Re: [Qemu-devel] [PATCH v1] qmp/hmp: add block_set_io_throttle and enhance query_block

[Stefan Hajnoczi]

On Thu, Aug 4, 2011 at 5:34 AM, Zhi Yong Wu <address@hidden> wrote:
> @@ -1387,6 +1422,11 @@ void bdrv_set_io_limits(BlockDriverState *bs,
>  {
>     memset(&bs->io_limits, 0, sizeof(BlockIOLimit));
>     bs->io_limits = *io_limits;
> +    if (bdrv_io_limits_enabled(bs)) {
> +        bs->io_limits_enabled = true;
> +    } else {
> +        bs->io_limits_enabled = false;
> +    }

Or in one line:
bs->io_limits_enabled = bdrv_io_limits_enabled(bs);

>  }
>
>  /* Recognize floppy formats */
> @@ -1621,6 +1661,7 @@ BlockDriverState *bdrv_find(const char *name)
>     return NULL;
>  }
>
> +/* disk I/O throttling */

Looks like this should not be here.

>  BlockDriverState *bdrv_next(BlockDriverState *bs)
>  {
>     if (!bs) {
> @@ -1784,6 +1825,16 @@ 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]");
>     }
> @@ -1816,10 +1867,22 @@ 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[2],
> +                                     bs->io_limits.bps[0],
> +                                     bs->io_limits.bps[1],
> +                                     bs->io_limits.iops[2],
> +                                     bs->io_limits.iops[0],
> +                                     bs->io_limits.iops[1]);
>             if (bs->backing_file[0] != '\0') {
>                 QDict *qdict = qobject_to_qdict(obj);
>                 qdict_put(qdict, "backing_file",
> @@ -2307,7 +2370,7 @@ static bool bdrv_exceed_io_limits(BlockDriverState *bs, 
> int nb_sectors,
>     }
>
>     /* If a limit was exceeded, immediately queue this request */
> -    if ((bs->req_from_queue == false)
> +    if (!bs->req_from_queue
>         && !QTAILQ_EMPTY(&bs->block_queue->requests)) {
>         if (bs->io_limits.bps[BLOCK_IO_LIMIT_TOTAL]
>             || bs->io_limits.bps[is_write] || bs->io_limits.iops[is_write]
> @@ -2362,14 +2425,14 @@ BlockDriverAIOCB *bdrv_aio_readv(BlockDriverState 
> *bs, int64_t sector_num,
>     trace_bdrv_aio_readv(bs, sector_num, nb_sectors, opaque);
>
>     if (!drv || bdrv_check_request(bs, sector_num, nb_sectors)) {
> -        if (bdrv_io_limits_enable(&bs->io_limits)) {
> +        if (bs->io_limits_enabled) {
>             bs->req_from_queue = false;
>         }
>         return NULL;
>     }
>
>     /* throttling disk read I/O */
> -    if (bdrv_io_limits_enable(&bs->io_limits)) {
> +    if (bs->io_limits_enabled) {
>         if (bdrv_exceed_io_limits(bs, nb_sectors, false, &wait_time)) {
>             ret = qemu_block_queue_enqueue(bs->block_queue, bs, 
> bdrv_aio_readv,
>                               sector_num, qiov, nb_sectors, cb, opaque);
> @@ -2388,14 +2451,14 @@ BlockDriverAIOCB *bdrv_aio_readv(BlockDriverState 
> *bs, int64_t sector_num,
>        bs->rd_bytes += (unsigned) nb_sectors * BDRV_SECTOR_SIZE;
>        bs->rd_ops ++;
>
> -        if (bdrv_io_limits_enable(&bs->io_limits)) {
> +        if (bs->io_limits_enabled) {
>             bs->io_disps.bytes[BLOCK_IO_LIMIT_READ] +=
>                               (unsigned) nb_sectors * BDRV_SECTOR_SIZE;
>             bs->io_disps.ios[BLOCK_IO_LIMIT_READ]++;
>         }
>     }
>
> -    if (bdrv_io_limits_enable(&bs->io_limits)) {
> +    if (bs->io_limits_enabled) {
>         bs->req_from_queue = false;
>     }
>
> @@ -2451,7 +2514,7 @@ BlockDriverAIOCB *bdrv_aio_writev(BlockDriverState *bs, 
> int64_t sector_num,
>
>     if (!drv || bs->read_only
>         || bdrv_check_request(bs, sector_num, nb_sectors)) {
> -        if (bdrv_io_limits_enable(&bs->io_limits)) {
> +        if (bs->io_limits_enabled) {
>             bs->req_from_queue = false;
>         }
>
> @@ -2466,7 +2529,7 @@ BlockDriverAIOCB *bdrv_aio_writev(BlockDriverState *bs, 
> int64_t sector_num,
>     }
>
>     /* throttling disk write I/O */
> -    if (bdrv_io_limits_enable(&bs->io_limits)) {
> +    if (bs->io_limits_enabled) {
>         if (bdrv_exceed_io_limits(bs, nb_sectors, true, &wait_time)) {
>             ret = qemu_block_queue_enqueue(bs->block_queue, bs, 
> bdrv_aio_writev,
>                                   sector_num, qiov, nb_sectors, cb, opaque);
> @@ -2488,14 +2551,14 @@ BlockDriverAIOCB *bdrv_aio_writev(BlockDriverState 
> *bs, int64_t sector_num,
>             bs->wr_highest_sector = sector_num + nb_sectors - 1;
>         }
>
> -        if (bdrv_io_limits_enable(&bs->io_limits)) {
> +        if (bs->io_limits_enabled) {
>             bs->io_disps.bytes[BLOCK_IO_LIMIT_WRITE] +=
>                                (unsigned) nb_sectors * BDRV_SECTOR_SIZE;
>             bs->io_disps.ios[BLOCK_IO_LIMIT_WRITE]++;
>         }
>     }
>
> -    if (bdrv_io_limits_enable(&bs->io_limits)) {
> +    if (bs->io_limits_enabled) {
>         bs->req_from_queue = false;
>     }
>
> diff --git a/block.h b/block.h
> index f0dac62..97d2177 100644
> --- a/block.h
> +++ b/block.h
> @@ -57,6 +57,11 @@ void bdrv_info(Monitor *mon, QObject **ret_data);
>  void bdrv_stats_print(Monitor *mon, const QObject *data);
>  void bdrv_info_stats(Monitor *mon, QObject **ret_data);
>
> +/* disk I/O throttling */
> +void bdrv_io_limits_res_init(BlockDriverState *bs);
> +void bdrv_io_limits_res_deinit(BlockDriverState *bs);
> +bool bdrv_io_limits_enabled(BlockDriverState *bs);
> +
>  void bdrv_init(void);
>  void bdrv_init_with_whitelist(void);
>  BlockDriver *bdrv_find_protocol(const char *filename);
> diff --git a/block_int.h b/block_int.h
> index 1ca826b..7c96094 100644
> --- a/block_int.h
> +++ b/block_int.h
> @@ -199,6 +199,8 @@ struct BlockDriverState {
>     BlockIODisp  io_disps;
>     BlockQueue   *block_queue;
>     QEMUTimer    *block_timer;
> +    bool         io_limits_enabled;
> +    bool         io_unlimit;
>     bool         req_from_queue;
>
>     /* I/O stats (display with "info blockstats"). */
> diff --git a/blockdev.c b/blockdev.c
> index aff6bb2..dc2e8a9 100644
> --- a/blockdev.c
> +++ b/blockdev.c
> @@ -376,7 +376,7 @@ DriveInfo *drive_init(QemuOpts *opts, int default_to_scsi)
>         return NULL;
>     }
>
> -    /* disk io limits */
> +    /* disk io throttling */
>     iol_flag = qemu_opt_io_limits_enable_flag(opts, iol_opts);
>     if (iol_flag) {
>         memset(&io_limits, 0, sizeof(BlockIOLimit));
> @@ -387,6 +387,14 @@ DriveInfo *drive_init(QemuOpts *opts, int 
> default_to_scsi)
>         io_limits.iops[2] = qemu_opt_get_number(opts, "iops", 0);
>         io_limits.iops[0] = qemu_opt_get_number(opts, "iops_rd", 0);
>         io_limits.iops[1] = qemu_opt_get_number(opts, "iops_wr", 0);
> +
> +        if (((io_limits.bps[2] != 0)
> +            && ((io_limits.bps[0] != 0) || (io_limits.bps[1] != 0)))
> +            || ((io_limits.iops[2] != 0)
> +            && ((io_limits.iops[0] != 0) || (io_limits.iops[1] != 0)))) {

Please define constants for read/write/total instead of using magic numbers.

> +            error_report("Some params for io throttling can not coexist");

This error message is vague.

"bps and bps_rd/bps_wr cannot be used at the same time"

> +            return NULL;
> +        }
>     }
>
>     on_write_error = BLOCK_ERR_STOP_ENOSPC;
> @@ -765,6 +773,82 @@ int do_change_block(Monitor *mon, const char *device,
>     return monitor_read_bdrv_key_start(mon, bs, NULL, NULL);
>  }
>
> +/* throttling disk I/O limits */
> +int do_block_set_io_throttle(Monitor *mon,
> +                       const QDict *qdict, QObject **ret_data)
> +{
> +    const char *devname = qdict_get_str(qdict, "device");
> +    uint64_t bps        = qdict_get_try_int(qdict, "bps", -1);
> +    uint64_t bps_rd     = qdict_get_try_int(qdict, "bps_rd", -1);
> +    uint64_t bps_wr     = qdict_get_try_int(qdict, "bps_wr", -1);
> +    uint64_t iops       = qdict_get_try_int(qdict, "iops", -1);
> +    uint64_t iops_rd    = qdict_get_try_int(qdict, "iops_rd", -1);
> +    uint64_t iops_wr    = qdict_get_try_int(qdict, "iops_wr", -1);
> +    BlockDriverState *bs;
> +
> +    bs = bdrv_find(devname);
> +    if (!bs) {
> +        qerror_report(QERR_DEVICE_NOT_FOUND, devname);
> +        return -1;
> +    }
> +
> +    if (devname && (bps == -1) && (bps_rd == -1) && (bps_wr == -1)
> +        && (iops == -1) && (iops_rd == -1) && (iops_wr == -1)) {

No need for the devname check.  It must be non-NULL since it is a
mandatory argument, also bdrv_find() would have crashed since devname
is used unchecked.

> +        qerror_report(QERR_IO_THROTTLE_NO_PARAM);
> +        return -1;
> +    }
> +
> +    if (((bps != -1) && ((bps_rd != -1) || (bps_wr != -1)))
> +        || ((iops != -1) && ((iops_rd != -1) || (iops_wr != -1)))) {
> +        qerror_report(QERR_IO_THROTTLE_PARAM_ERROR);
> +        return -1;
> +    }
> +
> +    if (bps != -1) {
> +        bs->io_limits.bps[2] = bps;
> +        bs->io_limits.bps[0] = 0;
> +        bs->io_limits.bps[1] = 0;
> +    }
> +
> +    if ((bps_rd != -1) || (bps_wr != -1)) {
> +        bs->io_limits.bps[0]  = (bps_rd == -1) ? bs->io_limits.bps[0] : 
> bps_rd;
> +        bs->io_limits.bps[1]  = (bps_wr == -1) ? bs->io_limits.bps[1] : 
> bps_wr;
> +        bs->io_limits.bps[2]  = 0;
> +    }
> +
> +    if (iops != -1) {
> +        bs->io_limits.iops[2] = iops;
> +        bs->io_limits.iops[0] = 0;
> +        bs->io_limits.iops[1] = 0;
> +    }
> +
> +    if ((iops_rd != -1) || (iops_wr != -1)) {
> +        bs->io_limits.iops[0] =
> +                      (iops_rd == -1) ? bs->io_limits.iops[0] : iops_rd;
> +        bs->io_limits.iops[1] =
> +                      (iops_wr == -1) ? bs->io_limits.iops[1] : iops_wr;
> +        bs->io_limits.iops[2] = 0;
> +    }
> +
> +    if (bdrv_io_limits_enabled(bs)) {
> +        if (!bs->io_limits_enabled) {
> +            bdrv_io_limits_res_init(bs);
> +        }
> +    } else {
> +        if (bs->io_limits_enabled) {
> +            BlockQueue *queue = bs->block_queue;
> +            if (!QTAILQ_EMPTY(&queue->requests)) {
> +                bs->io_unlimit = true;
> +                bs->io_limits_enabled = false;
> +            } else {
> +                bdrv_io_limits_res_deinit(bs);
> +            }
> +        }
> +    }

bdrv_io_limits_res_init() and bdrv_io_limits_res_deinit() are
basically enable/disable functions.  I would change this to:

if (!bs->io_limits_enabled && bdrv_io_limits_enabled(bs)) {
    bdrv_io_limits_enable(bs);
} else if (bs->io_limits_enabled && !bdrv_io_limits_enabled(bs)) {
    bdrv_io_limits_disable(bs);
}

And then remove the bs->io_unlimit field by immediately stopping I/O throttling:

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); /* <--- dispatch
queued requests */
        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;
}

The queue flushing code from bdrv_block_timer() could be moved into
qemu_block_queue_flush().  bdrv_block_timer() would call that function
instead of looping over the queue itself.

> +
> +    return 0;
> +}
> +
>  int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data)
>  {
>     const char *id = qdict_get_str(qdict, "id");
> diff --git a/blockdev.h b/blockdev.h
> index 0a5144c..d0d0d77 100644
> --- a/blockdev.h
> +++ b/blockdev.h
> @@ -63,6 +63,8 @@ int do_block_set_passwd(Monitor *mon, const QDict *qdict, 
> QObject **ret_data);
>  int do_change_block(Monitor *mon, const char *device,
>                     const char *filename, const char *fmt);
>  int do_drive_del(Monitor *mon, const QDict *qdict, QObject **ret_data);
> +int do_block_set_io_throttle(Monitor *mon,
> +                    const QDict *qdict, QObject **ret_data);
>  int do_snapshot_blkdev(Monitor *mon, const QDict *qdict, QObject **ret_data);
>  int do_block_resize(Monitor *mon, const QDict *qdict, QObject **ret_data);
>
> diff --git a/hmp-commands.hx b/hmp-commands.hx
> index aceba74..3ca496d 100644
> --- a/hmp-commands.hx
> +++ b/hmp-commands.hx
> @@ -1210,6 +1210,21 @@ ETEXI
>     },
>
>  STEXI
> address@hidden block_set_io_throttle @var{device} @var{bps} @var{bps_rd} 
> @var{bps_wr} @var{iops} @var{iops_rd} @var{iops_wr}
> address@hidden block_set_io_throttle
> +Change I/O throttle limits for a block drive to @var{bps} @var{bps_rd} 
> @var{bps_wr} @var{iops} @var{iops_rd} @var{iops_wr}
> +ETEXI
> +
> +    {
> +        .name       = "block_set_io_throttle",
> +        .args_type  = 
> "device:B,bps:i?,bps_rd:i?,bps_wr:i?,iops:i?,iops_rd:i?,iops_wr:i?",
> +        .params     = "device [bps] [bps_rd] [bps_wr] [iops] [iops_rd] 
> [iops_wr]",
> +        .help       = "change I/O throttle limts for a block drive",
> +        .user_print = monitor_user_noop,
> +        .mhandler.cmd_new = do_block_set_io_throttle,
> +    },
> +
> +STEXI
> address@hidden block_passwd @var{device} @var{password}
> address@hidden block_passwd
>  Set the encrypted device @var{device} password to @var{password}
> diff --git a/qerror.c b/qerror.c
> index d7fcd93..db04df7 100644
> --- a/qerror.c
> +++ b/qerror.c
> @@ -213,6 +213,14 @@ static const QErrorStringTable qerror_table[] = {
>         .error_fmt = QERR_VNC_SERVER_FAILED,
>         .desc      = "Could not start VNC server on %(target)",
>     },
> +    {
> +        .error_fmt = QERR_IO_THROTTLE_PARAM_ERROR,
> +        .desc      = "Some params for io throttling can not coexist",
> +    },
> +    {
> +        .error_fmt = QERR_IO_THROTTLE_NO_PARAM,
> +        .desc      = "No params for io throttling are specified",
> +    },
>     {}
>  };
>
> diff --git a/qerror.h b/qerror.h
> index 16c830d..892abbb 100644
> --- a/qerror.h
> +++ b/qerror.h
> @@ -181,4 +181,10 @@ QError *qobject_to_qerror(const QObject *obj);
>  #define QERR_FEATURE_DISABLED \
>     "{ 'class': 'FeatureDisabled', 'data': { 'name': %s } }"
>
> +#define QERR_IO_THROTTLE_PARAM_ERROR \
> +    "{ 'class': 'ParamsCoexistNotPermitted', 'data': {} }"

This error is not specific to I/O throttling.  Please add a generic error:

#define QERR_INVALID_PARAMETER_COMBINATION \
    "{ 'class': 'InvalidParameterCombination', 'data': { 'param1': %s,
'param2': %s } }"

> +#define QERR_IO_THROTTLE_NO_PARAM \
> +    "{ 'class': 'NoParamsSpecified', 'data': {} }"

QERR_MISSING_PARAMETER already does this.

> +
>  #endif /* QERROR_H */
> diff --git a/qmp-commands.hx b/qmp-commands.hx
> index 92c5c3a..0aaeae1 100644
> --- a/qmp-commands.hx
> +++ b/qmp-commands.hx
> @@ -828,6 +828,44 @@ Example:
>  EQMP
>
>     {
> +        .name       = "block_set_io_throttle",
> +        .args_type  = 
> "device:B,bps:i?,bps_rd:i?,bps_wr:i?,iops:i?,iops_rd:i?,iops_wr:i?",
> +        .params     = "device [bps[ [bps_rd] [bps_wr] [iops] [iops_rd] 
> [iops_wr]",

[bps]

> +        .help       = "change I/O throttle limts for a block drive",
> +        .user_print = monitor_user_noop,
> +        .mhandler.cmd_new = do_block_set_io_throttle,
> +    },
> +
> +SQMP
> +block_set_io_throttle
> +------------
> +
> +Change I/O throttle limts for a block drive.
> +
> +Arguments:
> +
> +- "device": device name (json-string)
> +- "bps":  total throughput value per second(json-int, optional)

Please document the units of bps ("bps" can mean bits per second or
bytes per second):

"total throughput limit in bytes per second (json-int, optional)"

> +- "bps_rd":  read throughput value per second(json-int, optional)
> +- "bps_wr":  read throughput value per second(json-int, optional)

Stefan