RFR: 8313332: Simplify lazy jmethodID cache in InstanceKlass [v3]

[Daniel D. Daugherty]

On Wed, 3 Apr 2024 23:05:24 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> This change simplifies the code that grows the jmethodID cache in InstanceKlass.  Instead of lazily, when there's a rare request for a jmethodID for an obsolete method, the jmethodID cache is grown during the RedefineClasses safepoint.  The InstanceKlass's jmethodID cache is lazily allocated when there's a jmethodID allocated, so not every InstanceKlass has a cache, but the growth now only happens in a safepoint.  This code will become racy with the potential change for deallocating jmethodIDs.
>> 
>> Tested with tier1-4, vmTestbase/nsk/jvmti java/lang/instrument tests (in case they're not in tier1-4).
>
> Coleen Phillimore has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix spacing and punctuation.  make log_info into log_debug.

Thanks for the fixes. There are a couple that you missed.

src/hotspot/share/oops/instanceKlass.cpp line 2313:

> 2311:       size_t size = idnum_allocated_count();
> 2312:       assert(size > (size_t)idnum, "should already have space");
> 2313:       jmeths = NEW_C_HEAP_ARRAY(jmethodID, size+1, mtClass);

nit: spaces around operator `+`

src/hotspot/share/oops/instanceKlass.cpp line 2346:

> 2344:       // Allocate a larger one and copy entries to the new one.
> 2345:       // They've already been updated to point to new methods where applicable (i.e., not obsolete).
> 2346:       jmethodID* new_cache = NEW_C_HEAP_ARRAY(jmethodID, size+1, mtClass);

nit: spaces around operator `+`

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Marked as reviewed by dcubed (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/18549#pullrequestreview-1978305784
PR Review Comment: https://git.openjdk.org/jdk/pull/18549#discussion_r1550653423
PR Review Comment: https://git.openjdk.org/jdk/pull/18549#discussion_r1550653504