[jboss-jira] [JBoss JIRA] (WFCORE-1150) Include -XX:MetaspaceSize in our default vm settings

[Brian Stansberry (JIRA)]

Brian Stansberry created WFCORE-1150:
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             Summary: Include -XX:MetaspaceSize in our default vm settings
                 Key: WFCORE-1150
                 URL: https://issues.jboss.org/browse/WFCORE-1150
             Project: WildFly Core
          Issue Type: Enhancement
          Components: Server
            Reporter: Brian Stansberry
             Fix For: 3.0.0.Alpha1


JDK 8 no longer has a perm gen, but it does have a "Metaspace" area of native memory where it stores some of the types of data previously stored in perm gen, class metadata in particular.

The default size of this are is, I believe 21MB on a 64 bit VM. Full WildFly uses over 50MB, excluding apps. The VM will increase the size once it gets over a certain percentage full, but it will do a full, stop-the-world GC before increasing. This means full WildFly has two full GCs as part of boot.

The -XX:MetaspaceSize JVM option allows the minimum size to be set. Using a reasonable value for this will help avoid unnecessary full GCs.

I'm not sure the best value to use. A minimum of 80MB was enough to avoid a full GC during a boot of standalone-full-ha.xml. But then any sort of deployments will trigger a full GC. OTOH, our host.xml jvm elements have historically included a -XX:PermSize setting of 256M, so that's another possible value. Perm Gen and Metaspace aren't completely equivalent (e.g. before JDK 7 perm gen included stuff like interned strings, which are now in the heap.)



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