Compiling Java For High Performance on Servers

Transcription

1 Compiling Java For High Performance on Servers Ken Kennedy Center for Research on Parallel Computation Rice University Goal: Achieve high performance without sacrificing language compatibility and portability. Outline: Java compilation strategies Java VM, unrestricted Java performance obstacles Preliminary results impact of inlining A Java program management environment

2 Motivation Java will be important - standard for the net - clean semantics, absolute portability - growing role in education - growing popularity equal to Fortran in primary use - widespread interest in use as a scientific language Some Java users will want high performance - server programming - portable code for scientific problems Some Java users will want easy-to-use parallelism - thread model complex and not universally applicable

3 Compilation Strategies Secure Java Environment Java Program HP Java Environment Java Front End Whole-Program Optimization Java Optimizer Java Bytecodes Source-to-Source Optimization Bytecode Compiler Conventional Optimizing Compiler Java VM with JIT Native Machine Code

4 What We Have Done Optimization in JavaSoft Compiler - Zoran Budimlic project at JavaSoft - bytecode-to-bytecode optimizer reconstruct source build SSA classical optimizations modest improvements ( 5%) Development of advanced inlining strategies - object inlining - code replication

5 What we Want to Do Source -to-source interprocedural optimizer - aggressive inlining - interprocedural management system - optional path through Java VM - no sematic deviation Aggressive server compilation - direct compilation to servers (no Java VM) - highest levels of optimization - no semantic deviation Introduction of data parallelism - conversion to thread model - distributed allocation

6 Impact of Inlining

7 Inlining Example class Foo{ private int x = 0; public void inc(){ x++; public void main(){ Goo goo = new Goo(); for(int i = 0; i<10; i++){ goo.dec(); x--; inc(); class Goo{ private int y = 0; public void dec(){ y--; Inlining violates encapsulation Inlining conflicts with types derived from Foo: class FooFoo extends Foo{ public void inc(){ x--;

8 Object Inlining public void main(){ // inlined: Goo goo = new Goo(); int goo_y = 0; for(int i = 0; i<10; i++){ inc(); x--; // inlined: goo.dec(); goo_y--; Disadvantages: Only works for objects instantiated in the same class Objects must be packed in containers to be passed to procedures.

9 Code Replication Version without whole-program management $main main Foo main inc FooFoo main inc

10 Code Replication With whole-program management: Foo Foo main inc main inc FooFoo FooFoo main inc main inc

11 Instantiation Analysis class Foo{ private int x = 0; public void inc(){ x++; public void usegoo(goo goo){ for(int i = 0; i<10; i++){ goo.dec(); x--; inc(); The Goo used here was instantiated as an object of which class?

12 Program Management System Source Importer Program Specifier Local Information Program Composition Program Compiler Interprocedural Analysis Local and Global Inlining Interprocedural Information Optimizing Compiler

13 Recompilation Management Source Importer Program Specifier Source Changes File Changes Inlining Info Program Compiler Determine Files to Recompile Optimizing Compiler Interprocedural Info Relied Upon

14 Changes Requiring Recompilation Optimum Performance - Rerun the source-to-source optimizer - Recompile any changed output files Preservation of Correctness - Modification to existing classes new method overriding an old method may require copying of methods into which overridden method has been inlined change to existing method recompile wherever inlined - New subclass if the new class overrides any method up the inheritance tree, code replication may be required

15 Data Parallelism in Java Language Extensions - parallel loops - specification of locality Source-to-Source - Gannon with Aart Bik - translation of data parallelism to Java threads - acceptable to Java VM Compilation direct to server - integration of existing HPF techniques - new techniques for advanced data structures

16 Java Compilation Summary Strategies for High Performance - Aggressive Use of Inlining - Extensions for data parallelism Compiler Technologies - Source-to-source inliner output for both Java VM and direct compiler global instantiation and overriding analysis - Program compilation management system global analysis procedure cloning recompilation analysis - Direct optimization for parallel server HPF-style optimizations for parallel machines