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8159464: DumpHeap.java hits assert in G1 code

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Reviewed-by: mgerdin, tschatzl
This commit is contained in:
Erik Helin 2016-07-21 14:55:54 +02:00
parent 73a516d68e
commit b630a3ff47
1 changed files with 76 additions and 61 deletions
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137
hotspot/src/share/vm/gc/g1/g1DefaultPolicy.cpp
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@ -97,47 +97,64 @@ void G1DefaultPolicy::note_gc_start() {
phase_times()->note_gc_start();
}
bool G1DefaultPolicy::predict_will_fit(uint young_length,
double base_time_ms,
uint base_free_regions,
double target_pause_time_ms) const {
if (young_length >= base_free_regions) {
// end condition 1: not enough space for the young regions
return false;
class G1YoungLengthPredictor VALUE_OBJ_CLASS_SPEC {
const bool _during_cm;
const double _base_time_ms;
const double _base_free_regions;
const double _target_pause_time_ms;
const G1DefaultPolicy* const _policy;
public:
G1YoungLengthPredictor(bool during_cm,
double base_time_ms,
double base_free_regions,
double target_pause_time_ms,
const G1DefaultPolicy* policy) :
_during_cm(during_cm),
_base_time_ms(base_time_ms),
_base_free_regions(base_free_regions),
_target_pause_time_ms(target_pause_time_ms),
_policy(policy) {}
bool will_fit(uint young_length) const {
if (young_length >= _base_free_regions) {
// end condition 1: not enough space for the young regions
return false;
}
const double accum_surv_rate = _policy->accum_yg_surv_rate_pred((int) young_length - 1);
const size_t bytes_to_copy =
(size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
const double copy_time_ms =
_policy->analytics()->predict_object_copy_time_ms(bytes_to_copy, _during_cm);
const double young_other_time_ms = _policy->analytics()->predict_young_other_time_ms(young_length);
const double pause_time_ms = _base_time_ms + copy_time_ms + young_other_time_ms;
if (pause_time_ms > _target_pause_time_ms) {
// end condition 2: prediction is over the target pause time
return false;
}
const size_t free_bytes = (_base_free_regions - young_length) * HeapRegion::GrainBytes;
// When copying, we will likely need more bytes free than is live in the region.
// Add some safety margin to factor in the confidence of our guess, and the
// natural expected waste.
// (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
// of the calculation: the lower the confidence, the more headroom.
// (100 + TargetPLABWastePct) represents the increase in expected bytes during
// copying due to anticipated waste in the PLABs.
const double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
const size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
if (expected_bytes_to_copy > free_bytes) {
// end condition 3: out-of-space
return false;
}
// success!
return true;
}
double accum_surv_rate = accum_yg_surv_rate_pred((int) young_length - 1);
size_t bytes_to_copy =
(size_t) (accum_surv_rate * (double) HeapRegion::GrainBytes);
double copy_time_ms = _analytics->predict_object_copy_time_ms(bytes_to_copy,
collector_state()->during_concurrent_mark());
double young_other_time_ms = _analytics->predict_young_other_time_ms(young_length);
double pause_time_ms = base_time_ms + copy_time_ms + young_other_time_ms;
if (pause_time_ms > target_pause_time_ms) {
// end condition 2: prediction is over the target pause time
return false;
}
size_t free_bytes = (base_free_regions - young_length) * HeapRegion::GrainBytes;
// When copying, we will likely need more bytes free than is live in the region.
// Add some safety margin to factor in the confidence of our guess, and the
// natural expected waste.
// (100.0 / G1ConfidencePercent) is a scale factor that expresses the uncertainty
// of the calculation: the lower the confidence, the more headroom.
// (100 + TargetPLABWastePct) represents the increase in expected bytes during
// copying due to anticipated waste in the PLABs.
double safety_factor = (100.0 / G1ConfidencePercent) * (100 + TargetPLABWastePct) / 100.0;
size_t expected_bytes_to_copy = (size_t)(safety_factor * bytes_to_copy);
if (expected_bytes_to_copy > free_bytes) {
// end condition 3: out-of-space
return false;
}
// success!
return true;
}
};
void G1DefaultPolicy::record_new_heap_size(uint new_number_of_regions) {
// re-calculate the necessary reserve
@ -279,31 +296,32 @@ G1DefaultPolicy::calculate_young_list_target_length(size_t rs_lengths,
assert(desired_max_length > base_min_length, "invariant");
uint max_young_length = desired_max_length - base_min_length;
double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
double survivor_regions_evac_time = predict_survivor_regions_evac_time();
size_t pending_cards = _analytics->predict_pending_cards();
size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true);
double base_time_ms =
const double target_pause_time_ms = _mmu_tracker->max_gc_time() * 1000.0;
const double survivor_regions_evac_time = predict_survivor_regions_evac_time();
const size_t pending_cards = _analytics->predict_pending_cards();
const size_t adj_rs_lengths = rs_lengths + _analytics->predict_rs_length_diff();
const size_t scanned_cards = _analytics->predict_card_num(adj_rs_lengths, /* gcs_are_young */ true);
const double base_time_ms =
predict_base_elapsed_time_ms(pending_cards, scanned_cards) +
survivor_regions_evac_time;
uint available_free_regions = _free_regions_at_end_of_collection;
uint base_free_regions = 0;
if (available_free_regions > _reserve_regions) {
base_free_regions = available_free_regions - _reserve_regions;
}
const uint available_free_regions = _free_regions_at_end_of_collection;
const uint base_free_regions =
available_free_regions > _reserve_regions ? available_free_regions - _reserve_regions : 0;
// Here, we will make sure that the shortest young length that
// makes sense fits within the target pause time.
if (predict_will_fit(min_young_length, base_time_ms,
base_free_regions, target_pause_time_ms)) {
G1YoungLengthPredictor p(collector_state()->during_concurrent_mark(),
base_time_ms,
base_free_regions,
target_pause_time_ms,
this);
if (p.will_fit(min_young_length)) {
// The shortest young length will fit into the target pause time;
// we'll now check whether the absolute maximum number of young
// regions will fit in the target pause time. If not, we'll do
// a binary search between min_young_length and max_young_length.
if (predict_will_fit(max_young_length, base_time_ms,
base_free_regions, target_pause_time_ms)) {
if (p.will_fit(max_young_length)) {
// The maximum young length will fit into the target pause time.
// We are done so set min young length to the maximum length (as
// the result is assumed to be returned in min_young_length).
@ -328,8 +346,7 @@ G1DefaultPolicy::calculate_young_list_target_length(size_t rs_lengths,
uint diff = (max_young_length - min_young_length) / 2;
while (diff > 0) {
uint young_length = min_young_length + diff;
if (predict_will_fit(young_length, base_time_ms,
base_free_regions, target_pause_time_ms)) {
if (p.will_fit(young_length)) {
min_young_length = young_length;
} else {
max_young_length = young_length;
@ -344,12 +361,10 @@ G1DefaultPolicy::calculate_young_list_target_length(size_t rs_lengths,
assert(min_young_length < max_young_length,
"otherwise we should have discovered that max_young_length "
"fits into the pause target and not done the binary search");
assert(predict_will_fit(min_young_length, base_time_ms,
base_free_regions, target_pause_time_ms),
assert(p.will_fit(min_young_length),
"min_young_length, the result of the binary search, should "
"fit into the pause target");
assert(!predict_will_fit(min_young_length + 1, base_time_ms,
base_free_regions, target_pause_time_ms),
assert(!p.will_fit(min_young_length + 1),
"min_young_length, the result of the binary search, should be "
"optimal, so no larger length should fit into the pause target");
}