RFR: Adaptive heuristics should poll all phases and update at the end of cycle

[Roman Kennke]

OK! Thanks!

Am 5. Mai 2017 14:00:41 MESZ schrieb Aleksey Shipilev <shade at redhat.com>:
>Hi,
>
>Overnight runs discovered the problem in adaptive heuristics. It
>adjusts the
>free threshold on recording the successful CM/UR, but that means it
>*misses* the
>counters from the rest of the cycle, only to capture them (if we are
>lucky) on
>the next cycle.
>
>The answer seems to be asking the heuristics to adjust at the end of
>the cycle,
>plus do the peak polling at the end of each phase and before cleanup.
>Doing
>after each phase is important because e.g. evac phase can do more
>allocations
>without further cleanup. We also have to care about both CM and UR to
>be happy
>before reducing the free threshold.
>
>Patch:
>http://cr.openjdk.java.net/~shade/shenandoah/adaptive-fullcycle/webrev.01/
>
>Coupled with printout improvements, this provides the clear view of the
>GC cycle:
>
>[gc,ergo] GC(13) Reducing free threshold to: 20% (2048M)
>...
>[gc,ergo] Concurrent marking triggered. Free: 2039M, Target Free:
>2048M,
>Allocated: 2039M, Threshold: 0M
>[gc     ] GC(14) Pause Init Mark 1.319ms
>[gc     ] GC(14) Concurrent marking 8204M->8908M(10240M) 873.952ms
>[gc,ergo] GC(14) Total Garbage: 6478M
>[gc,ergo] GC(14) Immediate Garbage: 36M, 9 regions
>[gc,ergo] GC(14) Garbage to be collected: 5715M (88% of total), 1540
>regions
>[gc,ergo] GC(14) Live objects to be evacuated: 443M
>[gc,ergo] GC(14) Live/garbage ratio in collected regions: 7%
>[gc     ] GC(14) Pause Final Mark 8908M->8880M(10240M) 10.791ms
>[gc     ] GC(14) Concurrent evacuation  8880M->9511M(10240M) 149.953ms
>[gc     ] GC(14) Pause Init Update Refs 9511M->9511M(10240M) 0.069ms
>[gc     ] GC(14) Concurrent update references  9511M->9892M(10240M)
>429.898ms
>[gc     ] GC(14) Pause Final Update Refs 9892M->3733M(10240M) 1.124ms
>[gc     ] GC(14) Concurrent reset bitmaps 7.109ms
>[gc,ergo] GC(14) Capacity: 10240M, Peak Occupancy: 9892M, Lowest Free:
>347M,
>Threshold Free: 307M
>[gc,ergo] GC(14) Reducing free threshold to: 19% (1945M)
>
>See e.g.: heuristics triggered CM at free threshold of 2048M. Peak
>occupancy was
>at the start of final UR -- 9892M -- and that what heuristics recorded
>and acted
>upon. We know it the target free is 307M (3%) and we have more, so
>threshold is
>reduced.
>
>Testing: SPECjbb2015
>
>Thanks,
>-Aleksey

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