Re: [Qemu-devel] [PATCH v5 3/4] block: add block timer and block throttling algorithm

[Ram Pai <linuxram@us.ibm.com>]

On Tue, Aug 09, 2011 at 12:17:51PM +0800, Zhi Yong Wu wrote:
> Note:
>       1.) When bps/iops limits are specified to a small value such as 511 bytes/s, this VM will hang up. We are considering how to handle this senario.
>       2.) When "dd" command is issued in guest, if its option bs is set to a large value such as "bs=1024K", the result speed will slightly bigger than the limits.
> 
> For these problems, if you have nice thought, pls let us know.:)
> 
> Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
> ---
>  block.c     |  347 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++--
>  block.h     |    6 +-
>  block_int.h |   30 +++++
>  3 files changed, 372 insertions(+), 11 deletions(-)
> 
> diff --git a/block.c b/block.c
> index 24a25d5..8fd6643 100644
> --- a/block.c
> +++ b/block.c
> @@ -29,6 +29,9 @@
>  #include "module.h"
>  #include "qemu-objects.h"
> 
> +#include "qemu-timer.h"
> +#include "block/blk-queue.h"
> +
>  #ifdef CONFIG_BSD
>  #include <sys/types.h>
>  #include <sys/stat.h>
> @@ -58,6 +61,13 @@ static int bdrv_read_em(BlockDriverState *bs, int64_t sector_num,
>  static int bdrv_write_em(BlockDriverState *bs, int64_t sector_num,
>                           const uint8_t *buf, int nb_sectors);
> 
> +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, uint64_t *wait);
> +
>  static QTAILQ_HEAD(, BlockDriverState) bdrv_states =
>      QTAILQ_HEAD_INITIALIZER(bdrv_states);
> 
> @@ -90,6 +100,68 @@ 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;
> +    bs->req_from_queue    = false;
> +
> +    if (bs->block_queue) {
> +        qemu_block_queue_flush(bs->block_queue);
> +        qemu_del_block_queue(bs->block_queue);
> +    }
> +
> +    if (bs->block_timer) {
> +        qemu_del_timer(bs->block_timer);
> +        qemu_free_timer(bs->block_timer);
> +    }
> +
> +    bs->slice_start[0]   = 0;
> +    bs->slice_start[1]   = 0;
> +
> +    bs->slice_end[0]     = 0;
> +    bs->slice_end[1]     = 0;
> +}
> +
> +static void bdrv_block_timer(void *opaque)
> +{
> +    BlockDriverState *bs = opaque;
> +    BlockQueue *queue = bs->block_queue;
> +
> +    qemu_block_queue_flush(queue);
> +}
> +
> +void bdrv_io_limits_enable(BlockDriverState *bs)
> +{
> +    bs->req_from_queue = false;
> +
> +    bs->block_queue    = qemu_new_block_queue();
> +    bs->block_timer    = qemu_new_timer_ns(vm_clock, bdrv_block_timer, bs);
> +
> +    bs->slice_start[BLOCK_IO_LIMIT_READ]  = qemu_get_clock_ns(vm_clock);
> +    bs->slice_start[BLOCK_IO_LIMIT_WRITE] = qemu_get_clock_ns(vm_clock);
 
a minor comment. better to keep the slice_start of the both the READ and WRITE
side the same.  

    bs->slice_start[BLOCK_IO_LIMIT_WRITE] = bs->slice_start[BLOCK_IO_LIMIT_READ];

saves  a call to qemu_get_clock_ns().

> +
> +    bs->slice_end[BLOCK_IO_LIMIT_READ]    =
> +                      qemu_get_clock_ns(vm_clock) + BLOCK_IO_SLICE_TIME;

    bs->slice_end[BLOCK_IO_LIMIT_READ] = bs->slice_start[BLOCK_IO_LIMIT_READ] +
			BLOCK_IO_SLICE_TIME;

saves one more call to qemu_get_clock_ns()

> +    bs->slice_end[BLOCK_IO_LIMIT_WRITE]   =
> +                      qemu_get_clock_ns(vm_clock) + BLOCK_IO_SLICE_TIME;


    bs->slice_end[BLOCK_IO_LIMIT_WRITE] = bs->slice_start[BLOCK_IO_LIMIT_WRITE] +
			BLOCK_IO_SLICE_TIME;

yet another call saving.


> +}
> +
> +bool bdrv_io_limits_enabled(BlockDriverState *bs)
> +{
> +    BlockIOLimit *io_limits = &bs->io_limits;
> +    if ((io_limits->bps[BLOCK_IO_LIMIT_READ] == 0)
> +         && (io_limits->bps[BLOCK_IO_LIMIT_WRITE] == 0)
> +         && (io_limits->bps[BLOCK_IO_LIMIT_TOTAL] == 0)
> +         && (io_limits->iops[BLOCK_IO_LIMIT_READ] == 0)
> +         && (io_limits->iops[BLOCK_IO_LIMIT_WRITE] == 0)
> +         && (io_limits->iops[BLOCK_IO_LIMIT_TOTAL] == 0)) {
> +        return false;
> +    }
> +
> +    return true;
> +}

can be optimized to:

	return (io_limits->bps[BLOCK_IO_LIMIT_READ]
		|| io_limits->bps[BLOCK_IO_LIMIT_WRITE]
		|| io_limits->bps[BLOCK_IO_LIMIT_TOTAL]
		|| io_limits->iops[BLOCK_IO_LIMIT_READ]
		|| io_limits->iops[BLOCK_IO_LIMIT_WRITE]
		|| io_limits->iops[BLOCK_IO_LIMIT_TOTAL]);

> +
>  /* check if the path starts with "<protocol>:" */
>  static int path_has_protocol(const char *path)
>  {
> @@ -642,6 +714,11 @@ int bdrv_open(BlockDriverState *bs, const char *filename, int flags,
>              bs->change_cb(bs->change_opaque, CHANGE_MEDIA);
>      }
> 
> +    /* throttling disk I/O limits */
> +    if (bs->io_limits_enabled) {
> +        bdrv_io_limits_enable(bs);
> +    }
> +
>      return 0;
> 
>  unlink_and_fail:
> @@ -680,6 +757,16 @@ void bdrv_close(BlockDriverState *bs)
>          if (bs->change_cb)
>              bs->change_cb(bs->change_opaque, CHANGE_MEDIA);
>      }
> +
> +    /* throttling disk I/O limits */
> +    if (bs->block_queue) {
> +        qemu_del_block_queue(bs->block_queue);
> +    }
> +
> +    if (bs->block_timer) {
> +        qemu_del_timer(bs->block_timer);
> +        qemu_free_timer(bs->block_timer);
> +    }
>  }
> 
>  void bdrv_close_all(void)
> @@ -1312,6 +1399,15 @@ void bdrv_get_geometry_hint(BlockDriverState *bs,
>      *psecs = bs->secs;
>  }
> 
> +/* throttling disk io limits */
> +void bdrv_set_io_limits(BlockDriverState *bs,
> +                            BlockIOLimit *io_limits)
> +{
> +    memset(&bs->io_limits, 0, sizeof(BlockIOLimit));
> +    bs->io_limits = *io_limits;
> +    bs->io_limits_enabled = bdrv_io_limits_enabled(bs);
> +}
> +
>  /* Recognize floppy formats */
>  typedef struct FDFormat {
>      FDriveType drive;
> @@ -1707,6 +1803,16 @@ static void bdrv_print_dict(QObject *obj, void *opaque)
>                              qdict_get_bool(qdict, "ro"),
>                              qdict_get_str(qdict, "drv"),
>                              qdict_get_bool(qdict, "encrypted"));
> +
> +        monitor_printf(mon, " bps=%" PRId64 " bps_rd=%" PRId64
> +                            " bps_wr=%" PRId64 " iops=%" PRId64
> +                            " iops_rd=%" PRId64 " iops_wr=%" PRId64,
> +                            qdict_get_int(qdict, "bps"),
> +                            qdict_get_int(qdict, "bps_rd"),
> +                            qdict_get_int(qdict, "bps_wr"),
> +                            qdict_get_int(qdict, "iops"),
> +                            qdict_get_int(qdict, "iops_rd"),
> +                            qdict_get_int(qdict, "iops_wr"));
>      } else {
>          monitor_printf(mon, " [not inserted]");
>      }
> @@ -1739,10 +1845,22 @@ void bdrv_info(Monitor *mon, QObject **ret_data)
>              QDict *bs_dict = qobject_to_qdict(bs_obj);
> 
>              obj = qobject_from_jsonf("{ 'file': %s, 'ro': %i, 'drv': %s, "
> -                                     "'encrypted': %i }",
> +                                     "'encrypted': %i, "
> +                                     "'bps': %" PRId64 ","
> +                                     "'bps_rd': %" PRId64 ","
> +                                     "'bps_wr': %" PRId64 ","
> +                                     "'iops': %" PRId64 ","
> +                                     "'iops_rd': %" PRId64 ","
> +                                     "'iops_wr': %" PRId64 "}",
>                                       bs->filename, bs->read_only,
>                                       bs->drv->format_name,
> -                                     bdrv_is_encrypted(bs));
> +                                     bdrv_is_encrypted(bs),
> +                                     bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL],
> +                                     bs->io_limits.bps[BLOCK_IO_LIMIT_READ],
> +                                     bs->io_limits.bps[BLOCK_IO_LIMIT_WRITE],
> +                                     bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL],
> +                                     bs->io_limits.iops[BLOCK_IO_LIMIT_READ],
> +                                     bs->io_limits.iops[BLOCK_IO_LIMIT_WRITE]);
>              if (bs->backing_file[0] != '\0') {
>                  QDict *qdict = qobject_to_qdict(obj);
>                  qdict_put(qdict, "backing_file",
> @@ -2111,6 +2229,165 @@ char *bdrv_snapshot_dump(char *buf, int buf_size, QEMUSnapshotInfo *sn)
>      return buf;
>  }
> 
> +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_disp, 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[is_write] - bs->slice_start[is_write];
> +    slice_time /= (BLOCK_IO_SLICE_TIME * 10.0);
> +    bytes_limit = bps_limit * slice_time;
> +    bytes_disp  = bs->io_disps.bytes[is_write];
> +    if (bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL]) {
> +        bytes_disp += bs->io_disps.bytes[!is_write];
> +    }
> +
> +    bytes_res   = (unsigned) nb_sectors * BDRV_SECTOR_SIZE;
> +
> +    if (bytes_disp + bytes_res <= bytes_limit) {
> +        if (wait) {
> +            *wait = 0;
> +        }
> +
> +        return false;
> +    }
> +
> +    /* Calc approx time to dispatch */
> +    wait_time = (bytes_disp + bytes_res) / bps_limit - elapsed_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_disp;
> +    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[is_write] - bs->slice_start[is_write];
> +    slice_time /= (BLOCK_IO_SLICE_TIME * 10.0);
> +    ios_limit  = iops_limit * slice_time;
> +    ios_disp   = bs->io_disps.ios[is_write];
> +    if (bs->io_limits.iops[BLOCK_IO_LIMIT_TOTAL]) {
> +        ios_disp += bs->io_disps.ios[!is_write];
> +    }
> +
> +    if (ios_disp + 1 <= ios_limit) {
> +        if (wait) {
> +            *wait = 0;
> +        }
> +
> +        return false;
> +    }
> +
> +    /* Calc approx time to dispatch */
> +    wait_time = (ios_disp + 1) / iops_limit;
> +    if (wait_time > elapsed_time) {
> +        wait_time = wait_time - elapsed_time;
> +    } else {
> +        wait_time = 0;
> +    }
> +
> +    if (wait) {
> +        *wait = wait_time * BLOCK_IO_SLICE_TIME * 10;
> +    }
> +
> +    return true;
> +}

bdrv_exceed_bps_limits() and bdrv_exceed_iops_limits() has almost similar logic.
Probably can be abstracted into a single function.

RP