[LLVMdev] please stabilize the trunk

[Daniel Dunbar]

On Wed, Jul 15, 2009 at 7:52 PM, Nick Lewycky<nlewycky at google.com> wrote:
> 2009/7/15 Dale Johannesen <dalej at apple.com>
>>
>> On Jul 15, 2009, at 4:48 PMPDT, Daniel Dunbar wrote:
>>
>> > That depends on what you call a false positive. The public buildbot
>> > regularly fails because of mailing Frontend tests, and I have had
>> > continues failures of some DejaGNU tests for a long time on some
>> > builders. Its not a false positive per se, but one starts to ignore
>> > the failures because they aren't unexpected.
>>
>> Yes.  Probably the only way this will work better is if we get the
>> testsuite to 0 failures, everywhere, conditionalizing as necessary to
>> get rid of expected failures.  Then regressions will be more visible.
>> I doubt that will happen unless we freeze the tree for a while and get
>> everybody to fix bugs, or disable tests, instead of doing new stuff
>> (at least, that was the case for gcc).
>
> This is exactly what we're supposed to do for releases, and in theory, all
> of the time.
>
> We've been having a lot of churn lately. This is a good thing overall, since
> it means there's lots of contributions going into the project. What's
> different about this is that we have a lot of large-scale, sweeping changes
> that touch a lot of code. In the past we've generally serialized this sort
> of thing between contributors, or broken changes up to be extremely
> incremental. The reason this is happening less now is that we, as
> developers, are growing more ambitious with our fixes to LLVM systematic
> problems, and doing so on a tigher schedule. Once again, this is a good
> thing.

+1

> There's two issues with buildbots. Firstly, we need more buildbots on more
> platforms. For example, there are no Darwin buildbots, so if I commit a
> change that breaks Darwin I won't get immediate notice about it, nor a log
> of the failure.

I plan to solve this this week by serving a Darwin buildbot off my
home machine. I also hope to add an MSVC cmake based (and very slow)
buildbot relatively soon.

That will bring me up to serving a total of 4 buildslaves out of my
house, so if anyone else wants to contribute, please step up.

However, as Bill notes we have lots of internal bots and its fair that
Apple people have to maintain them (even if the breakage is due to an
external commit).

> We could even consider having a buildbot a prerequisite to
> being a release-blocking platform. The other is that we need some level of
> quality control on buildbots.

I'm not really sure what this means. The llvm-gcc problem I regard as
a bug in the LLVM test suite.

> We can accomplish this by either publishing a
> few buildbot guidelines (ie., don't install llvm-gcc on your buildbot
> machine because it will cause false-positives as llvm and llvm-gcc get out
> of step) and by enhancing the buildbot system to let us mark problems as
> expected. We already have part of that by XFAILing tests.

What actual enhancements would we need?

> Even so, better buildbots will improve visibility into how the tree is
> progressing on a commit-by-commit basis, but it does nothing to prevent
> breakage in the first place. I suspect most of our grief will go away as
> some of the current major changes finish.

I agree.

 - Daniel

> If not, we'll have to come up with a better way to handle so many large changes, maybe something like a
> "schedule of merges" so that committers don't step all over each other. I
> think GCC does something like this already?
>
> We've deferred imposing structure like that until we discover that we need
> it, and I'm not conviced we're quite there yet, but perhaps it's time to
> start thinking about it.
>
> Nick
>
>> > - Daniel
>> >
>> > On Wed, Jul 15, 2009 at 4:10 PM, Bill Wendling<isanbard at gmail.com>
>> > wrote:
>> >> On Wed, Jul 15, 2009 at 3:43 PM, Eli
>> >> Friedman<eli.friedman at gmail.com> wrote:
>> >>> On Wed, Jul 15, 2009 at 3:01 PM, Bill Wendling<isanbard at gmail.com>
>> >>> wrote:
>> >>>> The core problem, in my opinion, is that people *don't* pay
>> >>>> attention
>> >>>> to the build bot failure messages that come along.
>> >>>
>> >>> That's largely because of the number of false positives.
>> >>>
>> >> There have been fewer and fewer of these in recent times.
>> >>
>> >> -bw
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