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

[Erik Joelsson]

Build changes look ok to me.

/Erik

On 2018-11-26 13:39, Roman Kennke wrote:
> Hi,
>
> This is the first round of changes for including Shenandoah GC into
> mainline.
> I divided the review into parts that roughly correspond to the mailing lists
> that would normally review it, and I divided it into 'shared' code
> changes and
> 'shenandoah' code changes (actually, mostly additions). The intend is to
> eventually
> push them as single 'combined' changeset, once reviewed.
>
> JEP:
>    https://openjdk.java.net/jeps/189
> Bug entry:
>
>   https://bugs.openjdk.java.net/browse/JDK-8214259
>
> Webrevs:
>    http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/00/
>
> For those who want to see the full change, have a look at the
> shenandoah-complete
> <http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/00/shenandoah-complete/>
> directory,
> it contains the full combined webrev. Alternatively, there is the file
> shenandoah-master.patch
> <http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/00/shenandoah-master.patch>,
> which is what I intend to commit (and which should be equivalent to the
> 'shenandoah-complete' webrev).
>
> Sections to review (at this point) are the following:
>   *) shenandoah-gc
> <http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/00/shenandoah-gc/>
>      - Actual Shenandoah implementation, almost completely residing in
> gc/shenandoah
>
>   *) shared-gc
> <http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/00/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)
>      - taskqueue.hpp has some small adjustments to enable subclassing
>
>   *) shared-serviceability
> <http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/00/shared-serviceability/>
>      - The usual code to support another GC
>
>   *) shared-runtime
> <http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/00/shared-runtime/>
>      - A number of friends declarations to allow Shenandoah iterators to
> hook up with,
>        e.g. ClassLoaderData, CodeCache, etc
>      - Warning and disabling JFR LeakProfiler
>      - fieldDescriptor.hpp added is_stable() accessor, for use in
> Shenandoah C2 optimizations
>      - Locks initialization in mutexLocker.cpp as usual
>      - VM operations defines for Shenandoah's VM ops
>      - globalDefinitions.hpp added UINT64_FORMAT_HEX_W for use in
> Shenandoah's logging
>      - The usual macros in macro.hpp
>
>   *) shared-build
> <http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/00/shared-build/>
>      - Add shenandoah feature, enabled by default, as agreed with
> Vladimir K. beforehand
>      - Some flags for shenandoah-enabled compilation to get
> SUPPORT_BARRIER_ON_PRIMITIVES
>        and SUPPORT_NOT_TO_SPACE_INVARIANT which is required for
> Shenandoah's barriers
>      - --param inline-unit-growth=1000 settings for 2 shenandoah source
> files, which is
>        useful to get the whole marking loop inlined (observed significant
> regression if we
>        don't)
>
>   *) shared-tests
> <http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/00/shared-tests/>
>      - Test infrastructure to support Shenandoah
>      - Shenandoah test groups
>      - Exclude Shenandoah in various tests that can be run with selected GC
>      - Enable/add configure for Shenandoah for tests that make sense to
> run with it
>
>   *) shenandoah-tests
> <http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/00/shenandoah-tests/>
>      - Shenandoah specific tests, most reside in gc/shenandoah subdirectory
>      - A couple of tests configurations have been added, e.g.
> TestGCBasherWithShenandoah.java
>
> I intentionally left out shared-compiler for now, because we have some
> work left to do
> there, but if you click around you'll find the patch anyway, in case you
> want to take
> a peek at it.
>
> We have regular builds on:
>    - {Linux} x {x86_64, x86_32, armhf, aarch64, ppc64el, s390x}
>    - {Windows} x {x86_64},
>    - {MacOS X} x {x86_64}
>
> This also routinely passes:
>    - the new Shenandoah tests
>    - jcstress with/without aggressive Shenandoah verification
>    - specjvm2008 with/without aggressive Shenandoah verification
>
>
> I'd like to thank my collegues at Red Hat: Christine Flood, she deserves
> the credit for being the original inventor of Shenandoah, Aleksey
> Shiplëv, Roland Westrelin & Zhengyu Gu for their countless
> contributions, everybody else in Red Hat's OpenJDK team for testing,
> advice and support, my collegues in Oracle's GC, runtime and compiler
> teams for tirelessly helping with and reviewing all the GC interface and
> related changes, and of course the many early adopters for reporting
> bugs and success stories and feature requests: we wouldn't be here
> without any of you!
>
> Best regards,
> Roman
>