Java example source code file (adaptiveSizePolicy.cpp)
The adaptiveSizePolicy.cpp Java example source code
/*
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* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
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* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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#include "precompiled.hpp"
#include "gc_implementation/shared/adaptiveSizePolicy.hpp"
#include "gc_interface/gcCause.hpp"
#include "memory/collectorPolicy.hpp"
#include "runtime/timer.hpp"
#include "utilities/ostream.hpp"
#include "utilities/workgroup.hpp"
elapsedTimer AdaptiveSizePolicy::_minor_timer;
elapsedTimer AdaptiveSizePolicy::_major_timer;
bool AdaptiveSizePolicy::_debug_perturbation = false;
// The throughput goal is implemented as
// _throughput_goal = 1 - ( 1 / (1 + gc_cost_ratio))
// gc_cost_ratio is the ratio
// application cost / gc cost
// For example a gc_cost_ratio of 4 translates into a
// throughput goal of .80
AdaptiveSizePolicy::AdaptiveSizePolicy(size_t init_eden_size,
size_t init_promo_size,
size_t init_survivor_size,
double gc_pause_goal_sec,
uint gc_cost_ratio) :
_eden_size(init_eden_size),
_promo_size(init_promo_size),
_survivor_size(init_survivor_size),
_gc_pause_goal_sec(gc_pause_goal_sec),
_throughput_goal(1.0 - double(1.0 / (1.0 + (double) gc_cost_ratio))),
_gc_overhead_limit_exceeded(false),
_print_gc_overhead_limit_would_be_exceeded(false),
_gc_overhead_limit_count(0),
_latest_minor_mutator_interval_seconds(0),
_threshold_tolerance_percent(1.0 + ThresholdTolerance/100.0),
_young_gen_change_for_minor_throughput(0),
_old_gen_change_for_major_throughput(0) {
assert(AdaptiveSizePolicyGCTimeLimitThreshold > 0,
"No opportunity to clear SoftReferences before GC overhead limit");
_avg_minor_pause =
new AdaptivePaddedAverage(AdaptiveTimeWeight, PausePadding);
_avg_minor_interval = new AdaptiveWeightedAverage(AdaptiveTimeWeight);
_avg_minor_gc_cost = new AdaptiveWeightedAverage(AdaptiveTimeWeight);
_avg_major_gc_cost = new AdaptiveWeightedAverage(AdaptiveTimeWeight);
_avg_young_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);
_avg_old_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);
_avg_eden_live = new AdaptiveWeightedAverage(AdaptiveSizePolicyWeight);
_avg_survived = new AdaptivePaddedAverage(AdaptiveSizePolicyWeight,
SurvivorPadding);
_avg_pretenured = new AdaptivePaddedNoZeroDevAverage(
AdaptiveSizePolicyWeight,
SurvivorPadding);
_minor_pause_old_estimator =
new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
_minor_pause_young_estimator =
new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
_minor_collection_estimator =
new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
_major_collection_estimator =
new LinearLeastSquareFit(AdaptiveSizePolicyWeight);
// Start the timers
_minor_timer.start();
_young_gen_policy_is_ready = false;
}
// If the number of GC threads was set on the command line,
// use it.
// Else
// Calculate the number of GC threads based on the number of Java threads.
// Calculate the number of GC threads based on the size of the heap.
// Use the larger.
int AdaptiveSizePolicy::calc_default_active_workers(uintx total_workers,
const uintx min_workers,
uintx active_workers,
uintx application_workers) {
// If the user has specifically set the number of
// GC threads, use them.
// If the user has turned off using a dynamic number of GC threads
// or the users has requested a specific number, set the active
// number of workers to all the workers.
uintx new_active_workers = total_workers;
uintx prev_active_workers = active_workers;
uintx active_workers_by_JT = 0;
uintx active_workers_by_heap_size = 0;
// Always use at least min_workers but use up to
// GCThreadsPerJavaThreads * application threads.
active_workers_by_JT =
MAX2((uintx) GCWorkersPerJavaThread * application_workers,
min_workers);
// Choose a number of GC threads based on the current size
// of the heap. This may be complicated because the size of
// the heap depends on factors such as the thoughput goal.
// Still a large heap should be collected by more GC threads.
active_workers_by_heap_size =
MAX2((size_t) 2U, Universe::heap()->capacity() / HeapSizePerGCThread);
uintx max_active_workers =
MAX2(active_workers_by_JT, active_workers_by_heap_size);
// Limit the number of workers to the the number created,
// (workers()).
new_active_workers = MIN2(max_active_workers,
(uintx) total_workers);
// Increase GC workers instantly but decrease them more
// slowly.
if (new_active_workers < prev_active_workers) {
new_active_workers =
MAX2(min_workers, (prev_active_workers + new_active_workers) / 2);
}
// Check once more that the number of workers is within the limits.
assert(min_workers <= total_workers, "Minimum workers not consistent with total workers");
assert(new_active_workers >= min_workers, "Minimum workers not observed");
assert(new_active_workers <= total_workers, "Total workers not observed");
if (ForceDynamicNumberOfGCThreads) {
// Assume this is debugging and jiggle the number of GC threads.
if (new_active_workers == prev_active_workers) {
if (new_active_workers < total_workers) {
new_active_workers++;
} else if (new_active_workers > min_workers) {
new_active_workers--;
}
}
if (new_active_workers == total_workers) {
if (_debug_perturbation) {
new_active_workers = min_workers;
}
_debug_perturbation = !_debug_perturbation;
}
assert((new_active_workers <= (uintx) ParallelGCThreads) &&
(new_active_workers >= min_workers),
"Jiggled active workers too much");
}
if (TraceDynamicGCThreads) {
gclog_or_tty->print_cr("GCTaskManager::calc_default_active_workers() : "
"active_workers(): %d new_acitve_workers: %d "
"prev_active_workers: %d\n"
" active_workers_by_JT: %d active_workers_by_heap_size: %d",
active_workers, new_active_workers, prev_active_workers,
active_workers_by_JT, active_workers_by_heap_size);
}
assert(new_active_workers > 0, "Always need at least 1");
return new_active_workers;
}
int AdaptiveSizePolicy::calc_active_workers(uintx total_workers,
uintx active_workers,
uintx application_workers) {
// If the user has specifically set the number of
// GC threads, use them.
// If the user has turned off using a dynamic number of GC threads
// or the users has requested a specific number, set the active
// number of workers to all the workers.
int new_active_workers;
if (!UseDynamicNumberOfGCThreads ||
(!FLAG_IS_DEFAULT(ParallelGCThreads) && !ForceDynamicNumberOfGCThreads)) {
new_active_workers = total_workers;
} else {
new_active_workers = calc_default_active_workers(total_workers,
2, /* Minimum number of workers */
active_workers,
application_workers);
}
assert(new_active_workers > 0, "Always need at least 1");
return new_active_workers;
}
int AdaptiveSizePolicy::calc_active_conc_workers(uintx total_workers,
uintx active_workers,
uintx application_workers) {
if (!UseDynamicNumberOfGCThreads ||
(!FLAG_IS_DEFAULT(ConcGCThreads) && !ForceDynamicNumberOfGCThreads)) {
return ConcGCThreads;
} else {
int no_of_gc_threads = calc_default_active_workers(
total_workers,
1, /* Minimum number of workers */
active_workers,
application_workers);
return no_of_gc_threads;
}
}
bool AdaptiveSizePolicy::tenuring_threshold_change() const {
return decrement_tenuring_threshold_for_gc_cost() ||
increment_tenuring_threshold_for_gc_cost() ||
decrement_tenuring_threshold_for_survivor_limit();
}
void AdaptiveSizePolicy::minor_collection_begin() {
// Update the interval time
_minor_timer.stop();
// Save most recent collection time
_latest_minor_mutator_interval_seconds = _minor_timer.seconds();
_minor_timer.reset();
_minor_timer.start();
}
void AdaptiveSizePolicy::update_minor_pause_young_estimator(
double minor_pause_in_ms) {
double eden_size_in_mbytes = ((double)_eden_size)/((double)M);
_minor_pause_young_estimator->update(eden_size_in_mbytes,
minor_pause_in_ms);
}
void AdaptiveSizePolicy::minor_collection_end(GCCause::Cause gc_cause) {
// Update the pause time.
_minor_timer.stop();
if (gc_cause != GCCause::_java_lang_system_gc ||
UseAdaptiveSizePolicyWithSystemGC) {
double minor_pause_in_seconds = _minor_timer.seconds();
double minor_pause_in_ms = minor_pause_in_seconds * MILLIUNITS;
// Sample for performance counter
_avg_minor_pause->sample(minor_pause_in_seconds);
// Cost of collection (unit-less)
double collection_cost = 0.0;
if ((_latest_minor_mutator_interval_seconds > 0.0) &&
(minor_pause_in_seconds > 0.0)) {
double interval_in_seconds =
_latest_minor_mutator_interval_seconds + minor_pause_in_seconds;
collection_cost =
minor_pause_in_seconds / interval_in_seconds;
_avg_minor_gc_cost->sample(collection_cost);
// Sample for performance counter
_avg_minor_interval->sample(interval_in_seconds);
}
// The policy does not have enough data until at least some
// minor collections have been done.
_young_gen_policy_is_ready =
(_avg_minor_gc_cost->count() >= AdaptiveSizePolicyReadyThreshold);
// Calculate variables used to estimate pause time vs. gen sizes
double eden_size_in_mbytes = ((double)_eden_size)/((double)M);
update_minor_pause_young_estimator(minor_pause_in_ms);
update_minor_pause_old_estimator(minor_pause_in_ms);
if (PrintAdaptiveSizePolicy && Verbose) {
gclog_or_tty->print("AdaptiveSizePolicy::minor_collection_end: "
"minor gc cost: %f average: %f", collection_cost,
_avg_minor_gc_cost->average());
gclog_or_tty->print_cr(" minor pause: %f minor period %f",
minor_pause_in_ms,
_latest_minor_mutator_interval_seconds * MILLIUNITS);
}
// Calculate variable used to estimate collection cost vs. gen sizes
assert(collection_cost >= 0.0, "Expected to be non-negative");
_minor_collection_estimator->update(eden_size_in_mbytes, collection_cost);
}
// Interval times use this timer to measure the mutator time.
// Reset the timer after the GC pause.
_minor_timer.reset();
_minor_timer.start();
}
size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden,
uint percent_change) {
size_t eden_heap_delta;
eden_heap_delta = cur_eden / 100 * percent_change;
return eden_heap_delta;
}
size_t AdaptiveSizePolicy::eden_increment(size_t cur_eden) {
return eden_increment(cur_eden, YoungGenerationSizeIncrement);
}
size_t AdaptiveSizePolicy::eden_decrement(size_t cur_eden) {
size_t eden_heap_delta = eden_increment(cur_eden) /
AdaptiveSizeDecrementScaleFactor;
return eden_heap_delta;
}
size_t AdaptiveSizePolicy::promo_increment(size_t cur_promo,
uint percent_change) {
size_t promo_heap_delta;
promo_heap_delta = cur_promo / 100 * percent_change;
return promo_heap_delta;
}
size_t AdaptiveSizePolicy::promo_increment(size_t cur_promo) {
return promo_increment(cur_promo, TenuredGenerationSizeIncrement);
}
size_t AdaptiveSizePolicy::promo_decrement(size_t cur_promo) {
size_t promo_heap_delta = promo_increment(cur_promo);
promo_heap_delta = promo_heap_delta / AdaptiveSizeDecrementScaleFactor;
return promo_heap_delta;
}
double AdaptiveSizePolicy::time_since_major_gc() const {
_major_timer.stop();
double result = _major_timer.seconds();
_major_timer.start();
return result;
}
// Linear decay of major gc cost
double AdaptiveSizePolicy::decaying_major_gc_cost() const {
double major_interval = major_gc_interval_average_for_decay();
double major_gc_cost_average = major_gc_cost();
double decayed_major_gc_cost = major_gc_cost_average;
if(time_since_major_gc() > 0.0) {
decayed_major_gc_cost = major_gc_cost() *
(((double) AdaptiveSizeMajorGCDecayTimeScale) * major_interval)
/ time_since_major_gc();
}
// The decayed cost should always be smaller than the
// average cost but the vagaries of finite arithmetic could
// produce a larger value in decayed_major_gc_cost so protect
// against that.
return MIN2(major_gc_cost_average, decayed_major_gc_cost);
}
// Use a value of the major gc cost that has been decayed
// by the factor
//
// average-interval-between-major-gc * AdaptiveSizeMajorGCDecayTimeScale /
// time-since-last-major-gc
//
// if the average-interval-between-major-gc * AdaptiveSizeMajorGCDecayTimeScale
// is less than time-since-last-major-gc.
//
// In cases where there are initial major gc's that
// are of a relatively high cost but no later major
// gc's, the total gc cost can remain high because
// the major gc cost remains unchanged (since there are no major
// gc's). In such a situation the value of the unchanging
// major gc cost can keep the mutator throughput below
// the goal when in fact the major gc cost is becoming diminishingly
// small. Use the decaying gc cost only to decide whether to
// adjust for throughput. Using it also to determine the adjustment
// to be made for throughput also seems reasonable but there is
// no test case to use to decide if it is the right thing to do
// don't do it yet.
double AdaptiveSizePolicy::decaying_gc_cost() const {
double decayed_major_gc_cost = major_gc_cost();
double avg_major_interval = major_gc_interval_average_for_decay();
if (UseAdaptiveSizeDecayMajorGCCost &&
(AdaptiveSizeMajorGCDecayTimeScale > 0) &&
(avg_major_interval > 0.00)) {
double time_since_last_major_gc = time_since_major_gc();
// Decay the major gc cost?
if (time_since_last_major_gc >
((double) AdaptiveSizeMajorGCDecayTimeScale) * avg_major_interval) {
// Decay using the time-since-last-major-gc
decayed_major_gc_cost = decaying_major_gc_cost();
if (PrintGCDetails && Verbose) {
gclog_or_tty->print_cr("\ndecaying_gc_cost: major interval average:"
" %f time since last major gc: %f",
avg_major_interval, time_since_last_major_gc);
gclog_or_tty->print_cr(" major gc cost: %f decayed major gc cost: %f",
major_gc_cost(), decayed_major_gc_cost);
}
}
}
double result = MIN2(1.0, decayed_major_gc_cost + minor_gc_cost());
return result;
}
void AdaptiveSizePolicy::clear_generation_free_space_flags() {
set_change_young_gen_for_min_pauses(0);
set_change_old_gen_for_maj_pauses(0);
set_change_old_gen_for_throughput(0);
set_change_young_gen_for_throughput(0);
set_decrease_for_footprint(0);
set_decide_at_full_gc(0);
}
void AdaptiveSizePolicy::check_gc_overhead_limit(
size_t young_live,
size_t eden_live,
size_t max_old_gen_size,
size_t max_eden_size,
bool is_full_gc,
GCCause::Cause gc_cause,
CollectorPolicy* collector_policy) {
// Ignore explicit GC's. Exiting here does not set the flag and
// does not reset the count. Updating of the averages for system
// GC's is still controlled by UseAdaptiveSizePolicyWithSystemGC.
if (GCCause::is_user_requested_gc(gc_cause) ||
GCCause::is_serviceability_requested_gc(gc_cause)) {
return;
}
// eden_limit is the upper limit on the size of eden based on
// the maximum size of the young generation and the sizes
// of the survivor space.
// The question being asked is whether the gc costs are high
// and the space being recovered by a collection is low.
// free_in_young_gen is the free space in the young generation
// after a collection and promo_live is the free space in the old
// generation after a collection.
//
// Use the minimum of the current value of the live in the
// young gen or the average of the live in the young gen.
// If the current value drops quickly, that should be taken
// into account (i.e., don't trigger if the amount of free
// space has suddenly jumped up). If the current is much
// higher than the average, use the average since it represents
// the longer term behavor.
const size_t live_in_eden =
MIN2(eden_live, (size_t) avg_eden_live()->average());
const size_t free_in_eden = max_eden_size > live_in_eden ?
max_eden_size - live_in_eden : 0;
const size_t free_in_old_gen = (size_t)(max_old_gen_size - avg_old_live()->average());
const size_t total_free_limit = free_in_old_gen + free_in_eden;
const size_t total_mem = max_old_gen_size + max_eden_size;
const double mem_free_limit = total_mem * (GCHeapFreeLimit/100.0);
const double mem_free_old_limit = max_old_gen_size * (GCHeapFreeLimit/100.0);
const double mem_free_eden_limit = max_eden_size * (GCHeapFreeLimit/100.0);
const double gc_cost_limit = GCTimeLimit/100.0;
size_t promo_limit = (size_t)(max_old_gen_size - avg_old_live()->average());
// But don't force a promo size below the current promo size. Otherwise,
// the promo size will shrink for no good reason.
promo_limit = MAX2(promo_limit, _promo_size);
if (PrintAdaptiveSizePolicy && (Verbose ||
(free_in_old_gen < (size_t) mem_free_old_limit &&
free_in_eden < (size_t) mem_free_eden_limit))) {
gclog_or_tty->print_cr(
"PSAdaptiveSizePolicy::check_gc_overhead_limit:"
" promo_limit: " SIZE_FORMAT
" max_eden_size: " SIZE_FORMAT
" total_free_limit: " SIZE_FORMAT
" max_old_gen_size: " SIZE_FORMAT
" max_eden_size: " SIZE_FORMAT
" mem_free_limit: " SIZE_FORMAT,
promo_limit, max_eden_size, total_free_limit,
max_old_gen_size, max_eden_size,
(size_t) mem_free_limit);
}
bool print_gc_overhead_limit_would_be_exceeded = false;
if (is_full_gc) {
if (gc_cost() > gc_cost_limit &&
free_in_old_gen < (size_t) mem_free_old_limit &&
free_in_eden < (size_t) mem_free_eden_limit) {
// Collections, on average, are taking too much time, and
// gc_cost() > gc_cost_limit
// we have too little space available after a full gc.
// total_free_limit < mem_free_limit
// where
// total_free_limit is the free space available in
// both generations
// total_mem is the total space available for allocation
// in both generations (survivor spaces are not included
// just as they are not included in eden_limit).
// mem_free_limit is a fraction of total_mem judged to be an
// acceptable amount that is still unused.
// The heap can ask for the value of this variable when deciding
// whether to thrown an OutOfMemory error.
// Note that the gc time limit test only works for the collections
// of the young gen + tenured gen and not for collections of the
// permanent gen. That is because the calculation of the space
// freed by the collection is the free space in the young gen +
// tenured gen.
// At this point the GC overhead limit is being exceeded.
inc_gc_overhead_limit_count();
if (UseGCOverheadLimit) {
if (gc_overhead_limit_count() >=
AdaptiveSizePolicyGCTimeLimitThreshold){
// All conditions have been met for throwing an out-of-memory
set_gc_overhead_limit_exceeded(true);
// Avoid consecutive OOM due to the gc time limit by resetting
// the counter.
reset_gc_overhead_limit_count();
} else {
// The required consecutive collections which exceed the
// GC time limit may or may not have been reached. We
// are approaching that condition and so as not to
// throw an out-of-memory before all SoftRef's have been
// cleared, set _should_clear_all_soft_refs in CollectorPolicy.
// The clearing will be done on the next GC.
bool near_limit = gc_overhead_limit_near();
if (near_limit) {
collector_policy->set_should_clear_all_soft_refs(true);
if (PrintGCDetails && Verbose) {
gclog_or_tty->print_cr(" Nearing GC overhead limit, "
"will be clearing all SoftReference");
}
}
}
}
// Set this even when the overhead limit will not
// cause an out-of-memory. Diagnostic message indicating
// that the overhead limit is being exceeded is sometimes
// printed.
print_gc_overhead_limit_would_be_exceeded = true;
} else {
// Did not exceed overhead limits
reset_gc_overhead_limit_count();
}
}
if (UseGCOverheadLimit && PrintGCDetails && Verbose) {
if (gc_overhead_limit_exceeded()) {
gclog_or_tty->print_cr(" GC is exceeding overhead limit "
"of %d%%", GCTimeLimit);
reset_gc_overhead_limit_count();
} else if (print_gc_overhead_limit_would_be_exceeded) {
assert(gc_overhead_limit_count() > 0, "Should not be printing");
gclog_or_tty->print_cr(" GC would exceed overhead limit "
"of %d%% %d consecutive time(s)",
GCTimeLimit, gc_overhead_limit_count());
}
}
}
// Printing
bool AdaptiveSizePolicy::print_adaptive_size_policy_on(outputStream* st) const {
// Should only be used with adaptive size policy turned on.
// Otherwise, there may be variables that are undefined.
if (!UseAdaptiveSizePolicy) return false;
// Print goal for which action is needed.
char* action = NULL;
bool change_for_pause = false;
if ((change_old_gen_for_maj_pauses() ==
decrease_old_gen_for_maj_pauses_true) ||
(change_young_gen_for_min_pauses() ==
decrease_young_gen_for_min_pauses_true)) {
action = (char*) " *** pause time goal ***";
change_for_pause = true;
} else if ((change_old_gen_for_throughput() ==
increase_old_gen_for_throughput_true) ||
(change_young_gen_for_throughput() ==
increase_young_gen_for_througput_true)) {
action = (char*) " *** throughput goal ***";
} else if (decrease_for_footprint()) {
action = (char*) " *** reduced footprint ***";
} else {
// No actions were taken. This can legitimately be the
// situation if not enough data has been gathered to make
// decisions.
return false;
}
// Pauses
// Currently the size of the old gen is only adjusted to
// change the major pause times.
char* young_gen_action = NULL;
char* tenured_gen_action = NULL;
char* shrink_msg = (char*) "(attempted to shrink)";
char* grow_msg = (char*) "(attempted to grow)";
char* no_change_msg = (char*) "(no change)";
if (change_young_gen_for_min_pauses() ==
decrease_young_gen_for_min_pauses_true) {
young_gen_action = shrink_msg;
} else if (change_for_pause) {
young_gen_action = no_change_msg;
}
if (change_old_gen_for_maj_pauses() == decrease_old_gen_for_maj_pauses_true) {
tenured_gen_action = shrink_msg;
} else if (change_for_pause) {
tenured_gen_action = no_change_msg;
}
// Throughput
if (change_old_gen_for_throughput() == increase_old_gen_for_throughput_true) {
assert(change_young_gen_for_throughput() ==
increase_young_gen_for_througput_true,
"Both generations should be growing");
young_gen_action = grow_msg;
tenured_gen_action = grow_msg;
} else if (change_young_gen_for_throughput() ==
increase_young_gen_for_througput_true) {
// Only the young generation may grow at start up (before
// enough full collections have been done to grow the old generation).
young_gen_action = grow_msg;
tenured_gen_action = no_change_msg;
}
// Minimum footprint
if (decrease_for_footprint() != 0) {
young_gen_action = shrink_msg;
tenured_gen_action = shrink_msg;
}
st->print_cr(" UseAdaptiveSizePolicy actions to meet %s", action);
st->print_cr(" GC overhead (%%)");
st->print_cr(" Young generation: %7.2f\t %s",
100.0 * avg_minor_gc_cost()->average(),
young_gen_action);
st->print_cr(" Tenured generation: %7.2f\t %s",
100.0 * avg_major_gc_cost()->average(),
tenured_gen_action);
return true;
}
bool AdaptiveSizePolicy::print_adaptive_size_policy_on(
outputStream* st,
uint tenuring_threshold_arg) const {
if (!AdaptiveSizePolicy::print_adaptive_size_policy_on(st)) {
return false;
}
// Tenuring threshold
bool tenuring_threshold_changed = true;
if (decrement_tenuring_threshold_for_survivor_limit()) {
st->print(" Tenuring threshold: (attempted to decrease to avoid"
" survivor space overflow) = ");
} else if (decrement_tenuring_threshold_for_gc_cost()) {
st->print(" Tenuring threshold: (attempted to decrease to balance"
" GC costs) = ");
} else if (increment_tenuring_threshold_for_gc_cost()) {
st->print(" Tenuring threshold: (attempted to increase to balance"
" GC costs) = ");
} else {
tenuring_threshold_changed = false;
assert(!tenuring_threshold_change(), "(no change was attempted)");
}
if (tenuring_threshold_changed) {
st->print_cr("%u", tenuring_threshold_arg);
}
return true;
}
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