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6944166: G1: explicit GCs are not always handled correctly

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G1 was not handling explicit GCs correctly in many ways. It does now. See the CR for the list of improvements contained in this changeset.

Reviewed-by: iveresov, ysr, johnc
This commit is contained in:
Antonios Printezis 2010-06-28 14:13:17 -04:00
parent 968deb7658
commit dfc84e8c89
12 changed files with 291 additions and 71 deletions
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52
hotspot/src/share/vm/gc_implementation/g1/g1CollectorPolicy.cpp
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@ -154,7 +154,6 @@ G1CollectorPolicy::G1CollectorPolicy() :
_known_garbage_bytes(0),
_young_gc_eff_seq(new TruncatedSeq(TruncatedSeqLength)),
_target_pause_time_ms(-1.0),
_recent_prev_end_times_for_all_gcs_sec(new TruncatedSeq(NumPrevPausesForHeuristics)),
@ -1635,8 +1634,6 @@ void G1CollectorPolicy::record_collection_pause_end(bool abandoned) {
double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
adjust_concurrent_refinement(update_rs_time, update_rs_processed_buffers, update_rs_time_goal_ms);
// </NEW PREDICTION>
_target_pause_time_ms = -1.0;
}
// <NEW PREDICTION>
@ -2366,7 +2363,6 @@ G1CollectorPolicy_BestRegionsFirst::should_do_collection_pause(size_t
if (reached_target_length) {
assert( young_list_length > 0 && _g1->young_list()->length() > 0,
"invariant" );
_target_pause_time_ms = max_pause_time_ms;
return true;
}
} else {
@ -2398,6 +2394,17 @@ bool G1CollectorPolicy_BestRegionsFirst::assertMarkedBytesDataOK() {
}
#endif
bool
G1CollectorPolicy::force_initial_mark_if_outside_cycle() {
bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
if (!during_cycle) {
set_initiate_conc_mark_if_possible();
return true;
} else {
return false;
}
}
void
G1CollectorPolicy::decide_on_conc_mark_initiation() {
// We are about to decide on whether this pause will be an
@ -2864,7 +2871,8 @@ void G1CollectorPolicy::print_collection_set(HeapRegion* list_head, outputStream
#endif // !PRODUCT
bool
G1CollectorPolicy_BestRegionsFirst::choose_collection_set() {
G1CollectorPolicy_BestRegionsFirst::choose_collection_set(
double target_pause_time_ms) {
// Set this here - in case we're not doing young collections.
double non_young_start_time_sec = os::elapsedTime();
@ -2877,26 +2885,19 @@ G1CollectorPolicy_BestRegionsFirst::choose_collection_set() {
start_recording_regions();
guarantee(_target_pause_time_ms > -1.0
NOT_PRODUCT(|| Universe::heap()->gc_cause() == GCCause::_scavenge_alot),
"_target_pause_time_ms should have been set!");
#ifndef PRODUCT
if (_target_pause_time_ms <= -1.0) {
assert(ScavengeALot && Universe::heap()->gc_cause() == GCCause::_scavenge_alot, "Error");
_target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
}
#endif
assert(_collection_set == NULL, "Precondition");
guarantee(target_pause_time_ms > 0.0,
err_msg("target_pause_time_ms = %1.6lf should be positive",
target_pause_time_ms));
guarantee(_collection_set == NULL, "Precondition");
double base_time_ms = predict_base_elapsed_time_ms(_pending_cards);
double predicted_pause_time_ms = base_time_ms;
double target_time_ms = _target_pause_time_ms;
double time_remaining_ms = target_time_ms - base_time_ms;
double time_remaining_ms = target_pause_time_ms - base_time_ms;
// the 10% and 50% values are arbitrary...
if (time_remaining_ms < 0.10*target_time_ms) {
time_remaining_ms = 0.50 * target_time_ms;
if (time_remaining_ms < 0.10 * target_pause_time_ms) {
time_remaining_ms = 0.50 * target_pause_time_ms;
_within_target = false;
} else {
_within_target = true;
@ -3059,7 +3060,18 @@ choose_collection_set_end:
_recorded_non_young_cset_choice_time_ms =
(non_young_end_time_sec - non_young_start_time_sec) * 1000.0;
return abandon_collection;
// Here we are supposed to return whether the pause should be
// abandoned or not (i.e., whether the collection set is empty or
// not). However, this introduces a subtle issue when a pause is
// initiated explicitly with System.gc() and
// +ExplicitGCInvokesConcurrent (see Comment #2 in CR 6944166), it's
// supposed to start a marking cycle, and it's abandoned. So, by
// returning false here we are telling the caller never to consider
// a pause to be abandoned. We'll actually remove all the code
// associated with abandoned pauses as part of CR 6963209, but we are
// just disabling them this way for the moment to avoid increasing
// further the amount of changes for CR 6944166.
return false;
}
void G1CollectorPolicy_BestRegionsFirst::record_full_collection_end() {