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

Roman Kennke rkennke at redhat.com
Tue Nov 27 09:38:31 UTC 2018

Thanks for reviewing, Erik!

Roman

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 isstable() 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 UINT64FORMATHEXW 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 SUPPORTBARRIERONPRIMITIVES and SUPPORTNOTTOSPACEINVARIANT 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 {x8664, x8632, armhf, aarch64, ppc64el, s390x} - {Windows} x {x8664}, - {MacOS X} x {x8664} 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

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