs->throttled_reqs);
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}
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/* check if the path starts with "<protocol>:" */
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static int path_has_protocol(const char *path)
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{
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@ -718,6 +768,11 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
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bdrv_dev_change_media_cb(bs, true);
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}
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/* throttling disk I/O limits */
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if (bs->io_limits_enabled) {
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bdrv_io_limits_enable(bs);
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}
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return 0;
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unlink_and_fail:
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@ -753,6 +808,11 @@ void bdrv_close(BlockDriverState *bs)
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bdrv_dev_change_media_cb(bs, false);
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}
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/*throttling disk I/O limits*/
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if (bs->io_limits_enabled) {
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bdrv_io_limits_disable(bs);
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}
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}
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void bdrv_close_all(void)
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@ -1298,6 +1358,11 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
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return -EIO;
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}
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/* throttling disk read I/O */
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if (bs->io_limits_enabled) {
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bdrv_io_limits_intercept(bs, false, nb_sectors);
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}
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return drv->bdrv_co_readv(bs, sector_num, nb_sectors, qiov);
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}
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@ -1328,6 +1393,11 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
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return -EIO;
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}
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/* throttling disk write I/O */
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if (bs->io_limits_enabled) {
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bdrv_io_limits_intercept(bs, true, nb_sectors);
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}
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ret = drv->bdrv_co_writev(bs, sector_num, nb_sectors, qiov);
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if (bs->dirty_bitmap) {
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@ -2519,6 +2589,170 @@ void bdrv_aio_cancel(BlockDriverAIOCB *acb)
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acb->pool->cancel(acb);
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}
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/* block I/O throttling */
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static bool bdrv_exceed_bps_limits(BlockDriverState *bs, int nb_sectors,
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bool is_write, double elapsed_time, uint64_t *wait)
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{
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uint64_t bps_limit = 0;
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double bytes_limit, bytes_base, bytes_res;
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double slice_time, wait_time;
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if (bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL]) {
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bps_limit = bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL];
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} else if (bs->io_limits.bps[is_write]) {
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bps_limit = bs->io_limits.bps[is_write];
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} else {
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if (wait) {
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*wait = 0;
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}
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return false;
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}
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slice_time = bs->slice_end - bs->slice_start;
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slice_time /= (NANOSECONDS_PER_SECOND);
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bytes_limit = bps_limit * slice_time;
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bytes_base = bs->nr_bytes[is_write] - bs->io_base.bytes[is_write];
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if (bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL]) {
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bytes_base += bs->nr_bytes[!is_write] - bs->io_base.bytes[!is_write];
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}
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/* bytes_base: the bytes of data which have been read/written; and
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* it is obtained from the history statistic info.
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* bytes_res: the remaining bytes of data which need to be read/written.
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* (bytes_base + bytes_res) / bps_limit: used to calcuate
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* the total time for completing reading/writting all data.
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*/
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bytes_res = (unsigned) nb_sectors * BDRV_SECTOR_SIZE;
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if (bytes_base + bytes_res <= bytes_limit) {
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if (wait) {
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*wait = 0;
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}
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return false;
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}
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/* Calc approx time to dispatch */
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wait_time = (bytes_base + bytes_res) / bps_limit - elapsed_time;
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/* When the I/O rate at runtime exceeds the limits,
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* bs->slice_end need to be extended in order that the current statistic
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* info can be kept until the timer fire, so it is increased and tuned
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* based on the result of experiment.
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*/
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bs->slice_time = wait_time * BLOCK_IO_SLICE_TIME * 10;
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bs->slice_end += bs->slice_time - 3 * BLOCK_IO_SLICE_TIME;
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if (wait) {
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*wait = wait_time * BLOCK_IO_SLICE_TIME * 10;
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}
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return true;
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}
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static bool bdrv_exceed_iops_limits(BlockDriverState *bs, bool is_write,
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double elapsed_time, uint64_t *wait)
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{
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uint64_t iops_limit = 0;
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double ios_limit, ios_base;
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double slice_time, wait_time;
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if (bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL]) {
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iops_limit = bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL];
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} else if (bs->io_limits.iops[is_write]) {
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iops_limit = bs->io_limits.iops[is_write];
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} else {
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if (wait) {
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*wait = 0;
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}
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return false;
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}
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slice_time = bs->slice_end - bs->slice_start;
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slice_time /= (NANOSECONDS_PER_SECOND);
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ios_limit = iops_limit * slice_time;
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ios_base = bs->nr_ops[is_write] - bs->io_base.ios[is_write];
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if (bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL]) {
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ios_base += bs->nr_ops[!is_write] - bs->io_base.ios[!is_write];
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}
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if (ios_base + 1 <= ios_limit) {
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if (wait) {
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*wait = 0;
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}
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return false;
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}
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/* Calc approx time to dispatch */
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wait_time = (ios_base + 1) / iops_limit;
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if (wait_time > elapsed_time) {
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wait_time = wait_time - elapsed_time;
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} else {
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wait_time = 0;
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}
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bs->slice_time = wait_time * BLOCK_IO_SLICE_TIME * 10;
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bs->slice_end += bs->slice_time - 3 * BLOCK_IO_SLICE_TIME;
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if (wait) {
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*wait = wait_time * BLOCK_IO_SLICE_TIME * 10;
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}
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return true;
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}
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static bool bdrv_exceed_io_limits(BlockDriverState *bs, int nb_sectors,
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bool is_write, int64_t *wait)
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{
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int64_t now, max_wait;
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uint64_t bps_wait = 0, iops_wait = 0;
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double elapsed_time;
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int bps_ret, iops_ret;
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now = qemu_get_clock_ns(vm_clock);
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if ((bs->slice_start < now)
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&& (bs->slice_end > now)) {
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bs->slice_end = now + bs->slice_time;
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} else {
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bs->slice_time = 5 * BLOCK_IO_SLICE_TIME;
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bs->slice_start = now;
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bs->slice_end = now + bs->slice_time;
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bs->io_base.bytes[is_write] = bs->nr_bytes[is_write];
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bs->io_base.bytes[!is_write] = bs->nr_bytes[!is_write];
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bs->io_base.ios[is_write] = bs->nr_ops[is_write];
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bs->io_base.ios[!is_write] = bs->nr_ops[!is_write];
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}
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elapsed_time = now - bs->slice_start;
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elapsed_time /= (NANOSECONDS_PER_SECOND);
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bps_ret = bdrv_exceed_bps_limits(bs, nb_sectors,
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is_write, elapsed_time, &bps_wait);
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iops_ret = bdrv_exceed_iops_limits(bs, is_write,
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elapsed_time, &iops_wait);
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if (bps_ret || iops_ret) {
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max_wait = bps_wait > iops_wait ? bps_wait : iops_wait;
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if (wait) {
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*wait = max_wait;
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}
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now = qemu_get_clock_ns(vm_clock);
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if (bs->slice_end < now + max_wait) {
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bs->slice_end = now + max_wait;
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}
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return true;
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}
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if (wait) {
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*wait = 0;
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}
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return false;
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}
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/**************************************************************/
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/* async block device emulation */
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1
block.h
1
block.h
@ -100,6 +100,7 @@ void bdrv_info_stats(Monitor *mon, QObject **ret_data);
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/* disk I/O throttling */
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void bdrv_io_limits_enable(BlockDriverState *bs);
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void bdrv_io_limits_disable(BlockDriverState *bs);
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bool bdrv_io_limits_enabled(BlockDriverState *bs);
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void bdrv_init(void);
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@ -39,6 +39,7 @@
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#define BLOCK_IO_LIMIT_TOTAL 2
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#define BLOCK_IO_SLICE_TIME 100000000
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#define NANOSECONDS_PER_SECOND 1000000000.0
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#define BLOCK_OPT_SIZE "size"
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#define BLOCK_OPT_ENCRYPT "encryption"
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