[8] RFR: Cherry-pick JDK-8231201: hs_err should print coalesced safepoint operations in Events section

[Aleksey Shipilev]

Pushed; builds are rebuilding.

On 11/5/19 11:43 AM, Roman Kennke wrote:
> Ok, that makes sense. Do it!
> 
> Thanks,
> Roman
> 
>> Looking at hs_errs from Alexander, I suspect there are more VM operations happening than meets the
>> eye. See for example:
>>
>> Event: 749.332 Executing VM operation: FindDeadlocks
>> Event: 749.333 Pause Init Update Refs
>> Event: 751.083 Pause Init Update Refs done
>> Event: 751.083 Executing VM operation: FindDeadlocks done
>>
>> Where's the "Executing VM operation: ShenandoahInitUpdateRefs"? The answer is here:
>>   https://bugs.openjdk.java.net/browse/JDK-8231201
>>
>> I requested the jdk8u backport here:
>>   https://mail.openjdk.java.net/pipermail/jdk8u-dev/2019-November/010552.html
>>
>> ...but it would be a while before it lands in sh/jdk8. So, let's cherry-pick it:
>>
>> diff -r e8582ad276a2 src/share/vm/runtime/vmThread.cpp
>> --- a/src/share/vm/runtime/vmThread.cpp Mon Nov 04 12:25:21 2019 +0100
>> +++ b/src/share/vm/runtime/vmThread.cpp Mon Nov 04 19:23:12 2019 +0100
>> @@ -505,10 +505,11 @@
>>          // the queue until there are none left
>>          do {
>>            _cur_vm_operation = safepoint_ops;
>>            if (_cur_vm_operation != NULL) {
>>              do {
>> +              EventMark em("Executing coalesced VM operation: %s", _cur_vm_operation->name());
>>                // evaluate_operation deletes the op object so we have
>>                // to grab the next op now
>>                VM_Operation* next = _cur_vm_operation->next();
>>                _vm_queue->set_drain_list(next);
>>                evaluate_operation(_cur_vm_operation);
>>
>> Testing: hotspot_gc_shenandoah
>>
> 


-- 
Thanks,
-Aleksey