RFR (round 1), JDK-8214259: Implementation: JEP 189: Shenandoah: A Low-Pause Garbage Collector (original) (raw)

Roman Kennke rkennke at redhat.com
Wed Nov 28 12:41:24 UTC 2018

Hi Kim,

On Nov 27, 2018, at 4:46 AM, Roman Kennke <rkennke at redhat.com> wrote:

Hi Kim,

Sections to review (at this point) are the following:

*) shared-gc - This is mostly boilerplate that is common to any GC - referenceProcessor.cpp has a little change to make one assert not fail (next to CMS and G1) Ick. But I don’t have a better suggestion that doesn’t involve adding a new API to CollectedHeap for use by this assertion, which seems a bit excessive if there are no other uses. Yeah. I guess we could add a config discoveryisconcurrent or similar in RP, and check that. Or maybe one of discoveryismt or discoveryisatomic already covers that? I couldn't immediately tell/100% understand their semantics. Seems worthy to look at after this? It might be equivalent to discoveryisatomic; I don’t remember the exact semantics right now. I think it’s unrelated to discoveryismt. Yes, looking at this later is fine. Please file an RFE.

Ok, done: https://bugs.openjdk.java.net/browse/JDK-8214441

- taskqueue.hpp has some small adjustments to enable subclassing

Why this change instead of JDK-8204947? As the description from that RFE says: "The ShenandoahTaskTerminator from the Shenandoah project is a much better implementation of a task terminator.” Yeah, see Zhengyu's comment. Let's ignore those changes for this review (for now), expect our impl ported to taskqueue.hpp/cpp soon. I’m okay with that plan. Maybe add a comment in JDK-8204947 about this?

https://bugs.openjdk.java.net/browse/JDK-8204947?focusedCommentId=14226307&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14226307

Thanks for reviewing, Roman

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