Re: [Qemu-devel] [PATCH v10 2/3] block: add I/O throttling algorithm

[Stefan Hajnoczi]

On Tue, Nov 1, 2011 at 7:40 AM, Zhi Yong Wu <address@hidden> wrote:
> +static void bdrv_io_limits_intercept(BlockDriverState *bs,
> +                                     int nb_sectors)
> +{
> +    int64_t wait_time = -1;
> +
> +    if (!qemu_co_queue_empty(&bs->throttled_reqs)) {
> +        qemu_co_queue_wait(&bs->throttled_reqs);
> +        goto resume;
> +    } else if (bdrv_exceed_io_limits(bs, nb_sectors, false, &wait_time)) {
> +        if (wait_time != -1) {
> +            qemu_mod_timer(bs->block_timer,
> +                           wait_time + qemu_get_clock_ns(vm_clock));
> +        }
> +
> +        qemu_co_queue_wait(&bs->throttled_reqs);
> +
> +resume:
> +        while (bdrv_exceed_io_limits(bs, nb_sectors, false, &wait_time)) {

is_write needs to be passed in to bdrv_exceed_io_limits().  Currently
this accounts every I/O as a read.

> +            qemu_mod_timer(bs->block_timer,
> +                           wait_time + qemu_get_clock_ns(vm_clock));

Do you need if (wait_time != -1) here?

Stefan