How to redirect verbose garbage collection output to a file?
How do I redirect verbose garbage collection output to a file? Sun’s website shows an example for Unix but it doesn't work for Windows.
From the output of java -X
:
-Xloggc:<file> log GC status to a file with time stamps
Documented here:
-Xloggc:filename
Sets the file to which verbose GC events information should be redirected for logging. The information written to this file is similar to the output of
-verbose:gc
with the time elapsed since the first GC event preceding each logged event. The-Xloggc
option overrides-verbose:gc
if both are given with the samejava
command.Example:
-Xloggc:garbage-collection.log
So the output looks something like this:
0.590: [GC 896K->278K(5056K), 0.0096650 secs] 0.906: [GC 1174K->774K(5056K), 0.0106856 secs] 1.320: [GC 1670K->1009K(5056K), 0.0101132 secs] 1.459: [GC 1902K->1055K(5056K), 0.0030196 secs] 1.600: [GC 1951K->1161K(5056K), 0.0032375 secs] 1.686: [GC 1805K->1238K(5056K), 0.0034732 secs] 1.690: [Full GC 1238K->1238K(5056K), 0.0631661 secs] 1.874: [GC 62133K->61257K(65060K), 0.0014464 secs]
If in addition you want to pipe the output to a separate file, you can do:
On a Sun JVM:
-Xloggc:C:\whereever\jvm.log -verbose:gc -XX:+PrintGCDateStamps
ON an IBM JVM:
-Xverbosegclog:C:\whereever\jvm.log
Java 9 & Unified JVM Logging
JEP 158 introduces a common logging system for all components of the JVM which will change (and IMO simplify) how logging works with GC. JEP 158 added a new command-line option to control logging from all components of the JVM:
-Xlog
For example, the following option:
-Xlog:gc
will log messages tagged with gc
tag using info
level to stdout
. Or this one:
-Xlog:gc=debug:file=gc.txt:none
would log messages tagged with gc
tag using debug
level to a file called gc.txt
with no decorations. For more detailed discussion, you can checkout the examples in the JEP page.