[llvm-dev] amount of camelCase refactoring causing some downstream overhead

Wed Feb 19 13:02:04 PST 2020

With this kind of discussion, it's probably good to keep in mind that
every individual developer is really their own little downstream most
of the time.

Given how slow the LLVM review process is, many developers probably
have a few changes in flight most of the time. Gratuitous churn forces
them into rebases, as well. So "being nice to downstreams" and "being
nice to all LLVM developers" is often very well aligned and not in
conflict at all!

Cheers,
Nicolai

On Wed, Feb 19, 2020 at 9:49 PM David Blaikie via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>
>
>
> On Wed, Feb 19, 2020 at 12:10 PM Robinson, Paul via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>
>> Hi Philip,
>>
>>
>>
>> I think you might be reading more into the suggestion/discussion than is actually there.
>>
>>
>>
>> I do not want upstream developers "trying to be polite" if that delays otherwise worthwhile work.
>>
>> Nobody suggested that.  It’s perfectly possible to “be polite” and still not delay worthwhile work.
>>
>>
>>
>> The current policy is "downstream is on their own".
>>
>> Nobody disputes that.
>>
>>
>>
>> There was nothing even remotely unreasonable done in the patch series which triggered this discussion and I don't want any upstream contributor coming to believe there was.
>>
>> I disagree with you about “nothing even remotely unreasonable” in that I think it was done slightly unreasonably, and I think it’s worthwhile to have other upstream contributors acknowledge that feeling.
>>
>>
>>
>> What I’m aware of is a series of 5 separate patches, each of which re-capitalized a select subset of APIs in the same area.  This fixing-up is *long overdue* and I’m very happy to see it done.  But I will dispute the “reasonableness” of doing it in 5 separate stages (plus a few other related cleanups that were not simply re-capitalizing existing names).
>
>
> Yeah, I'm not sure how I'd have done it - imagine I'd have done it more likely at either extreme - renaming one function at a time (which probably would've been more disruptive than what happened, I guess) or the whole class.
>
>>
>> The notion of “reviewable size” is not relevant, because these patches were not reviewed (in accordance with current policy, that this kind of mechanical fixup is “obvious” and does not require pre-commit review).
>
>
> FWIW, post-commit review is still important to me (& revertability of patches, even those made through automated means - though, in the case of reformats/renames that can argue in favor of larger patches rather than having to figure out how to revert a whole series of dependent patches because the changes are very close together).
>
>>
>> The patches were not really very distinct, with a HUGE overlap in the set of affected files.
>
>
> I'm not sure the set of affected files weighs much in my mind in this - if the changes are sufficiently separated within those files.
>
>>
>>  We do like to minimize churn; this kind of fixup clearly qualifies as churn, but I respectfully submit that the way it was done does not *minimize* the churn.
>
>
> Churn to me is changing and rechanging the same things - and sometimes "change for the sake of change"/large scale changes in general (with the concerns around difficult blame, etc) - the sort of changes that are likely to disrupt existing outstanding patches, etc. (perhaps that's a good place where there's overlap in motives/incentives - outstanding upstream patches suffer some of the same problems as downstream forks (essentially a very large amount of indefinitely outstanding patches) - and making choices that reduce the frequency/total amount of work to keep those patches up to date is generally a good thing, but is weighed against other benefits for sure)
>
>>
>>  And minimizing the churn is good for both the project and those of us who live downstream of it.
>>
>> --paulr
>>
>>
>>
>> From: llvm-dev <llvm-dev-bounces at lists.llvm.org> On Behalf Of Philip Reames via llvm-dev
>> Sent: Wednesday, February 19, 2020 2:07 PM
>> To: Eric Christopher <echristo at gmail.com>
>> Cc: llvm-dev <llvm-dev at lists.llvm.org>; Valentin Churavy <v.churavy at gmail.com>
>> Subject: Re: [llvm-dev] amount of camelCase refactoring causing some downstream overhead
>>
>>
>>
>> Eric,
>>
>> I disagree.  Strongly.   I see the very fact we're engaging in the discussion of "just being polite" here as normalizing a proposed change in policy which has potentially profound negative consequences for the project long term.  I do not want upstream developers "trying to be polite" if that delays otherwise worthwhile work.  The current policy is "downstream is on their own".  There was nothing even remotely unreasonable done in the patch series which triggered this discussion and I don't want any upstream contributor coming to believe there was.
>>
>> Again, I'm open to carefully weighted proposals to change current policy.  I also have a downstream repo which is kept up to date and I understand the pain point being raised.  I just want to be very careful to distinguish between existing status, and any proposed changes.  I want the proposed changes to be carefully weighed before being put into effect.
>>
>> Philip
>>
>> On 2/18/20 4:39 PM, Eric Christopher wrote:
>>
>> Hi Philip,
>>
>>
>>
>> While it's true we don't I think Valentin is reasonable in saying "hey, when people do this let's try to combine them if it makes sense". It's just being polite to everyone, especially if it doesn't risk the patches or upstream stability. I don't think there's a policy change being proposed, just a "hey, let's see what we can do in the future".
>>
>>
>>
>> -eric
>>
>>
>>
>> On Tue, Feb 18, 2020 at 4:05 PM Philip Reames via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>
>> Valentin,
>>
>> You are proposing to change existing policy.  Current policy is that we don't consider downstream *at all*.  Your proposal may seem reasonable - it may even *be* reasonable - but it is definitely a change from historical practice and must be considered as such.
>>
>> Philip
>>
>> On 2/18/20 3:03 PM, Valentin Churavy wrote:
>>
>> I don't think anyone is arguing to change longstanding policy. From a downstream perspective many small renaming changes do increase overhead for us.
>>
>>
>>
>> One thing that happens to downstream projects is that they support more than one LLVM version, we (JuliaLang) currently try to support latest stable + master.
>>
>>
>>
>> So for me the question is more, are renaming changes worth downstream projects not being able to test and provide feedback to upstream?  One way of mitigating that is to consciously schedule them just before a release and do them all in short succession.
>>
>>
>>
>> -V
>>
>>
>>
>>
>>
>> On Tue, Feb 18, 2020, 17:00 Philip Reames via llvm-dev <llvm-dev at lists.llvm.org> wrote:
>>
>> As others have said, our long standing policy has been that downstream
>> projects must fend for themselves.  We're certainly not going to reverse
>> that policy without careful discussion of the tradeoffs.
>>
>> I'm personally of the opinion that there could be a middle ground which
>> allows upstream to move quickly while reducing headache for downstream
>> projects.  Given I wear both hats, I know I'd certainly appreciate such
>> a state.  However, it's important to state that such decisions would
>> need to be carefully considered and would require some very careful
>> drafting of proposal to balance the competing interests at hand.
>>
>> If anyone is curious, I'm happy to share some ideas offline on what
>> starting points might be, but I have neither the time nor the interest
>> to drive such a conversion on list.
>>
>> Philip
>>
>> On 2/18/20 1:37 AM, Ties Stuij via llvm-dev wrote:
>> > During that variable renaming debate, there was a discussion about discussion about doing things all at once, piecemeal or not at all. An issue that wasn't really resolved I think. I had the impression that the efforts fizzled out a bit, and I thought this renaming was maybe related to that, but I'm neutral on if we should do variable renaming.
>> >
>> > All I'm asking as a kindness if we could be kind on poor downstream maintainers not on the issue of variable renaming at large, but on the micro level of not pushing 5/6 patches of this kind covering closely related functionality in two days but collating them in 1. I don't think that would slow down development, and I wanted to highlight the issue, as people might not be aware that they could save some pain in a simple way. Especially if indeed there is going to be a big renaming push and this would be a continuous thing.
>> >
>> > Cheers,
>> > /Ties
>> >
>> > ________________________________________
>> > From: Michael Kruse <llvmdev at meinersbur.de>
>> > Sent: 17 February 2020 21:16
>> > To: Ties Stuij
>> > Cc: llvm-dev
>> > Subject: Re: [llvm-dev] amount of camelCase refactoring causing some downstream overhead
>> >
>> > My understanding is that LLVM's general policy is to not let
>> > downstream slow down upstream development. The C++ API explicitly
>> > unstable.
>> >
>> > Note that we are even considering renaming variables globally:
>> > https://lists.llvm.org/pipermail/llvm-dev/2019-September/134921.html
>> >
>> > Michael
>> >
>> > Am Mo., 17. Feb. 2020 um 06:04 Uhr schrieb Ties Stuij via llvm-dev
>> > <llvm-dev at lists.llvm.org>:
>> >> Hi there,
>> >>
>> >> At the end of last week we saw a number of commits go in that were camelCasing batches of MCStreamer::Emit* and AsmPrinter::Emit* functions.
>> >>
>> >> For example:
>> >> - https://reviews.llvm.org/rG549b436beb4129854e729a3e1398f03429149691
>> >> - https://reviews.llvm.org/rGa55daa146166353236aa528546397226bee9363b
>> >> - https://reviews.llvm.org/rG0bc77a0f0d1606520c7ad0ea72c434661786a956
>> >>
>> >> Unfortunately all these individual commits trigger the same merge conflicts over and over again with our downstream repo, which takes us some manual intervention every time.
>> >>
>> >> I understand uniformity is a nice to have, but:
>> >> 1 - is it worth it to do this work right now? I can remember the casing debate a few months back, which seems unrelated to this work which seems manual, but I'm unsure of the outcome.
>> >> 2 - If this work should be done, it would be nice if all of the work is done in one batch, to save us some of the downstream overhead.
>> >>
>> >> Thanks
>> >> /Ties
>> >> _______________________________________________
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