Moulali Shikalwadi created WFCORE-4904:
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Summary: Remove setting Metaspace
Key: WFCORE-4904
URL:
https://issues.redhat.com/browse/WFCORE-4904
Project: WildFly Core
Issue Type: Enhancement
Reporter: Moulali Shikalwadi
Assignee: Moulali Shikalwadi
Unlike perm gen, it is typically not necessary to set a max/min metaspace size[1] for the
following reasons:
*Metaspace size is unlimited by default. Since it only holds class metadata, size
requirements are minimal.
*It does not require a full gc to resize the metaspace, as it did with the perm
generation.
MaxMetaspaceSize includes CompressedClassSpaceSize, so MaxMetaspaceSize should be larger
than CompressedClassSpaceSize.
The default MaxMetaspaceSize is 1g:
java -XX:+PrintFlagsFinal -version | grep CompressedClassSpaceSize
uintx CompressedClassSpaceSize = 1073741824
{product}
If MaxMetaspaceSize is set smaller than CompressedClassSpaceSize, the JVM auto adjusts
CompressedClassSpaceSize as follows: CompressedClassSpaceSize = MaxMetaspaceSize - (2 *
InitialBootClassLoaderMetaspaceSize).[2]
The default EAP Metaspace sizes are less than the default CompressedClassSpaceSize:
-XX:MetaspaceSize=96M -XX:MaxMetaspaceSize=256m
This adjusts down the MaxMetaspaceSize to 248m:
java -XX:MetaspaceSize=96M -XX:MaxMetaspaceSize=256m -XX:+PrintFlagsFinal -version | grep
CompressedClassSpaceSize
uintx CompressedClassSpaceSize := 260046848 {product}
We have had a lot of OOME Metaspace cases[3], and support is no longer recommending
customers set Metaspace:
"In general, you should not need to set a maximum size, unless you are experiencing
large metaspace leaks and would prefer it to fail rather than keep increasing memory
size."[1]
This was discussed with the OpenJDK developers[4], and their recommendation was to remove
the Metaspace settings, and especially in the context of containers.
References:
[
1]https://access.redhat.com/solutions/1489263
[
2]https://access.redhat.com/solutions/2132101
[
3]https://access.redhat.com/solutions/2038983
[
4]http://post-office.corp.redhat.com/archives/support-openjdk/2019-July/m...
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