Re: [Qemu-devel] [libvirt] [PATCH] qemu: Get memory balloon info correctly for text monitor

[Adam Litke <agl@us.ibm.com>]

On 08/15/2011 11:50 AM, Daniel P. Berrange wrote:
> On Mon, Aug 15, 2011 at 11:27:43AM -0500, Adam Litke wrote:
>> On 08/15/2011 08:23 AM, Osier Yang wrote:
>>> 于 2011年08月15日 21:58, Osier Yang 写道:
>>>> * src/qemu/qemu_monitor_text.c: BALLOON_PREFIX was defined as
>>>> "balloon: actual=", which cause "actual=" is stripped early before
>>>> the real parsing. This patch changes BALLOON_PREFIX into "balloon: ",
>>>> and modifies related functions, also renames
>>>> "qemuMonitorParseExtraBalloonInfo" to "qemuMonitorParseBalloonInfo",
>>>> as after the changing, it parses all the info returned by "info balloon".
>>>
>>> Forgot to mention the problem, e.g. "virsh dommemstat $domain" returns empty
>>> result.
>>
>> That is because qemu has disabled stats reporting and so the extra
>> fields are not present in the info balloon response.
> 
> I'd completely forgotten about this problem. We really should try to
> get this fixed & renabled in QEMU sometime in the not too distant
> future.

I agree.  The problem is that qemu lacks a proper interface for
asynchronous commands so an unresponsive guest could freeze the monitor.
 QMP is undergoing a significant overhaul as a result of the new QAPI
framework.  It is my understanding that this new framework will provide
a robust async interface, allowing us to re-enable balloon stats.

-- 
Adam Litke
IBM Linux Technology Center