Call for Discussion: New Project: Lilliput

Roman Kennke rkennke at
Fri Mar 12 22:50:10 UTC 2021

>> I would propose myself as the project lead for Lilliput. :-)
>> For initial committers I think we need all expertise in runtime and GC 
>> that we can get. From the top of my head I’m thinking of John Rose, 
>> Dave Dice, Andrew Dinn, Andrew Haley, Erik Österlund, Aleksey 
>> Shipilev, Coleen Phillimore, Stefan Karlsson, Per Liden. Please 
>> suggest anybody who you think should be involved in this too. (Or 
>> yourself if you want to be in, or if you have no interest in it.)
> Yes, please. I'd like to be a committer.

+1 :-)

>  I had done experiments with a 
> klass pointer indirection, which could effectively be a klass index.

I had a little exchange with Thomas Stuefe, and we believe we can split 
Klass into fixed-sized part, and variable-sized part, have the 
fixed-size base reference the variable-sized part. Then we can allocate 
the fixed Klass instances into a 'flat' array in a contiguous memory 
region, and with some smart placement and aligmment we can use a 
compressed pointer to address it, which will effectively be an index 
into that array. Which means that with N bits of 
compressed-class-pointer we could address 2^N Klasses :-) No indirection 
needed if done so afaict.

But hey, let's get the project off the ground asap, and have technical 
discussions there, yes? :-)

> In JDK 18, we're going to be removing BiasedLocking so that removes one 
> use of the markWord.



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