RFR (S): 8010916: Add tenuring threshold to young garbage collection events

[Erik Helin]

Hi Jesper,

thanks for the review! I would also like to thank Stefan for taking a 
look at the code offline.

On 04/02/2013 12:33 PM, Jesper Wilhelmsson wrote:
> Erik,
>
> I'm OK with this change as is but I think it is unfortunate that you
> chose not to follow the pattern used by the other events where we
> register a value at some point and then, in the end, report the event. I
> realize that in this case it would probably result in registering the
> tenuring threshold and then at the next line reporting the YC event. I'm
> not sure which is worse. I don't really like that you need to pass the
> tenuring threshold to report_young_gc_end.

The change has been updated to now saving the value in the young gc 
tracer and then report it at the end. I would prefer to not have to deal 
with this extra state, but it has to be this way because the young gc 
event needs the GC end time, and the end time is only passed to 
report_gc_end (thanks Stefan for pointing this out).

Please see new webrev at:
http://cr.openjdk.java.net/~ehelin/8010916/webrev.01/

Thanks,
Erik

> /Jesper
>
>
> Erik Helin skrev 1/4/13 11:04 AM:
>> Hi all,
>>
>> this change adds the field "tenuringThreshold" to the
>> "vm/gc/collector/young_garbage_collection" event.
>>
>> The code in gcTrace.hpp/cpp have been slightly adjusted to support this.
>> The hierarchy of tracers is:
>>
>>      G1NewTracer -> YoungGCTracer -> GCTracer
>>
>> where "->" means "inherits from".
>>
>> Previously, the method "report_gc_end_impl" was virtual in "GCTracer"
>> to enable
>> "YoungGCTracer" to send the young GC event when "report_gc_end" was
>> called on a
>> GCTracer, as in the following:
>>
>>      void GCTracer::report_gc_end(...) {
>>        // do other stuff
>>        report_gc_end_impl(...);
>>      }
>>
>>      void YoungGCTracer::report_gc_end_impl(...) {
>>        // send young gc event here
>>      }
>>
>> In this change, YoungGCTracer now has a method "report_young_gc_end"
>> that is
>> virtual and that G1NewTracer overrides. This means that YoungGCTracer
>> does not
>> need to override the method "report_gc_end_impl" from GCTracer. This
>> also means
>> that all young collectors now also must call "report_young_gc_end".
>>
>> This change was needed, since report_young_gc_end must take the tenuring
>> threshold as a parameter, something that was not possible to do with
>> "report_gc_end_impl".
>>
>> Webrev:
>> http://cr.openjdk.java.net/~ehelin/8010916/webrev.00/
>>
>> Bug:
>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8010916
>>
>> Testing:
>> JPRT
>>
>> Thanks,
>> Erik