RFR: 8224661: Parallel GC: Use WorkGang (3: UpdateDensePrefixAndCompactionTask)

[Kim Barrett]

> On May 27, 2019, at 4:21 AM, Leo Korinth <leo.korinth at oracle.com> wrote:
> […]
> Enhancement:
>  https://bugs.openjdk.java.net/browse/JDK-8224661
> 
> Webrev:
> http://cr.openjdk.java.net/~lkorinth/workgang/0/_8224661-Parallel-GC-Use-WorkGang-3-UpdateDensePrefixAndCompactionTask/
>  http://cr.openjdk.java.net/~lkorinth/workgang/0/all/
> 
> Testing (on the whole patch series):
>  mach5 remote-build-and-test --build-profiles linux-x64,linux-x64-debug,macosx-x64,solaris-sparcv9,windows-x64 --test open/test/hotspot/jtreg/:hotspot_gc -a -XX:+UseParallelGC
>  gc test suite
> 
> Thanks,
> Leo

http://cr.openjdk.java.net/~lkorinth/workgang/1/_8224661-Parallel-GC-Use-WorkGang-3-UpdateDensePrefixAndCompactionTask/
http://cr.openjdk.java.net/~lkorinth/workgang/1/_8224661-Parallel-GC-Use-WorkGang-3-UpdateDensePrefixAndCompactionTask-fixup-1/

Looks good.

A few minor comments.

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src/hotspot/share/gc/parallel/psParallelCompact.hpp
33 #include "gc/shared/taskqueue.hpp"

I don't see any changes to this file that need this #include.
Presumably it's needed by some .cpp files, but they should be doing
the #include.

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src/hotspot/share/gc/parallel/psParallelCompact.cpp
2467     guarantee(_backing_array != NULL, "alloc failure");

Not needed; NEW_C_HEAP_ARRAY uses EXIT_OOM for the allocation failure
mode.

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src/hotspot/share/gc/parallel/psParallelCompact.cpp
2618 static void compaction_with_stealing_task(ParallelTaskTerminator* terminator, uint which) {

s/which/worker_id/

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src/hotspot/share/gc/parallel/psParallelCompact.cpp
2684   TaskQueue task_queue(last_space_id*(active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING + 1));

Some breadcrumbs to explain that calculation would be really helpful.
Maybe comments, or splitting up the calculation with helpful variable
names, or something.

Anyway, I think it's correct, but harder to verify than it could be.

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