JDK-8201313 : Times of sub-phases of ext root scan may be larger than the sum of individual timings
  • Type: Bug
  • Component: hotspot
  • Sub-Component: gc
  • Affected Version: 11
  • Priority: P4
  • Status: Closed
  • Resolution: Won't Fix
  • Submitted: 2018-04-09
  • Updated: 2024-11-07
  • Resolved: 2024-11-07
Related Reports
Relates :  
JDK-6672778 - G1 should trim task queues more aggressively during evacuation pauses
Relates :  
JDK-8230706 - Waiting on completion of strong nmethod processing causes long pause times with G1
Description
The BufferingOopClosure and partial task queue trimming introduced in JDK-6672778 may do some work that that is attributed to the ObjCopy phase at the end of root processing.

This time is properly removed from the total ext root scan time at the end of root processing during evacuation.
However this time is not in any way subtracted from the individual sub-timings of ext root scan, so it is possible that the sum of time spent in the individual tasks is larger than the total time spent.

Note that this is purely an issue with log display.
Comments
This is a minor inconvenience/error in logging, and there is no simple fix. It has been pushed along since JDK 11, so it is unlikely to be fixed, so closing it as WNF for now.
07-11-2024