[libvirt] The design choice for how to enable block I/O throttling function in libvirt

[shu ming]

See commens below.
Zhi Yong Wu:
> HI, folks,
>
> I am trying to enable block I/O throttling function in libvirt. But
> currently i met some design questions, and don't make sure if we
> should extend blkiotune to support block I/O throttling or introduce
> one new libvirt command "blkiothrottle" to cover it or not. If you
> have some better idea, pls don't hesitate to drop your comments.
>
> If one new libvirt command "blkiothrottle" is introduced, I plan to
> design its usage syntax as below:
>
> virsh # help blkiothrottle
>    NAME
>      blkiothrottle - Set or display a block disk I/O throttle setting.
>
>    SYNOPSIS
>      blkiothrottle<domain>  <device>  [--bps<number>] [--bps_rd
> <number>] [--bps_wr<number>] [--iops<number>] [--iops_rd<number>]
> [--iops_wr<number>]
>
>    DESCRIPTION
>      Set or display a block disk I/O throttle setting.
>
>    OPTIONS
>      [--domain]<string>   domain name, id or uuid
>      [--device]<string>   block device
>      --bps<number>    total throughput limits in bytes/s
>      --bps_rd<number>   read throughput limits in bytes/s
>      --bps_wr<number>   write throughput limits in bytes/s
>      --iops<number>   total operation limits in numbers/s
>      --iops_rd<number>   read operation limits in numbers/s
>      --iops_wr<number>   write operation limits in numbers/s
>

How to display the current I/O throttle setting of a specific block 
device here?
I prfer to have less command to be as simple as possible for users.  But 
it seems
that we need another command here instead of having a block IO specific 
command like "iothrottle".
Supposely,  the next step of I/O throttling will be network device 
limit.  Shoud we have another
new command like "niciothrottle"?