JEP 271: Unified GC Logging

[Kirk Pepperdine]

Hi Bengt,

> 
> 
>> 
>> 
>> 
>> For example, if you are not interested in the timing of the different phases, but still want to know the eden/survivor usage you can run with -Xlog:gc,gc+heap=debug and you get this information for each GC:
>> 
>> [0,771s][info   ][gc     ] GC#14 start [young, G1 Evacuation Pause]
>> [0,788s][debug  ][gc,heap] GC#14 Eden:     Used before: 15,0M Used after:    0,0B Capacity:   14,0M
>> [0,788s][debug  ][gc,heap] GC#14 Survivor: Used before: 3072,0K Used after: 3072,0K Capacity: 3072,0K
>> [0,788s][debug  ][gc,heap] GC#14 Heap:     Used before: 111,2M Used after:   97,1M Capacity:  128,0M
>> [0,788s][info   ][gc     ] GC#14 end [111,2M->97,1M(128,0M)] [16,651 ms]

I should have added that I never saw the point to the more verbose lines Eden: Used before and so on when the summary 111.2M->97M conveyed the exact same information. I’ve not found anyone in my performance tuning workshop that is put off with that format either. In fact, every generally goes straight to using tooling and I have to cattle prod them to look at the log. If you think you need the information for debugging so be it.

Kind regards,
Kirk

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