Re: Scalable Event Channel ABI design (draft A)

[David Vrabel <david.vrabel@citrix.com>]

On 05/02/13 18:05, George Dunlap wrote:
> On Tue, Feb 5, 2013 at 3:16 PM, Wei Liu <wei.liu2@citrix.com
> <mailto:wei.liu2@citrix.com>> wrote:
> 
>     > Since the ABI needs to be changed to support more event channels
>     anyway,
>     > it seems an ideal point to revisit the design.
>     >
> 
>     Right. I do care about better design and good implementation. Can we
>     build a prototype of this design? We are less than two months away from
>     4.3 feature freeze, and the event channel scalability is planned for
>     that release, which means we need to be hurried. :-)

Two months doesn't seem possible even if I could work on this full time.

> I think the general consensus is that scaling event channels is pretty
> important -- probably important enough to slip the release a bit if
> necessary.  (Although it would certainly be better not to.)

What to do here is a non-trivial decision.  Possible options include:

1. Merge the 3-level ABI for 4.3.  Work on the FIFO-based ABI in
parallel, aiming to get this in for 4.4.  This means maintaining 3 event
channel ABIs in Xen.

2. Slip the 4.3 release for 2-3 months and merge the FIFO-based ABI in.

3. Status quo.  Defer extending the event channel ABI to 4.4.

The preferable option may be to:

4. Get the 3-level ABI to a mergable state. In parallel develop a
prototype of the FIFO-based ABI.  When the prototype is ready or the 4.3
freeze is here, evaluate it and make a decision then.

David