Product lifecycles and kernel impacts

[Josh Boyer]

Hi All,

I've seen a lot of discussion around release cycles and lifetimes.
I've not heard any specific requests for what impacts any of the
current ideas would have to the kernel, but that doesn't mean they
won't be coming.  We should probably start thinking about various
things we can support today, what we could possibly support in the
future, and what we'd need to do it.  I've CC'd the Product liaisons
so they can see this.  Please keep them on CC.

The first scenario I can think of is probably some kind of "long-term"
release.  Exactly what long-term means here is undefined, but we
already support a Fedora release for 13 months or so.  We do that
today with rolling kernel releases.  We could possibly continue, but I
expect the Products to desire something more "stable".

What that implies is that we'd likely need to base on an upstream
longterm kernel.  That means:

1) No new kernel features.
2) No new hardware enablement outside of things acceptable for an
upstream longterm commit (basically just adding a new USB/PCI id to an
existing driver).
3) Bugfixes will primarily come from the upstream longterm tree
4) There will be no alternative kernels supported on the Fedora
longterm release.
5) There are no guarantees on bugfixes, response time, etc.

If any of the above are desired, people are better off picking an
Enterprise distro where you have contracted support.

So if that's the case, the feasibility of this is going to hinge a lot
on timing.  I would think from a kernel perspective we'd know up-front
when a Fedora longterm was going to happen, and we'd try and align
that release with the newest official longterm stable kernel.  Those
are maintained for 2 years, which seems to be a good fit for a Fedora
longterm release.  Any longer than that and you're back in the
Enterprise space again.

The second scenario I can think of is products with mismatched release
cycles.  E.g. Server doing a 2 year longterm and developing the
Server.next release on top of Base, which releases every 6 months.  Or
Workstation doing a release once a year while Base moves every 6
months.  Etc.  It's hard to come up with a concrete scenario since
none of the products have gotten this far.  It's worth noting that
FESCo is basically disallowing this for the first releases, so this is
a secondary concern.

I would propose that for Base, we continue our current method of
rebasing with each kernel release.  That has been working very well
for the past few Fedora releases, and gets us the most "bang for the
buck" in terms of features, hardware support, and fixes. A year long
release for e.g. Workstation would likely also desire the newer
support and features, so they could probably just update their kernel
in the same way.  This keeps our maintenance costs down to today's and
gives products flexibility.

In the Server LTS + Server.next development scenario, I would expect
the LTS to use the longterm kernel as suggested above which means
whenever they cut over to LTS mode it would need to coincide with an
upstream longterm kernel.  That would be something we have to watch
and plan for.  Server.next would continue to use Base until it was
ready to cut over and repeat.  I hope that makes sense.

In terms of people, the only major change I see would be the longterm
addition.  That might be something we can tuck, but having additional
QA and maintainer resources would allow us to cover development and
support better.  If there was any major deviation in which kernel was
used in the various products, we'd likely need either the Product
teams themselves to pick up maintenance or additional people on the
kernel team to handle that.  The desire here is to keep the kernel
common among as many Products and releases as we can.

This is mostly just some thoughts I've had on the topics so far.  Let
me know what you all are thinking and please ask questions or propose
alternatives as you see fit.

josh