RFR: 8253495: CDS generates non-deterministic output [v2]

[David Holmes]

On Wed, 9 Mar 2022 05:10:44 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:
> 
>   Fixed zero build

The "heap dump" aspect of this is not something I'm familiar with, but if the threads don't affect the list of classes dumped, they surely must affect what is in the heap dump otherwise their execution would not be an issue. So you must be sacrificing something by not having these threads start.

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