G1: "Other" time too long ?

[Simone Bordet]

Hi,

G1 with a 32 GiB heap (16 MiB region size), I was seeing high "Update
RS" and "Scan RS" times during mixed GCs.

I am aware of -XX:G1RSetRegionEntries, but I wanted to try another
path: whether reducing manually the region size caused less inter
region references and therefore reduced the probable coarsening that
was the cause of the long RS times.

So I set the region size to 2 MiB and re-run.

Now I get very high "Other" times, for example:

 [Other: 464.1 ms]
      [Choose CSet: 0.1 ms]
      [Ref Proc: 52.4 ms]
      [Ref Enq: 1.8 ms]
      [Redirty Cards: 19.4 ms]
      [Free CSet: 22.7 ms]

The sum of the subtask times is not close to the "Other" time so I was
wondering what else it's done in the "Other" processing, or whether
perhaps it is not reporting what I think (e.g. a sequential time vs a
parallel time).

I'd probably revert to a 16 MiB region size and setting
G1RSetRegionEntries, but I was wondering if someone can shed some
light on this.

Logs are too big for this mailing list, but I can provide them to
interested people.

Thanks !

-- 
Simone Bordet
http://bordet.blogspot.com
---
Finally, no matter how good the architecture and design are,
to deliver bug-free software with optimal performance and reliability,
the implementation technique must be flawless.   Victoria Livschitz