gcSim

Abstract

gcSim is a garbage collection simulator. It reads a trace that records mutator events, and simulates a garbage collector, collecting statistics about how the collector performs. Version 2003-0808 of gcSim can simulate three collectors: SEMI (a simple semispace copying collector), APPEL (a 2-generational collector with flexible-size nursery), and CBGC (a family of connectivity-based garbage collectors). All of these are simulated as single-processor, stop-the-world, copying collectors.

Download

gcSim source code:
gcSim-v2003-0808.tgz

gcSim input data:
The input data files are available here. There are 5 files for each of 17 benchmarks:

*-merlin.gz	The actual trace itself, with precise deathtime events from the Merlin algorithm. To understand the trace format, look at the code in package `readtrace`.
*-high_watermark	The maximum amount of live data of during the benchmark run. This is used by class `gcSim.GcSim` to determine the heap size.
-harris.gz, -type_dynamic.gz, and *-allocsite_dynamic.gz	Partitionings consisting of partition dags and partition maps. These are only needed for CBGC, not for SEMI or APPEL. To understand the file format, look at the code of class `gcSim.HeapCBGC`.

Documentation

Section 2.3 of my Ph.D. thesis describes the traces.
The OOPSLA 2003 paper Connectivity-Based Garbage Collection contains descriptions of gcSim, and of the data files, the methodology, and the CBGC family of garbage collectors.
The University of Colorado Technical Report CU-CS-958-03 Choosing a Set of Partitions to Collect in a Connectivity-Based Garbage Collector contains a detailed description of the flow-based chooser implemented in the CBGC part of gcSim.
For installation and usage documentation, download gcSim-(version).tgz, unpack it, and look at the README file. For understanding the code, we recommend you use eclipse, and start by understanding the classes gcSim.GcSim and gcSim.HeapSemi.

License, Copyright, Disclaimers

This material is based upon work supported by the National Science
Foundation under Grant No. CCR-0085792 and Grant No. CCR-0133457, and
by IBM. Any opinions, findings, and conclusions or recommendations
expressed in this material are those of the author(s) and do not
necessarily reflect the views of the sponsors.

Copyright 2003 University of Colorado.

gcSim is open source software. You can redistribute it and/or modify
it under the terms of the GNU General Public License (GPL) 
http://www.gnu.org/licenses/gpl.txt as published by the Free Software
Foundation.

THE SOFTWARE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. THE
UNIVERSITY DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT
NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
PARTICULAR PURPOSE. See the GNU GPL for more details.

Acknowledgments

Before we wrote gcSim, we were experimenting with a garbage collection simulator from the ALI Group at the University of Massachusetts. Thanks to the ALI group for sharing that with us!
We generated the traces that drive gcSim using a tracer we wrote in Jikes RVM, a research virtual machine for Java written in Java. Thanks to the people at IBM for providing this great research infrastructure, and for supporting us users!
Throughout our research on CBGC using gcSim, Michael Hind at IBM provided us with guidance and support. Thanks, Mike!

Martin Hirzel (

), Amer Diwan (

), last updated 12/12/2005