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-6362677 - Change parallel GC collector default number of parallel GC threads.
Relates :  
JDK-8078703 - Ensure that GC's use of processor count is correct
Relates :  
JDK-6947591 - JDK ParallelGCThreads does not honor cpu/zone capping issue
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.