RFC: Draft JEP: Improved Metaspace allocator

[Thomas Schatzl]

On Wed, 2019-03-20 at 20:19 +0100, Thomas Stüfe wrote:
> Dear all,
> 
> I would like to hear what you think about the following proposal:
> 
> https://bugs.openjdk.java.net/browse/JDK-8221173
> 
> Do you consider this worthwhile?

Yes, definitely!

At the beginning of this month we were internally looking at a
metaspace stress application, and it took some time to nail the problem
on metaspace fragmentation. Improving fragmentation, the visibility of
such problems (fragmentation statistics) and potential options to e.g.
favor compactness vs. performance.

> I debated with myself whether a JEP is the correct umbrella for it.
> In the past I did larger changes like this without JEP but in this
> case I feel better with a confirmed and sponsored JEP behind me -
> from a certain size on it just feels more appropriate.
> 
> As usual, I am not sure where to put Metaspace-related proposals to
> catch all interested people, so I start with hs-dev. Please feel free
> to redirect if needed.

You are right that a JEP is the only way to get guaranteed visibility
to people. JEPs are mostly the only source for third party "what's new
in JDK XX" write-ups.
So if you want to reach a wide (non-hotspot-dev) audience, JEPs are
basically the only way. I could kind of see that this might be the
case.

Thanks,
  Thomas