JDK-6947595 : Change parallel GC collector default number of parallel GC threads
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 6u19
  • Priority: P3
  • Status: Open
  • Resolution: Unresolved
  • OS: solaris_10
  • CPU: sparc
  • Submitted: 2010-04-27
  • Updated: 2019-02-11
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tbdUnresolved
Related Reports
Relates :  
JDK-6947591 - JDK ParallelGCThreads does not honor cpu/zone capping issue
Relates :  
JDK-6362677 - Change parallel GC collector default number of parallel GC threads.
Relates :  
JDK-8078703 - Ensure that GC's use of processor count is correct
Description
6362677 Change parallel GC collector default number of parallel GC threads.
considered Niagra platform but seems to not consider
other Sparc servers with large # of Cpu's , such as the M9000
which can have 64 or more cpus. There may be others.

In this particular case, the customer had an M9000 w/64 cpu's
JDK 6.0_19

It used the 

8 + (n - 8) * 5/8

where n is the number of hardware threads.  The
exception is for Niagara2 and later CMT machines
where it is 

8 + (n - 8) * 5/16


If it was a Niagra the 5/16 rule would have been used
rather than 5/8 rule.