7185699: G1: Prediction model discrepancies
Summary: Correct the result value of G1CollectedHeap::pending_card_num(). Change the code that calculates the GC efficiency of a non-young heap region to use historical data from mixed GCs and the actual number of live bytes when predicting how long it would take to collect the region. Changes were also reviewed by Thomas Schatzl.
Reviewed-by: azeemj, brutisso
/*
* Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* questions.
*
*/
#include "precompiled.hpp"
#include "gc_implementation/g1/concurrentG1Refine.hpp"
#include "gc_implementation/g1/concurrentMark.hpp"
#include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
#include "gc_implementation/g1/g1CollectorPolicy.hpp"
#include "gc_implementation/g1/g1ErgoVerbose.hpp"
#include "gc_implementation/g1/g1GCPhaseTimes.hpp"
#include "gc_implementation/g1/g1Log.hpp"
#include "gc_implementation/g1/heapRegionRemSet.hpp"
#include "gc_implementation/shared/gcPolicyCounters.hpp"
#include "runtime/arguments.hpp"
#include "runtime/java.hpp"
#include "runtime/mutexLocker.hpp"
#include "utilities/debug.hpp"
// Different defaults for different number of GC threads
// They were chosen by running GCOld and SPECjbb on debris with different
// numbers of GC threads and choosing them based on the results
// all the same
static double rs_length_diff_defaults[] = {
0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0
};
static double cost_per_card_ms_defaults[] = {
0.01, 0.005, 0.005, 0.003, 0.003, 0.002, 0.002, 0.0015
};
// all the same
static double young_cards_per_entry_ratio_defaults[] = {
1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0
};
static double cost_per_entry_ms_defaults[] = {
0.015, 0.01, 0.01, 0.008, 0.008, 0.0055, 0.0055, 0.005
};
static double cost_per_byte_ms_defaults[] = {
0.00006, 0.00003, 0.00003, 0.000015, 0.000015, 0.00001, 0.00001, 0.000009
};
// these should be pretty consistent
static double constant_other_time_ms_defaults[] = {
5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0, 5.0
};
static double young_other_cost_per_region_ms_defaults[] = {
0.3, 0.2, 0.2, 0.15, 0.15, 0.12, 0.12, 0.1
};
static double non_young_other_cost_per_region_ms_defaults[] = {
1.0, 0.7, 0.7, 0.5, 0.5, 0.42, 0.42, 0.30
};
G1CollectorPolicy::G1CollectorPolicy() :
_parallel_gc_threads(G1CollectedHeap::use_parallel_gc_threads()
? ParallelGCThreads : 1),
_recent_gc_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
_stop_world_start(0.0),
_concurrent_mark_remark_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
_concurrent_mark_cleanup_times_ms(new TruncatedSeq(NumPrevPausesForHeuristics)),
_alloc_rate_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
_prev_collection_pause_end_ms(0.0),
_rs_length_diff_seq(new TruncatedSeq(TruncatedSeqLength)),
_cost_per_card_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
_young_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
_mixed_cards_per_entry_ratio_seq(new TruncatedSeq(TruncatedSeqLength)),
_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
_mixed_cost_per_entry_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
_cost_per_byte_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
_cost_per_byte_ms_during_cm_seq(new TruncatedSeq(TruncatedSeqLength)),
_constant_other_time_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
_young_other_cost_per_region_ms_seq(new TruncatedSeq(TruncatedSeqLength)),
_non_young_other_cost_per_region_ms_seq(
new TruncatedSeq(TruncatedSeqLength)),
_pending_cards_seq(new TruncatedSeq(TruncatedSeqLength)),
_rs_lengths_seq(new TruncatedSeq(TruncatedSeqLength)),
_pause_time_target_ms((double) MaxGCPauseMillis),
_gcs_are_young(true),
_during_marking(false),
_in_marking_window(false),
_in_marking_window_im(false),
_recent_prev_end_times_for_all_gcs_sec(
new TruncatedSeq(NumPrevPausesForHeuristics)),
_recent_avg_pause_time_ratio(0.0),
_initiate_conc_mark_if_possible(false),
_during_initial_mark_pause(false),
_last_young_gc(false),
_last_gc_was_young(false),
_eden_bytes_before_gc(0),
_survivor_bytes_before_gc(0),
_capacity_before_gc(0),
_eden_cset_region_length(0),
_survivor_cset_region_length(0),
_old_cset_region_length(0),
_collection_set(NULL),
_collection_set_bytes_used_before(0),
// Incremental CSet attributes
_inc_cset_build_state(Inactive),
_inc_cset_head(NULL),
_inc_cset_tail(NULL),
_inc_cset_bytes_used_before(0),
_inc_cset_max_finger(NULL),
_inc_cset_recorded_rs_lengths(0),
_inc_cset_recorded_rs_lengths_diffs(0),
_inc_cset_predicted_elapsed_time_ms(0.0),
_inc_cset_predicted_elapsed_time_ms_diffs(0.0),
#ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
#pragma warning( disable:4355 ) // 'this' : used in base member initializer list
#endif // _MSC_VER
_short_lived_surv_rate_group(new SurvRateGroup(this, "Short Lived",
G1YoungSurvRateNumRegionsSummary)),
_survivor_surv_rate_group(new SurvRateGroup(this, "Survivor",
G1YoungSurvRateNumRegionsSummary)),
// add here any more surv rate groups
_recorded_survivor_regions(0),
_recorded_survivor_head(NULL),
_recorded_survivor_tail(NULL),
_survivors_age_table(true),
_gc_overhead_perc(0.0) {
// Set up the region size and associated fields. Given that the
// policy is created before the heap, we have to set this up here,
// so it's done as soon as possible.
HeapRegion::setup_heap_region_size(Arguments::min_heap_size());
HeapRegionRemSet::setup_remset_size();
G1ErgoVerbose::initialize();
if (PrintAdaptiveSizePolicy) {
// Currently, we only use a single switch for all the heuristics.
G1ErgoVerbose::set_enabled(true);
// Given that we don't currently have a verboseness level
// parameter, we'll hardcode this to high. This can be easily
// changed in the future.
G1ErgoVerbose::set_level(ErgoHigh);
} else {
G1ErgoVerbose::set_enabled(false);
}
// Verify PLAB sizes
const size_t region_size = HeapRegion::GrainWords;
if (YoungPLABSize > region_size || OldPLABSize > region_size) {
char buffer[128];
jio_snprintf(buffer, sizeof(buffer), "%sPLABSize should be at most "SIZE_FORMAT,
OldPLABSize > region_size ? "Old" : "Young", region_size);
vm_exit_during_initialization(buffer);
}
_recent_prev_end_times_for_all_gcs_sec->add(os::elapsedTime());
_prev_collection_pause_end_ms = os::elapsedTime() * 1000.0;
_phase_times = new G1GCPhaseTimes(_parallel_gc_threads);
int index = MIN2(_parallel_gc_threads - 1, 7);
_rs_length_diff_seq->add(rs_length_diff_defaults[index]);
_cost_per_card_ms_seq->add(cost_per_card_ms_defaults[index]);
_young_cards_per_entry_ratio_seq->add(
young_cards_per_entry_ratio_defaults[index]);
_cost_per_entry_ms_seq->add(cost_per_entry_ms_defaults[index]);
_cost_per_byte_ms_seq->add(cost_per_byte_ms_defaults[index]);
_constant_other_time_ms_seq->add(constant_other_time_ms_defaults[index]);
_young_other_cost_per_region_ms_seq->add(
young_other_cost_per_region_ms_defaults[index]);
_non_young_other_cost_per_region_ms_seq->add(
non_young_other_cost_per_region_ms_defaults[index]);
// Below, we might need to calculate the pause time target based on
// the pause interval. When we do so we are going to give G1 maximum
// flexibility and allow it to do pauses when it needs to. So, we'll
// arrange that the pause interval to be pause time target + 1 to
// ensure that a) the pause time target is maximized with respect to
// the pause interval and b) we maintain the invariant that pause
// time target < pause interval. If the user does not want this
// maximum flexibility, they will have to set the pause interval
// explicitly.
// First make sure that, if either parameter is set, its value is
// reasonable.
if (!FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
if (MaxGCPauseMillis < 1) {
vm_exit_during_initialization("MaxGCPauseMillis should be "
"greater than 0");
}
}
if (!FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
if (GCPauseIntervalMillis < 1) {
vm_exit_during_initialization("GCPauseIntervalMillis should be "
"greater than 0");
}
}
// Then, if the pause time target parameter was not set, set it to
// the default value.
if (FLAG_IS_DEFAULT(MaxGCPauseMillis)) {
if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
// The default pause time target in G1 is 200ms
FLAG_SET_DEFAULT(MaxGCPauseMillis, 200);
} else {
// We do not allow the pause interval to be set without the
// pause time target
vm_exit_during_initialization("GCPauseIntervalMillis cannot be set "
"without setting MaxGCPauseMillis");
}
}
// Then, if the interval parameter was not set, set it according to
// the pause time target (this will also deal with the case when the
// pause time target is the default value).
if (FLAG_IS_DEFAULT(GCPauseIntervalMillis)) {
FLAG_SET_DEFAULT(GCPauseIntervalMillis, MaxGCPauseMillis + 1);
}
// Finally, make sure that the two parameters are consistent.
if (MaxGCPauseMillis >= GCPauseIntervalMillis) {
char buffer[256];
jio_snprintf(buffer, 256,
"MaxGCPauseMillis (%u) should be less than "
"GCPauseIntervalMillis (%u)",
MaxGCPauseMillis, GCPauseIntervalMillis);
vm_exit_during_initialization(buffer);
}
double max_gc_time = (double) MaxGCPauseMillis / 1000.0;
double time_slice = (double) GCPauseIntervalMillis / 1000.0;
_mmu_tracker = new G1MMUTrackerQueue(time_slice, max_gc_time);
_sigma = (double) G1ConfidencePercent / 100.0;
// start conservatively (around 50ms is about right)
_concurrent_mark_remark_times_ms->add(0.05);
_concurrent_mark_cleanup_times_ms->add(0.20);
_tenuring_threshold = MaxTenuringThreshold;
// _max_survivor_regions will be calculated by
// update_young_list_target_length() during initialization.
_max_survivor_regions = 0;
assert(GCTimeRatio > 0,
"we should have set it to a default value set_g1_gc_flags() "
"if a user set it to 0");
_gc_overhead_perc = 100.0 * (1.0 / (1.0 + GCTimeRatio));
uintx reserve_perc = G1ReservePercent;
// Put an artificial ceiling on this so that it's not set to a silly value.
if (reserve_perc > 50) {
reserve_perc = 50;
warning("G1ReservePercent is set to a value that is too large, "
"it's been updated to %u", reserve_perc);
}
_reserve_factor = (double) reserve_perc / 100.0;
// This will be set when the heap is expanded
// for the first time during initialization.
_reserve_regions = 0;
initialize_all();
_collectionSetChooser = new CollectionSetChooser();
_young_gen_sizer = new G1YoungGenSizer(); // Must be after call to initialize_flags
}
void G1CollectorPolicy::initialize_flags() {
set_min_alignment(HeapRegion::GrainBytes);
set_max_alignment(GenRemSet::max_alignment_constraint(rem_set_name()));
if (SurvivorRatio < 1) {
vm_exit_during_initialization("Invalid survivor ratio specified");
}
CollectorPolicy::initialize_flags();
}
G1YoungGenSizer::G1YoungGenSizer() : _sizer_kind(SizerDefaults), _adaptive_size(true) {
assert(G1DefaultMinNewGenPercent <= G1DefaultMaxNewGenPercent, "Min larger than max");
assert(G1DefaultMinNewGenPercent > 0 && G1DefaultMinNewGenPercent < 100, "Min out of bounds");
assert(G1DefaultMaxNewGenPercent > 0 && G1DefaultMaxNewGenPercent < 100, "Max out of bounds");
if (FLAG_IS_CMDLINE(NewRatio)) {
if (FLAG_IS_CMDLINE(NewSize) || FLAG_IS_CMDLINE(MaxNewSize)) {
warning("-XX:NewSize and -XX:MaxNewSize override -XX:NewRatio");
} else {
_sizer_kind = SizerNewRatio;
_adaptive_size = false;
return;
}
}
if (FLAG_IS_CMDLINE(NewSize)) {
_min_desired_young_length = MAX2((uint) (NewSize / HeapRegion::GrainBytes),
1U);
if (FLAG_IS_CMDLINE(MaxNewSize)) {
_max_desired_young_length =
MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
1U);
_sizer_kind = SizerMaxAndNewSize;
_adaptive_size = _min_desired_young_length == _max_desired_young_length;
} else {
_sizer_kind = SizerNewSizeOnly;
}
} else if (FLAG_IS_CMDLINE(MaxNewSize)) {
_max_desired_young_length =
MAX2((uint) (MaxNewSize / HeapRegion::GrainBytes),
1U);
_sizer_kind = SizerMaxNewSizeOnly;
}
}
uint G1YoungGenSizer::calculate_default_min_length(uint new_number_of_heap_regions) {
uint default_value = (new_number_of_heap_regions * G1DefaultMinNewGenPercent) / 100;
return MAX2(1U, default_value);
}
uint G1YoungGenSizer::calculate_default_max_length(uint new_number_of_heap_regions) {
uint default_value = (new_number_of_heap_regions * G1DefaultMaxNewGenPercent) / 100;
return MAX2(1U, default_value);
}
void G1YoungGenSizer::heap_size_changed(uint new_number_of_heap_regions) {
assert(new_number_of_heap_regions > 0, "Heap must be initialized");
switch (_sizer_kind) {
case SizerDefaults:
_min_desired_young_length = calculate_default_min_length(new_number_of_heap_regions);
_max_desired_young_length = calculate_default_max_length(new_number_of_heap_regions);
break;
case SizerNewSizeOnly:
_max_desired_young_length = calculate_default_max_length(new_number_of_heap_regions);
_max_desired_young_length = MAX2(_min_desired_young_length, _max_desired_young_length);
break;
case SizerMaxNewSizeOnly:
_min_desired_young_length = calculate_default_min_length(new_number_of_heap_regions);
_min_desired_young_length = MIN2(_min_desired_young_length, _max_desired_young_length);
break;
case SizerMaxAndNewSize:
// Do nothing. Values set on the command line, don't update them at runtime.
break;
case SizerNewRatio:
_min_desired_young_length = new_number_of_heap_regions / (NewRatio + 1);
_max_desired_young_length = _min_desired_young_length;
break;
default:
ShouldNotReachHere();
}
assert(_min_desired_young_length <= _max_desired_young_length, "Invalid min/max young gen size values");
}
void G1CollectorPolicy::init() {
// Set aside an initial future to_space.
_g1 = G1CollectedHeap::heap();
assert(Heap_lock->owned_by_self(), "Locking discipline.");
initialize_gc_policy_counters();
if (adaptive_young_list_length()) {
_young_list_fixed_length = 0;
} else {
_young_list_fixed_length = _young_gen_sizer->min_desired_young_length();
}
_free_regions_at_end_of_collection = _g1->free_regions();
update_young_list_target_length();
_prev_eden_capacity = _young_list_target_length * HeapRegion::GrainBytes;
// We may immediately start allocating regions and placing them on the
// collection set list. Initialize the per-collection set info
start_incremental_cset_building();
}
// Create the jstat counters for the policy.
void G1CollectorPolicy::initialize_gc_policy_counters() {
_gc_policy_counters = new GCPolicyCounters("GarbageFirst", 1, 3);
}
bool G1CollectorPolicy::predict_will_fit(uint young_length,
double base_time_ms,
uint base_free_regions,
double target_pause_time_ms) {
if (young_length >= base_free_regions) {
// end condition 1: not enough space for the young regions
return false;
}
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 = predict_object_copy_time_ms(bytes_to_copy);
double young_other_time_ms = 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;
if ((2.0 * sigma()) * (double) bytes_to_copy > (double) free_bytes) {
// end condition 3: out-of-space (conservatively!)
return false;
}
// success!
return true;
}
void G1CollectorPolicy::record_new_heap_size(uint new_number_of_regions) {
// re-calculate the necessary reserve
double reserve_regions_d = (double) new_number_of_regions * _reserve_factor;
// We use ceiling so that if reserve_regions_d is > 0.0 (but
// smaller than 1.0) we'll get 1.
_reserve_regions = (uint) ceil(reserve_regions_d);
_young_gen_sizer->heap_size_changed(new_number_of_regions);
}
uint G1CollectorPolicy::calculate_young_list_desired_min_length(
uint base_min_length) {
uint desired_min_length = 0;
if (adaptive_young_list_length()) {
if (_alloc_rate_ms_seq->num() > 3) {
double now_sec = os::elapsedTime();
double when_ms = _mmu_tracker->when_max_gc_sec(now_sec) * 1000.0;
double alloc_rate_ms = predict_alloc_rate_ms();
desired_min_length = (uint) ceil(alloc_rate_ms * when_ms);
} else {
// otherwise we don't have enough info to make the prediction
}
}
desired_min_length += base_min_length;
// make sure we don't go below any user-defined minimum bound
return MAX2(_young_gen_sizer->min_desired_young_length(), desired_min_length);
}
uint G1CollectorPolicy::calculate_young_list_desired_max_length() {
// Here, we might want to also take into account any additional
// constraints (i.e., user-defined minimum bound). Currently, we
// effectively don't set this bound.
return _young_gen_sizer->max_desired_young_length();
}
void G1CollectorPolicy::update_young_list_target_length(size_t rs_lengths) {
if (rs_lengths == (size_t) -1) {
// if it's set to the default value (-1), we should predict it;
// otherwise, use the given value.
rs_lengths = (size_t) get_new_prediction(_rs_lengths_seq);
}
// Calculate the absolute and desired min bounds.
// This is how many young regions we already have (currently: the survivors).
uint base_min_length = recorded_survivor_regions();
// This is the absolute minimum young length, which ensures that we
// can allocate one eden region in the worst-case.
uint absolute_min_length = base_min_length + 1;
uint desired_min_length =
calculate_young_list_desired_min_length(base_min_length);
if (desired_min_length < absolute_min_length) {
desired_min_length = absolute_min_length;
}
// Calculate the absolute and desired max bounds.
// We will try our best not to "eat" into the reserve.
uint absolute_max_length = 0;
if (_free_regions_at_end_of_collection > _reserve_regions) {
absolute_max_length = _free_regions_at_end_of_collection - _reserve_regions;
}
uint desired_max_length = calculate_young_list_desired_max_length();
if (desired_max_length > absolute_max_length) {
desired_max_length = absolute_max_length;
}
uint young_list_target_length = 0;
if (adaptive_young_list_length()) {
if (gcs_are_young()) {
young_list_target_length =
calculate_young_list_target_length(rs_lengths,
base_min_length,
desired_min_length,
desired_max_length);
_rs_lengths_prediction = rs_lengths;
} else {
// Don't calculate anything and let the code below bound it to
// the desired_min_length, i.e., do the next GC as soon as
// possible to maximize how many old regions we can add to it.
}
} else {
// The user asked for a fixed young gen so we'll fix the young gen
// whether the next GC is young or mixed.
young_list_target_length = _young_list_fixed_length;
}
// Make sure we don't go over the desired max length, nor under the
// desired min length. In case they clash, desired_min_length wins
// which is why that test is second.
if (young_list_target_length > desired_max_length) {
young_list_target_length = desired_max_length;
}
if (young_list_target_length < desired_min_length) {
young_list_target_length = desired_min_length;
}
assert(young_list_target_length > recorded_survivor_regions(),
"we should be able to allocate at least one eden region");
assert(young_list_target_length >= absolute_min_length, "post-condition");
_young_list_target_length = young_list_target_length;
update_max_gc_locker_expansion();
}
uint
G1CollectorPolicy::calculate_young_list_target_length(size_t rs_lengths,
uint base_min_length,
uint desired_min_length,
uint desired_max_length) {
assert(adaptive_young_list_length(), "pre-condition");
assert(gcs_are_young(), "only call this for young GCs");
// In case some edge-condition makes the desired max length too small...
if (desired_max_length <= desired_min_length) {
return desired_min_length;
}
// We'll adjust min_young_length and max_young_length not to include
// the already allocated young regions (i.e., so they reflect the
// min and max eden regions we'll allocate). The base_min_length
// will be reflected in the predictions by the
// survivor_regions_evac_time prediction.
assert(desired_min_length > base_min_length, "invariant");
uint min_young_length = desired_min_length - base_min_length;
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 = (size_t) get_new_prediction(_pending_cards_seq);
size_t adj_rs_lengths = rs_lengths + predict_rs_length_diff();
size_t scanned_cards = predict_young_card_num(adj_rs_lengths);
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;
}
// 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)) {
// 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)) {
// 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).
min_young_length = max_young_length;
} else {
// The maximum possible number of young regions will not fit within
// the target pause time so we'll search for the optimal
// length. The loop invariants are:
//
// min_young_length < max_young_length
// min_young_length is known to fit into the target pause time
// max_young_length is known not to fit into the target pause time
//
// Going into the loop we know the above hold as we've just
// checked them. Every time around the loop we check whether
// the middle value between min_young_length and
// max_young_length fits into the target pause time. If it
// does, it becomes the new min. If it doesn't, it becomes
// the new max. This way we maintain the loop invariants.
assert(min_young_length < max_young_length, "invariant");
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)) {
min_young_length = young_length;
} else {
max_young_length = young_length;
}
assert(min_young_length < max_young_length, "invariant");
diff = (max_young_length - min_young_length) / 2;
}
// The results is min_young_length which, according to the
// loop invariants, should fit within the target pause time.
// These are the post-conditions of the binary search above:
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),
"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),
"min_young_length, the result of the binary search, should be "
"optimal, so no larger length should fit into the pause target");
}
} else {
// Even the minimum length doesn't fit into the pause time
// target, return it as the result nevertheless.
}
return base_min_length + min_young_length;
}
double G1CollectorPolicy::predict_survivor_regions_evac_time() {
double survivor_regions_evac_time = 0.0;
for (HeapRegion * r = _recorded_survivor_head;
r != NULL && r != _recorded_survivor_tail->get_next_young_region();
r = r->get_next_young_region()) {
survivor_regions_evac_time += predict_region_elapsed_time_ms(r, gcs_are_young());
}
return survivor_regions_evac_time;
}
void G1CollectorPolicy::revise_young_list_target_length_if_necessary() {
guarantee( adaptive_young_list_length(), "should not call this otherwise" );
size_t rs_lengths = _g1->young_list()->sampled_rs_lengths();
if (rs_lengths > _rs_lengths_prediction) {
// add 10% to avoid having to recalculate often
size_t rs_lengths_prediction = rs_lengths * 1100 / 1000;
update_young_list_target_length(rs_lengths_prediction);
}
}
HeapWord* G1CollectorPolicy::mem_allocate_work(size_t size,
bool is_tlab,
bool* gc_overhead_limit_was_exceeded) {
guarantee(false, "Not using this policy feature yet.");
return NULL;
}
// This method controls how a collector handles one or more
// of its generations being fully allocated.
HeapWord* G1CollectorPolicy::satisfy_failed_allocation(size_t size,
bool is_tlab) {
guarantee(false, "Not using this policy feature yet.");
return NULL;
}
#ifndef PRODUCT
bool G1CollectorPolicy::verify_young_ages() {
HeapRegion* head = _g1->young_list()->first_region();
return
verify_young_ages(head, _short_lived_surv_rate_group);
// also call verify_young_ages on any additional surv rate groups
}
bool
G1CollectorPolicy::verify_young_ages(HeapRegion* head,
SurvRateGroup *surv_rate_group) {
guarantee( surv_rate_group != NULL, "pre-condition" );
const char* name = surv_rate_group->name();
bool ret = true;
int prev_age = -1;
for (HeapRegion* curr = head;
curr != NULL;
curr = curr->get_next_young_region()) {
SurvRateGroup* group = curr->surv_rate_group();
if (group == NULL && !curr->is_survivor()) {
gclog_or_tty->print_cr("## %s: encountered NULL surv_rate_group", name);
ret = false;
}
if (surv_rate_group == group) {
int age = curr->age_in_surv_rate_group();
if (age < 0) {
gclog_or_tty->print_cr("## %s: encountered negative age", name);
ret = false;
}
if (age <= prev_age) {
gclog_or_tty->print_cr("## %s: region ages are not strictly increasing "
"(%d, %d)", name, age, prev_age);
ret = false;
}
prev_age = age;
}
}
return ret;
}
#endif // PRODUCT
void G1CollectorPolicy::record_full_collection_start() {
_full_collection_start_sec = os::elapsedTime();
// Release the future to-space so that it is available for compaction into.
_g1->set_full_collection();
}
void G1CollectorPolicy::record_full_collection_end() {
// Consider this like a collection pause for the purposes of allocation
// since last pause.
double end_sec = os::elapsedTime();
double full_gc_time_sec = end_sec - _full_collection_start_sec;
double full_gc_time_ms = full_gc_time_sec * 1000.0;
_trace_gen1_time_data.record_full_collection(full_gc_time_ms);
update_recent_gc_times(end_sec, full_gc_time_ms);
_g1->clear_full_collection();
// "Nuke" the heuristics that control the young/mixed GC
// transitions and make sure we start with young GCs after the Full GC.
set_gcs_are_young(true);
_last_young_gc = false;
clear_initiate_conc_mark_if_possible();
clear_during_initial_mark_pause();
_in_marking_window = false;
_in_marking_window_im = false;
_short_lived_surv_rate_group->start_adding_regions();
// also call this on any additional surv rate groups
record_survivor_regions(0, NULL, NULL);
_free_regions_at_end_of_collection = _g1->free_regions();
// Reset survivors SurvRateGroup.
_survivor_surv_rate_group->reset();
update_young_list_target_length();
_collectionSetChooser->clear();
}
void G1CollectorPolicy::record_stop_world_start() {
_stop_world_start = os::elapsedTime();
}
void G1CollectorPolicy::record_collection_pause_start(double start_time_sec,
size_t start_used) {
// We only need to do this here as the policy will only be applied
// to the GC we're about to start. so, no point is calculating this
// every time we calculate / recalculate the target young length.
update_survivors_policy();
assert(_g1->used() == _g1->recalculate_used(),
err_msg("sanity, used: "SIZE_FORMAT" recalculate_used: "SIZE_FORMAT,
_g1->used(), _g1->recalculate_used()));
double s_w_t_ms = (start_time_sec - _stop_world_start) * 1000.0;
_trace_gen0_time_data.record_start_collection(s_w_t_ms);
_stop_world_start = 0.0;
phase_times()->_cur_collection_start_sec = start_time_sec;
_cur_collection_pause_used_at_start_bytes = start_used;
_cur_collection_pause_used_regions_at_start = _g1->used_regions();
_pending_cards = _g1->pending_card_num();
_collection_set_bytes_used_before = 0;
_bytes_copied_during_gc = 0;
YoungList* young_list = _g1->young_list();
_eden_bytes_before_gc = young_list->eden_used_bytes();
_survivor_bytes_before_gc = young_list->survivor_used_bytes();
_capacity_before_gc = _g1->capacity();
_last_gc_was_young = false;
// do that for any other surv rate groups
_short_lived_surv_rate_group->stop_adding_regions();
_survivors_age_table.clear();
assert( verify_young_ages(), "region age verification" );
}
void G1CollectorPolicy::record_concurrent_mark_init_end(double
mark_init_elapsed_time_ms) {
_during_marking = true;
assert(!initiate_conc_mark_if_possible(), "we should have cleared it by now");
clear_during_initial_mark_pause();
_cur_mark_stop_world_time_ms = mark_init_elapsed_time_ms;
}
void G1CollectorPolicy::record_concurrent_mark_remark_start() {
_mark_remark_start_sec = os::elapsedTime();
_during_marking = false;
}
void G1CollectorPolicy::record_concurrent_mark_remark_end() {
double end_time_sec = os::elapsedTime();
double elapsed_time_ms = (end_time_sec - _mark_remark_start_sec)*1000.0;
_concurrent_mark_remark_times_ms->add(elapsed_time_ms);
_cur_mark_stop_world_time_ms += elapsed_time_ms;
_prev_collection_pause_end_ms += elapsed_time_ms;
_mmu_tracker->add_pause(_mark_remark_start_sec, end_time_sec, true);
}
void G1CollectorPolicy::record_concurrent_mark_cleanup_start() {
_mark_cleanup_start_sec = os::elapsedTime();
}
void G1CollectorPolicy::record_concurrent_mark_cleanup_completed() {
_last_young_gc = true;
_in_marking_window = false;
}
void G1CollectorPolicy::record_concurrent_pause() {
if (_stop_world_start > 0.0) {
double yield_ms = (os::elapsedTime() - _stop_world_start) * 1000.0;
_trace_gen0_time_data.record_yield_time(yield_ms);
}
}
bool G1CollectorPolicy::need_to_start_conc_mark(const char* source, size_t alloc_word_size) {
if (_g1->concurrent_mark()->cmThread()->during_cycle()) {
return false;
}
size_t marking_initiating_used_threshold =
(_g1->capacity() / 100) * InitiatingHeapOccupancyPercent;
size_t cur_used_bytes = _g1->non_young_capacity_bytes();
size_t alloc_byte_size = alloc_word_size * HeapWordSize;
if ((cur_used_bytes + alloc_byte_size) > marking_initiating_used_threshold) {
if (gcs_are_young()) {
ergo_verbose5(ErgoConcCycles,
"request concurrent cycle initiation",
ergo_format_reason("occupancy higher than threshold")
ergo_format_byte("occupancy")
ergo_format_byte("allocation request")
ergo_format_byte_perc("threshold")
ergo_format_str("source"),
cur_used_bytes,
alloc_byte_size,
marking_initiating_used_threshold,
(double) InitiatingHeapOccupancyPercent,
source);
return true;
} else {
ergo_verbose5(ErgoConcCycles,
"do not request concurrent cycle initiation",
ergo_format_reason("still doing mixed collections")
ergo_format_byte("occupancy")
ergo_format_byte("allocation request")
ergo_format_byte_perc("threshold")
ergo_format_str("source"),
cur_used_bytes,
alloc_byte_size,
marking_initiating_used_threshold,
(double) InitiatingHeapOccupancyPercent,
source);
}
}
return false;
}
// Anything below that is considered to be zero
#define MIN_TIMER_GRANULARITY 0.0000001
void G1CollectorPolicy::record_collection_pause_end(double pause_time_ms) {
double end_time_sec = os::elapsedTime();
assert(_cur_collection_pause_used_regions_at_start >= cset_region_length(),
"otherwise, the subtraction below does not make sense");
size_t rs_size =
_cur_collection_pause_used_regions_at_start - cset_region_length();
size_t cur_used_bytes = _g1->used();
assert(cur_used_bytes == _g1->recalculate_used(), "It should!");
bool last_pause_included_initial_mark = false;
bool update_stats = !_g1->evacuation_failed();
#ifndef PRODUCT
if (G1YoungSurvRateVerbose) {
gclog_or_tty->print_cr("");
_short_lived_surv_rate_group->print();
// do that for any other surv rate groups too
}
#endif // PRODUCT
last_pause_included_initial_mark = during_initial_mark_pause();
if (last_pause_included_initial_mark) {
record_concurrent_mark_init_end(0.0);
} else if (!_last_young_gc && need_to_start_conc_mark("end of GC")) {
// Note: this might have already been set, if during the last
// pause we decided to start a cycle but at the beginning of
// this pause we decided to postpone it. That's OK.
set_initiate_conc_mark_if_possible();
}
_mmu_tracker->add_pause(end_time_sec - pause_time_ms/1000.0,
end_time_sec, false);
size_t freed_bytes =
_cur_collection_pause_used_at_start_bytes - cur_used_bytes;
size_t surviving_bytes = _collection_set_bytes_used_before - freed_bytes;
double survival_fraction =
(double)surviving_bytes/
(double)_collection_set_bytes_used_before;
if (update_stats) {
_trace_gen0_time_data.record_end_collection(pause_time_ms, phase_times());
// this is where we update the allocation rate of the application
double app_time_ms =
(phase_times()->_cur_collection_start_sec * 1000.0 - _prev_collection_pause_end_ms);
if (app_time_ms < MIN_TIMER_GRANULARITY) {
// This usually happens due to the timer not having the required
// granularity. Some Linuxes are the usual culprits.
// We'll just set it to something (arbitrarily) small.
app_time_ms = 1.0;
}
// We maintain the invariant that all objects allocated by mutator
// threads will be allocated out of eden regions. So, we can use
// the eden region number allocated since the previous GC to
// calculate the application's allocate rate. The only exception
// to that is humongous objects that are allocated separately. But
// given that humongous object allocations do not really affect
// either the pause's duration nor when the next pause will take
// place we can safely ignore them here.
uint regions_allocated = eden_cset_region_length();
double alloc_rate_ms = (double) regions_allocated / app_time_ms;
_alloc_rate_ms_seq->add(alloc_rate_ms);
double interval_ms =
(end_time_sec - _recent_prev_end_times_for_all_gcs_sec->oldest()) * 1000.0;
update_recent_gc_times(end_time_sec, pause_time_ms);
_recent_avg_pause_time_ratio = _recent_gc_times_ms->sum()/interval_ms;
if (recent_avg_pause_time_ratio() < 0.0 ||
(recent_avg_pause_time_ratio() - 1.0 > 0.0)) {
#ifndef PRODUCT
// Dump info to allow post-facto debugging
gclog_or_tty->print_cr("recent_avg_pause_time_ratio() out of bounds");
gclog_or_tty->print_cr("-------------------------------------------");
gclog_or_tty->print_cr("Recent GC Times (ms):");
_recent_gc_times_ms->dump();
gclog_or_tty->print_cr("(End Time=%3.3f) Recent GC End Times (s):", end_time_sec);
_recent_prev_end_times_for_all_gcs_sec->dump();
gclog_or_tty->print_cr("GC = %3.3f, Interval = %3.3f, Ratio = %3.3f",
_recent_gc_times_ms->sum(), interval_ms, recent_avg_pause_time_ratio());
// In debug mode, terminate the JVM if the user wants to debug at this point.
assert(!G1FailOnFPError, "Debugging data for CR 6898948 has been dumped above");
#endif // !PRODUCT
// Clip ratio between 0.0 and 1.0, and continue. This will be fixed in
// CR 6902692 by redoing the manner in which the ratio is incrementally computed.
if (_recent_avg_pause_time_ratio < 0.0) {
_recent_avg_pause_time_ratio = 0.0;
} else {
assert(_recent_avg_pause_time_ratio - 1.0 > 0.0, "Ctl-point invariant");
_recent_avg_pause_time_ratio = 1.0;
}
}
}
bool new_in_marking_window = _in_marking_window;
bool new_in_marking_window_im = false;
if (during_initial_mark_pause()) {
new_in_marking_window = true;
new_in_marking_window_im = true;
}
if (_last_young_gc) {
// This is supposed to to be the "last young GC" before we start
// doing mixed GCs. Here we decide whether to start mixed GCs or not.
if (!last_pause_included_initial_mark) {
if (next_gc_should_be_mixed("start mixed GCs",
"do not start mixed GCs")) {
set_gcs_are_young(false);
}
} else {
ergo_verbose0(ErgoMixedGCs,
"do not start mixed GCs",
ergo_format_reason("concurrent cycle is about to start"));
}
_last_young_gc = false;
}
if (!_last_gc_was_young) {
// This is a mixed GC. Here we decide whether to continue doing
// mixed GCs or not.
if (!next_gc_should_be_mixed("continue mixed GCs",
"do not continue mixed GCs")) {
set_gcs_are_young(true);
}
}
_short_lived_surv_rate_group->start_adding_regions();
// do that for any other surv rate groupsx
if (update_stats) {
double cost_per_card_ms = 0.0;
if (_pending_cards > 0) {
cost_per_card_ms = phase_times()->_update_rs_time / (double) _pending_cards;
_cost_per_card_ms_seq->add(cost_per_card_ms);
}
size_t cards_scanned = _g1->cards_scanned();
double cost_per_entry_ms = 0.0;
if (cards_scanned > 10) {
cost_per_entry_ms = phase_times()->_scan_rs_time / (double) cards_scanned;
if (_last_gc_was_young) {
_cost_per_entry_ms_seq->add(cost_per_entry_ms);
} else {
_mixed_cost_per_entry_ms_seq->add(cost_per_entry_ms);
}
}
if (_max_rs_lengths > 0) {
double cards_per_entry_ratio =
(double) cards_scanned / (double) _max_rs_lengths;
if (_last_gc_was_young) {
_young_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
} else {
_mixed_cards_per_entry_ratio_seq->add(cards_per_entry_ratio);
}
}
// This is defensive. For a while _max_rs_lengths could get
// smaller than _recorded_rs_lengths which was causing
// rs_length_diff to get very large and mess up the RSet length
// predictions. The reason was unsafe concurrent updates to the
// _inc_cset_recorded_rs_lengths field which the code below guards
// against (see CR 7118202). This bug has now been fixed (see CR
// 7119027). However, I'm still worried that
// _inc_cset_recorded_rs_lengths might still end up somewhat
// inaccurate. The concurrent refinement thread calculates an
// RSet's length concurrently with other CR threads updating it
// which might cause it to calculate the length incorrectly (if,
// say, it's in mid-coarsening). So I'll leave in the defensive
// conditional below just in case.
size_t rs_length_diff = 0;
if (_max_rs_lengths > _recorded_rs_lengths) {
rs_length_diff = _max_rs_lengths - _recorded_rs_lengths;
}
_rs_length_diff_seq->add((double) rs_length_diff);
size_t copied_bytes = surviving_bytes;
double cost_per_byte_ms = 0.0;
if (copied_bytes > 0) {
cost_per_byte_ms = phase_times()->_obj_copy_time / (double) copied_bytes;
if (_in_marking_window) {
_cost_per_byte_ms_during_cm_seq->add(cost_per_byte_ms);
} else {
_cost_per_byte_ms_seq->add(cost_per_byte_ms);
}
}
double all_other_time_ms = pause_time_ms -
(phase_times()->_update_rs_time + phase_times()->_scan_rs_time + phase_times()->_obj_copy_time + phase_times()->_termination_time);
double young_other_time_ms = 0.0;
if (young_cset_region_length() > 0) {
young_other_time_ms =
phase_times()->_recorded_young_cset_choice_time_ms +
phase_times()->_recorded_young_free_cset_time_ms;
_young_other_cost_per_region_ms_seq->add(young_other_time_ms /
(double) young_cset_region_length());
}
double non_young_other_time_ms = 0.0;
if (old_cset_region_length() > 0) {
non_young_other_time_ms =
phase_times()->_recorded_non_young_cset_choice_time_ms +
phase_times()->_recorded_non_young_free_cset_time_ms;
_non_young_other_cost_per_region_ms_seq->add(non_young_other_time_ms /
(double) old_cset_region_length());
}
double constant_other_time_ms = all_other_time_ms -
(young_other_time_ms + non_young_other_time_ms);
_constant_other_time_ms_seq->add(constant_other_time_ms);
double survival_ratio = 0.0;
if (_collection_set_bytes_used_before > 0) {
survival_ratio = (double) _bytes_copied_during_gc /
(double) _collection_set_bytes_used_before;
}
_pending_cards_seq->add((double) _pending_cards);
_rs_lengths_seq->add((double) _max_rs_lengths);
}
_in_marking_window = new_in_marking_window;
_in_marking_window_im = new_in_marking_window_im;
_free_regions_at_end_of_collection = _g1->free_regions();
update_young_list_target_length();
// Note that _mmu_tracker->max_gc_time() returns the time in seconds.
double update_rs_time_goal_ms = _mmu_tracker->max_gc_time() * MILLIUNITS * G1RSetUpdatingPauseTimePercent / 100.0;
adjust_concurrent_refinement(phase_times()->_update_rs_time, phase_times()->_update_rs_processed_buffers, update_rs_time_goal_ms);
_collectionSetChooser->verify();
}
#define EXT_SIZE_FORMAT "%.1f%s"
#define EXT_SIZE_PARAMS(bytes) \
byte_size_in_proper_unit((double)(bytes)), \
proper_unit_for_byte_size((bytes))
void G1CollectorPolicy::print_heap_transition() {
if (G1Log::finer()) {
YoungList* young_list = _g1->young_list();
size_t eden_bytes = young_list->eden_used_bytes();
size_t survivor_bytes = young_list->survivor_used_bytes();
size_t used_before_gc = _cur_collection_pause_used_at_start_bytes;
size_t used = _g1->used();
size_t capacity = _g1->capacity();
size_t eden_capacity =
(_young_list_target_length * HeapRegion::GrainBytes) - survivor_bytes;
gclog_or_tty->print_cr(
" [Eden: "EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT")->"EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT") "
"Survivors: "EXT_SIZE_FORMAT"->"EXT_SIZE_FORMAT" "
"Heap: "EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT")->"
EXT_SIZE_FORMAT"("EXT_SIZE_FORMAT")]",
EXT_SIZE_PARAMS(_eden_bytes_before_gc),
EXT_SIZE_PARAMS(_prev_eden_capacity),
EXT_SIZE_PARAMS(eden_bytes),
EXT_SIZE_PARAMS(eden_capacity),
EXT_SIZE_PARAMS(_survivor_bytes_before_gc),
EXT_SIZE_PARAMS(survivor_bytes),
EXT_SIZE_PARAMS(used_before_gc),
EXT_SIZE_PARAMS(_capacity_before_gc),
EXT_SIZE_PARAMS(used),
EXT_SIZE_PARAMS(capacity));
_prev_eden_capacity = eden_capacity;
} else if (G1Log::fine()) {
_g1->print_size_transition(gclog_or_tty,
_cur_collection_pause_used_at_start_bytes,
_g1->used(), _g1->capacity());
}
}
void G1CollectorPolicy::adjust_concurrent_refinement(double update_rs_time,
double update_rs_processed_buffers,
double goal_ms) {
DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
ConcurrentG1Refine *cg1r = G1CollectedHeap::heap()->concurrent_g1_refine();
if (G1UseAdaptiveConcRefinement) {
const int k_gy = 3, k_gr = 6;
const double inc_k = 1.1, dec_k = 0.9;
int g = cg1r->green_zone();
if (update_rs_time > goal_ms) {
g = (int)(g * dec_k); // Can become 0, that's OK. That would mean a mutator-only processing.
} else {
if (update_rs_time < goal_ms && update_rs_processed_buffers > g) {
g = (int)MAX2(g * inc_k, g + 1.0);
}
}
// Change the refinement threads params
cg1r->set_green_zone(g);
cg1r->set_yellow_zone(g * k_gy);
cg1r->set_red_zone(g * k_gr);
cg1r->reinitialize_threads();
int processing_threshold_delta = MAX2((int)(cg1r->green_zone() * sigma()), 1);
int processing_threshold = MIN2(cg1r->green_zone() + processing_threshold_delta,
cg1r->yellow_zone());
// Change the barrier params
dcqs.set_process_completed_threshold(processing_threshold);
dcqs.set_max_completed_queue(cg1r->red_zone());
}
int curr_queue_size = dcqs.completed_buffers_num();
if (curr_queue_size >= cg1r->yellow_zone()) {
dcqs.set_completed_queue_padding(curr_queue_size);
} else {
dcqs.set_completed_queue_padding(0);
}
dcqs.notify_if_necessary();
}
double
G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards,
size_t scanned_cards) {
return
predict_rs_update_time_ms(pending_cards) +
predict_rs_scan_time_ms(scanned_cards) +
predict_constant_other_time_ms();
}
double
G1CollectorPolicy::predict_base_elapsed_time_ms(size_t pending_cards) {
size_t rs_length = predict_rs_length_diff();
size_t card_num;
if (gcs_are_young()) {
card_num = predict_young_card_num(rs_length);
} else {
card_num = predict_non_young_card_num(rs_length);
}
return predict_base_elapsed_time_ms(pending_cards, card_num);
}
size_t G1CollectorPolicy::predict_bytes_to_copy(HeapRegion* hr) {
size_t bytes_to_copy;
if (hr->is_marked())
bytes_to_copy = hr->max_live_bytes();
else {
assert(hr->is_young() && hr->age_in_surv_rate_group() != -1, "invariant");
int age = hr->age_in_surv_rate_group();
double yg_surv_rate = predict_yg_surv_rate(age, hr->surv_rate_group());
bytes_to_copy = (size_t) ((double) hr->used() * yg_surv_rate);
}
return bytes_to_copy;
}
double
G1CollectorPolicy::predict_region_elapsed_time_ms(HeapRegion* hr,
bool for_young_gc) {
size_t rs_length = hr->rem_set()->occupied();
size_t card_num;
// Predicting the number of cards is based on which type of GC
// we're predicting for.
if (for_young_gc) {
card_num = predict_young_card_num(rs_length);
} else {
card_num = predict_non_young_card_num(rs_length);
}
size_t bytes_to_copy = predict_bytes_to_copy(hr);
double region_elapsed_time_ms =
predict_rs_scan_time_ms(card_num) +
predict_object_copy_time_ms(bytes_to_copy);
// The prediction of the "other" time for this region is based
// upon the region type and NOT the GC type.
if (hr->is_young()) {
region_elapsed_time_ms += predict_young_other_time_ms(1);
} else {
region_elapsed_time_ms += predict_non_young_other_time_ms(1);
}
return region_elapsed_time_ms;
}
void
G1CollectorPolicy::init_cset_region_lengths(uint eden_cset_region_length,
uint survivor_cset_region_length) {
_eden_cset_region_length = eden_cset_region_length;
_survivor_cset_region_length = survivor_cset_region_length;
_old_cset_region_length = 0;
}
void G1CollectorPolicy::set_recorded_rs_lengths(size_t rs_lengths) {
_recorded_rs_lengths = rs_lengths;
}
void G1CollectorPolicy::update_recent_gc_times(double end_time_sec,
double elapsed_ms) {
_recent_gc_times_ms->add(elapsed_ms);
_recent_prev_end_times_for_all_gcs_sec->add(end_time_sec);
_prev_collection_pause_end_ms = end_time_sec * 1000.0;
}
size_t G1CollectorPolicy::expansion_amount() {
double recent_gc_overhead = recent_avg_pause_time_ratio() * 100.0;
double threshold = _gc_overhead_perc;
if (recent_gc_overhead > threshold) {
// We will double the existing space, or take
// G1ExpandByPercentOfAvailable % of the available expansion
// space, whichever is smaller, bounded below by a minimum
// expansion (unless that's all that's left.)
const size_t min_expand_bytes = 1*M;
size_t reserved_bytes = _g1->max_capacity();
size_t committed_bytes = _g1->capacity();
size_t uncommitted_bytes = reserved_bytes - committed_bytes;
size_t expand_bytes;
size_t expand_bytes_via_pct =
uncommitted_bytes * G1ExpandByPercentOfAvailable / 100;
expand_bytes = MIN2(expand_bytes_via_pct, committed_bytes);
expand_bytes = MAX2(expand_bytes, min_expand_bytes);
expand_bytes = MIN2(expand_bytes, uncommitted_bytes);
ergo_verbose5(ErgoHeapSizing,
"attempt heap expansion",
ergo_format_reason("recent GC overhead higher than "
"threshold after GC")
ergo_format_perc("recent GC overhead")
ergo_format_perc("threshold")
ergo_format_byte("uncommitted")
ergo_format_byte_perc("calculated expansion amount"),
recent_gc_overhead, threshold,
uncommitted_bytes,
expand_bytes_via_pct, (double) G1ExpandByPercentOfAvailable);
return expand_bytes;
} else {
return 0;
}
}
void G1CollectorPolicy::print_tracing_info() const {
_trace_gen0_time_data.print();
_trace_gen1_time_data.print();
}
void G1CollectorPolicy::print_yg_surv_rate_info() const {
#ifndef PRODUCT
_short_lived_surv_rate_group->print_surv_rate_summary();
// add this call for any other surv rate groups
#endif // PRODUCT
}
#ifndef PRODUCT
// for debugging, bit of a hack...
static char*
region_num_to_mbs(int length) {
static char buffer[64];
double bytes = (double) (length * HeapRegion::GrainBytes);
double mbs = bytes / (double) (1024 * 1024);
sprintf(buffer, "%7.2lfMB", mbs);
return buffer;
}
#endif // PRODUCT
uint G1CollectorPolicy::max_regions(int purpose) {
switch (purpose) {
case GCAllocForSurvived:
return _max_survivor_regions;
case GCAllocForTenured:
return REGIONS_UNLIMITED;
default:
ShouldNotReachHere();
return REGIONS_UNLIMITED;
};
}
void G1CollectorPolicy::update_max_gc_locker_expansion() {
uint expansion_region_num = 0;
if (GCLockerEdenExpansionPercent > 0) {
double perc = (double) GCLockerEdenExpansionPercent / 100.0;
double expansion_region_num_d = perc * (double) _young_list_target_length;
// We use ceiling so that if expansion_region_num_d is > 0.0 (but
// less than 1.0) we'll get 1.
expansion_region_num = (uint) ceil(expansion_region_num_d);
} else {
assert(expansion_region_num == 0, "sanity");
}
_young_list_max_length = _young_list_target_length + expansion_region_num;
assert(_young_list_target_length <= _young_list_max_length, "post-condition");
}
// Calculates survivor space parameters.
void G1CollectorPolicy::update_survivors_policy() {
double max_survivor_regions_d =
(double) _young_list_target_length / (double) SurvivorRatio;
// We use ceiling so that if max_survivor_regions_d is > 0.0 (but
// smaller than 1.0) we'll get 1.
_max_survivor_regions = (uint) ceil(max_survivor_regions_d);
_tenuring_threshold = _survivors_age_table.compute_tenuring_threshold(
HeapRegion::GrainWords * _max_survivor_regions);
}
bool G1CollectorPolicy::force_initial_mark_if_outside_cycle(
GCCause::Cause gc_cause) {
bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
if (!during_cycle) {
ergo_verbose1(ErgoConcCycles,
"request concurrent cycle initiation",
ergo_format_reason("requested by GC cause")
ergo_format_str("GC cause"),
GCCause::to_string(gc_cause));
set_initiate_conc_mark_if_possible();
return true;
} else {
ergo_verbose1(ErgoConcCycles,
"do not request concurrent cycle initiation",
ergo_format_reason("concurrent cycle already in progress")
ergo_format_str("GC cause"),
GCCause::to_string(gc_cause));
return false;
}
}
void
G1CollectorPolicy::decide_on_conc_mark_initiation() {
// We are about to decide on whether this pause will be an
// initial-mark pause.
// First, during_initial_mark_pause() should not be already set. We
// will set it here if we have to. However, it should be cleared by
// the end of the pause (it's only set for the duration of an
// initial-mark pause).
assert(!during_initial_mark_pause(), "pre-condition");
if (initiate_conc_mark_if_possible()) {
// We had noticed on a previous pause that the heap occupancy has
// gone over the initiating threshold and we should start a
// concurrent marking cycle. So we might initiate one.
bool during_cycle = _g1->concurrent_mark()->cmThread()->during_cycle();
if (!during_cycle) {
// The concurrent marking thread is not "during a cycle", i.e.,
// it has completed the last one. So we can go ahead and
// initiate a new cycle.
set_during_initial_mark_pause();
// We do not allow mixed GCs during marking.
if (!gcs_are_young()) {
set_gcs_are_young(true);
ergo_verbose0(ErgoMixedGCs,
"end mixed GCs",
ergo_format_reason("concurrent cycle is about to start"));
}
// And we can now clear initiate_conc_mark_if_possible() as
// we've already acted on it.
clear_initiate_conc_mark_if_possible();
ergo_verbose0(ErgoConcCycles,
"initiate concurrent cycle",
ergo_format_reason("concurrent cycle initiation requested"));
} else {
// The concurrent marking thread is still finishing up the
// previous cycle. If we start one right now the two cycles
// overlap. In particular, the concurrent marking thread might
// be in the process of clearing the next marking bitmap (which
// we will use for the next cycle if we start one). Starting a
// cycle now will be bad given that parts of the marking
// information might get cleared by the marking thread. And we
// cannot wait for the marking thread to finish the cycle as it
// periodically yields while clearing the next marking bitmap
// and, if it's in a yield point, it's waiting for us to
// finish. So, at this point we will not start a cycle and we'll
// let the concurrent marking thread complete the last one.
ergo_verbose0(ErgoConcCycles,
"do not initiate concurrent cycle",
ergo_format_reason("concurrent cycle already in progress"));
}
}
}
class KnownGarbageClosure: public HeapRegionClosure {
G1CollectedHeap* _g1h;
CollectionSetChooser* _hrSorted;
public:
KnownGarbageClosure(CollectionSetChooser* hrSorted) :
_g1h(G1CollectedHeap::heap()), _hrSorted(hrSorted) { }
bool doHeapRegion(HeapRegion* r) {
// We only include humongous regions in collection
// sets when concurrent mark shows that their contained object is
// unreachable.
// Do we have any marking information for this region?
if (r->is_marked()) {
// We will skip any region that's currently used as an old GC
// alloc region (we should not consider those for collection
// before we fill them up).
if (_hrSorted->should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
_hrSorted->add_region(r);
}
}
return false;
}
};
class ParKnownGarbageHRClosure: public HeapRegionClosure {
G1CollectedHeap* _g1h;
CSetChooserParUpdater _cset_updater;
public:
ParKnownGarbageHRClosure(CollectionSetChooser* hrSorted,
uint chunk_size) :
_g1h(G1CollectedHeap::heap()),
_cset_updater(hrSorted, true /* parallel */, chunk_size) { }
bool doHeapRegion(HeapRegion* r) {
// Do we have any marking information for this region?
if (r->is_marked()) {
// We will skip any region that's currently used as an old GC
// alloc region (we should not consider those for collection
// before we fill them up).
if (_cset_updater.should_add(r) && !_g1h->is_old_gc_alloc_region(r)) {
_cset_updater.add_region(r);
}
}
return false;
}
};
class ParKnownGarbageTask: public AbstractGangTask {
CollectionSetChooser* _hrSorted;
uint _chunk_size;
G1CollectedHeap* _g1;
public:
ParKnownGarbageTask(CollectionSetChooser* hrSorted, uint chunk_size) :
AbstractGangTask("ParKnownGarbageTask"),
_hrSorted(hrSorted), _chunk_size(chunk_size),
_g1(G1CollectedHeap::heap()) { }
void work(uint worker_id) {
ParKnownGarbageHRClosure parKnownGarbageCl(_hrSorted, _chunk_size);
// Back to zero for the claim value.
_g1->heap_region_par_iterate_chunked(&parKnownGarbageCl, worker_id,
_g1->workers()->active_workers(),
HeapRegion::InitialClaimValue);
}
};
void
G1CollectorPolicy::record_concurrent_mark_cleanup_end(int no_of_gc_threads) {
_collectionSetChooser->clear();
uint region_num = _g1->n_regions();
if (G1CollectedHeap::use_parallel_gc_threads()) {
const uint OverpartitionFactor = 4;
uint WorkUnit;
// The use of MinChunkSize = 8 in the original code
// causes some assertion failures when the total number of
// region is less than 8. The code here tries to fix that.
// Should the original code also be fixed?
if (no_of_gc_threads > 0) {
const uint MinWorkUnit = MAX2(region_num / no_of_gc_threads, 1U);
WorkUnit = MAX2(region_num / (no_of_gc_threads * OverpartitionFactor),
MinWorkUnit);
} else {
assert(no_of_gc_threads > 0,
"The active gc workers should be greater than 0");
// In a product build do something reasonable to avoid a crash.
const uint MinWorkUnit = MAX2(region_num / (uint) ParallelGCThreads, 1U);
WorkUnit =
MAX2(region_num / (uint) (ParallelGCThreads * OverpartitionFactor),
MinWorkUnit);
}
_collectionSetChooser->prepare_for_par_region_addition(_g1->n_regions(),
WorkUnit);
ParKnownGarbageTask parKnownGarbageTask(_collectionSetChooser,
(int) WorkUnit);
_g1->workers()->run_task(&parKnownGarbageTask);
assert(_g1->check_heap_region_claim_values(HeapRegion::InitialClaimValue),
"sanity check");
} else {
KnownGarbageClosure knownGarbagecl(_collectionSetChooser);
_g1->heap_region_iterate(&knownGarbagecl);
}
_collectionSetChooser->sort_regions();
double end_sec = os::elapsedTime();
double elapsed_time_ms = (end_sec - _mark_cleanup_start_sec) * 1000.0;
_concurrent_mark_cleanup_times_ms->add(elapsed_time_ms);
_cur_mark_stop_world_time_ms += elapsed_time_ms;
_prev_collection_pause_end_ms += elapsed_time_ms;
_mmu_tracker->add_pause(_mark_cleanup_start_sec, end_sec, true);
}
// Add the heap region at the head of the non-incremental collection set
void G1CollectorPolicy::add_old_region_to_cset(HeapRegion* hr) {
assert(_inc_cset_build_state == Active, "Precondition");
assert(!hr->is_young(), "non-incremental add of young region");
assert(!hr->in_collection_set(), "should not already be in the CSet");
hr->set_in_collection_set(true);
hr->set_next_in_collection_set(_collection_set);
_collection_set = hr;
_collection_set_bytes_used_before += hr->used();
_g1->register_region_with_in_cset_fast_test(hr);
size_t rs_length = hr->rem_set()->occupied();
_recorded_rs_lengths += rs_length;
_old_cset_region_length += 1;
}
// Initialize the per-collection-set information
void G1CollectorPolicy::start_incremental_cset_building() {
assert(_inc_cset_build_state == Inactive, "Precondition");
_inc_cset_head = NULL;
_inc_cset_tail = NULL;
_inc_cset_bytes_used_before = 0;
_inc_cset_max_finger = 0;
_inc_cset_recorded_rs_lengths = 0;
_inc_cset_recorded_rs_lengths_diffs = 0;
_inc_cset_predicted_elapsed_time_ms = 0.0;
_inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
_inc_cset_build_state = Active;
}
void G1CollectorPolicy::finalize_incremental_cset_building() {
assert(_inc_cset_build_state == Active, "Precondition");
assert(SafepointSynchronize::is_at_safepoint(), "should be at a safepoint");
// The two "main" fields, _inc_cset_recorded_rs_lengths and
// _inc_cset_predicted_elapsed_time_ms, are updated by the thread
// that adds a new region to the CSet. Further updates by the
// concurrent refinement thread that samples the young RSet lengths
// are accumulated in the *_diffs fields. Here we add the diffs to
// the "main" fields.
if (_inc_cset_recorded_rs_lengths_diffs >= 0) {
_inc_cset_recorded_rs_lengths += _inc_cset_recorded_rs_lengths_diffs;
} else {
// This is defensive. The diff should in theory be always positive
// as RSets can only grow between GCs. However, given that we
// sample their size concurrently with other threads updating them
// it's possible that we might get the wrong size back, which
// could make the calculations somewhat inaccurate.
size_t diffs = (size_t) (-_inc_cset_recorded_rs_lengths_diffs);
if (_inc_cset_recorded_rs_lengths >= diffs) {
_inc_cset_recorded_rs_lengths -= diffs;
} else {
_inc_cset_recorded_rs_lengths = 0;
}
}
_inc_cset_predicted_elapsed_time_ms +=
_inc_cset_predicted_elapsed_time_ms_diffs;
_inc_cset_recorded_rs_lengths_diffs = 0;
_inc_cset_predicted_elapsed_time_ms_diffs = 0.0;
}
void G1CollectorPolicy::add_to_incremental_cset_info(HeapRegion* hr, size_t rs_length) {
// This routine is used when:
// * adding survivor regions to the incremental cset at the end of an
// evacuation pause,
// * adding the current allocation region to the incremental cset
// when it is retired, and
// * updating existing policy information for a region in the
// incremental cset via young list RSet sampling.
// Therefore this routine may be called at a safepoint by the
// VM thread, or in-between safepoints by mutator threads (when
// retiring the current allocation region) or a concurrent
// refine thread (RSet sampling).
double region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, gcs_are_young());
size_t used_bytes = hr->used();
_inc_cset_recorded_rs_lengths += rs_length;
_inc_cset_predicted_elapsed_time_ms += region_elapsed_time_ms;
_inc_cset_bytes_used_before += used_bytes;
// Cache the values we have added to the aggregated informtion
// in the heap region in case we have to remove this region from
// the incremental collection set, or it is updated by the
// rset sampling code
hr->set_recorded_rs_length(rs_length);
hr->set_predicted_elapsed_time_ms(region_elapsed_time_ms);
}
void G1CollectorPolicy::update_incremental_cset_info(HeapRegion* hr,
size_t new_rs_length) {
// Update the CSet information that is dependent on the new RS length
assert(hr->is_young(), "Precondition");
assert(!SafepointSynchronize::is_at_safepoint(),
"should not be at a safepoint");
// We could have updated _inc_cset_recorded_rs_lengths and
// _inc_cset_predicted_elapsed_time_ms directly but we'd need to do
// that atomically, as this code is executed by a concurrent
// refinement thread, potentially concurrently with a mutator thread
// allocating a new region and also updating the same fields. To
// avoid the atomic operations we accumulate these updates on two
// separate fields (*_diffs) and we'll just add them to the "main"
// fields at the start of a GC.
ssize_t old_rs_length = (ssize_t) hr->recorded_rs_length();
ssize_t rs_lengths_diff = (ssize_t) new_rs_length - old_rs_length;
_inc_cset_recorded_rs_lengths_diffs += rs_lengths_diff;
double old_elapsed_time_ms = hr->predicted_elapsed_time_ms();
double new_region_elapsed_time_ms = predict_region_elapsed_time_ms(hr, gcs_are_young());
double elapsed_ms_diff = new_region_elapsed_time_ms - old_elapsed_time_ms;
_inc_cset_predicted_elapsed_time_ms_diffs += elapsed_ms_diff;
hr->set_recorded_rs_length(new_rs_length);
hr->set_predicted_elapsed_time_ms(new_region_elapsed_time_ms);
}
void G1CollectorPolicy::add_region_to_incremental_cset_common(HeapRegion* hr) {
assert(hr->is_young(), "invariant");
assert(hr->young_index_in_cset() > -1, "should have already been set");
assert(_inc_cset_build_state == Active, "Precondition");
// We need to clear and set the cached recorded/cached collection set
// information in the heap region here (before the region gets added
// to the collection set). An individual heap region's cached values
// are calculated, aggregated with the policy collection set info,
// and cached in the heap region here (initially) and (subsequently)
// by the Young List sampling code.
size_t rs_length = hr->rem_set()->occupied();
add_to_incremental_cset_info(hr, rs_length);
HeapWord* hr_end = hr->end();
_inc_cset_max_finger = MAX2(_inc_cset_max_finger, hr_end);
assert(!hr->in_collection_set(), "invariant");
hr->set_in_collection_set(true);
assert( hr->next_in_collection_set() == NULL, "invariant");
_g1->register_region_with_in_cset_fast_test(hr);
}
// Add the region at the RHS of the incremental cset
void G1CollectorPolicy::add_region_to_incremental_cset_rhs(HeapRegion* hr) {
// We should only ever be appending survivors at the end of a pause
assert( hr->is_survivor(), "Logic");
// Do the 'common' stuff
add_region_to_incremental_cset_common(hr);
// Now add the region at the right hand side
if (_inc_cset_tail == NULL) {
assert(_inc_cset_head == NULL, "invariant");
_inc_cset_head = hr;
} else {
_inc_cset_tail->set_next_in_collection_set(hr);
}
_inc_cset_tail = hr;
}
// Add the region to the LHS of the incremental cset
void G1CollectorPolicy::add_region_to_incremental_cset_lhs(HeapRegion* hr) {
// Survivors should be added to the RHS at the end of a pause
assert(!hr->is_survivor(), "Logic");
// Do the 'common' stuff
add_region_to_incremental_cset_common(hr);
// Add the region at the left hand side
hr->set_next_in_collection_set(_inc_cset_head);
if (_inc_cset_head == NULL) {
assert(_inc_cset_tail == NULL, "Invariant");
_inc_cset_tail = hr;
}
_inc_cset_head = hr;
}
#ifndef PRODUCT
void G1CollectorPolicy::print_collection_set(HeapRegion* list_head, outputStream* st) {
assert(list_head == inc_cset_head() || list_head == collection_set(), "must be");
st->print_cr("\nCollection_set:");
HeapRegion* csr = list_head;
while (csr != NULL) {
HeapRegion* next = csr->next_in_collection_set();
assert(csr->in_collection_set(), "bad CS");
st->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
HR_FORMAT_PARAMS(csr),
csr->prev_top_at_mark_start(), csr->next_top_at_mark_start(),
csr->age_in_surv_rate_group_cond());
csr = next;
}
}
#endif // !PRODUCT
bool G1CollectorPolicy::next_gc_should_be_mixed(const char* true_action_str,
const char* false_action_str) {
CollectionSetChooser* cset_chooser = _collectionSetChooser;
if (cset_chooser->is_empty()) {
ergo_verbose0(ErgoMixedGCs,
false_action_str,
ergo_format_reason("candidate old regions not available"));
return false;
}
size_t reclaimable_bytes = cset_chooser->remaining_reclaimable_bytes();
size_t capacity_bytes = _g1->capacity();
double perc = (double) reclaimable_bytes * 100.0 / (double) capacity_bytes;
double threshold = (double) G1HeapWastePercent;
if (perc < threshold) {
ergo_verbose4(ErgoMixedGCs,
false_action_str,
ergo_format_reason("reclaimable percentage lower than threshold")
ergo_format_region("candidate old regions")
ergo_format_byte_perc("reclaimable")
ergo_format_perc("threshold"),
cset_chooser->remaining_regions(),
reclaimable_bytes, perc, threshold);
return false;
}
ergo_verbose4(ErgoMixedGCs,
true_action_str,
ergo_format_reason("candidate old regions available")
ergo_format_region("candidate old regions")
ergo_format_byte_perc("reclaimable")
ergo_format_perc("threshold"),
cset_chooser->remaining_regions(),
reclaimable_bytes, perc, threshold);
return true;
}
void G1CollectorPolicy::finalize_cset(double target_pause_time_ms) {
double young_start_time_sec = os::elapsedTime();
YoungList* young_list = _g1->young_list();
finalize_incremental_cset_building();
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 time_remaining_ms = target_pause_time_ms - base_time_ms;
ergo_verbose4(ErgoCSetConstruction | ErgoHigh,
"start choosing CSet",
ergo_format_size("_pending_cards")
ergo_format_ms("predicted base time")
ergo_format_ms("remaining time")
ergo_format_ms("target pause time"),
_pending_cards, base_time_ms, time_remaining_ms, target_pause_time_ms);
_last_gc_was_young = gcs_are_young() ? true : false;
if (_last_gc_was_young) {
_trace_gen0_time_data.increment_young_collection_count();
} else {
_trace_gen0_time_data.increment_mixed_collection_count();
}
// The young list is laid with the survivor regions from the previous
// pause are appended to the RHS of the young list, i.e.
// [Newly Young Regions ++ Survivors from last pause].
uint survivor_region_length = young_list->survivor_length();
uint eden_region_length = young_list->length() - survivor_region_length;
init_cset_region_lengths(eden_region_length, survivor_region_length);
HeapRegion* hr = young_list->first_survivor_region();
while (hr != NULL) {
assert(hr->is_survivor(), "badly formed young list");
hr->set_young();
hr = hr->get_next_young_region();
}
// Clear the fields that point to the survivor list - they are all young now.
young_list->clear_survivors();
_collection_set = _inc_cset_head;
_collection_set_bytes_used_before = _inc_cset_bytes_used_before;
time_remaining_ms -= _inc_cset_predicted_elapsed_time_ms;
predicted_pause_time_ms += _inc_cset_predicted_elapsed_time_ms;
ergo_verbose3(ErgoCSetConstruction | ErgoHigh,
"add young regions to CSet",
ergo_format_region("eden")
ergo_format_region("survivors")
ergo_format_ms("predicted young region time"),
eden_region_length, survivor_region_length,
_inc_cset_predicted_elapsed_time_ms);
// The number of recorded young regions is the incremental
// collection set's current size
set_recorded_rs_lengths(_inc_cset_recorded_rs_lengths);
double young_end_time_sec = os::elapsedTime();
phase_times()->_recorded_young_cset_choice_time_ms =
(young_end_time_sec - young_start_time_sec) * 1000.0;
// Set the start of the non-young choice time.
double non_young_start_time_sec = young_end_time_sec;
if (!gcs_are_young()) {
CollectionSetChooser* cset_chooser = _collectionSetChooser;
cset_chooser->verify();
const uint min_old_cset_length = cset_chooser->calc_min_old_cset_length();
const uint max_old_cset_length = cset_chooser->calc_max_old_cset_length();
uint expensive_region_num = 0;
bool check_time_remaining = adaptive_young_list_length();
HeapRegion* hr = cset_chooser->peek();
while (hr != NULL) {
if (old_cset_region_length() >= max_old_cset_length) {
// Added maximum number of old regions to the CSet.
ergo_verbose2(ErgoCSetConstruction,
"finish adding old regions to CSet",
ergo_format_reason("old CSet region num reached max")
ergo_format_region("old")
ergo_format_region("max"),
old_cset_region_length(), max_old_cset_length);
break;
}
double predicted_time_ms = predict_region_elapsed_time_ms(hr, gcs_are_young());
if (check_time_remaining) {
if (predicted_time_ms > time_remaining_ms) {
// Too expensive for the current CSet.
if (old_cset_region_length() >= min_old_cset_length) {
// We have added the minimum number of old regions to the CSet,
// we are done with this CSet.
ergo_verbose4(ErgoCSetConstruction,
"finish adding old regions to CSet",
ergo_format_reason("predicted time is too high")
ergo_format_ms("predicted time")
ergo_format_ms("remaining time")
ergo_format_region("old")
ergo_format_region("min"),
predicted_time_ms, time_remaining_ms,
old_cset_region_length(), min_old_cset_length);
break;
}
// We'll add it anyway given that we haven't reached the
// minimum number of old regions.
expensive_region_num += 1;
}
} else {
if (old_cset_region_length() >= min_old_cset_length) {
// In the non-auto-tuning case, we'll finish adding regions
// to the CSet if we reach the minimum.
ergo_verbose2(ErgoCSetConstruction,
"finish adding old regions to CSet",
ergo_format_reason("old CSet region num reached min")
ergo_format_region("old")
ergo_format_region("min"),
old_cset_region_length(), min_old_cset_length);
break;
}
}
// We will add this region to the CSet.
time_remaining_ms -= predicted_time_ms;
predicted_pause_time_ms += predicted_time_ms;
cset_chooser->remove_and_move_to_next(hr);
_g1->old_set_remove(hr);
add_old_region_to_cset(hr);
hr = cset_chooser->peek();
}
if (hr == NULL) {
ergo_verbose0(ErgoCSetConstruction,
"finish adding old regions to CSet",
ergo_format_reason("candidate old regions not available"));
}
if (expensive_region_num > 0) {
// We print the information once here at the end, predicated on
// whether we added any apparently expensive regions or not, to
// avoid generating output per region.
ergo_verbose4(ErgoCSetConstruction,
"added expensive regions to CSet",
ergo_format_reason("old CSet region num not reached min")
ergo_format_region("old")
ergo_format_region("expensive")
ergo_format_region("min")
ergo_format_ms("remaining time"),
old_cset_region_length(),
expensive_region_num,
min_old_cset_length,
time_remaining_ms);
}
cset_chooser->verify();
}
stop_incremental_cset_building();
ergo_verbose5(ErgoCSetConstruction,
"finish choosing CSet",
ergo_format_region("eden")
ergo_format_region("survivors")
ergo_format_region("old")
ergo_format_ms("predicted pause time")
ergo_format_ms("target pause time"),
eden_region_length, survivor_region_length,
old_cset_region_length(),
predicted_pause_time_ms, target_pause_time_ms);
double non_young_end_time_sec = os::elapsedTime();
phase_times()->_recorded_non_young_cset_choice_time_ms =
(non_young_end_time_sec - non_young_start_time_sec) * 1000.0;
}
void TraceGen0TimeData::record_start_collection(double time_to_stop_the_world_ms) {
if(TraceGen0Time) {
_all_stop_world_times_ms.add(time_to_stop_the_world_ms);
}
}
void TraceGen0TimeData::record_yield_time(double yield_time_ms) {
if(TraceGen0Time) {
_all_yield_times_ms.add(yield_time_ms);
}
}
void TraceGen0TimeData::record_end_collection(double pause_time_ms, G1GCPhaseTimes* phase_times) {
if(TraceGen0Time) {
_total.add(pause_time_ms);
_other.add(pause_time_ms - phase_times->accounted_time_ms());
_root_region_scan_wait.add(phase_times->_root_region_scan_wait_time_ms);
_parallel.add(phase_times->_cur_collection_par_time_ms);
_ext_root_scan.add(phase_times->_ext_root_scan_time);
_satb_filtering.add(phase_times->_satb_filtering_time);
_update_rs.add(phase_times->_update_rs_time);
_scan_rs.add(phase_times->_scan_rs_time);
_obj_copy.add(phase_times->_obj_copy_time);
_termination.add(phase_times->_termination_time);
double parallel_known_time = phase_times->_ext_root_scan_time +
phase_times->_satb_filtering_time +
phase_times->_update_rs_time +
phase_times->_scan_rs_time +
phase_times->_obj_copy_time +
+ phase_times->_termination_time;
double parallel_other_time = phase_times->_cur_collection_par_time_ms - parallel_known_time;
_parallel_other.add(parallel_other_time);
_clear_ct.add(phase_times->_cur_clear_ct_time_ms);
}
}
void TraceGen0TimeData::increment_young_collection_count() {
if(TraceGen0Time) {
++_young_pause_num;
}
}
void TraceGen0TimeData::increment_mixed_collection_count() {
if(TraceGen0Time) {
++_mixed_pause_num;
}
}
void TraceGen0TimeData::print_summary(const char* str,
const NumberSeq* seq) const {
double sum = seq->sum();
gclog_or_tty->print_cr("%-27s = %8.2lf s (avg = %8.2lf ms)",
str, sum / 1000.0, seq->avg());
}
void TraceGen0TimeData::print_summary_sd(const char* str,
const NumberSeq* seq) const {
print_summary(str, seq);
gclog_or_tty->print_cr("%+45s = %5d, std dev = %8.2lf ms, max = %8.2lf ms)",
"(num", seq->num(), seq->sd(), seq->maximum());
}
void TraceGen0TimeData::print() const {
if (!TraceGen0Time) {
return;
}
gclog_or_tty->print_cr("ALL PAUSES");
print_summary_sd(" Total", &_total);
gclog_or_tty->print_cr("");
gclog_or_tty->print_cr("");
gclog_or_tty->print_cr(" Young GC Pauses: %8d", _young_pause_num);
gclog_or_tty->print_cr(" Mixed GC Pauses: %8d", _mixed_pause_num);
gclog_or_tty->print_cr("");
gclog_or_tty->print_cr("EVACUATION PAUSES");
if (_young_pause_num == 0 && _mixed_pause_num == 0) {
gclog_or_tty->print_cr("none");
} else {
print_summary_sd(" Evacuation Pauses", &_total);
print_summary(" Root Region Scan Wait", &_root_region_scan_wait);
print_summary(" Parallel Time", &_parallel);
print_summary(" Ext Root Scanning", &_ext_root_scan);
print_summary(" SATB Filtering", &_satb_filtering);
print_summary(" Update RS", &_update_rs);
print_summary(" Scan RS", &_scan_rs);
print_summary(" Object Copy", &_obj_copy);
print_summary(" Termination", &_termination);
print_summary(" Parallel Other", &_parallel_other);
print_summary(" Clear CT", &_clear_ct);
print_summary(" Other", &_other);
}
gclog_or_tty->print_cr("");
gclog_or_tty->print_cr("MISC");
print_summary_sd(" Stop World", &_all_stop_world_times_ms);
print_summary_sd(" Yields", &_all_yield_times_ms);
}
void TraceGen1TimeData::record_full_collection(double full_gc_time_ms) {
if (TraceGen1Time) {
_all_full_gc_times.add(full_gc_time_ms);
}
}
void TraceGen1TimeData::print() const {
if (!TraceGen1Time) {
return;
}
if (_all_full_gc_times.num() > 0) {
gclog_or_tty->print("\n%4d full_gcs: total time = %8.2f s",
_all_full_gc_times.num(),
_all_full_gc_times.sum() / 1000.0);
gclog_or_tty->print_cr(" (avg = %8.2fms).", _all_full_gc_times.avg());
gclog_or_tty->print_cr(" [std. dev = %8.2f ms, max = %8.2f ms]",
_all_full_gc_times.sd(),
_all_full_gc_times.maximum());
}
}