ZGC: RFR: 8207756: jstat should show CGC STW phases of ZGC

[Yasumasa Suenaga]

Hi Erik, Per,

Thank you for your comment.
I uploaded new webrev. It has CGC counter in ZServiceability.

   http://cr.openjdk.java.net/~ysuenaga/JDK-8207756/webrev.01/

I know ZGC has three STW phases. They are called by VM_ZOperation. So I had added CGC counter in it at first. However I agree with you if ZServiceability should have it.


Yasumasa


On 2018/07/26 23:19, Erik Österlund wrote:
> Hi Yasumasa,
> 
> There is only one global instance of CollectorCounters. Do we really have to pass it around into constructors and dump it in ZDriver?
> I don't see why it would be in any way problematic to just put this global instance of counters in ZServiceabilityCounters. And put the TraceCollectorStats tcs(_cgc_counters); stuff in ZServiceabilityCountersTracer or something like that.
> 
> Also I saw this: _cgc_counters = new CollectorCounters("Z stop-the-world phases", 2);
> 
> Does this assume there are two pauses for a ZGC collection cycle? There are at least 3, but possibly more:
> 
> 1) Mark start
> 2) Mark end (this could recur multiple times due to unlucky races with mutators resurrecting weak references right before hitting mark end, causing a new concurrent phase if a large object graph was reachable from this weak ref). So we really can't know for sure how many pauses there will be.
> 3) Relocate start (done after reference processing and concurrent selection of relocaiton set)
> 
> Thanks,
> /Erik
> 
> On 2018-07-26 15:44, Yasumasa Suenaga wrote:
>> CC'ing to hotspot-gc-dev
>>
>> Hi Per,
>>
>> I've looked at ZServiceabilityCounters in zServiceability.cpp .
>> IMHO it is unsuitable because CGC counter means STW in concurrent GC. So I think it is suitable to implement in VMOperation for ZGC.
>>
>> Thanks,
>>
>> Yasumasa
>>
>>
>> On 2018/07/26 22:30, Per Lidén wrote:
>>> Hi,
>>>
>>> Please have a look at the zServiceability class, which is where code like this is intended to live.
>>>
>>> /Per
>>>
>>>> On 26 Jul 2018, at 14:30, Yasumasa Suenaga <yasuenag at gmail.com> wrote:
>>>>
>>>> PING: Could you review it?
>>>>
>>>>>    webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8207756/webrev.00/
>>>>
>>>>
>>>> Yasumasa
>>>>
>>>>
>>>>> On 2018/07/18 11:59, Yasumasa Suenaga wrote:
>>>>> Hi all,
>>>>> Please review this change:
>>>>>    JBS: https://bugs.openjdk.java.net/browse/JDK-8207756
>>>>>    webrev: http://cr.openjdk.java.net/~ysuenaga/JDK-8207756/webrev.00/
>>>>> jstat shows CGC STW phases as CGC and CGCT fields since JDK-8153333 .
>>>>> However, ZGC does not adapt to it yet as following:
>>>>> ```
>>>>> $ jstat -gc 1234 1 1
>>>>>   S0C S1C S0U S1U EC EU OC OU MC MU CCSC CCSU YGC YGCT FGC FGCT CGC CGCT GCT
>>>>>    - - - - - - 514048.0 12288.0 4352.0 3731.2 0.0 0.0 - - - - - - 0.000
>>>>> ```
>>>>> I uploaded webrev which is for jdk/jdk repo. Please tell me if it
>>>>> should be for zgc repo.
>>>>> I'm not an author of ZGC. So I need a sponsor.
>>>>> (I'm a Reviewer of jdk. If this change should be pushed to jdk/jdk,
>>>>> please tell me. I will push it after reviewing.)
>>>>> Thanks,
>>>>> Yasumasa
>>>
>