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Created by Iris Clark, last modified by Ron Pressler on Aug 03, 2018

Loom

Fibers, Continuations and Tail-Calls

Welcome to the Loom Project!

The goal of this Project is to explore and incubate Java VM features and APIs built on top of them for the implementation of lightweight user-mode threads (fibers), delimited continuations, and related features, such as explicit tail-calls.

This OpenJDK project is sponsored by the HotSpot Group.

Source Code

http://hg.openjdk.java.net/loom/loom/

Talks

JVMLS 2018 – Video

JFokus 2018 – Video

Mailing List

Subscribe | Archive

Project

Proposal | JEP | Members | Page

Note

Loom is under active development, which means that information and advice given here might change in the future.

Supported Platforms

Mac and Linux on x86-64

Download and Build from Source

$ hg clone http://hg.openjdk.java.net/loom/loom  
$ cd loom  
$ hg update -r fibers 
$ sh configure   
$ make images

(Note that you must switch to the fibers branch before building)

Missing Features

JVM TI support (fiber debugging)
Forced preemption
Cloning continuations
Serialization of fiber/continuation

Continuations

Design

The primitive continuation construct is that of a scoped (AKA multiple-named-prompt), stackful, one-shot (non-reentrant) delimited continuation. The continuation can be cloned, and thus used to implement reentrant

Implementation

Performance

Fibers

Design

Implementation

Fibers are implemented in the core libraries. A fiber is implemented as a continuation (of fiber scope) that is wrapped as a task and scheduled by a j.u.c.Executor.

Tail Calls

Design

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