Draft JEP 8315737: AOT Linked Classes

[John Rose]

Dear colleagues,

Having recently delivered a Leyden EA Build of our “premain” work, the Leyden team is very happy to post our first JEP for public review.

https://openjdk.org/jeps/8315737

Covering a subset of the functionality in the EA Build, this JEP describes our plans for introducing, to the JDK, the first course of startup and warmup enhancements which have been “cooking” since last February.

Because CDS is a somewhat obscure technology, and because startup and warmup are very tricky (even refractory) problems in our ecosystem, we are striving to make the JEP as clear and informative as possible.  It covers the nature of the problem, and the past solutions in HotSpot, as well as the present proposal.  (Although there are many excellent and inspiring proposals for this problem beyond HotSpot, this JEP does not attempt to address them; that is for another paper.)  We hope you find it an interesting and useful mix of “high level” and “nitty gritty” details.

Though the actual proposal (the Description) section may seem surprisingly simple, the implications are pervasive and subtle.  As the JEP explains, the proposed changes will be felt all the more in the AOT technologies built on top, as can be seen in our EA Build.

The Non-Goals section gives guidance about where we expect to go after this JEP.
So if there seems to be a missing piece in this JEP, please look for it first among the non-goals!  We are working on more JEPs to come after this one.  Let’s get this one sorted so we can do more.

Like the EA Build, this work has not been possible without the participation of the Java community.  Special thanks to our Red Hat and Spring colleagues, and to everyone who is now sampling that EA Build.  Also, special thanks to our very demanding early reviewers, notably Alex Buckley, Brian Goetz, my co-authors Dan and Ioi, and the other members of the premain team.

Your comments on the JEP will surely improve it as well.

Best wishes,

— John Rose