Proposal: Fully Concurrent ClassLoading (original) (raw)

David Holmes david.holmes at oracle.com
Mon Dec 10 03:54:26 UTC 2012

On 6/12/2012 9:35 PM, Alan Bateman wrote:

On 05/12/2012 11:59, David Holmes wrote:

Java 7 introduced support for parallel classloading by adding to each class loader a ConcurrentHashMap, referenced through a new field, parallelLockMap. This contains a mapping from class names to Objects to use as a classloading lock for that class name. This scheme has a number of inefficiencies. To address this we propose for Java 8 the notion of a fully concurrent classloader ...

This is a fairly simple proposal that I've written up as a blog entry: https://blogs.oracle.com/dholmes/entry/parallelclassloadingrevisitedfullyconcurrent The jdk7 implementation is very unfortunate, it's a pity this wasn't caught before 7 shipped. I think the proposal is good, it preserves compatibility, and if there are loaders calling registerAsParallelCapable now (probably very few) then it they may be able to change to using registerAsFullyConcurrent without too much work.

Thanks for your comments and support Alan.

I am tempted to suggest that registerAsParallelCapable should be deprecated too.

I think that may be premature for 8, perhaps for 9?

David

-Alan.

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