RFR: 8253495: CDS generates non-deterministic output [v4]

[Kim Barrett]

On Fri, 11 Mar 2022 04:56:23 GMT, Ioi Lam <iklam at openjdk.org> wrote:

>> This patch makes the result of "java -Xshare:dump" deterministic:
>> - Disabled new Java threads from launching. This is harmless. See comments in jvm.cpp
>> - Fixed a problem in hashtable ordering in heapShared.cpp
>> - BasicHashtableEntry has a gap on 64-bit platforms that may contain random bits. Added code to zero it.
>> - Enabled checking of $JAVA_HOME/lib/server/classes.jsa in make/scripts/compare.sh
>> 
>> Note:  $JAVA_HOME/lib/server/classes_ncoops.jsa is still non-deterministic. This will be fixed in [JDK-8282828](https://bugs.openjdk.java.net/browse/JDK-8282828).
>> 
>> Testing under way:
>> - tier1~tier5
>> - Run all *-cmp-baseline jobs 20 times each (linux-aarch64-cmp-baseline, windows-x86-cmp-baseline, .... etc).
>
> Ioi Lam has updated the pull request incrementally with one additional commit since the last revision:
> 
>   zero GC heap filler arrays

Changes requested by kbarrett (Reviewer).

src/hotspot/share/gc/shared/collectedHeap.cpp line 449:

> 447:   allocator.initialize(start);
> 448:   DEBUG_ONLY(zap_filler_array(start, words, zap);)
> 449:   if (DumpSharedSpaces) {

Probably shouldn't both zap and clear for dumping, to avoid wasting time.

-------------

PR: https://git.openjdk.java.net/jdk/pull/7748