Commit 98f90dba authored by Zhi Yong Wu's avatar Zhi Yong Wu Committed by Kevin Wolf
Browse files

block: add I/O throttling algorithm 



Signed-off-by: default avatarZhi Yong Wu <wuzhy@linux.vnet.ibm.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent e9e6295b

block.c

+234 −0
Original line number Diff line number Diff line
@@ -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 */

block.h

+1 −0
Original line number Diff line number Diff line
@@ -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);

block_int.h

+1 −0
Original line number Diff line number Diff line
@@ -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"