Re: [Qemu-devel] [PATCH 6/6] qmp: add balloon-get-memory-stats & event

[Anthony Liguori <aliguori@us.ibm.com>]

On 02/17/2012 11:09 AM, Michael Roth wrote:
> On Fri, Feb 17, 2012 at 10:55:41AM -0600, Anthony Liguori wrote:
>> On 02/08/2012 02:30 PM, Luiz Capitulino wrote:
>>> This commit adds a QMP API for the guest provided memory statistics
>>> (long disabled by commit 07b0403dfc2b2ac179ae5b48105096cc2d03375a).
>>>
>>> The approach taken by the original commit
>>> (625a5befc2e3200b396594f002218d235e375da5) was to extend the
>>> query-balloon command. It introduced a severe bug though: query-balloon
>>> would hang if the guest didn't respond.
>>>
>>> The approach taken by this commit is asynchronous and thus avoids
>>> any QMP hangs.
>>>
>>> First, a client has to issue the balloon-get-memory-stats command.
>>> That command gets the process started by only sending a request to
>>> the guest, it doesn't block. When the memory stats are made available
>>> by the guest, they are returned to the client as an QMP event.
>>>
>>> Signed-off-by: Luiz Capitulino<lcapitulino@redhat.com>
>>
>> Do we need this to be stable in 1.1?
>>
>> We can do this pretty nicely through QOM.  We can have a polling
>> property in the virtio-balloon driver, that when set, will enable
>> the virtio-balloon device to poll the guest for statistics.
>>
>> We can also have properties for each of the memory statistics and a
>> timestamp for when the last update was.
>>
>> I think this is a friendlier approach for clients, and a cleaner
>> approach from a QEMU perspective.
>>
>> There's nothing generic about this functionality.  It's extremely
>> specific to virtio-balloon.  We just lacked ways to expose device
>> specific function pre-QOM.
>
> I'm not so sure, I think proxying guest agent commands through QMP
> would hit very similar snags, for instance.

We would proxy guest agent commands as asynchronous QMP commands, no?

Regards,

Anthony Liguori

>
>>
>> Regards,
>>
>> Anthony Liguori
>>
>>
>
>