Java is a general-purpose programming language. Compiled Java code can run on all platforms that support Java, without the need for recompilation. Java applications are typically compiled to bytecode that can run on any Java virtual machine (JVM) regardless of the underlying computer architecture. Note: there are multiple programming languages such as Kotlin, Scala, and Groovy that compile to byte code and run on top of the JVM, so those also tend to be highly portable across architectures. Wikipedia
Java is well supported and generally performant out-of-the-box on arm64. Amazon Corretto, a no-cost, multiplatform, production-ready distribution of the Open Java Development Kit (OpenJDK) supports Graviton-powered instances. While Java 8 is fully supported on Arm processors, some customers haven't been able to obtain Graviton's full performance benefit until they switched to Java 11.
This page includes specific details about building and tuning Java application on Graviton.
JDK binaries for arm64 are available from a number of different sources. Amazon Corretto is continuing to improve performance of Java workloads running on Graviton processors and if you have the choice of a JDK to use we recommend using Corretto as it provides the fastest way to get access to the performance improvements AWS is making.
Versions of Corretto released since October 2020 are built to use the most optimal atomic operations within the JVM: Corretto11 (all variants); Correto8 (on Amazon Linux 2 only). This has shown to reduce GC time in some workloads, and avoids contention in net-intensive workloads like Apache Kafka.
Versions of Corretto11 (>=11.0.12) come with additional enhancements to improve
performance on workloads with light to moderate lock-contention: improved spin-lock behavior inside the JVM,
enhanced implementation of Thread.onSpinWait() on Graviton.
There are numerous options that control the JVM and may lead to better performance.
-
Flags
-XX:-TieredCompilation -XX:ReservedCodeCacheSize=64M -XX:InitialCodeCacheSize=64Mhave shown large (1.5x) improvements in some Java workloads. Corretto 17 needs two additional flags:-XX:CICompilerCount=2 -XX:CompilationMode=high-only.ReservedCodeCacheSize/InitialCodeCacheSizeshould be equal and can be in range: 64M...127M. The JIT compiler stores generated code in the code cache. The flags change the size of the code cache from the default 240M to the smaller one. The smaller code cache may help CPU to improve the caching and prediction of jitted code. The flags disable the tiered compilation to make the JIT compiler able to use the smaller code cache. These are helpful on some workloads but can hurt on others so testing with and without them is essential. -
Crypto algorithm AES/GCM used by TLS has been optimized for Graviton. On Graviton2 GCM encrypt/decrypt performance improves by 3.5x to 5x. The optimization is enabled by default in Corretto and OpenJDK 18 and later. The optimization has been backported to Corretto and OpenJDK 11 and 17 and can be enabled with the flags
-XX:+UnlockDiagnosticVMOptions -XX:+UseAESCTRIntrinsics. As an alternative, you can use Amazon Corretto Crypto Provider JNI libraries.
The default stack size for Java threads (i.e. ThreadStackSize) is 2mb on aarch64 (compared to 1mb on x86_64). You can check the default with:
$ java -XX:+PrintFlagsFinal -version | grep ThreadStackSize
intx CompilerThreadStackSize = 2048 {pd product} {default}
intx ThreadStackSize = 2048 {pd product} {default}
intx VMThreadStackSize = 2048 {pd product} {default}
The default can be easily changed on the command line with either -XX:ThreadStackSize=<kbytes> or -Xss<bytes>. Notice that -XX:ThreadStackSize interprets its argument as kilobytes whereas -Xss interprets it as bytes. So -XX:ThreadStackSize=1024 and -Xss1m will both set the stack size for Java threads to 1 megabyte:
$ java -Xss1m -XX:+PrintFlagsFinal -version | grep ThreadStackSize
intx CompilerThreadStackSize = 2048 {pd product} {default}
intx ThreadStackSize = 1024 {pd product} {command line}
intx VMThreadStackSize = 2048 {pd product} {default}
Usually, there's no need to change the default, because the thread stack will be committed lazily as it grows. So no matter what's the default, the thread will always only commit as much stack as it really uses (at page size granularity). However there's one exception to this rule if Transparent Huge Pages (THP) are turned on by default on a system. In such a case the THP page size of 2mb matches exactly with the 2mb default stack size on aarch64 and most stacks will be backed up by a single huge page of 2mb. This means that the stack will be completely committed to memory right from the start. If you're using hundreds or even thousands of threads, this memory overhead can be considerable.
To mitigate this issue, you can either manually change the stack size on the command line (as described above) or you can change the default for THP from always to madvise on Linux distributions like AL2 (with Linux kernel 5 and higher) on which the setting defaults to always:
# cat /sys/kernel/mm/transparent_hugepage/enabled
[always] madvise never
# echo madvise > /sys/kernel/mm/transparent_hugepage/enabled
# cat /sys/kernel/mm/transparent_hugepage/enabled
always [madvise] never
Notice that even if the the default is changed from always to madvise, the JVM can still use THP for the Java heap and code cache if you specify -XX:+UseTransparentHugePages on the command line.
Java JARs can include shared-objects that are architecture specific. Some Java libraries check if these shared objects are found and if they are they use a JNI to call to the native library instead of relying on a generic Java implementation of the function. While the code might work, without the JNI the performance can suffer.
A quick way to check if a JAR contains such shared objects is to simply unzip it and check if any of the resulting files are shared-objects and if an aarch64 (arm64) shared-object is missing:
$ unzip foo.jar
$ find . -name "*.so" -exec file {} \;
For each x86-64 ELF file, check there is a corresponding aarch64 ELF file in the binaries. With some common packages (e.g. commons-crypto) we've seen that even though a JAR can be built supporting Arm manually, artifact repositories such as Maven don't have updated versions. To see if a certain artifact version may have Arm support, consult our Common JARs with native code Table. Feel free to open an issue in this GitHub repo or contact us at [email protected] for advice on getting Arm support for a required Jar.
Java is meant to be a write once, and run anywhere language. When building Java artifacts that contain native code, it is important to build those libraries for each major architecture to provide a seamless and optimally performing experience for all consumers. Code that runs well on both Graviton and x86 based instances increases the package's utility.
There is nominally a multi-step process to build the native shared objects for each supported architecture before doing the final packaging with Maven, SBT, Gradle etc. Below is an example of how to create your JAR using Maven that contains shared libraries for multiple distributions and architectures for running your Java application interchangeably on AWS EC2 instances based on x86 and Graviton processors:
# Create two build instances, one x86 and one Graviton instance.
# Pick one instance to be the primary instance.
# Log into the secondary instance
$ cd java-lib
$ mvn package
$ find target/ -name "*.so" -type f -print
# Note the directory this so file is in, it will be in a directory
# such as: target/classes/org/your/class/hierarchy/native/OS/ARCH/lib.so
# Log into the primary build instance
$ cd java-lib
$ mvn package
# Repeat the below two steps for each OS and ARCH combination you want to release
$ mkdir target/classes/org/your/class/hierarchy/native/OS/ARCH
$ scp slave:~/your-java-lib/target/classes/org/your/class/hierarchy/native/OS/ARCH/lib.so target/classes/org/your/class/hierarchy/native/OS/ARCH/
# Create the jar packaging with maven. It will include the additional
# native libraries even though they were not built directly by this maven process.
$ mvn package
# When creating a single Jar for all platform native libraries,
# the release plugin's configuration must be modified to specify
# the plugin's `preparationGoals` to not include the clean goal.
# See http://maven.apache.org/maven-release/maven-release-plugin/prepare-mojo.html#preparationGoals
# For more details.
# To do a release to Maven Central and/or Sonatype Nexus:
$ mvn release:prepare
$ mvn release:perform
This is one way to do the JAR packaging with all the libraries in a single JAR. To build all the JARs, we recommend to build on native machines, but it can also be done via Docker using the buildx plug-in, or by cross-compiling inside your build-environment.
Additional options for releasing jars with native code is to: use a manager plugin such as the nar maven plugin
to manage each platform specific Jar. Release individual architecture specific jars, and then use the primary
instance to download these released jars and package them into a combined Jar with a final mvn release:perform.
An example of this methd can be found in the Leveldbjni-native pom.xml files.
For languages that rely on a JIT (such an Java), the symbol information that is
captured is lacking, making it difficult to understand where runtime is being consumed.
Similar to the code profiling example above, libperf-jvmti.so can be used to dump symbols for
JITed code as the JVM runs.
# Compile your Java application with -g
# find where libperf-jvmti.so is on your distribution
# Run your java app with -agentpath:/path/to/libperf-jvmti.so added to the command line
# Launch perf record on the system
$ perf record -g -k 1 -a -o perf.data sleep 5
# Inject the generated methods information into the perf.data file
$ perf inject -j -i perf.data -o perf.data.jit
# View the perf report with symbol info
$ perf report -i perf.data.jit
# Process the new file, for instance via Brendan Gregg's Flamegraph tools
$ perf script -i perf.data.jit | ./FlameGraph/stackcollapse-perf.pl | ./FlameGraph/flamegraph.pl > ./flamegraph.svgAmazon Linux 2 does not package libperf-jvmti.so by default with the perf yum package for kernel versions <5.10.
Build the libperf-jvmti.so shared library using the following steps:
$ sudo amazon-linux-extras enable corretto8
$ sudo yum install -y java-1.8.0-amazon-corretto-devel
$ cd $HOME
$ sudo yumdownloader --source kernel
$ cat > .rpmmacros << __EOF__
%_topdir %(echo $HOME)/kernel-source
__EOF__
$ rpm -ivh ./kernel-*.amzn2.src.rpm
$ sudo yum-builddep kernel
$ cd kernel-source/SPECS
$ rpmbuild -bp kernel.spec
$ cd ../BUILD
$ cd kernel-*.amzn2
$ cd linux-*.amzn2.aarch64
$ cd tools/perf
$ make