Build and Usage Instructions

The easiest way to build and use Maxine is through the beehivelab/maxine-dev docker image. This image comes with all dependencies installed and configured. You only need to get the latest maxine sources and build them through the container.

Prerequisites

The docker image expects the source code to be in the layout shown below:

$ tree -L 1 maxine-src
maxine-src
├── maxine
└── mx

To get the source code in this layout execute:

$ mkdir maxine-src
$ git clone https://github.com/graalvm/mx.git maxine-src/mx
$ git clone https://github.com/beehive-lab/Maxine-VM.git maxine-src/maxine

Creating the docker container

From the directory maxine-src, that we created in the previous step, run:

docker create -u=$(id -u):$(id -g) \
    --mount src="$(pwd)",target="/maxine-src",type=bind \
    --mount src="$HOME/.mx",target="/.mx",type=bind \
    --mount src="/tmp/.X11-unix",target="/tmp/.X11-unix",type=bind \
    -e DISPLAY=unix$DISPLAY --cap-add=SYS_PTRACE \
    --name maxine-dev -ti beehivelab/maxine-dev

This will create a container named maxine-dev.

  • -u=$(id -u):$(id -g) instructs docker to write and read files as the current user instead of root which is the default.
  • --mount src="$(pwd)",target="/maxine-src",type=bind essentially mounts the current directory to the docker container under the /maxine-src directory. Similarly, –mount src=”$HOME/.mx”,target=”/.mx”,type=bind does the same for the ~/.mx directory. Any changes performed to mounted folders outside the docker container are visible in the container and vice versa.
  • --mount src="/tmp/.X11-unix",target="/tmp/.X11-unix",type=bind mounts the host X11 socket to the container socket.
  • -e DISPLAY=unix$DISPLAY passes in the DISPLAY environment variable.
  • --cap-add=SYS_PTRACE enables ptrace capability for the container.
  • --name maxine-dev names the new image so that it can later be referenced (to start it, stop it, attach to it etc.).
  • -ti instructs docker to create an interactive session with a pseudo-tty, to allow us to interact with the container.

Using the maxine-dev container

To use the container issue docker start -i maxine-dev. This will start the container and open a bash shell in it. From this shell you can build and run maxine.

To exit the shell and stop the container type Ctrl-D.

Build

  • Enter the maxine source directory:

    cd $MAXINE_HOME

  • Compile the source code:

    mx build

Executing mx build in the $MAXINE_HOME directory compiles the Java source code of Maxine to class files using javac (or the Eclipse batch compiler if you use the -jdt option) and compiles the native code of Maxine to executable code using your platform’s C compiler.

The build process attempts to download some necessary files from the internet. If you are behind a firewall set the HTTP_PROXY environment variable appropriately before starting the build.

  • Generate the boot image:

    mx image

The mx image command is used to generate a boot image. This command runs Maxine on a host JVM to configure a prototype, then compiles its own code and data to create an executable program for the target platform.

Running

With the native substrate and a boot image built, the Maxine VM can now be executed.

The mx vm command handles the details of class and library paths and provides an interface similar to the standard java launcher command.

The mx script includes a command to run a simple HelloWorld program to verify that the VM is working:

mx helloworld

Now let’s use Maxine to run a more substantial program:

mx vm -cp test/bin test.output.GCTest2

To launch the VM (or any other command for that matter) without using mx, the -v option echoes the commands issued by the mx script:

mx -v helloworld

Profiling

Various profiling tools are available for the Java platform, with varying degrees of overhead. Some tools require VM support and the Maxine VM includes two such tools. The first is a simple sampling based profiler with minimal overhead that is provided in the standard VM image and enabled by the -Xprof command line option. The second tool is the Virtual Machine Level Analysis (VMA) system that works by instrumenting compiled code. Using VMA requires a custom VM image to be built.

Sampling Profiler

Maxine includes a simple sampling-based profiler. It is enabled with the -Xprof command line option. The full syntax for the option is -Xprof:frequency=f,depth=d,dump=s,flat=t,sort=t,systhreads=t, where everything after the -Xprof is optional. The control arguments have the following interpretation:

  • frequency=f: Sets the frequency of the samples to f milliseconds. The default is 10.
  • depth=d: Records the stacks of threads at sample points to a depth of d. The default is 16.
  • dump=s: Dumps the accumulated stack traces every s seconds. The default is zero which results in the traces being output only at VM termination.
  • sort=t: Sorts the stack traces by thread and sample counts if t is true. The default value is true unless dump is non-zero, as the sorting incurs both CPU and allocation overhead. In unsorted mode the stack traces are output in an arbitrary order, each followed by the list of threads and sample counts for that trace. In sorted mode, the traces for each thread are output separately, with the traces ordered from highest to lowest sample count.
  • flat=t: If t is true, the output is sorted and, for each sample, only the method at the top of the stack is listed. Therefore, this option also implies depth=1. The default value is true.
  • systhreads=t: Include system (VM) threads in the analysis if t is true. The default is false.

If the =t in the truth-valued options is omitted, it is the same as t=true.

The profiler is implemented as a separate thread that wakes up periodically, based on the given frequency (slightly randomized), stops all threads and records their stack traces. Since threads only stop at safepoints there is some inevitable inaccuracy in the reported trace. In particular, a hot method that contains no loops will not appear in the output. However, the stack trace will likely show the closest caller that contains a loop (or a system call that will cause the thread to reach a safepoint).

The data is output using the Maxine log mechanism, so can be captured in a file by setting the MAXINE_LOG_FILE environment variable.

Building Maxine without docker

Dependencies

Maxine depends on the MX tool for its build process. To get it and add it to your PATH execute:

sudo apt-get install python2.7           # MX depends on python 2.7
mkdir -p $WORKDIR
cd $WORKDIR
git clone https://github.com/graalvm/mx
export PATH=$PATH:$(pwd)/mx

Maxine also depends on openJDK 8. To get it from the ubuntu repositories run:

sudo apt-get install openjdk-8-jdk

Maxine is open source software, licensed under the GPL version 2.0 and is hosted on GitHub. Since Maxine is hosted in a git repository we need to install git as well:

sudo apt-get install git

Environment variables

To build maxine natively we first need to define a number of environment variables:

  1. Define the directory you want to work in:

    export WORKDIR=/path/to/workdir

  2. Define the JDK to be used:

    export JAVA_HOME=/usr/lib/jvm/java-8-openjdk-amd64

  3. Define MAXINE_HOME:

    export MAXINE_HOME=$WORKDIR/maxine

  4. Optionally (needed to run maxvm binary directly):

  • Extend PATH to include the to be generated maxvm:

    export PATH=$PATH:$MAXINE_HOME/com.oracle.max.vm.native/generated/linux/

  • Define LD_LIBRARY_PATH:

    export LD_LIBRARY_PATH=$MAXINE_HOME/com.oracle.max.vm.native/generated/linux/

Get the source code

  1. Make sure the project directory exists and enter it:

    mkdir -p $WORKDIR
cd $WORKDIR

  2. Get the Maxine VM source code:

    git clone https://github.com/beehive-lab/Maxine-VM.git maxine

This command will create a directory named maxine with the contents checked out from the git repository.

Choice of Optimizing Compiler

Maxine provides two optimizing compilers, C1X and Graal. The former, an evolution of the Hostpot client compiler, is very stable but no longer under development. Graal is more akin to the Hotspot server compiler and is under active development and improvement. The default image build still uses C1X as the optimizing compiler, but it is possible to select Graal, both for runtime compilations and for compiling the VM boot image (the latter is currently unstable). To build a boot image with Graal as the runtime optimizing compiler, use the following command:

mx image @c1xgraal

In this case the optimizing compiler is actually a hybrid of C1X and Graal, with C1X being used as a fallback option if the Graal compilation fails. Note that the VM boot image is considerably larger (~100MB) with Graal included.

To compile the boot image itself with Graal, do:

mx image @c1xgraal-boot

The Graal-compiled VM boot image will execute a few simple test programs but currently is not robust enough to be the default.