Garbage Collection

JIRA applications are robust applications that rarely require in-depth garbage collection (GC) tuning. However, on large-scale installations, GC tuning can improve the performance of JIRA applications. Analysis of GC logs can also assist in troubleshooting performance problems with a JIRA application. Starting from JIRA 7.4, GC logs are generated automatically, and you can find them in <installation-directory>/logs.

Diagnosis

Verbose garbage collection will generate log statements that indicate when Java is collecting garbage, how long this process takes, and how much memory has been freed. You can enable verbose garbage collection by adding the below options to the JVM, as in our Setting Properties and Options on Startup documentation.

Using Linux/Unix (Java up to 8):

-XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintGCTimeStamps -XX:+PrintGCCause -Xloggc:<PATH_TO_GC_LOGS>/atlassian-jira-gc-%t.log -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=20M

Using Linux/Unix (Java 9 and later):

-Xlog:gc*:file=<PATH_TO_GC_LOGS>/atlassian-jira-gc-%t.log:tags,time,uptime,level:filecount=5,filesize=20M

Using Windows (Java up to 8):

-Xlog:gc*:file=<PATH_TO_GC_LOGS>\atlassian-jira-gc-%t.log:tags,time,uptime,level:filecount=5,filesize=20M
-XX:+PrintGCDetails

-XX:+PrintGCDateStamps
-XX:+PrintGCTimeStamps
-XX:+PrintGCCause
-Xloggc:<PATH_TO_GC_LOGS>\atlassian-jira-gc-%t.log
-XX:+UseGCLogFileRotation
-XX:NumberOfGCLogFiles=5
-XX:GCLogFileSize=20M

Using Windows (Java 9 and later):

-Xlog:gc*:file=<PATH_TO_GC_LOGS>\atlassian-jira-gc-%t.log:tags,time,uptime,level:filecount=5,filesize=20M

We advise setting the <PATH_TO_GC_LOGS> the same as Jira's installation directory (catalina_home), eg. /opt/atlassian/jira/logs. This allows the GC logs to be included in Support Zips.

Where to set the parameters

You may follow the Setting properties and options on startup guide to set the parameters. We advise filling the JVM_GC_ARGS or JVM_SUPPORT_RECOMMENDED_ARGS if the first's not present.

Be mindful that some parameters may already be present elsewhere in the setenv.sh/setenv.bat. We advise removing them from elsewhere to avoid duplicates and confusion on later editions fo the file.

Analysis

1. Once you have added these options and restarted your JIRA applications, the log specified by the -Xloggc parameter will record memory usage information that can be analyzed using tools like GCViewer.
2. A more complete guide to the practices and principles of GC tuning can be found at Garbage Collection (GC) Tuning Guide.
3. Java VisualVM can also be installed and used to bind to the process that is running your JIRA applications. This can be used to analyze CPU utilization by GC, along with the heap usage. The visualGC plugin is recommended to be installed as it will provide a visual breakdown of each heap space.
4. To better understand GC, you can also take a look at third-party blogs, such as Java Garbage Collection Distilled. 

In addition to GC logging, you can also use heap dumps for analysis. For more information, see Analyze OutofMemory errors in Jira server with heap dumps.

Recommendations

It is unwise to provide general recommendations for all situations - there is no substitute for an in-depth assessment using analysis tools. Atlassian recommends engaging the services of an Atlassian Partner for performance analysis of your JIRA applications and the environment it runs in.