Re: [Qemu-devel] [PATCH V3 for-1.6 2/5] block: Modify the throttling code to implement the leaky bucket algorithm.

["Benoît Canet" <benoit.canet@irqsave.net>]

> I think it is easier to understand written like this:
> 
>            int64_t total_leak = ((bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL] * delta) /
>                           NANOSECONDS_PER_SECOND);
>            if (ios[BLOCK_IO_LIMIT_READ] <= total_leak / 2) {
>               read_leak = ios[BLOCK_IO_LIMIT_READ];
>               write_leak = total_leak - read_leak;
>            /* symetric case */
>            } else if (ios[BLOCK_IO_LIMIT_WRITE] <= total_leak / 2) {
>               write_leak = ios[BLOCK_IO_LIMIT_WRITE];
>               read_leak = total_leak - write_leak;
>            /* both bucket above leak count use half the total leak for both */
>            } else {
>               write_leak = total_leak / 2;
>               read_leak = (total_leak + 1) / 2;
>            }

Thanks,
I will propagate these changes in the new infinite HZ algorithm I am currently
writing.

> 
> > +    /* else we consider that limits are separated */
> > +    } else {
> > +        read_leak = (bs->io_limits.iops[BLOCK_IO_LIMIT_READ] * delta) /
> > +                    NANOSECONDS_PER_SECOND;
> > +        write_leak = (bs->io_limits.iops[BLOCK_IO_LIMIT_WRITE] * delta) /
> > +                     NANOSECONDS_PER_SECOND;
> > +    }
> > +
> > +    /* make the buckets leak */
> > +    ios[BLOCK_IO_LIMIT_READ]  = MAX(ios[BLOCK_IO_LIMIT_READ] - read_leak, 0);
> > +    ios[BLOCK_IO_LIMIT_WRITE] = MAX(ios[BLOCK_IO_LIMIT_WRITE] - write_leak, 0);
> > +}
> > +
> > +static void bdrv_leak_if_needed(BlockDriverState *bs)
> > +{
> > +    int64_t now;
> > +    int64_t delta;
> > +
> > +    if (!bs->must_leak) {
> > +        return;
> > +    }
> > +
> > +    bs->must_leak = false;
> > +
> > +    now = qemu_get_clock_ns(rt_clock);
> > +    delta = now - bs->previous_leak;
> > +    bs->previous_leak = now;
> > +
> > +    bdrv_make_bps_buckets_leak(bs, delta);
> > +    bdrv_make_iops_buckets_leak(bs, delta);
> > +}
> > +
> > +static void bdrv_block_timer_disable(BlockDriverState *bs)
> > +{
> > +    if (!bs->block_timer) {
> > +        return;
> >      }
> >  
> > -    bs->slice_start = 0;
> > -    bs->slice_end   = 0;
> > +    qemu_del_timer(bs->block_timer);
> > +    qemu_free_timer(bs->block_timer);
> > +    bs->block_timer = NULL;
> > +}
> > +
> > +static bool bdrv_throttling_is_iddle(BlockDriverState *bs)
> 
> I don't quite understad the wording here, is iddle equivalent to idle?
> 
> > +{
> > +    int64_t delta = qemu_get_clock_ns(rt_clock) - bs->previous_leak;
> > +
> > +    if (delta < BLOCK_IO_THROTTLE_PERIOD * 2) {
> > +        return false;
> > +    }
> > +
> > +    /* iddle */
> > +    return true;
> >  }
> >  
> > +/* This callback is the timer in charge of making the leaky buckets leak */
> >  static void bdrv_block_timer(void *opaque)
> 
> Will be more readable for me if you could rename it to
> bdrv_clock_timer_cb.

> 
> >  {
> >      BlockDriverState *bs = opaque;
> >  
> > +    /* disable throttling time on iddle for economy purpose */
> > +    if (bdrv_throttling_is_iddle(bs)) {
> > +        bdrv_block_timer_disable(bs);
> > +        return;
> > +    }
> > +
> > +    /* rearm the timer */
> > +    qemu_mod_timer(bs->block_timer,
> > +                   qemu_get_clock_ns(vm_clock) +
> > +                   BLOCK_IO_THROTTLE_PERIOD);
> > +
> > +    bs->must_leak = true;
> >      qemu_co_enter_next(&bs->throttled_reqs);
> >  }
> >  
> > +static void bdrv_block_timer_enable(BlockDriverState *bs)
> > +{
> > +    if (bs->block_timer) {
> > +        return;
> > +    }
> > +
> > +    bs->block_timer = qemu_new_timer_ns(vm_clock, bdrv_block_timer, bs);
> > +    bs->previous_leak = qemu_get_clock_ns(rt_clock);
> > +    qemu_mod_timer(bs->block_timer,
> > +                   qemu_get_clock_ns(vm_clock) +
> > +                   BLOCK_IO_THROTTLE_PERIOD);
> > +}
> > +
> >  void bdrv_io_limits_enable(BlockDriverState *bs)
> >  {
> >      qemu_co_queue_init(&bs->throttled_reqs);
> > -    bs->block_timer = qemu_new_timer_ns(vm_clock, bdrv_block_timer, bs);
> >      bs->io_limits_enabled = true;
> >  }
> >  
> > @@ -165,15 +302,118 @@ bool bdrv_io_limits_enabled(BlockDriverState *bs)
> >           || io_limits->iops[BLOCK_IO_LIMIT_TOTAL];
> >  }
> >  
> > +/* This function check if the correct bandwith threshold has been exceeded
> 
> What does the "correct bandwidth threshold" mean?
> 
> And s/bandwith/bandwidth/, series wide.
> 
> > + *
> > + * @is_write: true if the current IO is a write, false if it's a read
> > + * @ret:      true if threshold has been exceeded else false
> > + */
> > +static bool bdrv_is_bps_threshold_exceeded(BlockDriverState *bs, bool is_write)
> > +{
> > +    /* limit is on total read + write bps : do the sum and compare with total
> > +     * threshold
> > +     */
> > +    if (bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL]) {
> > +        int64_t bytes = bs->leaky_buckets.bytes[BLOCK_IO_LIMIT_READ] +
> > +                        bs->leaky_buckets.bytes[BLOCK_IO_LIMIT_WRITE];
> > +        return bs->io_limits.bps_threshold[BLOCK_IO_LIMIT_TOTAL] < bytes;
> > +    }
> > +
> > +    /* check wether the threshold corresponding to the current io type (read,
> > +     * write) has been exceeded
> > +     */
> > +    if (bs->io_limits.bps[is_write]) {
> 
> It looks dangerous to use is_write as index of the array.
> 
> > +        return bs->io_limits.bps_threshold[is_write] <
> > +               bs->leaky_buckets.bytes[is_write];
> > +    }
> > +
> > +    /* no limit */
> > +    return false;
> > +}
> > +
> > +/* This function check if the correct iops threshold has been exceeded
> > + *
> > + * @is_write: true if the current IO is a write, false if it's a read
> > + * @ret:      true if threshold has been exceeded else false
> > + */
> > +static bool bdrv_is_iops_threshold_exceeded(BlockDriverState *bs, bool is_write)
> > +{
> > +    /* limit is on total read + write iops : do the sum and compare with total
> > +     * threshold
> > +     */
> > +    if (bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL]) {
> > +        double ios = bs->leaky_buckets.ios[BLOCK_IO_LIMIT_READ] +
> > +                     bs->leaky_buckets.ios[BLOCK_IO_LIMIT_WRITE];
> > +        return bs->io_limits.iops_threshold[BLOCK_IO_LIMIT_TOTAL] < ios;
> > +    }
> > +
> > +    /* check wether the threshold corresponding to the current io type (read,
> > +     * write) has been exceeded
> > +     */
> > +    if (bs->io_limits.iops[is_write]) {
> > +        return bs->io_limits.iops_threshold[is_write] <
> > +               bs->leaky_buckets.ios[is_write];
> > +    }
> > +
> > +    /* no limit */
> > +    return false;
> > +}
> > +
> > +/* This function check if any bandwith or iops threshold has been exceeded
> > + *
> > + * @nb_sectors: the number of sectors of the current IO
> > + * @is_write:   true if the current IO is a write, false if it's a read
> > + * @ret:        true if any threshold has been exceeded else false
> > + */
> > +static bool bdrv_is_any_threshold_exceeded(BlockDriverState *bs, int nb_sectors,
> > +                                           bool is_write)
> > +{
> > +    bool bps_ret, iops_ret;
> > +
> > +    /* check if any bandwith or per IO threshold has been exceeded */
> > +    bps_ret = bdrv_is_bps_threshold_exceeded(bs, is_write);
> > +    iops_ret = bdrv_is_iops_threshold_exceeded(bs, is_write);
> > +
> > +    /* if so the IO will be blocked so do not account it and return true
> > +     * also return false if a bdrv_drain_all is in progress
> > +     */
> > +    if (!draining && (bps_ret || iops_ret)) {
> > +        return true;
> > +    }
> > +
> > +    /* NOTE: the counter can go above the threshold when authorizing an IO.
> > +     *       At next call the code will punish the guest by blocking the
> > +     *       next IO until the counter has been decremented below the threshold.
> > +     *       This way if a guest issue a jumbo IO bigger than the threshold it
> > +     *       will have a chance no be authorized and will not result in a guest
> > +     *       IO deadlock.
> > +     */
> > +
> > +    /* the IO is authorized so do the accounting and return false */
> > +    bs->leaky_buckets.bytes[is_write] += (int64_t)nb_sectors *
> > +                                         BDRV_SECTOR_SIZE;
> > +    bs->leaky_buckets.ios[is_write]++;
> > +
> > +    return false;
> > +}
> > +
> >  static void bdrv_io_limits_intercept(BlockDriverState *bs,
> >                                       bool is_write, int nb_sectors)
> >  {
> > -    int64_t wait_time = -1;
> > +    /* enable block timer if needed when intercepting I/Os */
> > +    if (!bs->block_timer) {
> 
> Already checking for bs->block_timer in bdrv_block_timer_enable().
> 
> > +        bdrv_block_timer_enable(bs);
> > +    }
> >  
> > +    bdrv_leak_if_needed(bs);
> > +    /* if some IOs are already queued because the bucket is full put the current
> > +     * IO at the end of the queue (FIFO)
> > +     */
> >      if (!qemu_co_queue_empty(&bs->throttled_reqs)) {
> >          qemu_co_queue_wait(&bs->throttled_reqs);
> >      }
> >  
> > +    bdrv_leak_if_needed(bs);
> > +
> >      /* 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
> > @@ -181,13 +421,19 @@ static void bdrv_io_limits_intercept(BlockDriverState *bs,
> >       * 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));
> > +    /* if a threshold is exceeded the leaky bucket is full so the code put the
> > +     * IO in the throttle_reqs queue until the bucket has leaked enough to be
> > +     * not full
> > +     */
> > +    while (bdrv_is_any_threshold_exceeded(bs, nb_sectors, is_write)) {
> > +        bdrv_leak_if_needed(bs);
> >          qemu_co_queue_wait_insert_head(&bs->throttled_reqs);
> > +        bdrv_leak_if_needed(bs);
> >      }
> >  
> > +    bdrv_leak_if_needed(bs);
> >      qemu_co_queue_next(&bs->throttled_reqs);
> > +    bdrv_leak_if_needed(bs);
> >  }
> >  
> >  /* check if the path starts with "<protocol>:" */
> > @@ -1439,6 +1685,9 @@ void bdrv_drain_all(void)
> >      BlockDriverState *bs;
> >      bool busy;
> >  
> > +    /* tell the throttling code we are draining */
> > +    draining = true;
> > +
> >      do {
> >          busy = qemu_aio_wait();
> >  
> > @@ -1457,6 +1706,8 @@ void bdrv_drain_all(void)
> >          assert(QLIST_EMPTY(&bs->tracked_requests));
> >          assert(qemu_co_queue_empty(&bs->throttled_reqs));
> >      }
> > +
> > +    draining = false;
> >  }
> >  
> >  /* make a BlockDriverState anonymous by removing from bdrv_state list.
> > @@ -1492,9 +1743,7 @@ static void bdrv_move_feature_fields(BlockDriverState *bs_dest,
> >      bs_dest->enable_write_cache = bs_src->enable_write_cache;
> >  
> >      /* i/o timing parameters */
> > -    bs_dest->slice_start        = bs_src->slice_start;
> > -    bs_dest->slice_end          = bs_src->slice_end;
> > -    bs_dest->slice_submitted    = bs_src->slice_submitted;
> > +    bs_dest->leaky_buckets      = bs_src->leaky_buckets;
> >      bs_dest->io_limits          = bs_src->io_limits;
> >      bs_dest->throttled_reqs     = bs_src->throttled_reqs;
> >      bs_dest->block_timer        = bs_src->block_timer;
> > @@ -3551,169 +3800,6 @@ void bdrv_aio_cancel(BlockDriverAIOCB *acb)
> >      acb->aiocb_info->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;
> > -    uint64_t extension;
> > -    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->slice_submitted.bytes[is_write];
> > -    if (bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL]) {
> > -        bytes_base += bs->slice_submitted.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.
> > -     */
> > -    extension = wait_time * NANOSECONDS_PER_SECOND;
> > -    extension = DIV_ROUND_UP(extension, BLOCK_IO_SLICE_TIME) *
> > -                BLOCK_IO_SLICE_TIME;
> > -    bs->slice_end += extension;
> > -    if (wait) {
> > -        *wait = wait_time * NANOSECONDS_PER_SECOND;
> > -    }
> > -
> > -    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->slice_submitted.ios[is_write];
> > -    if (bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL]) {
> > -        ios_base += bs->slice_submitted.ios[!is_write];
> > -    }
> > -
> > -    if (ios_base + 1 <= ios_limit) {
> > -        if (wait) {
> > -            *wait = 0;
> > -        }
> > -
> > -        return false;
> > -    }
> > -
> > -    /* Calc approx time to dispatch, in seconds */
> > -    wait_time = (ios_base + 1) / iops_limit;
> > -    if (wait_time > elapsed_time) {
> > -        wait_time = wait_time - elapsed_time;
> > -    } else {
> > -        wait_time = 0;
> > -    }
> > -
> > -    /* Exceeded current slice, extend it by another slice time */
> > -    bs->slice_end += BLOCK_IO_SLICE_TIME;
> > -    if (wait) {
> > -        *wait = wait_time * NANOSECONDS_PER_SECOND;
> > -    }
> > -
> > -    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 (now > bs->slice_end) {
> > -        bs->slice_start = now;
> > -        bs->slice_end   = now + BLOCK_IO_SLICE_TIME;
> > -        memset(&bs->slice_submitted, 0, sizeof(bs->slice_submitted));
> > -    }
> > -
> > -    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;
> > -    }
> > -
> > -    bs->slice_submitted.bytes[is_write] += (int64_t)nb_sectors *
> > -                                           BDRV_SECTOR_SIZE;
> > -    bs->slice_submitted.ios[is_write]++;
> > -
> > -    return false;
> > -}
> > -
> >  /**************************************************************/
> >  /* async block device emulation */
> >  
> > diff --git a/blockdev.c b/blockdev.c
> > index c5abd65..491e4d0 100644
> > --- a/blockdev.c
> > +++ b/blockdev.c
> > @@ -280,10 +280,25 @@ static int parse_block_error_action(const char *buf, bool is_read)
> >      }
> >  }
> >  
> > +static bool check_io_limit(int64_t limit)
> > +{
> > +    if (!limit) {
> > +        return false;
> > +    }
> > +
> > +    if (limit < (THROTTLE_HZ * 2)) {
> > +        return true;
> > +    }
> > +
> > +    return false;
> > +}
> > +
> >  static bool do_check_io_limits(BlockIOLimit *io_limits, Error **errp)
> >  {
> >      bool bps_flag;
> >      bool iops_flag;
> > +    bool bps_threshold_flag;
> > +    bool iops_threshold_flag;
> >  
> >      assert(io_limits);
> >  
> > @@ -299,13 +314,30 @@ static bool do_check_io_limits(BlockIOLimit *io_limits, Error **errp)
> >          return false;
> >      }
> >  
> > -    if (io_limits->bps[BLOCK_IO_LIMIT_TOTAL] < 0 ||
> > -        io_limits->bps[BLOCK_IO_LIMIT_WRITE] < 0 ||
> > -        io_limits->bps[BLOCK_IO_LIMIT_READ] < 0 ||
> > -        io_limits->iops[BLOCK_IO_LIMIT_TOTAL] < 0 ||
> > -        io_limits->iops[BLOCK_IO_LIMIT_WRITE] < 0 ||
> > -        io_limits->iops[BLOCK_IO_LIMIT_READ] < 0) {
> > -        error_setg(errp, "bps and iops values must be 0 or greater");
> > +    bps_threshold_flag  =
> > +        (io_limits->bps_threshold[BLOCK_IO_LIMIT_TOTAL] != 0)
> > +         && ((io_limits->bps_threshold[BLOCK_IO_LIMIT_READ] != 0)
> > +         || (io_limits->bps_threshold[BLOCK_IO_LIMIT_WRITE] != 0));
> > +    iops_threshold_flag =
> > +        (io_limits->iops_threshold[BLOCK_IO_LIMIT_TOTAL] != 0)
> > +         && ((io_limits->iops_threshold[BLOCK_IO_LIMIT_READ] != 0)
> > +         || (io_limits->iops_threshold[BLOCK_IO_LIMIT_WRITE] != 0));
> > +    if (bps_threshold_flag || iops_threshold_flag) {
> > +        error_setg(errp, "bps_threshold(iops_threshold) and "
> > +            "bps_rd_threshold/bps_wr_threshold"
> > +            "(iops_rd_threshold/iops_wr_threshold) "
> > +            "cannot be used at the same time");
> > +        return false;
> > +    }
> > +
> > +    if (check_io_limit(io_limits->bps[BLOCK_IO_LIMIT_TOTAL]) ||
> > +        check_io_limit(io_limits->bps[BLOCK_IO_LIMIT_WRITE]) ||
> > +        check_io_limit(io_limits->bps[BLOCK_IO_LIMIT_READ]) ||
> > +        check_io_limit(io_limits->iops[BLOCK_IO_LIMIT_TOTAL]) ||
> > +        check_io_limit(io_limits->iops[BLOCK_IO_LIMIT_WRITE]) ||
> > +        check_io_limit(io_limits->iops[BLOCK_IO_LIMIT_READ])) {
> > +        error_setg(errp, "bps and iops values must be %i or greater",
> > +                   THROTTLE_HZ * 2);
> >          return false;
> >      }
> >  
> > @@ -497,6 +529,18 @@ DriveInfo *drive_init(QemuOpts *all_opts, BlockInterfaceType block_default_type)
> >                             qemu_opt_get_number(opts, "iops_rd", 0);
> >      io_limits.iops[BLOCK_IO_LIMIT_WRITE] =
> >                             qemu_opt_get_number(opts, "iops_wr", 0);
> > +    io_limits.bps_threshold[BLOCK_IO_LIMIT_TOTAL] =
> > +                           io_limits.bps[BLOCK_IO_LIMIT_TOTAL] / THROTTLE_HZ;
> > +    io_limits.bps_threshold[BLOCK_IO_LIMIT_READ]  =
> > +                           io_limits.bps[BLOCK_IO_LIMIT_READ] / THROTTLE_HZ;
> > +    io_limits.bps_threshold[BLOCK_IO_LIMIT_WRITE] =
> > +                           io_limits.bps[BLOCK_IO_LIMIT_WRITE] / THROTTLE_HZ;
> > +    io_limits.iops_threshold[BLOCK_IO_LIMIT_TOTAL] =
> > +                           io_limits.iops[BLOCK_IO_LIMIT_TOTAL] / THROTTLE_HZ;
> > +    io_limits.iops_threshold[BLOCK_IO_LIMIT_READ]  =
> > +                           io_limits.iops[BLOCK_IO_LIMIT_READ] / THROTTLE_HZ;
> > +    io_limits.iops_threshold[BLOCK_IO_LIMIT_WRITE] =
> > +                           io_limits.iops[BLOCK_IO_LIMIT_WRITE] / THROTTLE_HZ;
> >  
> >      if (!do_check_io_limits(&io_limits, &error)) {
> >          error_report("%s", error_get_pretty(error));
> > @@ -1198,6 +1242,12 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
> >      io_limits.iops[BLOCK_IO_LIMIT_TOTAL]= iops;
> >      io_limits.iops[BLOCK_IO_LIMIT_READ] = iops_rd;
> >      io_limits.iops[BLOCK_IO_LIMIT_WRITE]= iops_wr;
> > +    io_limits.bps_threshold[BLOCK_IO_LIMIT_TOTAL] = bps / THROTTLE_HZ;
> > +    io_limits.bps_threshold[BLOCK_IO_LIMIT_READ]  = bps_rd / THROTTLE_HZ;
> > +    io_limits.bps_threshold[BLOCK_IO_LIMIT_WRITE] = bps_wr / THROTTLE_HZ;
> > +    io_limits.iops_threshold[BLOCK_IO_LIMIT_TOTAL] = iops / THROTTLE_HZ;
> > +    io_limits.iops_threshold[BLOCK_IO_LIMIT_READ]  = iops_rd / THROTTLE_HZ;
> > +    io_limits.iops_threshold[BLOCK_IO_LIMIT_WRITE] = iops_wr / THROTTLE_HZ;
> >  
> >      if (!do_check_io_limits(&io_limits, errp)) {
> >          return;
> > @@ -1209,11 +1259,10 @@ void qmp_block_set_io_throttle(const char *device, int64_t bps, int64_t bps_rd,
> >          bdrv_io_limits_enable(bs);
> >      } else if (bs->io_limits_enabled && !bdrv_io_limits_enabled(bs)) {
> >          bdrv_io_limits_disable(bs);
> > -    } else {
> > -        if (bs->block_timer) {
> > -            qemu_mod_timer(bs->block_timer, qemu_get_clock_ns(vm_clock));
> > -        }
> >      }
> > +
> > +    /* reset leaky bucket to get the system in a known state */
> > +    memset(&bs->leaky_buckets, 0, sizeof(bs->leaky_buckets));
> >  }
> >  
> >  int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
> > diff --git a/include/block/block_int.h b/include/block/block_int.h
> > index c6ac871..e32ad1f 100644
> > --- a/include/block/block_int.h
> > +++ b/include/block/block_int.h
> > @@ -43,8 +43,9 @@
> >  #define BLOCK_IO_LIMIT_WRITE    1
> >  #define BLOCK_IO_LIMIT_TOTAL    2
> >  
> > -#define BLOCK_IO_SLICE_TIME     100000000
> >  #define NANOSECONDS_PER_SECOND  1000000000.0
> > +#define THROTTLE_HZ 1
> > +#define BLOCK_IO_THROTTLE_PERIOD (NANOSECONDS_PER_SECOND / THROTTLE_HZ)
> >  
> >  #define BLOCK_OPT_SIZE              "size"
> >  #define BLOCK_OPT_ENCRYPT           "encryption"
> > @@ -73,11 +74,13 @@ typedef struct BdrvTrackedRequest {
> >  typedef struct BlockIOLimit {
> >      int64_t bps[3];
> >      int64_t iops[3];
> > +    int64_t bps_threshold[3];
> > +    int64_t iops_threshold[3];
> >  } BlockIOLimit;
> >  
> >  typedef struct BlockIOBaseValue {
> > -    uint64_t bytes[2];
> > -    uint64_t ios[2];
> > +    int64_t bytes[2];
> > +    double  ios[2];
> >  } BlockIOBaseValue;
> >  
> >  struct BlockDriver {
> > @@ -264,10 +267,10 @@ struct BlockDriverState {
> >      unsigned int copy_on_read_in_flight;
> >  
> >      /* the time for latest disk I/O */
> > -    int64_t slice_start;
> > -    int64_t slice_end;
> >      BlockIOLimit io_limits;
> > -    BlockIOBaseValue slice_submitted;
> > +    BlockIOBaseValue leaky_buckets;
> > +    int64_t      previous_leak;
> > +    bool         must_leak;
> >      CoQueue      throttled_reqs;
> >      QEMUTimer    *block_timer;
> >      bool         io_limits_enabled;
> > -- 
> > 1.7.10.4
> > 
> > 
> 
> -- 
> Fam
>