Date:	Thu, 1 May 2008 16:35:24 +0200
From:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Willy Tarreau <w@....eu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	David Miller <davem@...emloft.net>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jiri Slaby <jirislaby@...il.com>
Subject: Re: Slow DOWN, please!!!

On Thursday 01 May 2008, Rafael J. Wysocki wrote:
> On Thursday, 1 of May 2008, Bartlomiej Zolnierkiewicz wrote:
> > On Thursday 01 May 2008, Rafael J. Wysocki wrote:
> > > On Thursday, 1 of May 2008, Willy Tarreau wrote:
> > > > On Wed, Apr 30, 2008 at 06:19:56PM -0700, Linus Torvalds wrote:
> > > > > 
> > > > > 
> > > > > On Thu, 1 May 2008, Rafael J. Wysocki wrote:
> > > > > > 
> > > > > > > I do _not_ want to slow down development by setting some kind of "quality 
> > > > > > > bar" - but I do believe that we should keep our quality high, not because 
> > > > > > > of any hoops we need to jump through, but because we take pride in the 
> > > > > > > thing we do.
> > > > > > 
> > > > > > Well, we certainly should, but do we always remeber about it?  Honest, guv?
> > > > > 
> > > > > Hey, guv, do you _honestly_ believe that some kind of ISO-9000-like 
> > > > > process generates quality?
> > > > > 
> > > > > And I dislike how people try to conflate "quality" and "merging speed" as 
> > > > > if there was any reason what-so-ever to believe that they are related.
> > > > > 
> > > > > You (and Andrew) have tried to argue that slowing things down results in 
> > > > > better quality, and I simply don't for a moment believe that. I believe 
> > > > > the exact opposite.
> > > > 
> > > > Note that I'm not necessarily arguing for slowing down, but for reduced
> > > > functional conflicts (which slow down may help but it's not the only
> > > > solution). I think that refining the time resolution might achieve the
> > > > same goal. Instead of merging 10000 changes which each have 1% chance
> > > > of breaking any other area, and have all developers try to hunt bugs
> > > > caused by unrelated changes, I think we could do that in steps.
> > > > 
> > > > To illustrate, instead of changing 100 areas with one of them causing
> > > > breaking in the other ones, and having 100 victims try to hunt the
> > > > bug in 99 other areas, then theirs, and finally insult the faulty
> > > > author, we could merge 50 areas in version X and 50 in X+1 (or 3*33
> > > > or 4*25, etc...). That way, we would only have 50 victims trying to
> > > > find the bug in 49 other areas (or 32 or 24). Less people wasting
> > > > their time will mean faster validation of changes, and possibly
> > > > faster release cycle with better quality.
> > > > 
> > > > People send you their crap every two months. If you accept half of
> > > > it every month, they don't have to sleep on their code, and at the
> > > > same time at most half of them are in trouble during half the time
> > > > (since bugs are found faster).
> > > 
> > > Well, as far as I'm concerned, that will work too.
> > > 
> > > > > So if we can get the discussion *away* from the "let's slow things down", 
> > > > > then I'm interested. Because at that point we don't have to fight made-up 
> > > > > arguments about something irrelevant.
> > > > 
> > > > well, is "let's split changes" ok ?
> > > 
> > > How about:
> > > 
> > > (1) Merge a couple of trees at a time (one tree at a time would be ideal, but
> > >     that's impossible due to the total number of trees).
> > > (2) After (1) give testers some time to report problems introduced by the
> > >     merge.
> > > (3) Wait until the most urgent problems are resolved.  Revert the offending
> > >     changes if there's no solution within given time.
> > > (4) Repeat for another couple of trees.
> > > (5) Arrange things so that every tree gets merged once every two months.
> > > 
> > > This would also give us an idea of which trees introduce more problems.
> > 
> > ...and what would you do with such information?
> > 
> > I'm not actually worried about my tree but if (theoretically) it happens to
> > be amongst the "problematic" ones I would be a bit pissed by blame shifting,
> > especially given that it is very difficult to compare different trees as
> > they (usually) deal with quite different areas of the code (some are messy
> > and problematic, yet critical while others can be more forgiving).
> > 
> > Also slowing down things to focus on quality is really a bad idea.  You can
> > trust me on this one, I've tried it once on the smaller scale and it was a
> > big disaster cause people won't focus on quality just because you want them
> > to.  They'll continue to operate in the usual way and try to workaround you
> > instead (which in turn causes extra tensions which may become quiet warfare).
> > In the end you will have a lot more problems to deal with...
> 
> Well, I won't discuss with your experience.
> 
> > Same goes for any other kind of improvement by incorporating "punishment" as
> > the part of the process.  You are much better helping people and trying them
> > to understand that they should apply some changes to their way of work because
> > it would be also beneficial for _them_, not only for _you_.
> 
> I agree.
> 
> > Now regarding the development model - I think that there is really no need
> > for a revolution yet, instead we should focus on refining the current process
> > (which works great IMO), just to summarize various ideas given by people:
> > 
> > - try to persuade few black sheeps that skipping linux-next completely for
> >   whole patch series is a really bad idea and that they should try to spend
> >   a bit more time on planning for merge instead of LastMinute assembly+push
> >   (by doing it right they could spend more time after merge to prepare for
> >   the next one or fixing old bugs instead of chasing new regressions, overall
> >   they should have _more_ time for development by doing it right)
> > 
> > - encourage flatting of merges during the merge window so instead of 1-2 big
> >   merges per tree at the beginning of the merge you have few smaller ones
> >   (majority of maintainers do it this way already)
> > 
> > - more testing for linux-next, distros may be of a great help here (-mm and
> >   -next often catches bugs that you wouldn't have ever imagined in the first
> >   place and they get fixed before the problem propagates into Linus' tree)
> 
> There still are too many bugs of this kind that make it to the Linus' tree and
> they are the source of this thread.

Agreed but if you trace the way of these bugs into the Linus' tree many of
them follow one of two patterns:

* -mm / -next skipped completely

* short time in -mm / -next (< 2 weeks)

[ disclaimer: this is based on my observations, no hard data to prove it ]

Please also remember that linux-next concept is still quite _fresh_ with
a _plenty_ of room for enhancements like having kernel-du-jour packages for
the most popular distros, doing more automated testing + searching for
error strings in logs etc.

> > - more documentation for lowering the entry barrier for people who would like
> >   to review the code (what Al has mentioned in this thread is a great idea
> >   so no need for me to repeat it here)
> 
> Agreed.
> 
> > - more co-operation between people from different areas of the code
> >   (i.e. testing linux-next instead of your own tree)
> 
> Agreed.
> 
> > and just not to forget - changes happen by people actually putting the work
> > into them not by endless discussions.
> 
> Well, I'm not sure what that's supposed to mean, so I won't comment.

This was not directed at you (you are doing great work BTW) but rather
at some people trolling the thread.

Thanks,
Bart
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