[Qemu-devel] ARRAYS :QMP Declaration

[Qemu-devel] ARRAYS :QMP Declaration

[Saptarshi Sen]

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Hi,

   Is it possible to use fixed array data structures for use through the
qmp-interface.

   My aim is to monitor IDE level activity in terms of sectors being
accessed. So
   I plan to have a fixed size buffer. But I find no way of doing so when I
use the
   qapi-schema.json.

   I think the qmp -interface uses linked lists as a replacement for array
type structures.

   Can anybody clarify my doubt and whether is it possible to use arrays as
in my case.


Regards
Saptarshi Sen

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Re: [Qemu-devel] ARRAYS :QMP Declaration

[Luiz Capitulino]

On Tue, 16 Jul 2013 09:27:27 +0800
Saptarshi Sen <saptarshi.mrg@gmail.com> wrote:

> Hi,
> 
>    Is it possible to use fixed array data structures for use through the
> qmp-interface.
> 
>    My aim is to monitor IDE level activity in terms of sectors being
> accessed. So
>    I plan to have a fixed size buffer. But I find no way of doing so when I
> use the
>    qapi-schema.json.
> 
>    I think the qmp -interface uses linked lists as a replacement for array
> type structures.

Yes, what JSON calls an array is actually a list. Why can't you use that?

Re: [Qemu-devel] ARRAYS :QMP Declaration

[Michael Roth]

Quoting Saptarshi Sen (2013-07-15 20:27:27)
> Hi,
> 
>       Is it possible to use fixed array data structures for use through the
>    qmp-interface.
>     
>       My aim is to monitor IDE level activity in terms of sectors being
>    accessed. So
>       I plan to have a fixed size buffer. But I find no way of doing so when
>    I use the
>       qapi-schema.json.
>       I think the qmp -interface uses linked lists as a replacement for array
>    type structures.
> 
>       Can anybody clarify my doubt and whether is it possible to use arrays
>    as in my case.

Not currently, though there is a plan to support it, likely in 1.7.

You can have your implementation map the buffer to a linked list type before
sending a response though. It's not particularly efficient... but then again
how big is this buffer gonna be? capacity/sector_size? If so I don't think
that's realistic over QMP. A list of active sector numbers might actually
work better. That could still be done more efficiently using arrays if we
supported them currently, but in practice I don't think the extra overhead
would be that much worse (though I'm assuming here that the number of sectors
being concurrently accessed would be relatively small)

> 
>    Regards
>    Saptarshi Sen