Hi Ioi,
On 2020-04-27 07:22, Ioi Lam wrote:
https://bugs.openjdk.java.net/browse/JDK-8241071
http://cr.openjdk.java.net/~iklam/jdk15/8241071-deterministic-cds-archive.v02/
I can't really comment on the code changes, but I'd like to thank you
for the effort of getting a deterministic classes.jsa. This is a big
step towards the goal of getting deterministic, reproducible builds of
the JDK.
/Magnus
The goal is to for "java -Xshare:dump" to produce deterministic
contents in
the CDS archive that depend only on the contents of
$JAVA_HOME/lib/modules.
Problems:
[1] Symbols in the CDS archive may have non-deterministic order because
Arena allocation is non-deterministic.
[2] The contents of the CDS shared heap region may be randomized due to
ImmutableCollections.SALT32L.
Fixes:
[1] With -Xshare:dump, allocate Symbols from the class space (64-bit
only).
See changes in symbol.cpp for details.
[2] When running the VM with -Xshare:dump,
ImmutableCollections.SALT32L is
initialized with a deterministic seed. NOTE: this affects ONLY
when the
VM is running with the special flag -Xshare:dump to dump the CDS
archive.
It does NOT affect normal execution of Java programs.
---
I also cleaned up the -Xlog:cds output and print out the CRC of each
CDS region, to help diagnose why two CDS archives may have different
contents.
Thanks
- Ioi
