Re: [RFC: kdevops] Standardizing on failure rate nomenclature for expunges

[Matthew Wilcox <willy@infradead.org>]

On Thu, May 19, 2022 at 11:44:19PM +0800, Zorro Lang wrote:
> On Thu, May 19, 2022 at 03:58:31PM +0100, Matthew Wilcox wrote:
> > On Thu, May 19, 2022 at 07:24:50PM +0800, Zorro Lang wrote:
> > > Yes, we talked about this, but if I don't rememeber wrong, I recommended each
> > > downstream testers maintain their own "testing data/config", likes exclude
> > > list, failed ratio, known failures etc. I think they're not suitable to be
> > > fixed in the mainline fstests.
> > 
> > This assumes a certain level of expertise, which is a barrier to entry.
> > 
> > For someone who wants to check "Did my patch to filesystem Y that I have
> > never touched before break anything?", having non-deterministic tests
> > run by default is bad.
> > 
> > As an example, run xfstests against jfs.  Hundreds of failures, including
> > some very scary-looking assertion failures from the page allocator.
> > They're (mostly) harmless in fact, just being a memory leak, but it
> > makes xfstests useless for this scenario.
> > 
> > Even for well-maintained filesystems like xfs which is regularly tested,
> > I expect generic/270 and a few others to fail.  They just do, and they're
> > not an indication that *I* broke anything.
> > 
> > By all means, we want to keep tests around which have failures, but
> > they need to be restricted to people who have a level of expertise and
> > interest in fixing long-standing problems, not people who are looking
> > for regressions.
> 
> It's hard to make sure if a failure is a regression, if someone only run
> the test once. The testers need some experience, at least need some
> history test data.
> 
> If a tester find a case has 10% chance fail on his system, to make sure
> it's a regression or not, if he doesn't have history test data, at least
> he need to do the same test more times on old kernel version with his
> system. If it never fail on old kernel version, but can fail on new kernel.
> Then we suspect it's a regression.
> 
> Even if the tester isn't an expert of the fs he's testing, he can report
> this issue to that fs experts, to get more checking. For downstream kernel,
> he has to report to the maintainers of downstream, or check by himself.
> If a case pass on upstream, but fail on downstream, it might mean there's
> a patchset on upstream can be backported.
> 
> So, anyway, the testers need their own "experience" (include testing history
> data, known issue, etc) to judge if a failure is a suspected regression, or
> a known issue of downstream which hasn't been fixed (by backport).
> 
> That's my personal perspective :)

Right, but that's the personal perspective of an expert tester.  I don't
particularly want to build that expertise myself; I want to write patches
which touch dozens of filesystems, and I want to be able to smoke-test
those patches.  Maybe xfstests or kdevops doesn't want to solve that
problem, but that would seem like a waste of other peoples time.