RFR: 8256302: releasing oopStorage when deflating allows for faster deleting

[David Holmes]

On Tue, 22 Nov 2022 17:52:45 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

> Releasing ObjectMonitor oopStorage earlier when deflating allows ObjectMonitor
> deletion by a JavaThread (usually the MonitorDeflationThread) to happen while a
> ThreadBlockInVM helper is in place. This should improve time-to-safepoint.

I still think we should have been able to keep the release in the destructor guarded by some check:

if (! already_released) {
  assert(!safepoint_safe, "must be");
  _object.release(_oop_storage);
}

but perhaps there is no way to ask if "already_released"?

Thanks for the additional comments on the why of all this. The constraints on when you can access oopStorage were not clear before.

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PR: https://git.openjdk.org/jdk/pull/11296