Re: Maintainer-review fluff (was: Re: [PATCH 01/12] drm/i915: plumb VM into object operations)

[Ben Widawsky <ben@bwidawsk.net>]

On Sat, Jul 27, 2013 at 09:13:38AM +1000, Dave Airlie wrote:
> >
> > Hey, overall it's actually quite a bit of fun.
> >
> > I do agree that QA is really important for a fastpaced process, but
> > it's also not the only peace to get something in. Review (both of the
> > patch itself but also of  the test coverage) catches a lot of issues,
> > and in many cases not the same ones as QA would. Especially if the
> > testcoverage of a new feature is less than stellar, which imo is still
> > the case for gem due to the tons of finickle cornercases.
> 
> Just my 2c worth on this topic, since I like the current process, and
> I believe making it too formal is probably going to make things suck
> too much.
> 
> I'd rather Daniel was slowing you guys down up front more, I don't
> give a crap about Intel project management or personal manager relying
> on getting features merged when, I do care that you engineers when you
> merge something generally get transferred 100% onto something else and
> don't react strongly enough to issues on older code you have created
> that either have lain dormant since patches merged or are regressions
> since patches merged. So I believe the slowing down of merging
> features gives a better chance of QA or other random devs of finding
> the misc regressions while you are still focused on the code and
> hitting the long term bugs that you guys rarely get resourced to fix
> unless I threaten to stop pulling stuff.
> 
> So whatever Daniel says goes as far as I'm concerned, if I even
> suspect he's taken some internal Intel pressure to merge some feature,
> I'm going to stop pulling from him faster than I stopped pulling from
> the previous maintainers :-), so yeah engineers should be prepared to
> backup what they post even if Daniel is wrong, but on the other hand
> they need to demonstrate they understand the code they are pushing and
> sometimes with ppgtt and contexts I'm not sure anyone really
> understands how the hw works let alone the sw :-P
> 
> Dave.

Honestly, I wouldn't have responded if you didn't mention the Intel
program management thing...

The problem I am trying to emphasize, and let's use contexts/ppgtt as an
example, is we have three options:
1. It's complicated, and a big change, so let's not do it.
2. I continue to rebase the massive change on top of the extremely fast
paced i915 tree, with no QA coverage.
3. We get decent bits merged ASAP by putting it in a repo that both gets
much wider usage than my personal branch, and gets nightly QA coverage.

PPGTT + Contexts have existed for a while, and so we went with #1 for
quite a while.

Now we're at #2. There's two sides to your 'developer needs to
defend...' I need Daniel to give succinct feedback, and agree upon steps
required to get code merged. My original gripe was that it's hard to
deal with the, "that patch is too big" comments almost 2 months after
the first version was sent. Equally, "that looks funny" without a real
explanation of what looks funny, or sufficient thought up front about
what might look better is just as hard to deal with. Inevitably, yes -
it's a big scary series of patches - but if we're honest with ourselves,
it's almost guaranteed to blow up somewhere regardless of how much we
rework it, and who reviews it. Blowing up long before you merge would
always be better than the after you merge.

My desire is to get to something like #3. I had a really long paragraph
on why and how we could do that, but I've redacted it. Let's just leave
it as, I think that should be the goal.

Finally, let me clear that none of the discussion I'm having with Daniel
that spawned this thread are inspired by Intel program management. My
personal opinion is that your firm stance has really helped us
internally to fight back stupid decisions. Honestly, I wish you had a
more direct input into our management, and product planners.

-- 
Ben Widawsky, Intel Open Source Technology Center