Re: [Xen-devel] [RFC] PVFB: Add refresh period to XenStore parameters?

[Markus Armbruster <armbru@xxxxxxxxxx>]

Samuel Thibault <samuel.thibault@xxxxxxxxxxxxx> writes:

> Markus Armbruster, le Tue 06 May 2008 18:50:04 +0200, a Ãcrit :
>> > Instead of expressing idleness or "status", maybe we could rather
>> > express whether periodic update notifications are wanted or not, and let
>> > the backend request an explicit update notification when it feels the
>> > need for one (low-frequency thumbnail update). It has the advantage of
>> > only talking about the PVFB protocol itself and not something around it
>> > (idleness of the actual output).  That is also backward compatible in
>> > that a frontend which doesn't know these two events will just continue
>> > sending periodic update notifications, which is fine for the backend.
>> 
>> I think that's a better way to define this feature.
>
> More precisely, we could have an UPDATE_PERIOD event which carries
> an advice from the backend about how often the frontend should sent
> update notifications (0 if periodic notification is not useful), and a
> REQUEST_UPDATE event that requests a one-time update notification?  The
> latter could even contain the requested area? (not sure whether it'd be
> really useful considering the added complexity, though).
>
> Samuel

I figure your UPDATE_PERIOD advice event is a sensible way to solve
your problem.  Frontends are free to use the advice as they see fit.

Why do you need REQUEST_UPDATE?  Perhaps because your frontend doesn't
want to keep the shared framebuffer up-to-date?

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