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
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7u21Fixed 8Fixed hs24Fixed
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Description
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.

Comments
EVALUATION http://hg.openjdk.java.net/hsx/hotspot-gc/hotspot/rev/21595f05bc93
23-03-2012

EVALUATION See Description / Public Comments.
21-03-2012

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%.
21-03-2012