Need help on G1 GC young gen Update RS and Scan RS pause reduction

[Thomas Schatzl]

Hi Amit,

On Fri, 2017-01-20 at 10:51 +0000, Amit Mishra wrote:
> Thank you very much Thomas, after making said changes RSUpdate time
> is in control but Scan RS is still high.
>  

  can you summarize your GC parameters again, and also, are these high
Scan RS times you observe regular or not?

Did you check with -XX:+G1SummarizeRSetStats -
XX:G1SummarizeRSetStatsPeriod=<some value> whether there are still
coarsenings?

Could you also please provide a longer snippet of your log file
containing a few gcs before and after this occurrence?

Other worthwhile tries could be to fudge with -XX:ParallelGCThreads,
either decreasing or increasing them (up to your vcpus) by ten or so to
see whether that phase suffers from synchronization issues.

The high scan rs times could maybe also a bit mitigated by increasing
G1NewSizePercent to maybe two or three to see whether g1 can avoid
large young remembered sets by that (Object copy might go up a bit then
though).

It may be easier to think of causes for the issues you are experiencing
by having a little bit of more information.

Thanks,
  Thomas