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6902303: G1: ScavengeALot should cause an incremental, rather than a full, collection

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ScavengeALot now causes an incremental (but possibly partially young, in the G1 sense) collection. Some such collections may be abandoned on account of MMU specs. Band-aided a native leak associated with abandoned pauses, as well as an MMU tracker overflow related to frequent scavenge events in the face of a large MMU denominator interval; the latter is protected by a product flag that defaults to false.

Reviewed-by: tonyp
This commit is contained in:
Y. Srinivas Ramakrishna 2009-11-19 13:43:25 -08:00
parent c54bb4236d
commit b5af9f3408
8 changed files with 73 additions and 36 deletions
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20
hotspot/src/share/vm/gc_implementation/g1/g1MMUTracker.cpp
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@ -86,12 +86,22 @@ void G1MMUTrackerQueue::add_pause(double start, double end, bool gc_thread) {
// increase the array size (:-)
// remove the oldest entry (this might allow more GC time for
// the time slice than what's allowed)
// concolidate the two entries with the minimum gap between them
// (this mighte allow less GC time than what's allowed)
guarantee(0, "array full, currently we can't recover");
// consolidate the two entries with the minimum gap between them
// (this might allow less GC time than what's allowed)
guarantee(NOT_PRODUCT(ScavengeALot ||) G1ForgetfulMMUTracker,
"array full, currently we can't recover unless +G1ForgetfulMMUTracker");
// In the case where ScavengeALot is true, such overflow is not
// uncommon; in such cases, we can, without much loss of precision
// or performance (we are GC'ing most of the time anyway!),
// simply overwrite the oldest entry in the tracker: this
// is also the behaviour when G1ForgetfulMMUTracker is enabled.
_head_index = trim_index(_head_index + 1);
assert(_head_index == _tail_index, "Because we have a full circular buffer");
_tail_index = trim_index(_tail_index + 1);
} else {
_head_index = trim_index(_head_index + 1);
++_no_entries;
}
_head_index = trim_index(_head_index + 1);
++_no_entries;
_array[_head_index] = G1MMUTrackerQueueElem(start, end);
}