On Thu, 10 Mar 2022 13:51:56 GMT, Magnus Ihse Bursie <i...@openjdk.org> wrote:
>> Ioi Lam has updated the pull request incrementally with one additional >> commit since the last revision: >> >> Fixed zero build > > I think he already did. I'm quoting: > >> However, the CDS archive also contains a heap dump, which includes Java >> HashMaps. If I allow those 3 Java threads to start, some HashMaps in the >> module graph will have unstable ordering. I think the reason is concurrent >> thread execution causes unstable assignment of the identity_hash for objects >> in the heap dump. > @magicus the issue is not the list of classes dumped, or their format in the > dump. As Ioi indicated that list is fixed. The issue is with the heap dump > part of the archive. Running these other threads affects the heap so by not > running them with end up with a different heap. So the question is whether > there is anything about having a different heap dumped that we need to be > concerned about. We dump the heap into the archive for a reason and this > changes what we dump, To be clear, if multiple threads are running, classes could be loaded in a different order and the symbols will have different orders. This would cause the vtables in Klass objects to be laid out differently. Trying to fix this is very difficult. I have a different patch that makes it work but it's just too complicated. So, disabling the threads is also necessary for (easily) sorting the metaspace objects. ------------- PR: https://git.openjdk.java.net/jdk/pull/7748
