JVM

Awesome JVM ¶

A curated list of awesome JVM low level, performance and non-framework related stuff.

- [Communities](#communities)

Bytecode¶

Tools for bytecode manipulation and analysis.

asmtools - Used to develop tools for the production of Java .class files.
Byte Buddy - Code generation library creating Java classes at runtime without the help of a compiler.
Jitescript - Bytecode generation library similar to BiteScript.

Garbage collectors¶

Garbage collectors for the JVM.

Azul Pauseless Garbage Collection - Providing continuous, pauseless operation for Java applications.
Balanced GC - GC policy available in the Java Virtual Machine for IBM WebSphere Application Server V8.
Epsilon GC - Completely passive GC implementation with bounded allocation limit, and lowest runtime performance overhead possible.
G1 - The Garbage-First Garbage Collector.
Shenandoah - Ultra-Low-Pause-Time Garbage Collector.
The Garbage Collection Handbook - Book that addresses new challenges to garbage collection made by recent advances in hardware and software.
ZGC - Garbage collector optimized for low latency and very large heaps.

Load tools¶

Tools that generate load and measure the system accurately without coordinated omission

Gatling - Asynchronous non-blocking scenario driven load testing tool for testing HTTP servers.
wrk2 - A constant throughput, correct latency recording variant of wrk.

Languages¶

Languages running on the JVM. * Ceylon - Object-oriented, strong and static programming language with an emphasis on immutability, created by Red Hat. * Clojure - Dialect of Lisp created by Rich Hickey. Dynamically typed with emphasis on functional programming. * Erjang - A JVM-based Erlang VM. * Eta - Pure, lazy, strongly typed functional programming language on the JVM. * Frege - Pure functional programming language in the spirit of Haskell. * gojava - Java bindings for Go packages. * Golo - A simple dynamic language that makes extensive usage of invokedynamic. * Groovy - Optionally typed and dynamic language, with static-typing and static compilation capabilities. * Java - General-purpose, concurrent, strongly typed, class-based object-oriented language. * JRuby - Implementation of the Ruby language on the JVM. * JPHP - PHP on the Java VM. * Jython - Python for the Java Platform. * Kawa - Extension of the Scheme language, which is in the Lisp family of programming languages. * Kotlin - Statically typed programming language for the JVM, Android and the browser. * LuaJ - Java-centric implementation of lua vm built to leverage standard Java features. * Nashorn - Lightweight high-performance JavaScript runtime in Java with a native JVM. * OCaml-Java - Supports OCaml language v4. Generates plain Java bytecode and have seamless integration with Java. * Rembulan - Rembulan is an implementation of Lua 5.3 for the JVM, written in pure Java with minimal dependencies. * Renjin - JVM-based interpreter for the R language for the statistical analysis * Scala - Strong and static programming language that combine object-oriented and functional programming ideas. * Xtend - Flexible and expressive dialect of Java, which compiles into Java 5 source code.

Machine Learning¶

Deeplearning4j - Open-Source, Distributed, Deep Learning Library for the JVM.
H2O - Fast statistical, machine learning & math runtime.
Smile - Statistical Machine Intelligence & Learning Engine.

Memory and concurrency¶

Tools and data structures for efficient memory layout and concurrent access.

Agera - Reactive Programming for Android by Google.
Agrona - Library of data structures and utility methods that are a common need when building high-performance applications.
Apache Arrow - A high-performance cross-system data layer for columnar in-memory analytics.
bloofi - Java implementation of multidimensional Bloom filters
Cap’n Proto - Insanely fast data interchange format and capability-based RPC system.
caffeine - A high performance caching library for Java 8.
Chronicle-Bytes - Low level memory access wrappers.
Chronicle-Queue - Micro second messaging that stores everything to disk.
Chronicle-Map - In-memory key-value store designed for low-latency and/or multi-process applications.
clj-ds - Clojure's data structures modified for use outside of Clojure.
colfer - Binary serialization format and class generator.
commons-math - Library of lightweight, self-contained mathematics and statistics components.
CuckooFilter4J - Bloom filter replacement for approximated set-membership queries.
cyclops - Integration modules for RxJava, Reactor, FunctionalJava, Guava & Javaslang.
Eclipse Collections - Collections framework for Java.
externalsortinginjava - Sort very large files using multiple cores and an external-memory algorithm.
failsafe - A lightweight, zero-dependency library for handling failures.
fasttuple - Collections that are laid out adjacently in both on- and off-heap memory.
fast-uuid - Java library for quickly and efficiently parsing and writing UUIDs.
FlatBuffers - Efficient cross platform serialization library for C++, C#, Go, Java, JavaScript, PHP, and Python.
geohash - Java utility methods for geohashing.
gs-collections - Goldman Sachs collections framework.
hollow - Java library and comprehensive toolset for harnessing small to moderately sized in-memory datasets.
high-scale-lib - Cliff Click's High Scale Library.
hppc - High Performance Primitive Collections.
injector - A new Executor for Java.
java-concurrent-hash-trie-map - Java port of a concurrent trie hash map implementation from Scala collections.
java-hll - Java library for the HyperLogLog algorithm.
JavaFastPFOR - Library to compress and uncompress arrays of integers very fast.
java-string-similarity - String similarity and distance measures, including Levenshtein edit distance and sibblings, Jaro-Winkler, Longest Common Subsequence, cosine similarity etc.
JCTools - Concurrent data structures currently missing from the JDK.
DSL-JSON - High performance JSON library with advanced compile-time databinding.
jsoniter - Claims to be the fastest JSON parser ever (copy of DSL-JSON).
jOOL - Useful extensions to Java 8 lambdas.
Koloboke - Java Collections til the last breadcrumb of memory and performance.
LevelDB - Rewrite (port) of LevelDB in Java.
lightweight_trie - A very memory-efficient trie (radix tree) implementation.
lmdbjni - Java API to LMDB (HawtJNI) which is an ultra-fast, ultra-compact key-value embedded data store written in C.
lmdbjava - Java API to LMDB (JNR) which is an ultra-fast, ultra-compact key-value embedded data store written in C.
low-gc-membuffers - In-memory circular buffers that use direct ByteBuffers to minimize GC overhead.
lwjgl3 - Java library that enables cross-platform access to popular native APIs useful in the development of graphics (OpenGL), audio (OpenAL) and parallel computing (OpenCL) applications.
MapDB - Collections backed by off-heap or on-disk storage.
mph-table - Minimal Perfect Hash Tables are an immutable key/value store with efficient space utilization and fast reads.
mug - A small, zero-dep functional util library originating from Google.
netty-buffers - Memory buffer pool implementation similar to jemalloc.
ObjectLayout - A layout-optimized Java data structure package.
ohc - Java large off heap cache developed for Apache Cassandra 3.0.
okio - Modern Java IO library that do clever things to save CPU and memory.
onyx-java - Mirrors the Onyx Platform core API by providing a Java equivalent for each component of an Onyx workflow.
parquet - Columnar storage format that uses the record shredding and assembly algorithm described in the Dremel paper.
PauselessHashMap - A java.util.HashMap compatible map that won't stall puts or gets when resizing.
pcollections - A Persistent Java Collections Library.
protobuf - Google's data interchange format.
Quasar - Lightweight threads and actors for the JVM.
rtree - Immutable in-memory R-tree and R*-tree implementations in Java with reactive api.
RTree2D - RTree2D is a 2D immutable R-tree with STR (Sort-Tile-Recursive) packing for ultra-fast nearest and intersection queries on plane and spherical surfaces.
Reactive Streams - Standard for asynchronous stream processing with non-blocking back pressure.
Reactive Streams Utilities - Future standard utilities library for Reactive Streams.
RoaringBitmap - A better compressed bitset in Java.
rollinghashjava - Rolling hash functions in Java.
Reactor - Reactive data applications on the JVM for Java, Groovy, Clojure and other.
RxJava - Library for composing asynchronous and event-based programs using observable sequences.
SmoothieMap - java.util.Map impl with worst put latencies more than 100 times smaller than java.util.HashMap.
Simple Binary Encoding - High Performance Message Codec.
splitmap - A parallel bitmap implementation.
DataSketches - A Java software library of stochastic streaming algorithms.
stormpot - A fast object pool for the JVM.
stream-lib - A Java library for summarizing data in streams for which it is infeasible to store all events.
streamvbyte - Fast integer compression in C using the StreamVByte codec.
TraneIO - High-performance implementation of the Future abstraction.
transducers-java - Composable algorithmic transformations independent from the context of their input and output sources.
VarInt - No-deps variable int implementation without deps (by Bazel).
vavr - Functional Library for Java 8+.
wire - Clean, lightweight protocol buffers for Android and Java.
Zero-Allocation-Hashing - Hashing any sequences of bytes in Java, including all kinds of primitive arrays, buffers, CharSequences and more.

Metaprogramming¶

Parsers, interpreters, compilers and source generation targeted for the JVM.

Antlr - Parser generator for reading, processing, executing, or translating structured text or binary files.
auto - A collection of source code generators for Java.
Apache Calcite - Dynamic data management framework and SQL parser plugin.
Checker Framework - Compiler plug-ins that find bugs or verify their absence.
compile-testing - Testing tools for javac and annotation processors.
derive4j - Algebraic data types constructors, pattern-matching, morphisms, optics and typeclasses.
error-prone - Catch common Java mistakes as compile-time errors.
GHCVM - A Haskell to JVM compiler that supports GHC Haskell.
Graal - New experimental just-in-time compiler for Java that is integrated with the HotSpot virtual machine.
grappa - Java fork of Parboiled. Write grammars with no preprocessing phase.
immutables - Generate simple, safe and consistent value objects.
javacc - Parser generator for use with Java.
javaparser - Java 1.8 Parser and Abstract Syntax Tree for Java.
JavaPoet - A Java API for generating .java source files.
jparsec - Builds mini parsers in pure Java a la Haskell Parsec.
JSweet - A transpiler from Java to TypeScript/JavaScript.
MPS - Design and build extensible DSLs and editors.
lombok - Reduce the amount of boilerplate code that is commonly written for Java classes.
parboiled - Parsing of arbitrary input text based on parsing expression grammars.
Sulong - LLVM IR interpreter written in Java using Truffle and Graal.
TeaVM - Ahead-of-time translating compiler (transpiler) from Java bytecode to JavaScript.
Truffle - Framework for implementing languages as simple interpreters.
Xtext - Framework for development of programming languages and DSLs.

Native¶

Interconnecting JVM and native code

hawtjni - A JNI code generator based on the JNI generator used in Eclipse SWT.
Java Grinder - Compile Java bytecode to microcontroller assembly.
j2v8 - Java API for Google's V8 JavaScript engine.
JavaCPP - JavaCPP provides efficient access to native C++ inside Java.
jnr-ffi - Load native libraries without writing JNI code by hand.
jssembly - Execution of native assembly from Java.
NuProcess - A low-overhead, non-blocking I/O, external Process execution implementation for Java.
Project Panama - Enriching the connections between the JVM and APIs used by C programmers.

Network¶

Tools for network programming, packet capture, monitoring, testing and resiliency.

Aeron - Efficient reliable UDP unicast, UDP multicast, and IPC message transport.
armeria - Asynchronous RPC/API client/server library built on top of Java 8, Netty 4.1, HTTP/2, and Thrift.
Chronicle-Network - A High Performance Network library.
comcast - Simulating shitty network connections.
gor - HTTP traffic replay in real-time.
gRPC - A high performance, open source, general RPC framework that puts mobile and HTTP/2 first.
jRT - Measures response time of a java application to socket-based requests.
JXIO - Java API over AccelIO (C library), a high-performance asynchronous reliable messaging and RPC library optimized for hardware acceleration.
K3PO - Create arbitrary network traffic and behavior to certify whether a network endpoint behaves correctly.
muxy - Simulating real-world distributed system failures.
Netty - Async event-driven network library for high performance protocol servers & clients.
okhttp - An HTTP+HTTP/2 client for Android and Java applications.
one-nio - library for building high performance Java servers.
proteus-java - Proteus Java Client based on RSocket.
reactive-grpc - Reactive gRPC is a suite of libraries for using gRPC with Reactive Streams programming libraries.
RSocket - RSocket is a binary protocol for use on byte stream transports such as TCP, WebSockets, and Aeron.
SimianArmy - Resiliency tool that helps ensure that your applications can tolerate random instance failures.
pcap4j - Java library for capturing, crafting, and sending packets using libpcap.
pig - A Linux packet crafting tool.
tcpdump - Packet analyzer for network traffic capture.
tcpflow - Captures TCP connections flows in a way that is convenient for protocol analysis and debugging.
tcpreplay - Pcap editing and replay tools.

Nix tools¶

Useful nix tools when profiling the JVM and interaction with the host environment* * atoptool - Logging of system and process activity for long-term analysis, highlighting overloaded system. * bcc - Tools for BPF-based Linux IO analysis, networking, monitoring, and more. * Flame Graphs - Visualization of profiled software, allowing the most frequent code-paths to be identified quickly and accurately. * ioping - Simple disk I/0 latency measuring tool. * javap - Disassembles class files into code that reflects the java bytecode. * jhat - Java Heap Analysis Tool * jinfo - Prints configuration information for a given process. * jstack - Prints stack traces of threads for a given Java process. * jstat - Monitors GC and compiler statistics in the JVM. * hwloc - Reports the structure of the processor, number of cores, hyperthreads and cache size. * likwid - Read hardware performance counters on Intel and AMD processors. * numactl - Control NUMA policy for processes or shared memory. * oprofile - System-wide hardware performance monitoring with easy-to-use interface at low overhead. * perf - Linux profiling with performance counters. * perf-tools - Performance analysis tools based on Linux perf_events (aka perf) and ftrace. * sysdig - Capture system state and activity from a running Linux instance, then save, filter and analyze. * sysstat - Performance monitoring tools for Linux. * taskset/process-affinity - Retrieve or set a processes’s CPU affinity. * tiptop - Like top but also shows instructions per cycle (IPC).

Profilers¶

Tools that provide profiling and tracing information to aid program optimization

allocation-instrumenter - Java agent that rewrites bytecode to instrument allocation sites.
aprof - Java memory allocation profiler.
async-profiler - Sampling CPU profiler for Java featuring AsyncGetCallTrace + perf_events.
BTrace - a safe, dynamic tracing tool for the Java platform.
Byteman - tracing, monitoring and testing tool for Java
bytestacks - Turn JVM bytecode execution into flame graphs.
Chronon - Record your entire java program. Replay on any machine.
GCeasy - Machine learning guided Garbage collection log analysis tool. Auto-detect problems in the JVM GC logs and recommend solutions to it.
GCViewer - GCViewer is a tool that visualizes verbose GC output.
grav - A collection of tools to help visualise process execution.
hawkshaw - Tools for tracking down memory / JVM problems & generating predictable-as-possible VM behaviour.
HdrHistogram - A Histogram that supports recording and analyzing sampled data value counts.
hdrhistogram-metrics-reservoir - A Metrics Reservoir implementation backed by HdrHistogram.
HdrLogProcessing - Utilities for HDR Histogram logs manipulation.
heapster - Production heap profiling for the JVM.
honest-profiler - Sampling JVM profiler without the safepoint sample bias.
jamm - Measure actual object memory use including JVM overhead.
Java Flight Recorder (JFR) - Tool for collecting diagnostic and profiling data about a running Java application with almost no performance overhead.
java-sizeof - Memory consumption estimator for Java.
jcstress - Experimental harness and tests to aid the research in the correctness of concurrency support in the JVM, class libraries, and hardware.
jfr-flame-graph - Converting JFR Method Profiling Samples to FlameGraph compatible format.
jfr-report-tool - Tool for creating reports from Java Flight Recorder dumps.
jitwatch - Log analyser / visualiser for Java HotSpot JIT compiler.
jitwatch-intellij - JITWatch plugin for IntelliJ IDEA.
jHiccup - jHiccup is an open source tool designed to measure the pauses and stalls associated with an application’s underlying Java runtime platform.
jmh - Micro benchmarks written in Java and other languages targetting the JVM.
jmh-compare-gui - GUI for comparing JMH results.
JOL - Analyze actual object layout schemes, footprint, and references in JVMs.
JProfiler - Helps resolve performance bottlenecks, pin down memory leaks and understand threading issues.
JVMTI - Provide a native API to inspect the state and to control the execution of applications running in the JVM.
jvmtop - Lightweight console application to monitor running jvms on a machine in top-like manner.
jvm-profiler - Java Agent to collect various metrics and stacktraces for Hadoop/Spark JVM processes in a distributed way.
MAT - Java heap analyzer that help find memory leaks and reduce memory consumption.
leakcanary - A memory leak detection library for Android and Java.
metrics - Measure the behavior of critical components in production environment.
micrometer - An application metrics facade for the most popular monitoring tools.
osquery - osquery is an instrumentation framework that expose the operating system as a high-performance relational database.
Overseer - Low-Level Hardware Monitoring and Management for Java.
OpenTracing - A vendor-neutral open standard for distributed tracing.
perf-map-agent - Generate method mappings to use with the linux perf tool.
perfj - Linux perf for java programs.
polarbear - A tool to help diagnose OutOfMemoryError conditions.
Riemann JVM Profiler - JVM agent which sends function-level profiler telemetry to a Riemann server for analysis, visualization, and storage.
statsd-jvm-profiler - JVM agent profiler that sends profiling data to StatsD.
Swiss Java Knife - Small set of tools for JVM troublshooting, monitoring and profiling.
Takipi - Tells you when and why code breaks in production.
Tracer - Manages custom trace identifiers and carries them through distributed systems.
YourKit - Fully featured, easy to use, low overhead profiler.
Zipkin - A distributed tracing system gather timing data for disparate services developed by Twitter.

Runtimes¶

Tools for managing jvm runtime processes * Capsule - Dead-Simple Packaging and Deployment for JVM Apps. * CRaSH - The shell for the Java Platform. * Drip - Fast JVM launching without the hassle of persistent JVMs. * HotswapAgent - Redefine classes at runtime and skip the redeploy process. * jvmkill - Agent that forcibly terminates the JVM when it is unable to allocate memory or create a thread. * Nailgun - Nailgun is a client, protocol, and server for running Java programs from the command line without incurring the JVM startup overhead.

Virtual Machines¶

Virtual machines that implement the JVM specification or parts of it. * Avian - Lightweight highly portable JVM with an option for AOT compilation. * Dalvik - Android runtime (ART) is the managed runtime used by applications and some system services on Android. * DCEVM - Modification of Java HotSwap VM with unlimited support for reloading classes at runtime. * HotSpot - HotSpot virtual machine maintained and distributed by Oracle Corporation. * IBM J9 - JVM developed by IBM. * Eclipse OpenJ9 - Eclipse OpenJ9. * J2ObjC - Translator from Java source to Objective-C code. Keeps shared code between iOS native apps and Android native apps. * jvm.go - A JVM written in Go. * ParparVM - An Open Source Java bytecode to C translator for iOS native development. Designed as a part of the Codename One WORA for mobile project. * MobiDevelop's RoboVM Fork - Ahead of time compiler for JVM bytecode targeting iOS, Mac OSX and Linux. * Zing - The only JVM that eliminates Java garbage collection pauses for large heap sizes. * Zulu - The only certified multi-platform build of OpenJDK: Free, 100% open source Java.

Resources¶

Documentation¶

Documentation related to JVM * TCP Tracepoints Linux bcc/BPF using tcplife by Brendan Gregg * Linux tracing workshop - JVM monitoring with BPF, examples and hands-on labs for Linux tracing tools workshops. * JVM Anatomy Park - mini-post series where every post goes deep for only a single topic by Aleksey Shipilёv. * Coordinated Omission problem - Discussion on Mechanical Sympathy. * False sharing - Threads impact the performance of each other while modifying independent variables sharing the same cache line. Martin Thompson. * The JVM specification - The Java Virtual Machine Specification Java SE 8 Edition. * The Java Memory Model - Starting point for discussions of and information concerning the Java Memory Model. * The JSR-133 Cookbook for Compiler Writers - Unofficial guide to implementing the new Java Memory Model (JMM) specified by JSR-133. * Garbage Collection Tuning Guide - HotSpot Virtual Machine Garbage Collection Tuning Guide. * Safepoints - Where is my safepoint? Nitsan Wakart. * Topics in High-Performance Messaging - Design decisions, experience and constraints explained in high performance messaging systems. * Top 10 Performance Mistakes - Digest of the top 10 performance related mistakes Martin Thompson has seen in production. * The USE method - The Utilization Saturation and Errors (USE) Method is a methodology for analyzing the performance of any system. Brendan Gregg. * An introduction to distributed systems - Kyle Kingsbury (author of Jepsen). * Using JDK 9 Memory Order Modes - For expert programmers familiar with Java concurrency, but unfamiliar with the memory order modes available in JDK 9 provided by VarHandles. * CPU Utilization is Wrong - Measure instructions per cycle (IPC) for CPU utilization. Brendan Gregg. * Linux Load Averages: Solving the Mystery - Brendan Gregg. * What every programmer should know about solid-state drives - Emmanuel Goossaert. * Quick Tips for Fast Code on the JVM - Daniel Spiewak.

Communities¶

Active discussions.

concurrency-interest - Discussion list for JSR-166.
hotspot-compiler-dev - Technical discussion about the development of the HotSpot bytecode compilers.
hotspot-dev - HotSpot development mailing list.
hotspot-gc-dev - Technical discussion about the development of the HotSpot garbage collectors.
mechanical-sympathy - Discussing how to code sympathetically to and measure the underlying stack/platform so good performance can be extracted.
Performance Java User's Group - For expert Java developers who want to push their systems to the next level
Virtual Machine Meetup 2017 - Venue for discussing the latest research and developments in the area of managed language execution.

Media¶

People¶

People that share hard-earned, often undocumented, knowledge and data of the inner workings of the JVM * Aleksey Shipilëv - Developing Oracle/Open JDK/Hotspot and other Java-related technologies. * Andrey Breslav - Lead Language Designer of Kotlin @ JetBrains. * Brian Goetz - Java Language Architect at Oracle. * Ben Christensen - Facebook, Netflix, Apple engineering. * Brendan Gregg - Cloud performance, kernel engineer, speaker, author. * Charles Nutter - JRuby guy. * Claes Redestad - Working with OpenJDK stuff @ Oracle. * Cliff Click - Creator of the HotSpot Server Compiler. * Dave Dice - Senior research scientist in the Scalable Synchronization Research Group within Oracle. * Dávid Karnok - RxJava committer that blogs about advanced RxJava. * Doug Lea - Author of the Java memory model. * Gil Tene - Azul Systems. * Heinz Kabutz - Author of 250+ Java Specialists' Newsletters. * Ivan Krylov - JVM expert. * Jake Wharton - Square, Google, open source hacker. * John Rose - HotSpot developer. * Jonas Bonér - Founder & CTO of Lightbend. * Lukas Eder - Blogger. Author of JOOQ. * Marcus Lagergren - Java language team alumnus. * Mark Reinhold - Chief Architect, Java Platform Group, Oracle. * Martin Thompson - Pasty faced performance gangster. * Martijn Verburg - Java Champion. * Kirk Pepperdine - Working in high performance and distributed computing for nearly 20 years. * Nitsan Wakart - Azul Systems. * Norman Maurer - Netty developer. * Paul Phillips - Forever undisputed SLOC Scala compiler dev. * Per Liden - Hacking on the HotSpot JVM at Oracle. * Peter Lawrey - Innovative developer of high performance Java systems for competitive advantage. * Rafael Winterhalter - Author of ByteBuddy. * Richard Warburton - Developer, Speaker, Author. * Richard Startin - Performance Analyst, developer, blogger. * Ron Pressler - Parallel Universe. Leading Fibers and Continuations for the JVM. * Stephen Colebourne - Java Champion. Occasional blogger and speaker. Best known for Joda projects and JSR-310. * Todd L. Montgomery - Ex-CTO, Ex-NASA researcher, network geek, messaging middleware designer. * Stéphane Maldini - Project Reactor Lead @Pivotal. * Stuart Marks - Doctor Deprecator. Java/JDK/OpenJDK developer * Vladimir Ivanov - hacking HotSpot JVM @ Oracle. * Viktor Klang - Deputy CTO at Typesafe Inc.

Contributing¶

Contributions are very welcome!

Please have a look at contributing.md for guidelines.