JDK-8159979 : During initial mark, preparing all regions for marking may take a significant amount of time
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 9
  • Priority: P4
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2016-06-21
  • Updated: 2021-09-09
  • Resolved: 2021-08-31
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JDK 18
18 b13Fixed
Related Reports
Relates :  
JDK-8273206 - jdk/jfr/event/gc/collection/TestG1ParallelPhases.java fails after JDK-8159979
Relates :  
JDK-8152948 - More unaccounted other time on large machines
Relates :  
JDK-8227671 - G1: assert_used_and_recalculate_used_equal performs work in product builds
Description
During initial mark, in G1ConcurrentMark::checkpointRootsInitialPre() G1 iterates over all regions to set the next tams pointer to top.

On heaps with many regions 20k+ this can take a while, as this phase is single-threaded.
Comments
Changeset: 841e3943 Author: Ivan Walulya <iwalulya@openjdk.org> Date: 2021-08-31 12:30:14 +0000 URL: https://git.openjdk.java.net/jdk/commit/841e3943c480c95409446bb35fb9a56d7fc48c8a
31-08-2021