[Qemu-devel] Re: [RFD] virtio: Add memory statistics reporting to the balloon driver

[Avi Kivity <avi@redhat.com>]

On 01/07/2010 05:12 PM, Anthony Liguori wrote:
>
> 3) Make qemu request balloon stats regularly (maybe every 10 seconds) 
> and display the latest stats with info balloon.  This avoids the 
> problem in #2 but it means that qemu determines the poll rate instead 
> of a management tool.
>
> 4) Make info-balloon a proper asynchronous command.  We need new 
> infrastructure to allow a qmp handler to take a callback that can be 
> used to delay the completion of the command.  This addresses all of 
> the above problems but it introduces a new one.  Command completion 
> now depends on the guest.  This potentially could trip up a naive 
> management tool that doesn't realize that the info-balloon command may 
> never complete.
>
> I'm on the fence between 3 and 4 myself.
>

Can I tip you over to #4?  #3 means we have no idea when the stats were 
generated.  With #4, we can't be sure, but it usually be close to when 
the command returns.

The command should include a timeout so a broken guest won't hang a 
management tool thread.

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