JDK-6362677 : Change parallel GC collector default number of parallel GC threads.
  • Type: Bug
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 6
  • Priority: P1
  • Status: Closed
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2005-12-13
  • Updated: 2017-05-19
  • Resolved: 2011-04-20
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Other JDK 6 Other
5.0u23,hs12Fixed 6u14Fixed hs12Fixed
Related Reports
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JDK-6428776 - The jps and jstat tools should be run with -client
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JDK-6947591 - JDK ParallelGCThreads does not honor cpu/zone capping issue
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JDK-6947595 - Change parallel GC collector default number of parallel GC threads
Description
The parallel GC collector by default uses a number of parallel GC threads that is
equal to the number of cpu's.  That is too large a number on systems with more
that 8 cpu's.
Comments
SUGGESTED FIX The number of GC threads for hardware threads > 8 will be in most cases 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
15-10-2009
WORK AROUND For use by Solaris, there are two workarounds. One is to use the client vm, for which the default is the serial collector, which, as the name implies, is single-threaded. Use '-client'. The other is to specify the serial collector on the command line, vis. '-XX:+UseSerialGC'.
11-01-2008
EVALUATION The default to the number of parallel GC threads should be made if performance is not adversely affected.
20-12-2005