Re: [Xen-devel] [PATCH v2 2/7] libxl: add new hotplug interface support to hotplug script callers [and 1 more messages]

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On 18/04/13 19:52, Ian Jackson wrote:
> Roger Pau Monné writes ("Re: [Xen-devel] [PATCH v2 2/7] libxl: add new 
> hotplug interface support to hotplug script callers [and 1 more messages]"):
>> On 18/04/13 19:23, Ian Jackson wrote:
>>> AFAICT what happens after your series is applied is that we always
>>> call prepare just before add, and unprepare just after remove (if I
>>> may neglect local attach for now).  So I don't see why these new
>>> functions are necessary to your new scripts.
>>
>> Do you mean that both prepare and add are called after the domain on the
>> sender side is paused?
> 
> I don't know exactly what I mean :-).
> 
>> Disks are prepared on "initiate_domain_create", which is the first
>> function that gets called on domain creation, on the other hand they are
>> added much later.
> 
> You can't write that in the documentation because it's in terms of
> the internal workings of libxl.
> 
> What is the purpose of the distinction between prepare and add ?

The main purpose of this distinction is that during migration the
"prepare" action is called before the guest on the sender side is
paused, so it allows to offload work from the "add" action, thus
reducing the blackout phase during migration.

I guess you want me to add this to the Documentation?

Thanks, Roger.

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