RFR (S): 8150630: Add logging for ParScanThreadState merge phase

Thomas Schatzl thomas.schatzl at oracle.com
Thu Feb 25 13:35:18 UTC 2016

Hi all,

  can I have reviews for this small addition to the logging? It
measures the time gc takes for merging the information gathered by gc
worker threads down into the global state.

Recent work has shown that this phase may take a long time, because it
is O(#threads * size(young gen)), which is particularly bad on large
machines with a large young gen (like 200 threads, 20k young gen
regions). So I thought it would be nice to get timing measurement to
increase awareness of the problem. Or at least be able to rule it out
as a problem...

Again, I factored out the "phase" into an extra method to have all
relevant code together (timing + actual work).

This change is based on the changes for JDK-8076463.

jprt, test case


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