RFR(XXS): 8153176: ParOldGC's ParallelTaskTerminator peeks wrong TaskQueueSet

[Reingruber, Richard]

Hi,

I would like to contribute a fix for a bug in parallel old gc. The bug can cause long gc pauses, because work stealing while marking does not work as ParallelTaskTerminator peeks the wrong task queue set.

A microbenchmark that produces an object graph with large linear parts consistently shows 3x shorter gc pauses with the fix (see bug report). In a similar synthetic test the bug sporadically caused pauses 10x longer than average.

Webrev: http://www.sapjvm.com/rr/webrevs/8153176_paroldgc_wrong_taskqueueset_in_marking/webrev_01/
Bug:    https://bugs.openjdk.java.net/browse/JDK-8153176

The change needs to be sponsored as well, please.

Thanks, Richard.

--
Richard Reingruber | SAP JVM | CORE PLATFORM,  SAP SE 
Pflichtangaben/Mandatory Disclosure Statements: http://www.sap.com/company/legal/impressum.epx