RFR: 8242078: G1: Improve concurrent refinement analytics and logging

[Kim Barrett]

> On Apr 8, 2020, at 11:25 AM, Thomas Schatzl <thomas.schatzl at oracle.com> wrote:
> Some minor issues:
> 
> - G1CollectedHeap::gc_prologue - in new code doing timing measurements, please use Ticks/Tickspan instead of double/os::elapsedTime.

Done. I similarly updated the nearby calculation of prepare_tlab_time.
We really need some helpers for Tickspan conversions, or should be
recording Tickspans directly.

> - g1RemSetSummary.hpp:36: the "private" visibility specifier could be removed as well.

Done.

> - the modification to NonJavaThreadsList_lock maybe warrants a different change. It just does not seem to fit although it looks correct.

That change was for G1DetachedRefinementStats_lock, which I really
don't want to have to put at a lower rank than leaf.  I probably
should have called that out in the RFR email.

There is a related issue that I noticed but haven’t reported yet.  The description
for BarrierSet::on_thread_{attach,detach} say that for Java threads they are
called while holding the Threads_lock, but that isn’t true for detach.  It probably
should be.

> - pre-existing: G1Analytics::predict_concurrent_refine-rate_ms does not seem to be used. Also predict_logged_cards_rate_ms. Could that (and all associated code) be removed so that the latter does not need to be renamed?

That stuff is needed for work in progress to improve the concurrent
refinement thread control.

> Seems good otherwise.

Thanks.

New webrevs:
full: https://cr.openjdk.java.net/~kbarrett/8242078/open.01/
incr: https://cr.openjdk.java.net/~kbarrett/8242078/open.01.inc/

Testing: local (linux-x64) hotspot:tier1.