Intermittent JRuby json issue related to tiered or G1

[Charles Oliver Nutter]

On Wed, Feb 17, 2021 at 9:14 AM Aleksey Shipilev <shade at redhat.com> wrote:
>
> On 2/17/21 3:50 PM, Aleksey Shipilev wrote:
> > I think I'll submit two issues: one that codes fold_compares_helper more defensively like in the
> > patch above (this would be backportable)
>
> This would be:
>    https://bugs.openjdk.java.net/browse/JDK-8261912
>
> > and then the follow-up that targets to address the actual
> > problem (why do we have uncanonicalized test).
>
> And this would be:
>    https://bugs.openjdk.java.net/browse/JDK-8261914

This is outstanding sleuthing, thank you Aleksey! I'm not happy that
there's a JVM issue but at least we can stop banging our heads against
this as a JRuby bug.

Given your discoveries, I would have felt safe saying this is purely a
tiered JIT issue... but our users have reported that switching away
from G1 also eliminates the problem. Were they just lucky? Could there
be a separate issue?

I'm trying to come up with a short-term workaround with minimal
impact. Switching GC may not be in the cards but disabling tiered
compilation would probably be acceptable for production
environments...if that is sufficient.

 As always let me know if we can provide any more information. The
affected JRuby users and I will continue monitoring.

- Charlie