Java Garbage Collection Logging

Internal

• Java Garbage Collection

Command Line Options

Java 8

https://docs.oracle.com/javase/8/docs/technotes/tools/windows/java.html#BABFAFAE

Overview

In Java 8, GC logging is enabled with the -Xloggc:<file> (see below). The actual -XX values the JVM operates with are displayed at the top of the log file:

...
CommandLine flags: -XX:InitialHeapSize=268435456 -XX:MaxHeapSize=4294967296 -XX:+PrintGC -XX:+PrintGCTimeStamps -XX:+UseCompressedClassPointers -XX:+UseCompressedOops -XX:+UseParallelGC
...

Options

-Xloggc:

-Xloggc:<file>

where <file> can be absolute or relative. In case of a relative path, it is relative to the current directory.

If used, the option automatically turns on the following: [[]], [[]].

-XX:+PrintGC

-XX:+PrintGC

Enables printing of messages at every GC. By default, this option is disabled, but -Xloggc:<file> turns it on implicitly.

-XX:+PrintGCTimeStamps

-XX:+PrintGCTimeStamps

Enables printing of time stamps (time in seconds since the JVM started) at every GC. By default, this option is disabled. It is implicit turned on if -Xloggc:<file> is used. Time stamps recorded this way provide a chronology relative to the time the JVM started, but additional calculation is needed to translate the timestamps to normal timestamps, and it is only possible if the JVM start time is also recorded. A better way to record timestamps is to use [[]].

When used, the timestamps are recorded in the following format:

2017-02-12T19:26:03.328+0800:

-XX:+PrintGCDateStamps

-XX:+PrintGCDateStamps

-verbose:gc

-XX:+PrintGCDetails

-XX:+PrintGCDateStamps

-XX:+UseGCLogFileRotation

-XX:NumberOfGCLogFiles=5

-XX:GCLogFileSize=3M