JEP 271: Unified GC Logging

[Kirk Pepperdine]

Hi Bengt,

> 
>> 
>> 
>>> ...
>> 
>>> 
>>> [0,799s][debug  ][gc,phases ] GC#14    Clear CT: 2,7 ms
>>> [0,799s][debug  ][gc,phases ] GC#14    Other: 8,5 ms
>>> [0,800s][debug  ][gc,phases ] GC#14       Choose CSet: 0,0 ms
>>> [0,800s][debug  ][gc,phases ] GC#14       Ref Proc: 2,4 ms
>>> [0,800s][debug  ][gc,phases ] GC#14       Ref Enq: 0,0 ms
>>> [0,800s][debug  ][gc,phases ] GC#14       Redirty Cards: 2,0 ms
>>> [0,800s][debug  ][gc,phases ] GC#14       Humongous Register: 0,0 ms
>>> [0,800s][debug  ][gc,phases ] GC#14       Humongous Reclaim: 0,0 ms
>>> [0,800s][debug  ][gc,phases ] GC#14       Free CSet: 3,5 ms
>> 
>> BTW: I wonder if this is a single phase mabye a single line would be better:
>> 
>> [0,799s][debug  ][gc,phases ] GC#14    Other: 8,5 ms
>> [0,799s][debug  ][gc,phases,detail ] GC#14    Other Breakdown: Choose CSet 8,5ms, Ref Proc 2,4ms, Ref Enq 0,0ms ...
>> 
>> i.e. allow to select/deselect the other breakdown and make sure it is a single (extendable) record (savong lots of bytes).
> 
> Right. A more compact format may be nice. I'll play with that a bit.

This seems to imply that the time stamps will be relevant to when UL decorates them. I fear that there could be a fair bit of skidding between the start of the event and when UL decorates. I’ve been trying to find an example in the email chain to see if there is a time taken (aside from that given by UL) that would help me to anchor when the event actually took place. If we’ve got it, great. If not, I would suggest that there needs to be one time stamp taken at the event that would be included in the body of the log message. If there is one date stamp, it can be used with the time stamp (as an offset) to calculate dates for all other events. If this ends up as a decoration, not a problem because the difference in the decorated time stamp and the start of the event timestamp can be used to provide a reference point to calculate from. My immediate concern is that at the time for start of the event is captured and reported as UL timers will moved on.

Kind regards,
Kirk Pepperdine

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