Developers: Disassemble!

Week of May 23, 2022

Use hsdis to explore how the HotSpot JIT compiler optimizes Java code

The HotSpot Disassembler, hsdis, is a plugin for the HotSpot JVM that provides disassembly of JIT-compiled native code back into human-readable assembly language.

As Chris Newland writes, Java source code is compiled into bytecode, the language of the JVM. The bytecode is written into class files. When you run the program, the class files are loaded into the JVM, and then the bytecode is executed by the JVM’s bytecode interpreter.

While the JVM is running your program, it also profiles the application in real time to decide which parts are performed a lot (that is, it identifies the hot spots) and might benefit from being compiled from bytecode into the native code for the CPU on which your JVM is running.

This transformation from interpreted bytecode into native execution on your CPU is performed at runtime and is known as just-in-time (JIT) compilation.

What’s neat is that this runtime compilation can optimize your Java code to take advantage of advanced microprocessor instructions, resulting in surprising (and excellent) performance gains.

Chris breaks this all down using hsdis and JITWatch, his utility that processes the JIT compilation logs’ output by HotSpot and explains the optimization decisions made by the JIT compilers.

Take care,
Alan Zeichick
Editor in Chief, Java Magazine
@zeichick

P.S. On this subject, the GraalVM team has a new article, “Revolutionizing Java with GraalVM Native Image,” which technically compares GraalVM Native Image’s ahead-of-time compilation with HotSpot’s JIT compiler.

The newest Java Magazine articles

Developers disassemble! Using Java and hsdis
The HotSpot JVM does more than run your Java program’s bytecode. HotSpot also profiles the application in real time to determine which areas would most benefit from translating bytecode into your CPU’s native code via just-in-time (JIT) compilers. In his deep-dive article, Chris Newland uses hsdis and his JITWatch utility to see exactly how the JIT compilers optimize your code.

Recognize the intent of natural language inputs in Java
Intent recognition is the natural language processing task of discovering a user’s objective based on what the user typed or said. Intent recognition (also known as intent extraction or intent detection) has a wide range of practical applications such as automating the process of fulfilling the user’s needs for sales, booking, and customer service tasks. Yuli Vasiliev shows how to code intent recognition in Java using the Stanford CoreNLP library.

Coming to Java 19: Virtual threads and platform threads
Now that Project Loom’s JEP 425 officially previews virtual threads for Java 19, Nicolai Parlog takes a close look at them. Nicolai covers scheduling and memory management; mounting, unmounting, capturing, and pinning; observability; and what you can do to use virtual threads for optimal scalability.

Bruce Eckel on pattern matching in Java
JDK 16 finalized JEP 394 (Pattern matching for instanceof). Since then, the Java team has previewed new capabilities of pattern matching in switch statements and expressions. Bruce Eckel summarizes the changes found in JEP 394, JEP 406, and JEP 420.

Java Magazine articles about JVM internals

Other recent Java Magazine articles

The not-so-hidden gems in Java 18: The JDK Enhancement Proposals

The hidden gems in Java 18: The subtle changes

Curly Braces #4: Network data transmission and compression in Java

Bruce Eckel on switch expressions, arrow syntax, and case null

Lazy Java code makes applications elegant and sophisticated

Java 18’s Simple Web Server: A tool for the command line and beyond

Java 18 is here: 9 JEPs with core library improvements and updates

Java’s evolution into 2022: The state of the four big initiatives

Instrumenting applications with Java Flight Recorder

Visit Java Magazine

Get ready for Oracle CloudWorld

Oracle customers and partners from around the world will come to Las Vegas October 16 to 20 to share insights about Oracle Cloud Infrastructure and applications at the new Oracle CloudWorld conference. Sign up for the latest about registration and speakers.

Complimentary subscription to Java Magazine

Java Magazine is a deep dive into Java and the JVM. Find detailed explanations about the language and the platform written by experts and members of the Java development team.

Join a quarter of a million subscribers in getting useful, authoritative programming information delivered directly to your inbox.

Stay connected

#oraclejavamag | dev.java

This email was sent to you because you subscribed to this newsletter.

Copyright © 2022, Oracle and/or its affiliates. All rights reserved. Oracle Corporation - Worldwide Headquarters, 2300 Oracle Way, Austin, TX 78741, United States