JDK-8173398 : limit number of GC worker threads for smaller heaps
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 9
  • Priority: P3
  • Status: Closed
  • Resolution: Duplicate
  • OS: generic
  • CPU: generic
  • Submitted: 2017-01-26
  • Updated: 2017-01-27
  • Resolved: 2017-01-27
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JDK 10
10Resolved
Related Reports
Relates :  
JDK-8172792 - JEP 308: Improve Dynamic Number of Thread Sizing for G1
Description
The heuristics currently do not seem to take the size of the heap into account when calculating the default number of worker threads. This can often lead to a huge amount of thread overhead for small heaps. As an extreme example, on a on a 40 HW thread machine, 9-ea+144 will start up over 100 GC threads (G1) OOTB for a 16m heap.

This has caused performance issues in environments where many small processes are run in parallel.

This ER is to document the issue and prompt a discussion on whether we can improve the ergonomics for smaller heaps.