Health Check: Explicit Garbage Collection

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This article only applies to the Atlassian server platform. Learn more about the differences between cloud and server.

About the health check

A garbage collector (GC) is a memory management tool. This check verifies that you’re using the recommended JVM (Java Virtual Machine) startup parameters for explicit garbage collection (GC).

The check looks for two parameters:

  • ExplicitGCInvokesConcurrent 
  • DisableExplicitGC

If you use the Garbage-First (G1) garbage collector, we recommend configuring your JVM parameters to avoid the risk of explicit STW (stop the world) GC, which causes Jira to become unavailable while the garbage collection cycle runs.

(info) This health check is only shown if you use G1 GC. Other garbage collectors may require different parameters. For more information about G1 GC, check the Oracle documentation.

Understanding the results


IconResultWhat this means
(tick)

The startup parameter ExplicitGCInvokesConcurrent is used.

You're using the recommended configuration.

(warning)

ExplicitGCInvokesConcurrent is not used.

Without this parameter, there is a risk of STW (stop the world) GC.

How do I fix this?

We recommend adding ExplicitGCInvokesConcurrent to the list of startup parameters, as described below.

(warning)

The startup parameter DisableExplicitGC is used.

DisableExplicitGC overrides ExplicitGCInvokesConcurrent, which increases the risk of performance issues.

How do I fix this?

We recommend removing DisableExplicitGC from the list of startup parameters, as described below.

(warning)

The startup parameter DisableExplicitGC is used, and ExplicitGCInvokesConcurrent is not used.

Using DisableExplicitGC increases the risk of performance issues.

How do I fix this?

We recommend removing DisableExplicitGC, and adding ExplicitGCInvokesConcurrent, as described below.


Resolution

If you use G1 GC, we recommend manually adding ExplicitGCInvokesConcurrent to the JVM startup parameters:

  1. Add the following argument to the list of JVM startup parameters:

    -XX:+ExplicitGCInvokesConcurrent
  2. Check that there are no conflicting arguments. If you find the following parameters, remove them from the list of JVM arguments:

    -XX:+DisableExplicitGC
    -XX:+ExplicitGCInvokesConcurrentAndUnloadsClasses
  3. Restart Jira.


For step-by-step instructions for updating system properties, see Setting Properties and Options on Startup.

For more information about garbage collection, check our Garbage Collection (GC) Tuning Guide.

Last modified on Dec 17, 2019

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