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

[Bengt Rutisson]

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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