RFR (M) 8239786: Shenandoah: print per-cycle statistics

[Aleksey Shipilev]

On 4/23/20 10:30 PM, Roman Kennke wrote:
> Do I see it correctly that we get this with -Xlog:gc+stats=info ? I.e.
> the same that gives us the end-of-run-stats? Might that be too spammy
> for info? Maybe wire it to 'trace' instead?

I would prefer to keep it gc+stats=info, for several reasons:
 *) gc+stats is not enabled by default, and it is inherently opt-in;
 *) this logging is asynchronous, so bulk printing does not come with performance overhead;
 *) "trace" is usually for very fine-grained tracing, and this is rather high level.
 *) I think ZGC prints out the similar bunch of counters under gc+stats as well;

This might change once we reshuffle logging further...

I updated webrev a bit (copyrights, excess headers):
  https://cr.openjdk.java.net/~shade/8239786/webrev.02/

Ok?

-- 
Thanks,
-Aleksey