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authorZhi Yong Wu <wuzhy@linux.vnet.ibm.com>2011-11-08 13:00:14 +0800
committerKevin Wolf <kwolf@redhat.com>2011-12-05 14:51:35 +0100
commit98f90dba5ee56f699b28509a6cc7a9a8a57636eb (patch)
treec84af5d910421cad50039d1cb45756a0250e3e2b
parente9e6295b28b331762e67d466f77ba07a349edbbc (diff)
downloadqemu-arm-98f90dba5ee56f699b28509a6cc7a9a8a57636eb.tar.gz
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>
-rw-r--r--block.c234
-rw-r--r--block.h1
-rw-r--r--block_int.h1
3 files changed, 236 insertions, 0 deletions
diff --git a/block.c b/block.c
index 8cb41c0b41..42bd308639 100644
--- a/block.c
+++ b/block.c
@@ -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 */
diff --git a/block.h b/block.h
index 2d244088c3..83e17cad96 100644
--- a/block.h
+++ b/block.h
@@ -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);
diff --git a/block_int.h b/block_int.h
index 97b1c2be54..e2799e4f6b 100644
--- a/block_int.h
+++ b/block_int.h
@@ -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"