JDK-7146246 : G1: expose some of the -XX flags that drive which old regions to collect during mixed GCs
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: hs23
  • Priority: P3
  • Status: Closed
  • Resolution: Fixed
  • OS: generic
  • CPU: generic
  • Submitted: 2012-02-16
  • Updated: 2013-09-18
  • Resolved: 2012-03-31
The Version table provides details related to the release that this issue/RFE will be addressed.

Unresolved : Release in which this issue/RFE will be addressed.
Resolved: Release in which this issue/RFE has been resolved.
Fixed : Release in which this issue/RFE has been fixed. The release containing this fix may be available for download as an Early Access Release or a General Availability Release.

To download the current JDK release, click here.
JDK 7 JDK 8 Other
7u21Fixed 8Fixed hs24Fixed
Related Reports
Relates :  
Relates :  
The heuristics that drive which old regions to collect during mixed GCs and which not, introduced by:

7132029: G1: mixed GC phase lasts for longer than it should

and maybe further fine-tuned by:

7146242: G1: alternative heuristic on deciding which old regions not to collect

introduced several develop -XX flags. It will be good to expose some of them to the users so that they can adjust the "space efficiency" vs. "pause times duration" trade-off to what they feel it's appropriate for them.

We should decide what the minimum number of flags is and make sure their names are reasonable.

EVALUATION http://hg.openjdk.java.net/hsx/hotspot-gc/hotspot/rev/21595f05bc93

EVALUATION See Description / Public Comments.

PUBLIC COMMENTS We're turning the following two into product params: G1HeapWastePercent (previously called: G1OldReclaimableThresholdPercent) G1MixedGCCountTarget (previous called: G1MaxMixedGCNum) Also increased the default of the former from 1% to 5% and decreased the default for G1OldCSetRegionLiveThresholdPercent from 95% to 90%.