JEP 271: Unified GC Logging - First pre-review

[Yu Zhang]

Bengt,

Can you also provide an example with -XX:+PrintAdaptiveSize

http://cr.openjdk.java.net/~brutisso/JEP-271/pre-review.00/logs/G1-Xlog-gc-star-info.txt
[0.400s][info ][start,gc ] GC#1 GC young (G1 Evacuation Pause) start
[0.550s][info ][gc ] GC#1 To-space exhausted
It seems the other entries are [gc,xxx ], except for [start,gc], should 
it follow the same patten?
Also the 'to-space exhausted' is on a separate line. I understand it is 
a result of evacuation. But it might make parser easier to put them in 
single line.

[0.608s][info   ][start,gc    ] GC#4 GC young (G1 Evacuation Pause) start
[0.621s][info   ][gc,heap     ] GC#4 Eden: 28672K->0K(28672K)
[0.621s][info   ][gc,heap     ] GC#4 Survivor: 2048K->3072K(4096K)
[0.621s][info   ][gc,heap     ] GC#4 Old: 75120K->78080K(131072K)
[0.621s][info   ][gc,metaspace] GC#4 Metaspace: 2953K->2953K(1056768K)
[0.621s][info   ][gc          ] GC#4 GC young (G1 Evacuation Pause) end 103M->76M(128M) (0.608s, 0.621s) 12.894ms
I think the first 3 heap entries are for heap usage before gc, and the last line has the heap usage after gc, but those 2 formats are different. Probably better to stick to one. Also wondering those 2 timestamps in the parenthesis in the last line is helpful. Most of the time 12.894ms is more helpful.


Thanks,
Jenny

On 10/26/2015 5:26 AM, Bengt Rutisson wrote:
>
> Hi again everyone,
>
> An update on the work for JEP 271 Unified GC Logging.
>
> I now have a working prototype that covers all GCs. Here are some 
> examples comparing the old format (using -XX:+PrintGC and 
> -XX:+PrintGCDetails) with the new format (using -Xlog):
>
> http://cr.openjdk.java.net/~brutisso/JEP-271/pre-review.00/compare.html
>
> The new logging format, using -Xlog, is much more flexible than the 
> old format. So, the comparison table on the above page is by no means 
> complete. I hope it will give a good overview, but to get a real feel 
> for how the new logging works I think it is necessary to run locally 
> and play around with the logging options.
>
> Here is a webrev of the changes so far:
> http://cr.openjdk.java.net/~brutisso/JEP-271/pre-review.00/webrev.00/
>
> There is still work to do and I have some known issues with the code 
> changes. So, I am currently not asking for too much feedback on the 
> actual code changes. I am more looking for feedback on the logging 
> behavior. The webrev can be useful to get a feel for what the code 
> changes will look like but mostly I think it can be used to apply the 
> patch and build your own HotSpot to try out the new logging.
>
> Some changes based on the initial feedback:
> - Start and end timestamps for the GC included on the GC log line.
> - Printing the unit of a value without a space. I.e. "10.345ms" 
> instead of "10.345 ms". (Still working on fixing this in all places as 
> well as trying to use milliseconds instead of seconds in as many 
> places as possible.)
> - Printing heap change information with a fixed unit. I am now using M 
> for overall heap transition and K for detailed information on the 
> debug level.
> - Removed the "summary" tag. Instead the end logging for a GC includes 
> all relevant information.
>
> All feedback is very welcome!
>
> Thanks,
> Bengt

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