How do I control JIT behavior in the JVM?

First, let me explain my own test environment:

Ubuntu 12.04 x86-64,openjdk 7 64-bit Server VM (mixed mode)

MacOS 10.11,hotspot 7 64-bit Server VM (mixed mode)

1. How do I turn off JIT?

In general, JIT is turned on by default, so there is only one problem with how to turn it off.

When starting the JVM, simply increase the-xint or-Djava.compiler=NONE选项即可：

Java-xint Your_main_class_file_name

Java-Djava. Compiler Your_main_class_file_name

If you are booting from eclipse, you need to specify the above parameters in run configurations.

2. How do I view the JIT-generated assembly code?

Sometimes, we need to look at the JIT-generated assembly code to see how the JIT affects the execution of the code.

To complete this task, you need to install a support library, Hsdis, steps below.

Linux systems:

Download linux-hsdis-amd64.so or linux-hsdis-i386.so

Rename to hsdis-amd64.so or hsdis-i386.so

Copy to $java_home/jre/lib/amd64/directory

It's/usr/lib/jvm/java-7-openjdk-amd64/jre/lib/amd64/on my machine.

OS x System:

Download Gnu-bsd-libhsdis-amd64.dylib or Gnu-bsd-libhsdis-i386.dylib

Rename to Hsdis-amd64.dylib or Hsdis-i386.dylib

Copy to $java_home/jre/lib/directory

It's/library/java/javavirtualmachines/jdk1.7.0_79.jdk/contents/home/jre/lib/hsdis-amd64.dylib on my machine.

After installing the support library, you only need to add the following two options when starting the JVM:

java-xx:+unlockdiagnosticvmoptions-xx:+printassembly Your_main_class_file_name

Here is a link to the detailed description, you can refer to:

https://wiki.openjdk.java.net/display/HotSpot/PrintAssembly

In addition, if you do not install a support library, you will get the following error when you specify the options above and start the JVM:

Java HotSpot (TM) 64-bit Server VM warning:printassembly is enabled; Turning on debugnonsafepoints to gain additional output

Could not load hsdis-amd64.dylib; Library not loadable; Printassembly is disabled

How do I control JIT behavior in the JVM?