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

Roman Kennke rkennke at redhat.com
Thu Nov 29 11:12:39 UTC 2018


Thanks, Per!

I will do this. Check out round 3 when it arrives. ;-)

Roman

Am 29.11.18 um 12:07 schrieb Per Liden:
> Small comment on the build changes. Instead of checking for zero variant
> here:
> 
> +  # Only enable Shenandoah on supported arches
> +  AC_MSG_CHECKING([if shenandoah can be built])
> +  if HOTSPOT_CHECK_JVM_VARIANT(zero); then
> +    DISABLED_JVM_FEATURES="$DISABLED_JVM_FEATURES shenandoahgc"
> +    AC_MSG_RESULT([no, this JVM variant not supported])
> +  else
> 
> I think you should just add shanandoahgc to the existing check, here:
> 
>   # Disable unsupported GCs for Zero
>   if HOTSPOT_CHECK_JVM_VARIANT(zero); then
>     DISABLED_JVM_FEATURES="$DISABLED_JVM_FEATURES epsilongc g1gc zgc"
>   fi
> 
> cheers,
> Per
> 
> On 11/26/18 11:47 PM, Erik Joelsson wrote:
>> 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
>>>



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