[master] RFR: Add some inlining and avoid CAS for quick_enter for lightweight locking.

[Axel Boldt-Christmas]

On Mon, 1 Jul 2024 20:18:48 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

> This is sort of a simple change to inline the code that decides to go to LightweightSynchronizer in case the call has some negative effects for performance sensitive code.  Avoiding the CAS in try_enter was the most helpful.  With perf, I found that the CAS had a longer stall than with the code without the OM world refactoring.  The OM world table is off for this comparison.
> Tested with tier1-4, including some local changes to run tier1 tests with -XX:+UseObjectMonitorTable.

Marked as reviewed by aboldtch (Committer).

src/hotspot/share/runtime/lightweightSynchronizer.cpp line 578:

> 576: };
> 577: 
> 578: inline bool LightweightSynchronizer::check_unlocked(oop obj, LockStack& lock_stack, JavaThread* current) {

This could be called something like `fast_lock_try_enter` or `fast_lock_enter`. Or even `enter_fast_lock` (similar name to what is in synchronizer.cpp).

I think I like `fast_lock_try_enter`  or `fast_lock_enter` the best.

src/hotspot/share/runtime/objectMonitor.cpp line 385:

> 383: 
> 384: bool ObjectMonitor::try_enter(JavaThread* current) {
> 385:   if (LockingMode == LM_LIGHTWEIGHT) {

Could probably just do this for all LockingModes.

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PR Review: https://git.openjdk.org/lilliput/pull/187#pullrequestreview-2152862078
PR Review Comment: https://git.openjdk.org/lilliput/pull/187#discussion_r1661939993
PR Review Comment: https://git.openjdk.org/lilliput/pull/187#discussion_r1661941127