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

[coleen.phillimore at oracle.com]

Hi, I was going to review the runtime pieces of this change but there 
are none!  Nicely factored and thank you for upstreaming the runtime 
changes to support this already.

Coleen

On 6/1/18 5:41 PM, 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