RFR: 8204210: Implementation: JEP 333: ZGC: A Scalable Low-Latency Garbage Collector (Experimental)

[Magnus Ihse Bursie]

Hi Per,

Please always include build-dev when proposing build changes.

The changes in make/autoconf/hotspot.m4 looks a bit suspect. Since you 
are adding zgc to disabled jvm features, which always override enabled 
features, it will never be possible to enable zgc on any other platform. 
Is this intentional? Otherwise, I suggest instead adding zgc to the 
baseline set NON_MINIMAL_FEATURES for linux-x64.

/Magnus



On 2018-06-01 23:41, Per Liden wrote:
> Hi,
>
> Please review the implementation of JEP 333: ZGC: A Scalable 
> Low-Latency Garbage Collector (Experimental)
>
> Please see the JEP for more information about the project. The JEP is 
> currently in state "Proposed to Target" for JDK 11.
>
> https://bugs.openjdk.java.net/browse/JDK-8197831
>
> Additional information in can also be found on the ZGC project wiki.
>
> https://wiki.openjdk.java.net/display/zgc/Main
>
>
> Webrevs
> -------
>
> To make this easier to review, we've divided the change into two webrevs.
>
> * ZGC Master: http://cr.openjdk.java.net/~pliden/8204210/webrev.0-master
>
>   This patch contains the actual ZGC implementation, the new unit 
> tests and other changes needed in HotSpot.
>
> * ZGC Testing: 
> http://cr.openjdk.java.net/~pliden/8204210/webrev.0-testing
>
>   This patch contains changes to existing tests needed by ZGC.
>
>
> Overview of Changes
> -------------------
>
> Below follows a list of the files we add/modify in the master patch, 
> with a short summary describing each group.
>
> * Build support - Making ZGC an optional feature.
>
>   make/autoconf/hotspot.m4
>   make/hotspot/lib/JvmFeatures.gmk
>   src/hotspot/share/utilities/macros.hpp
>
> * C2 AD file - Additions needed to generate ZGC load barriers (adlc 
> does not currently offer a way to easily break this out).
>
>   src/hotspot/cpu/x86/x86.ad
>   src/hotspot/cpu/x86/x86_64.ad
>
> * C2 - Things that can't be easily abstracted out into ZGC specific 
> code, most of which is guarded behind a #if INCLUDE_ZGC and/or if 
> (UseZGC) condition. There should only be two logic changes (one in 
> idealKit.cpp and one in node.cpp) that are still active when ZGC is 
> disabled. We believe these are low risk changes and should not 
> introduce any real change i behavior when using other GCs.
>
>   src/hotspot/share/adlc/formssel.cpp
>   src/hotspot/share/opto/*
>   src/hotspot/share/compiler/compilerDirectives.hpp
>
> * General GC+Runtime - Registering ZGC as a collector.
>
>   src/hotspot/share/gc/shared/*
>   src/hotspot/share/runtime/vmStructs.cpp
>   src/hotspot/share/runtime/vm_operations.hpp
>   src/hotspot/share/prims/whitebox.cpp
>
> * GC thread local data - Increasing the size of data area by 32 bytes.
>
>   src/hotspot/share/gc/shared/gcThreadLocalData.hpp
>
> * ZGC - The collector itself.
>
>   src/hotspot/share/gc/z/*
>   src/hotspot/cpu/x86/gc/z/*
>   src/hotspot/os_cpu/linux_x86/gc/z/*
>   test/hotspot/gtest/gc/z/*
>
> * JFR - Adding new event types.
>
>   src/hotspot/share/jfr/*
>   src/jdk.jfr/share/conf/jfr/*
>
> * Logging - Adding new log tags.
>
>   src/hotspot/share/logging/*
>
> * Metaspace - Adding a friend declaration.
>
>   src/hotspot/share/memory/metaspace.hpp
>
> * InstanceRefKlass - Adjustments for concurrent reference processing.
>
>   src/hotspot/share/oops/instanceRefKlass.inline.hpp
>
> * vmSymbol - Disabled clone intrinsic for ZGC.
>
>   src/hotspot/share/classfile/vmSymbols.cpp
>
> * Oop Verification - In four cases we disabled oop verification 
> because it do not makes sense or is not applicable to a GC using load 
> barriers.
>
>   src/hotspot/cpu/x86/c1_LIRAssembler_x86.cpp
>   src/hotspot/cpu/x86/stubGenerator_x86_64.cpp
>   src/hotspot/share/compiler/oopMap.cpp
>   src/hotspot/share/runtime/jniHandles.cpp
>
> * StackValue - Apply a load barrier in case of OSR. This is a bit of a 
> hack. However, this will go away in the future, when we have the next 
> iteration of C2's load barriers in place (aka "C2 late barrier 
> insertion").
>
>   src/hotspot/share/runtime/stackValue.cpp
>
> * JVMTI - Adding an assert() to catch problems if the tagmap hashing 
> is changed in the future.
>
>   src/hotspot/share/prims/jvmtiTagMap.cpp
>
> * Legal - Adding copyright/license for 3rd party hash function used in 
> ZHash.
>
>   src/java.base/share/legal/c-libutl.md
>
> * SA - Adding basic ZGC support.
>
>   src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/*
>
>
> Testing
> -------
>
> * Unit testing
>
>   A number of new ZGC specific gtests have been added, in 
> test/hotspot/gtest/gc/z/
>
> * Regression testing
>
>   No new failures in Mach5, with ZGC enabled, tier{1,2,3,4,5,6}
>   No new failures in Mach5, with ZGC disabled, tier{1,2,3}
>
> * Stress testing
>
>   We have been continuously been running a number stress tests 
> throughout the development, these include:
>
>     specjbb2000
>     specjbb2005
>     specjbb2015
>     specjvm98
>     specjvm2008
>     dacapo2009
>     test/hotspot/jtreg/gc/stress/gcold
>     test/hotspot/jtreg/gc/stress/systemgc
>     test/hotspot/jtreg/gc/stress/gclocker
>     test/hotspot/jtreg/gc/stress/gcbasher
>     test/hotspot/jtreg/gc/stress/finalizer
>     Kitchensink
>
>
> Thanks!
>
> /Per, Stefan & the ZGC team