Jikes RVM

Chapter 4
Configuring Jikes RVM

The build process requires a number of build time parameters that specify the features and components for a Jikes RVM build. Typically the build parameters are defined within a property file located in the build/configs directory. The following table defines the parameters for the build configuration.

4.1 Jikes RVM Configurations

A typical user will use one of the existing build configurations and thus the build system only requires that the user specify the config.name property. The name should match one of the files located in the build/configs/ directory minus the ’.properties’ extension.

4.1.1 Logical Configurations

There are many possible Jikes RVM configurations. Therefore, we define four ”logical” configurations that are most suitable for casual or novice users of the system. The four configurations are:

• prototype: A simple, fast to build, but low performance configuration of Jikes RVM. This configuration does not include the optimizing compiler or adaptive system. Most useful for rapid prototyping of the core virtual machine.
• prototype-opt: A simple, fast to build, but low performance configuration of Jikes RVM. Unlike prototype, this configuration does include the optimizing compiler and adaptive system. Most useful for rapid prototyping of the core virtual machine, adaptive system, and optimizing compiler.
• development: A fully functional configuration of Jikes RVM with reasonable performance that includes the adaptive system and optimizing compiler. This configuration takes longer to build than the two prototype configurations.
• production: The same as the development configuration, except all assertions are disabled. This is the highest performance configuration of Jikes RVM and is the one to use for benchmarking and performance analysis. Build times are similar to the development configuration.

The mapping of logical to actual configurations may vary from release to release. In particular, it is expected that the choice of garbage collector for these logical configurations may be different as MMTk evolves.

Logical configurations that are not mentioned here are not recommended for novice users of the system.

4.1.2 Configurations in Depth

Most standard Jikes RVM configuration files follow the following naming scheme:

[ExtremeAssertions] (Base | Full | Fast) (Base | Adaptive) <garbage collector> where

• ExtremeAssertions is optional. Its presence indicates that the config.assertions configuration parameter is set to extreme. This turns on a number of expensive assertions.
• Base | Full | Fast determines the performance of the Jikes RVM boot image. Base denotes baseline compiler and enabled assertions, Full denotes optimizing compiler and enabled assertions, Fast denotes optimizing compiler and disabled assertions. Note that Fast is exclusive with ExtremeAssertions and that Full and Fast imply that adaptive system and optimizing compiler are included in the image.
• Base | Adaptive denotes whether or not the adaptive system and optimizing compiler are included in the build.
• the <garbage collector> is the garbage collection scheme used.

Each version of Jikes RVM provides several garbage collector choices. For a definitive list of garbage collector choices, please refer to the configurations that are shipped with your version of Jikes RVM. If you need a configuration that is not available by default, you can just define your own based on the existing ones (it’s easy!).

Some garbage collector suffixes that may be available are:

• ”NoGC” no garbage collection is performed.
• ”SemiSpace” a copying semi-space collector
• ”MarkSweep” a mark-and-sweep (non copying) collector
• ”GenCopy” a classic copying generational collector with a copying higher generation
• ”GenMS” a copying generational collector with a non-copying mark-and-sweep mature space
• ”CopyMS” a hybrid non-generational collector with a copying space (into which all allocation goes), and a non-copying space into which survivors go
• ”RefCount” a reference counting collector with synchronous (non-concurrent) cycle collection

For example, to specify a Jikes RVM configuration:

1. with a baseline-compiled boot image,
2. that will compile classes loaded at runtime using the baseline compiler and
3. that uses a non-generational semi-space copying garbage collector,

use the name ”BaseBaseSemiSpace”.

In configurations that include the adaptive system (denoted by ”Adaptive” in their name), methods are initially compiled by one compiler (by default the baseline compiler) and then online profiling is used to automatically select hot methods for recompilation by the optimizing compiler at an appropriate optimization level.

For example, to a build for an adaptive configuration with assertions, where the optimizing compiler is used to compile the boot image and the semi-space garbage collector is used, use the following command: