value of dense prefix address used?

[Srinivas Ramakrishna]

Hi Jo{h}n, all --

Is there some way i can get at the dense prefix value used for ParOld in
each (major) collection? I couldn't find an obvious product flag for
eliciting that info, but wondered if you knew/remembered.
JMX would be fine too -- as long as the info can be obtained in a product
build.

I am seeing a curious looking log where one specific major gc seems to have
greater user and real time, lower "parallelism" [=(user+sys)/real] and
takes much longer than the rest of the ParOld's. It
also lowers the footprint a tad more (but definitely not proportionately
more vis-a-vis the user time ratios) than the gc's preceding (but not
succeeding) that one, so one conjecture was that perhaps
something happens with the dense prefix computation at that time and we
somehow end up copying more. We'll see if we can get some data with
printing the ParOld phase times, but i wondered if
we might also be able to elicit the dense prefix address/size. I'll
continue to dig around meanwhile.

thanks for any info!
-- ramki
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