From 7cf868be27dec6539aca5e07f5ed58ac764c7d8f Mon Sep 17 00:00:00 2001 From: Sue Chaplain Date: Tue, 2 Jul 2019 16:41:27 +0100 Subject: [PATCH] Add content for JEP 331 OpenJ9 now provides an implementation of JEP 331, which enables heap profiling with minimal resources. There are a couple of restrictions, which are documented. Closes: #284 Signed-off-by: Sue Chaplain --- docs/version0.15.md | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/docs/version0.15.md b/docs/version0.15.md index 0103d66ef3..c5c9f1c827 100644 --- a/docs/version0.15.md +++ b/docs/version0.15.md @@ -33,6 +33,7 @@ - ![Start of content that applies only to Java 11 (LTS)](cr/java11.png) [ChaCha20 algorithm support for OpenSSL](#chacha20-algorithm-support-for-openssl)![End of content that applies only to Java 11 (LTS)](cr/java_close_lts.png) - [Support for OpenJDK HotSpot options](#support-for-openjdk-hotspot-options) - [Support for Transparent HugePage](#support-for-transparent-hugepage) +- ![Start of content that applies only to Java 11 (LTS)](cr/java11.png) [Support for JEP 331; low-overhead heap profiling](#support-for-jep-331;-low-overhead-heap-profiling) - [Removal of -Xdiagnosticscollector option](#removal-of-xdiagnosticscollector-option) @@ -65,10 +66,19 @@ The ChaCha20 and ChaCha20-Poly1305 algorithms can now use OpenSSL on Java 11. Fo For compatibility, the [`-XX:OnOutOfMemoryError`](xxonoutofmemoryerror.md) OpenJDK Hotspot option is now supported by OpenJ9. -### Support for Transparent HugePage +### ![Start of content that applies only to Java 11 (LTS)](cr/java11.png) Support for Transparent HugePage The VM now supports the allocation of huge pages on Linux when you use the `madvise` (`/sys/kernel/mm/transparent_hugepage/enabled`) setting. To enable this feature, set [`-XX:+TransparentHugePage`](xxtransparenthugepage.md) on the command line when you start your application. This option is currently not enabled by default. +### Support for JEP 331; low-overhead heap profiling + +[JEP 331](http://openjdk.java.net/jeps/331) provides a mechanism for sampling Java heap allocations with minimal resources, which can be achieved by using the JVM Tools Interface (JVMTI). + + **Restrictions:** JEP 331 is implemented for OpenJ9 with the following limitations: + +- The `balanced` and `metronome` garbage collection policies are not supported. +- The changes might not be compatible with the Health Center agent, which uses the same sampling interval. + ### Removal of -Xdiagnosticscollector option This option was redundant and has now been removed. If you try to use this option on the command line, the VM outputs this error message: