Integrated: 8252105: Parallel heap inspection for ZCollectedHeap

[Per Liden]

On Mon, 5 Oct 2020 15:40:52 GMT, Per Liden <pliden at openjdk.org> wrote:

> This patch changes the ZHeapIterator to also support parallel iteration, for use in
> ZCollectedHeap::parallel_object_iterator(). I initially looked at using the heap walking logic in ZMark, instead of
> also implementing it in ZHeapIterator. That's probably something we want to do at some point, but that would require
> some major restructuring of ZMark. In the mean time I've kept the heap walking logic in ZHeapIterator.  The
> ZHeapIterator now implements ParallelObjectIterator, and the same code paths is used for both serial and parallel
> iteration. Arrays are chunked using ObjArrayTask to reduce mark stack space. A terminator is used for better work
> stealing/balance.  Tested using `jmap -histo` and various benchmarks with `-XX:+ZVerifyObjects` and
> `-XX:+VerifyDuringGC` enabled.

This pull request has now been integrated.

Changeset: c73a0fff
Author:    Per Liden <pliden at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/c73a0fff
Stats:     307 lines in 8 files changed: 212 ins; 17 del; 78 mod

8252105: Parallel heap inspection for ZCollectedHeap

Reviewed-by: ayang, eosterlund

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PR: https://git.openjdk.java.net/jdk/pull/507