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SubjectRe: The direction linux is taking
Date
On Monday 31 December 2001 08:32 pm, Horst von Brand wrote:

> Hummm... I guess this is because yoiu see new (development, pre, ...)
> kernels each few days. Alan said he gets mosly line shifts (==
> non-overlapping patches, or "people should be talking to each other").
> Maybe due to the rapid version turnover? Maybe most of the merging is being
> done by the posters themselves during development, as Ye Kernel Gods refuse
> to do it for them?

Ye kernel gods can spend an afternoon reviewing 15 patches that apply cleanly
to see if their changes are a good idea, or they can spend that afternoon
cleaning up and merging one.

Cleaning up and marging is something the patch's author can do, or thousands
of other random developers on the list. Exerting editorial judgement on what
is and isn't a good idea is NOT something everybody else can do.

Which is a better use of the maintainer's time?

> I'm surprised that commercial shops see much merging. I'd assume they have
> direct access to the up-to-the-minute source, so _less_ merging should be
> necesary. Or they are (over)confident in their tools, and just work on
> stale sources?

Commercial shops believe that developers are interchangeable, and that
developers should know what it is they're going to do before they do it. So
if you have three pending changes in this area of the code, you assign them
to three developers in paralell as a matter of course. (Then there's code
reviews with people who disagree with your choice of variable and function
names EVERY TIME... But we won't go there.)

A medium-small change in a commercial shop can easily take two weeks, and you
have to check the code out to do it. (This locks the code you've changed so
nobody else can change it until you check the changed files back in or
somebody with administrator access breaks the lock.) So either:

You check out the files you're going to change and keep them checked out for
a week or two while you design, implement, test, code review, make the
changes the code reviewer wants (it's like getting your car inspected, they
always find something you need even if it's just busy-work), test again, yell
at the code reviewer for making a stupid suggestion that shows a profound
lack of understanding of the code, have a meeting to resolve it, lose, have
to write a workaround in a completely unrelated section of the code, wait for
the guy in the testing lab to get back from vacation...

Ahem. Either you keep the files checked out all that time, or you check them
out at the last minute (tracking down whoever has the last two files you need
checked out and getting them to check them back in), merge your changes with
what's there (often a good day's worth of work right there), and check it
back in. Except when you have to get your merge code reviewed, and then a
manager to sign off on the fact it's BEEN code reviewed, and then it goes to
test again...

Yes, merging is a big deal in Fortune 500 shops. Read the mythical
man-month... :)

> > Some sociology guy with a CS background should do a study on this and
> > explore the differences. Is fast change better? Is slow change better?
>
> I think the difference lies elsewhere.

Between the mythical man-month, the cathedral and the bazaar, and the
innovator's dilemma, I think the study's already been done. But since no
graduate student's taken credit for a thesis or dissertation on it yet, I'm
sure there's still an opportunity to take credit in the ivory towers of
academia...

Rob
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