Leaking LambdaForm classes?

[Vladimir Ivanov]

LambdaForm caches deliberately keep LF instances using SoftReferences.

The motivation is:
   (1) LFs are heavily shared;
   (2) LFs are expensive to construct (LF interpreter is turned off by 
default now); it involves the following steps: new LF instance + compile 
to bytecode + class loading.

So, keeping a LF instance for a while usually pays off, especially 
during startup/warmup. There should be some heap/metaspace pressure to 
get them cleared.

As a workaround, try -XX:SoftRefLRUPolicyMSPerMB=0 to make soft 
references behave as weak.

On 1/6/17 8:32 PM, Charles Oliver Nutter wrote:
> Anyone else encountered this?
>
> https://github.com/jruby/jruby/issues/4391

Not sure the problem relates to j.l.i & LFs since the report says indy 
in jruby is turned off. For heavy usages of indy/j.l.i 1000s of LFs are 
expected (<5k). The question is how does the count change over time.

Best regards,
Vladimir Ivanov


>
> We have a user reporting metaspace getting filled up with LambdaForm
> classes that have no instances. I would not expect this to happen given
> that they're generated via AnonymousClassloader and we would need to
> hold a reference to them to keep them alive.
>
> I'm trying to get a heap dump from this user. If anyone has other
> suggestions, feel free to comment on the issue.
>
> - Charlie
>
>
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