On Thu, 13 Jul 2023 21:25:17 GMT, Matias Saavedra Silva <[email protected]>
wrote:
> Currently we exit the VM after static dumping with
> `MetaspaceShared::exit_after_static_dump()`.
>
>
> // We have finished dumping the static archive. At this point, there may be
> pending VM
> // operations. We have changed some global states (such as
> vmClasses::_klasses) that
> // may cause these VM operations to fail. For safety, forget these
> operations and
> // exit the VM directly.
> void MetaspaceShared::exit_after_static_dump() {
> os::_exit(0);
> }
>
>
> As the comment suggests, the VM state is altered when preparing and
> performing the static dump, so this change aims to prevent these state
> changes so the VM can exit normally after the static dump completes. There
> are three major aspects to this change:
> 1. Since the resolved references array in the Constant Pool is altered when
> preparing for a static dump, a "scratch copy" is created and archived instead
> 2. Symbols are sorted by address and have their hash recalculated. Similarly
> to point 1, the copies of the symbols that are to be archived have their
> hashes updated as opposed to the originals.
> 3. The handling of -Xshare:dump during argument parsing such that the VM can
> continue and exit normally with an exit code of 0.
Hi Matias,
I'm not keen on having to teach the launcher about `-Xshare:dump` and that it
is a terminal operation. But after looking into it I have to admit it is a
cleaner and more consistent termination strategy. That said you need to be
aware that this will now do a clean shutdown of the VM after the dump, so
shutdown hooks will now run.
Lets see what core-libs folk think too.
Thanks.
src/hotspot/share/runtime/threads.cpp line 812:
> 810: if (DumpSharedSpaces) {
> 811: MetaspaceShared::preload_and_dump();
> 812: *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
This is only set when create_vm fails. A successful creation of the VM prevents
subsequent re-creation attempts.
-------------
PR Review: https://git.openjdk.org/jdk/pull/14879#pullrequestreview-1531828953
PR Review Comment: https://git.openjdk.org/jdk/pull/14879#discussion_r1264773183
