JDK-8254739 : G1: Optimize evacuation failure for regions with few failed objects
  • Type: Sub-task
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 16
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2020-10-14
  • Updated: 2021-12-17
  • Resolved: 2021-11-05
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JDK 18
18 b23Fixed
Related Reports
Blocks :  
JDK-8273626 - G1: Factor out concurrent segmented array from G1CardSetAllocator
Relates :  
JDK-8276721 - G1: Refine G1EvacFailureObjectsSet::iterate
Relates :  
JDK-8276148 - G1: Support reclaiming memory used in G1EvacFailureObjectsSet
Relates :  
JDK-8276094 - Region Pinning in G1
Relates :  
JDK-8236594 - G1: Provide object pinning
Relates :  
JDK-8273309 - G1: Handling objects that fail evacuation very slow
Relates :  
JDK-8278917 - Use Prev Bitmap for recording evac failed objects
Description
Eacuation failure with pinned regions often leaves only regions with few live objects.

Optimize evacuation failure handling for such failed regions.

One option could be, until a certain threshold, track failed objects on a per object basis, then at fixup time use that list (after sorting) instead of walking all objects.
Comments
Changeset: ed7ecca4 Author: Hamlin Li <mli@openjdk.org> Date: 2021-11-05 23:24:45 +0000 URL: https://git.openjdk.java.net/jdk/commit/ed7ecca401e5f4c3c07dc98e05a21396c6cdf594
05-11-2021
TODOs left by JDK-8273626: https://github.com/openjdk/jdk/pull/5478#discussion_r724814701 https://github.com/openjdk/jdk/pull/5478#discussion_r724825707 https://github.com/openjdk/jdk/pull/5478#discussion_r727983658
14-10-2021
Thanks Thomas for testing and collecting the data.
06-09-2021
Attached a graph (20210902-remove-self-forwards-improvement.png) showing improvement on "Remove Self Forwards" (Preserve Marks is negligible) after this change for specjbb2015 with fixed IR = 6000, 16gb heap, G1EvacuationFailureALot enabled (other evac failure options untouched). That time decreases from 80-180ms to 4-5ms...
03-09-2021