What is JVM startup parameter: -XX:+LogCompilation?

Usage:

This option allows the JVM to log compilation activity in detail to LogFile.

Since:

Starting from JDK 6.

Examples:

This will enable the JVM to log detailed compilation activity to the LogFile:

-XX:+LogCompilation

Description:

Enables logging of compilation activity to a file named hotspot.log in the current working directory. You can specify a different log file path and name using the -XX:LogFile option. The logs are displayed with an XML format (the size of the logs can reach 100 of MB or more) which will contain a detailed level of steps of the JVM compiler.

By default, this option is disabled and compilation activity isn’t logged. The -XX:+LogCompilation option has to be used together with the -XX:UnlockDiagnosticVMOptions option that unlocks diagnostic JVM options.

You can enable verbose diagnostic output with a message printed to the console every time a method is compiled by using the -XX:+PrintCompilation option.

Here is an example of an output of LogCompilation in case of the method String.equals:

<nmethod compile_id='3' compiler='C2' entry='0x00000000000001' size='468' address='0x00000000000001' relocation_offset='263' consts_offset='468' insts_offset='281' method='java/lang/String equals ()I' bytes='32' count='215' iicount='215' stamp='0.230'/>

As we can see, the format is a little difficult and not easy to read. But you can use tools such as LogCompilation to parse your compilation log.

Default Value:

By default, this option is disabled.

Arguments related:

LogFile, UnlockDiagnosticVMOptions

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