Proposal: Fully Concurrent ClassLoading (original) (raw)

Mandy Chung mandy.chung at oracle.com
Fri Dec 7 23:46:46 UTC 2012

On 12/5/12 3:59 AM, 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 It's a good and simple proposal and also handles the backward compatibility nicely.

I think having getClassLoadingLock() to return null for a fully concurrent loader is a good idea. In case if any code synchronizes on the returned value after migrating to fully concurrent class loader, it will catch such usage (it might be very rare)/

I agree with Alan's suggestion - we should consider deprecating registerAsParallelCapable.

Mandy

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