This project is a fork of original DCEVM project.
The purpose of the project is to maintain enhanced class redefinition functionality for OpenJDK HotSpot 7/8.
You can download binaries here.
hotspot/.hg/patches/ contains patches for all supported versions. Each patch is named by concatenating prefix full
or light
with the OpenJDK HotSpot tag. full
patches support full redefenition capabilities (including removal of superclasses, for example). light
patches are easier to maintain, but they only support limited functionality (generally, additions to class hierarchies are fine, removals are not).
HotSpot tag is the name of the tag in the corresponding HotSpot Mercurial repository (Java 8/Java 7).
You need the following software to build DCEVM:
- Java 7 or later. If you intend to run tests, it should be one of the supported versions (see list of patches/)
- C++ compiler toolchain (gcc). There is no strict version requirement except that it should be supported by HotSpot build scripts.
- Mercurial with Mercurial Queues Extension enabled.
Currently the build is not compatible with Clang on Mac OS X, you need to install gcc 4.8 using the Homebrew:
brew tap homebrew/versions
brew install gcc48
Then set the following environmental properties:
export CC=/usr/local/bin/gcc-4.8
export CFLAGS=-fobjc-exceptions
export CXX=/usr/local/bin/g++-4.8
export SA_LDFLAGS=-fobjc-exceptions
- Configure version you want in gradle.properties.
- Run
./gradlew patch
to retrieve HotSpot sources and patch them. - Run
./gradlew compileFastdebug
to buildfastdebug
version or./gradlew compileProduct
to buildproduct
version. - Compiled libraries are placed in
hotspot/build/fastdebug
orhotspot/build/product
.
- Replace
libjvm.so/jvm.dll/libjvm.dylib
in the target JRE. - Run
java -version
, it should includeDynamic Code Evolution
string.
Or you can install DCEVM using the gradle script:
- Run
./gradlew installFastdebug -PtargetJre=$JAVA_HOME/jre
or./gradlew installProduct -PtargetJre=$JAVA_HOME/jre
- DCEVM will be installed as "alternative" JVM. To use it, add
-XXaltjvm=dcevm
Alternatively, on Debian and Ubuntu systems DCEVM can be installed with the
openjdk-7-jre-dcevm
package and invoked by adding the -dcevm
command line parameter:
- Run
apt-get install openjdk-7-jre-dcevm
- Run
java -dcevm -version
, it should includeDynamic Code Evolution
string.
- Configure version you want in gradle.properties.
- Set
JAVA_HOME
to point to JDK you want to test against (should be compatible with the version you set in gradle.properties). - Run
./gradlew patch
to retrieve HotSpot sources and patch them. - Run
./gradlew test
to run tests. - Tests reports will be in
dcevm/build/reports/tests/index.html
To run tests from IDE, you need:
- Run
./gradlew agent:build
to build redefinition agent code. - Add JVM argument to use redefinition agent (
-javaagent:agent/build/libs/agent.jar
). - Add JVM argument to DCEVM VM if installed side-by-side (
-XXaltjvm=dcevm
).
DCEVM executes deoptimization (purge of code cache) after any class redefinition. It leads to decrease JVM's performance (after redefinition). This is especially problem on large scale projects with significant number of classes. Hotswap performance can be improved using an experimental option -XX:HotswapDeoptClassPath=
. One or more packages can be specified in comma separated list as parameters. Packages must contain all classes that will be potentially modified (redefined). Classes outside of this list won't be included in the deoptimization. Usually it is sufficient to specify application main or root package. If com.sun.proxy.Proxy
is used in the application or by application's framework, then this option should contain package com.sun.proxy
as well. If HotswapDeoptClassPath
option is not specified, then all classes will be deoptimized after redefinition. It is also recommended to clean all generated byte by reflection.
Example:
-XX:HotswapDeoptClassPath='com.myproject.,com.sun.proxy.$Proxy,sun.reflect.Generated'