RFR: 8309603: Deallocate hashtables in ClassLoaderData::unload

[Coleen Phillimore]

On Tue, 11 Jul 2023 00:01:54 GMT, Chad Rakoczy <duke at openjdk.org> wrote:

> [JDK-8309603](https://bugs.openjdk.org/browse/JDK-8309603)
> 
> Memory is released in `ClassLoaderdata::~ClassLoaderData` for the dictionary and module hashtables but they could be deleted earlier in `ClassLoaderdata::unload`. Since we're unloading the class loader is no longer being used for lookup.
> 
> Additional testing:
> - [x] Linux x86_64 fastdebug `tier2`
> - [x] Linux x86_64 release `tier2`
> - [x] Linux x86_64 fastdebug `gtest:all`
> - [x] Linux x86_64 release `gtest:all`
> - [x] Linux x86_64 fastdebug `test/hotspot/jtreg/runtime`
> - [x] Linux x86_64 release `test/hotspot/jtreg/runtime`

Changes requested by coleenp (Reviewer).

src/hotspot/share/classfile/classLoaderData.cpp line 749:

> 747:     delete _packages;
> 748:     _packages = nullptr;
> 749:   }

Can you do packages too?

src/hotspot/share/classfile/classLoaderData.cpp line 751:

> 749:   }
> 750: 
> 751:   if (_unnamed_module != nullptr) {

And maybe unnamed module?

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PR Review: https://git.openjdk.org/jdk/pull/14820#pullrequestreview-1525169726
PR Review Comment: https://git.openjdk.org/jdk/pull/14820#discussion_r1260290615
PR Review Comment: https://git.openjdk.org/jdk/pull/14820#discussion_r1260290887