JDK-8001425 : G1: Change the default values for certain G1 specific flags
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: hs25
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2012-10-23
  • Updated: 2013-09-18
  • Resolved: 2013-01-16
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JDK 7 JDK 8 Other
7u21Fixed 8Fixed hs24Fixed
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When testing footprint sensitive FAs; the performance team has realized that the default values are not good enough. Hence we propose the following - 
Change the default for G1OldCSetRegionLiveThresholdPercent to 65
Change the default for G1HeapWastePercent to 10

I think its OK to go ahead with the broadened scope of default changes for Nursery min & max percent. I was just being conservative with my original defaults change request.

After posting a webrev to the open jdk, the general feedback was why limit the revised values for NewSizePercent and MaxNewSizePercent to heaps under 4GB. There isn't any real reason not to extend these values to all heap sizes.

Additional suggestions from the performance team: * Increase MixedGCCountTarget from 4 to 8. * For heaps that do not exceed 4Gb reduce the NewSizePercent to 5 and reduce the MaxNewSizePercent to 60.