Any new ideas on JDK-8187338 (Per anonymous class class loader data is costly)?

[Thomas Stüfe]

Hi Zhengyu and Andrew,

Have you had any new ideas on how to deal with
https://bugs.openjdk.java.net/browse/JDK-8187338?

I also see this in my tests and I think this will be an issue with our
customers.

My thoughts are

1) as a first workaround to provide a threshold switch to change the
small-chunk-limit - the number of bytes a class loader has to allocate from
metaspace and classpace to qualify for medium sized chunks. With such a
switch, one could at least tune a system which shows a pathological
allocation pattern. E.g., using Zhengyu's new NMT per-classloader trace, if
I see that the majority of all class loaders stop allocating after 500K,
I'd set the threshold to 500K.

2) Future better solutions could involve some kind of self-regulating
mechanism: Somehow automatically identifying which are "tiny" class loaders
- loaders which have with a certain probability stopped allocoating while
still gnawing at their first or second medium chunk. And then, using that
number, dynamically adjusting the small-chunk-limit for future class
loaders.

(1) could be quite easily implemented. What do you think?

Kind Regards, Thomas