How to show the gc pause time with UseShenandoahGC

[Roman Kennke]

Hi there,

> I found the tool “jstat -gcuitl” not work with ShenandoahGC.  It
> would be better if have a similar tool. 

I just committed a change to our jdk8 tree that implements jvmstat and
jmx support for Shenandoah. I verified that jstat -gcutil works now. As
does JConsole, and other monitoring tools as well. Give it a try.

The change is not yet in our JDK9 repo, but should arrive there soon.

Let me know!

Cheers,
Roman


> 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
> >
> 
> 
>