JEP 271: Unified GC Logging

[Bengt Rutisson]

On 2015-09-24 19:02, Kirk Pepperdine wrote:
> 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.

Am I interpreting you correctly that you think the three lines for 
eden/survivor/heap are too verbose. That the "111,2M->97,1M(128,0M)" 
logging is enough? That's a valid comment I just wanted to make sure I 
understand you correctly.

I've had to explain that output so many times to different people that I 
thought it would be better to be a bit more verbose and hopefully ease 
the understanding of the log output a bit. But I'm open to changing it.

Cheers,
Bengt

>
> Kind regards,
> Kirk
>