Java MeetsFine-grain Multithreading

Yoshihiro Oyama

Kenjiro Taura

Akinori Yonezawa{oyama,tau,yonezawa}@is.s.u-tokyo.ac.jp

University of Tokyo

Goal

We are planning to implement Java systemrealizing

Thread creation with very very low cost High scalability

Sample Program

class Pfib { public static int pfib(int n) { if (n < 2) return 1; else { int x, y; sync { fork { x = pfib(n-1); } fork { y = pfib(n-2); } } return x + y; } }}

Synchronization block

Thread creation

Prototype Implemented

On top of the Extensible Java PreProcessor Kit EPP (by Y. Ichisugi in ETL, Japan) Java source to source translation one fork ⇔ one Java thread creation Only 500-line EPP code

Its performance is out of the question

How to Implement?Q: How can we reduce thread creation cost?

A: Lazy Task Creation (LTC) technique seems useful

Traditional compilers based on LTC: Stack is managed tricky by compilers and/or runtimes

Java allows to manipulate stack only with call/return/throweven in a bytecode level

But...

Problem

E.g., stack frame info is put into a data structure explicitly

Alternativesto Implement Fine-grain Threads

Extending an existing native compiler? Extending an existing JVM/JIT? Writing Java source to source translator?