JDK-8198510 : Enable UseDynamicNumberOfGCThreads by default
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2018-02-21
  • Updated: 2018-03-30
  • Resolved: 2018-03-13
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JDK 11
11 b07Fixed
Related Reports
CSR :  
JDK-8198547 - Enable UseDynamicNumberOfGCThreads by default
Relates :  
JDK-8190937 - Always lazily allocate threads in G1
Sub Tasks
JDK-8199513 :  
Release Note: Garbage Collectors Adaptively Scale the Number of Threads by Default - Closed
Description
The VM currently starts a large amount of GC threads on systems with many CPUs regardless of the Java heap size.
This doesn't make sense for very small heap sizes.

The number of ParallelGCThreads which currently really get started can be observed by e.g.:
jdk/bin/java -Xmx128m -XX:+PrintFlagsFinal -version|grep GCThreads

The existing option UseDynamicNumberOfGCThreads should be enabled by default to prevent more threads than needed from getting started.