[llvm-dev] buildbot failure in LLVM on clang-native-arm-cortex-a9

Mehdi Amini via llvm-dev llvm-dev at lists.llvm.org
Wed Aug 26 09:01:51 PDT 2015

> On Aug 26, 2015, at 8:21 AM, Renato Golin via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> On 26 August 2015 at 15:44, Tobias Grosser <tobias at grosser.es> wrote:
>> What time-line do you have in mind for this fix? If you are in charge
>> and can make this happen within a day, giving cmake + ninja a chance seems
>> OK.
> It's not my bot. All my bots are CMake+Ninja based and are stable enough.
>> However, if the owner of the buildbot is not known or the fix can not come
>> soon, I am in favor of disabling the noise and (re)enabling it when someone
>> found time to address the problem and verify the solution.
> That's up to Galina. We haven't had any action against unstable bots
> so far, and this is not the only one. There are lots of Windows and
> sanitizer bots that break randomly and provide little information, are
> we going to disable them all? How about the perf bots that still fail
> occasionally and we haven't managed to fix the root cause, are we
> going to disable then, too?
> You're asking to reduce considerably the quality of testing on some
> areas so that you can reduce the time spent looking at spurious
> failures. I don't agree with that in principle.

That’s not how I understand his point. In my opinion, he is asking to increase the quality of testing. You just happen to disagree on his solution :)

The situation does not seem that black and white to me here. In the end, it seems to me that is is about a threshold: if a bot is crashing 90% of the time, does it really contributes to increase the quality of testing or on the opposite it is just adding noise? Same question with 20%, 40%, 60%, …  We may all have a different answer, but I’m pretty sure we could reach an agreement on what seems appropriate

Another way of considering in general the impact of a bot on the quality is: “how many legit failures were found by this bot in the last x years that weren’t covered by another bot”.
Because sometimes you may just having a HW lab stress rack, without providing any increased coverage for the software.



> There were other
> threads focusing on how to make them less spurious, more stable, less
> noisy, and some work is being done on the GreenDragon bot structure.
> But killing everything that looks suspicious now will reduce our
> ability to validate LLVM on the range of configurations that we do
> today, and that, for me, is a lot worse than a few minutes' worth of
> some engineers.
>> The cost of
>> buildbot noise is very high, both in terms of developer time spent, but
>> more importantly due to people starting to ignore them when monitoring them
>> becomes costly.
> I think you're overestimating the cost.
> When I get bot emails, I click on the link and if it was timeout, I
> always ignore it. If I can't make heads or tails (like the sanitizer
> ones), I ignore it temporarily, then look again next day.
> My assumption is that the bot owner will make me aware if the reason
> is not obvious, as I do with my bots. I always wait for people to
> realise, and fix. But if they can't, either because the bot was
> already broken, or because the breakage isn't clear, I let people know
> where to search for the information in the bot itself. This is my
> responsibility as a bot owner.
> I appreciate the benefit of having green / red bots, but you also have
> to appreciate that hardware is not perfect, and they will invariably
> fail once in a while. I had some Polly bots failing randomly and it
> took me only a couple of seconds to infer so. I'm not asking to remove
> them, even those that fail more than pass throughout the year. I
> assume that, if they're still there, it provides *some* value to
> someone.
> cheers,
> --renato
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