How to show the gc pause time with UseShenandoahGC

[Chunhui Shen]

Thanks Roman for the detailed explanation. It's helpful.
>When you turn on -XX:+PrintGCDetails you will find interesting pause
>statistics on program termination. E.g. number of pauses, avg and max
>pause time, std deviation, etc.
Is it possible to get such pause statistics  during the program running?
I found the tool “jstat -gcuitl” not work with ShenandoahGC.  It would be better if have a similar tool. 
Thanks.

At 2015-10-23 18:10:37, "Roman Kennke" <rkennke at redhat.com> wrote:
>I think you are looking at the right logs. Shenandoah does two pauses:
>InitMark and InitEvac. You can find it in the log:
>
>> 2015-10-23T15:10:35.930+0800: 1738.287: [GC InitMark end, 0.017967
>> secs total = 75497472 K, used = 51861702 K free = 23635769 K]
>
>Here you got 12.9 ms for InitMark.
>
>The other pause is a bit more difficult to find, because it spans over
>several intervals:
>The first is FinalMark:
>> 2015-10-23T15:10:36.182+0800: 1738.538: [GC FinalMark end, 0.034520
>> secs total = 75497472 K, used = 52252771 K free = 23244700 K]
>
>34.5ms
>
>Then PrepareEvac:
>
>> 2015-10-23T15:10:36.183+0800: 1738.539: [GC PrepareEvac end, 0.000964
>> secs total = 75497472 K, used = 23712714 K free = 51784757 K]
>
>0.96ms
>
>and InitEvac:
>
>> 2015-10-23T15:10:36.190+0800: 1738.547: [GC InitEvac end, 0.007175
>> secs total = 75497472 K, used = 23715364 K free = 51782108 K]
>
>7.1ms
>
>They all add up to a total pause of 42,56ms
>
>Since they all go in one pause, we should probably make a measurement
>interval around them for better usability.
>
>When you turn on -XX:+PrintGCDetails you will find interesting pause
>statistics on program termination. E.g. number of pauses, avg and max
>pause time, std deviation, etc.
>
>I hope it helps, let us know!
>
>Roman
>