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

Per Liden per.liden at oracle.com
Thu Nov 29 15:36:58 UTC 2018


Oh, I filed a bug [1] and sent out a fix for review, before noticing 
Jini's mail.

[1] https://bugs.openjdk.java.net/browse/JDK-8214484

/Per

On 11/29/18 5:39 AM, Jini George wrote:
> Hi Roman,
> 
> The SA tests which iterate over the heap (ClhsdbJhisto.java, 
> TestHeapDumpFor*.java) fail if ZGC is passed as an option to these also 
> (Am planning on fixing these). It might be better to avoid invoking 
> those tests for Shenandoah now with an @requires tag.
> 
> Thank you,
> Jini
> 
> On 11/29/2018 3:59 AM, Roman Kennke wrote:
>> Alright, we fixed:
>> - The minor issues that Kim reported in shared-gc
>> - A lot of fixes in shared-tests according to Leonid's review
>> - Disabled SA heapdumping similar to ZGC as Per suggested
>>
>> Some notes:
>> Leonid:  test/hotspot/jtreg/gc/TestFullGCCount.java was actually
>> correct. The @requires there means to exclude runs with both CMS and
>> ExplicitGCInvokesConcurrent at the same time, because that would be
>> (expectedly) failing. It can run CMS, default GC and any other GC just
>> fine. Adding the same clause for Shenandoah means the same, and filters
>> the combination (+UseShenandoahGC)+(+ExplicitGCInvokesConcurrent). I
>> made the condition a bit clearer by avoiding triple-negation.
>>
>> See:
>> http://mail.openjdk.java.net/pipermail/shenandoah-dev/2018-November/008457.html 
>>
>>
>> Per: Disabling the SA part for heapdumping makes 2 tests fail:
>> - test/hotspot/jtreg/serviceability/sa/ClhsdbJhisto.java
>> - test/hotspot/jtreg/serviceability/sa/TestHeapDumpForLargeArray.java
>>
>> we filter them for Shenandoah now. I'm wondering: how do you get past
>> those with ZGC?
>>
>> See:
>> http://mail.openjdk.java.net/pipermail/shenandoah-dev/2018-November/008466.html 
>>
>>
>> (Note to Leonid and tests reviewers: I'll add those related filters in
>> next round).
>>
>> Vladimir: Roland integrated a bunch of changes to make loop* code look
>> better. I can tell that we're not done with C2 yet. Can you look over
>> the code and see what is ok, and especially what is not ok, so that we
>> can focus our efforts on the relevant parts?
>>
>> Updated set of webrevs:
>> http://cr.openjdk.java.net/~rkennke/shenandoah-upstream/01/
>>
>> Thanks,
>> Roman
>>
>>
>>> 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
>>>
>>


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