RFR: 8253495: CDS generates non-deterministic output [v6]

[Calvin Cheung]

On Fri, 11 Mar 2022 06:55:23 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:
> 
>   Added helper function CollectedHeap::zap_filler_array_with

CDS changes look good. One minor comment on a test.

test/hotspot/jtreg/runtime/cds/appcds/javaldr/LockDuringDumpAgent.java line 65:

> 63:                     if (elapsed >= timeout) {
> 64:                         System.out.println("This JVM may decide to not launch any Java threads during -Xshare:dump.");
> 65:                         System.out.println("This is OK because no string objects be in a locked state during heap dump.");

Should `no string objects be` be `no string objects could be`?

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Marked as reviewed by ccheung (Reviewer).

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