WITHDRAWN Re: Proposal: Fully Concurrent ClassLoading

Peter Levart peter.levart at gmail.com
Thu Jan 31 13:07:23 UTC 2013

Hi David,

Could the parallel classloading be at least space optimized somehow in 
the JDK8 timeframe if there was a solution ready?

Regards, Peter

On 01/31/2013 10:26 AM, David Holmes wrote:
> Regretfully this proposal has to be withdrawn from Java 8. The VM 
> facilities that this depends upon have not been specified formally and 
> so an update to the Java Virtual Machine Specification (JVMS) and 
> further updates to the ClassLoader.defineClass method are required. 
> There was simply no time to get this work specified and completed 
> before the M6 milestone - taking into account other constraints (ie 
> people and time). Further, testing has indicated that there may be 
> some further issues to work out in the VM's "parallel defineClass" path.
> I plan to submit a new JEP for this and work on it for Java 9.
> David Holmes
> ------------
> On 5/12/2012 9:59 PM, 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/parallel_classloading_revisited_fully_concurrent 
>> Please discuss this proposal here.
>> Thanks,
>> David Holmes

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