RFR: JDK-8055845 - Add trace event for promoted objects

[Erik Gahlin]

Looks good

Bengt Rutisson skrev 2014-08-26 10:50:
>
> Hi all,
>
> Staffan sent me an updated webrev based on Erik's comments. I uploaded 
> it here:
> http://cr.openjdk.java.net/~brutisso/8055845/webrev.01/
>
> Thanks,
> Bengt
>
>
> On 2014-08-25 19:32, Staffan Friberg wrote:
>> Hi Erik,
>>
>> No issue with naming the field class, since the event is similar to 
>> the Allocation event I used that as a starting point and it also uses 
>> class as name together with a couple of other events.
>>
>> Will go through the descriptions and remove periods.
>>
>> Object age is basically the how many times an object has been kept in 
>> survivor region, it is incremented each time a YC happens and the 
>> object is aged.
>> Will see how I can update the description to make it clearer. Calling 
>> the field tenuringAge might help?
>>
>>> From the documentation, 
>>> http://docs.oracle.com/javase/8/docs/technotes/tools/unix/java.html
>>>
>>> -XX:MaxTenuringThreshold=/threshold/
>>>
>>>     Sets the maximum tenuring threshold for use in adaptive GC
>>>     sizing. The largest value is 15. The default value is 15 for the
>>>     parallel (throughput) collector, and 6 for the CMS collector.
>>>
>>>     The following example shows how to set the maximum tenuring
>>>     threshold to 10:
>>>
>>>     -XX:MaxTenuringThreshold=10
>>>
>>>
>>> -XX:+PrintTenuringDistribution
>>>
>>>     Enables printing of tenuring age information. The following is
>>>     an example of the output:
>>>
>>>     Desired survivor size 48286924 bytes, new threshold 10 (max 10)
>>>     - age 1: 28992024 bytes, 28992024 total
>>>     - age 2: 1366864 bytes, 30358888 total
>>>     - age 3: 1425912 bytes, 31784800 total
>>>     ...
>>>
>>>     Age 1 objects are the youngest survivors (they were created
>>>     after the previous scavenge, survived the latest scavenge, and
>>>     moved from eden to survivor space). Age 2 objects have survived
>>>     two scavenges (during the second scavenge they were copied from
>>>     one survivor space to the next). And so on.
>>>
>>>     In the preceding example, 28 992 024 bytes survived one scavenge
>>>     and were copied from eden to survivor space, 1 366 864 bytes are
>>>     occupied by age 2 objects, etc. The third value in each row is
>>>     the cumulative size of objects of age n or less.
>>>
>>>     By default, this option is disabled.
>>>
>>
>> Thanks for the comments,
>> Staffan
>>
>> On 08/25/2014 09:55 AM, Erik Gahlin wrote:
>>> Did you manage to call the field "class"? It's a reserved word in 
>>> C++, so we had to use "klass" in the past
>>>
>>> Descriptions with only one sentence shouldn't end with "."
>>>
>>> How is "Object Age" measured?
>>>
>>> As a user, I would expect the number to be in seconds/minutes/hours, 
>>> but that is not the case. Perhaps an explanation in the description 
>>> and/or a field name that better reflects what we really mean with age.
>>>
>>> Otherwise trace.xml looks good!
>>>
>>> Erik
>>>
>>> Staffan Friberg skrev 25/08/14 18:28:
>>>> Hi,
>>>>
>>>> Could I please get reviews for this RFE that adds a trace event for 
>>>> aging and promotion for young collections in G1, CMS and Parallel GC.
>>>> It works similarly to allocation events, and generates the event on 
>>>> the slow path when either a direct copy occurs or a new PLAB is 
>>>> request.
>>>>
>>>> Since I'm adding an event I cc:ed the serviceability list in case 
>>>> anyone has any comments on the event and changes to trace.xml.
>>>>
>>>> RFE: https://bugs.openjdk.java.net/browse/JDK-8055845
>>>> Webrev: http://cr.openjdk.java.net/~brutisso/8055845/webrev.00
>>>>
>>>> Bengt has been kind and agreed to both sponsor and host the the 
>>>> webrev.
>>>>
>>>> Thanks,
>>>> Staffan
>>>>
>>>
>>
>

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