RFR: JDK-8289524: Add JFR JIT restart event [v3]

[Erik Gahlin]

On Thu, 14 Jul 2022 14:26:01 GMT, Matthias Baesken <mbaesken at openjdk.org> wrote:

>> The JIT compiler restarts (see restart_compiler in NMethodSweeper::sweep_code_cache) would be a helpful addition to the JFR events. Currently we log the JIT stop operations in JFR (EventCodeCacheFull) but no restart.
>
> Matthias Baesken has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Bring back JitRestart event, add codeCacheMaxCapacity

src/hotspot/share/code/codeCache.cpp line 1369:

> 1367:     event.set_unallocatedCapacity(heap->unallocated_capacity());
> 1368:     event.set_fullCount(heap->full_count());
> 1369:     event.set_codeCacheMaxCapacity(CodeCache::max_capacity());

Add test of field in TestCodeCacheFull

src/hotspot/share/jfr/metadata/metadata.xml line 561:

> 559:   </Event>
> 560: 
> 561:   <Event name="JitRestart" category="Java Virtual Machine, Compiler" label="JIT restart" stackTrace="false" startTime="false" thread="true">

"JITRestart" . The convention for other events have been to use capital laters for acronyms. 

"JIT restart" -> "JIT Restart"

src/hotspot/share/jfr/metadata/metadata.xml line 563:

> 561:   <Event name="JitRestart" category="Java Virtual Machine, Compiler" label="JIT restart" stackTrace="false" startTime="false" thread="true">
> 562:     <Field type="int" name="freedMemory" label="Freed Memory" />
> 563:     <Field type="ulong" name="codeCacheMaxCapacity" label="CodeCache maximum capacity" />

Should be "Code Cache Maximum Capacity"

src/hotspot/share/jfr/metadata/metadata.xml line 620:

> 618:     <Field type="ulong" contentType="bytes" name="unallocatedCapacity" label="Unallocated" />
> 619:     <Field type="int" name="fullCount" label="Full Count" />
> 620:     <Field type="ulong" name="codeCacheMaxCapacity" label="CodeCache maximum capacity" />

Should be "Code Cache Maximum Capacity"

src/hotspot/share/runtime/sweeper.cpp line 440:

> 438:     log.debug("restart compiler");
> 439:     log_sweep("restart_compiler");
> 440:     EventJitRestart event;

It would be good to have a sanity test of the event. 

If the event can't be provoked reliably, retry or accept as OK.

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PR: https://git.openjdk.org/jdk/pull/9334