RFR: 8259808: Add JFR event to detect GC locker stall [v2]

[Denghui Dong]

On Mon, 18 Jan 2021 08:04:38 GMT, Stefan Karlsson <stefank at openjdk.org> wrote:

>> Denghui Dong has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Refactor based on comments
>
> src/hotspot/share/utilities/ticks.hpp line 241:
> 
>> 239:   friend class GCTimerTest;
>> 240:   friend class CompilerEvent;
>> 241:   friend class GCLocker;
> 
> I don't think this should be needed.

Fixed.

> src/hotspot/share/gc/shared/gcLocker.cpp line 112:
> 
>> 110: #if INCLUDE_JFR
>> 111:     if (EventGCLocker::is_enabled()) {
>> 112:       _needs_gc_start_timestamp = JfrTicks::now();
> 
> Do you really need to use JfrTicks instead of Ticks here? If not, could you remove all references and includes of JfrTicks? We usually use pass in Ticks when we send JFR events.

Fixed.

> src/hotspot/share/prims/whitebox.cpp line 44:
> 
>> 42: #include "gc/shared/genArguments.hpp"
>> 43: #include "gc/shared/genCollectedHeap.hpp"
>> 44: #include "gc/shared/gcLocker.inline.hpp"
> 
> Sort includes.

Fixed.

> src/hotspot/share/jfr/metadata/metadata.xml line 1080:
> 
>> 1078:     <Field type="uint" name="stallCount" label="Stall Count" />
>> 1079:   </Event>
>> 1080: 
> 
> You add this between two Shenandoah events. Could you put it somewhere where it's not splitting up a group of events?

Fixed.

-------------

PR: https://git.openjdk.java.net/jdk/pull/2088