On Mon, Apr 27, 2020 at 8:23 AM David Holmes <david.hol...@oracle.com> wrote:
> Hi Ioi, > > On 27/04/2020 3:22 pm, Ioi Lam wrote: > > https://bugs.openjdk.java.net/browse/JDK-8241071 > > > http://cr.openjdk.java.net/~iklam/jdk15/8241071-deterministic-cds-archive.v02/ > > > > > > 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). > > I'm not seeing what restricts this to 64-bit only ?? > > Will changing the allocation of symbols cause any problems with the > amount of "class space" we need? > I think also this is improbable but still possible. ccs size is set to 1G when we dump which is usually oversized. But a theoretical case where a customer were to use a large portion of it and we put the Symbols atop of it may bring us over that limit. > > > 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 can't say I like adding in the VM call for this. Another alternative > would be a VM defined system property. But I'll let core-libs folk make > the call here. > > > --- > > 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. > > Generally seems okay. A couple of minor nits: > > src/hotspot/share/oops/symbol.cpp > > typo: adresses -> addresses > > test/hotspot/jtreg/runtime/cds/DeterministicDump.java > > Should the test use @driver mode? > > 39 // use of SharedArchiveFile argument. > > s/argument/arguments/ > > 40 // methods to form command line to create/use shared archive. > > s/line/lines/ > > s/shared/the shared/ > > 71 if (n0 == 0) { > > Shouldn't this check come before the loop at line 63? > > Thanks, > David > ----- > > > Thanks > > - Ioi >
