Java example source code file (collectorPolicy.cpp)
The collectorPolicy.cpp Java example source code/*
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#include "precompiled.hpp"
#include "gc_implementation/shared/adaptiveSizePolicy.hpp"
#include "gc_implementation/shared/gcPolicyCounters.hpp"
#include "gc_implementation/shared/vmGCOperations.hpp"
#include "memory/cardTableRS.hpp"
#include "memory/collectorPolicy.hpp"
#include "memory/gcLocker.inline.hpp"
#include "memory/genCollectedHeap.hpp"
#include "memory/generationSpec.hpp"
#include "memory/space.hpp"
#include "memory/universe.hpp"
#include "runtime/arguments.hpp"
#include "runtime/globals_extension.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/java.hpp"
#include "runtime/thread.inline.hpp"
#include "runtime/vmThread.hpp"
#include "utilities/macros.hpp"
#if INCLUDE_ALL_GCS
#include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp"
#include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp"
#endif // INCLUDE_ALL_GCS
// CollectorPolicy methods.
CollectorPolicy::CollectorPolicy() :
_space_alignment(0),
_heap_alignment(0),
_initial_heap_byte_size(InitialHeapSize),
_max_heap_byte_size(MaxHeapSize),
_min_heap_byte_size(Arguments::min_heap_size()),
_max_heap_size_cmdline(false),
_size_policy(NULL),
_should_clear_all_soft_refs(false),
_all_soft_refs_clear(false)
{}
#ifdef ASSERT
void CollectorPolicy::assert_flags() {
assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes");
assert(InitialHeapSize % _heap_alignment == 0, "InitialHeapSize alignment");
assert(MaxHeapSize % _heap_alignment == 0, "MaxHeapSize alignment");
}
void CollectorPolicy::assert_size_info() {
assert(InitialHeapSize == _initial_heap_byte_size, "Discrepancy between InitialHeapSize flag and local storage");
assert(MaxHeapSize == _max_heap_byte_size, "Discrepancy between MaxHeapSize flag and local storage");
assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes");
assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes");
assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes");
assert(_min_heap_byte_size % _heap_alignment == 0, "min_heap_byte_size alignment");
assert(_initial_heap_byte_size % _heap_alignment == 0, "initial_heap_byte_size alignment");
assert(_max_heap_byte_size % _heap_alignment == 0, "max_heap_byte_size alignment");
}
#endif // ASSERT
void CollectorPolicy::initialize_flags() {
assert(_space_alignment != 0, "Space alignment not set up properly");
assert(_heap_alignment != 0, "Heap alignment not set up properly");
assert(_heap_alignment >= _space_alignment,
err_msg("heap_alignment: " SIZE_FORMAT " less than space_alignment: " SIZE_FORMAT,
_heap_alignment, _space_alignment));
assert(_heap_alignment % _space_alignment == 0,
err_msg("heap_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT,
_heap_alignment, _space_alignment));
if (FLAG_IS_CMDLINE(MaxHeapSize)) {
if (FLAG_IS_CMDLINE(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
vm_exit_during_initialization("Initial heap size set to a larger value than the maximum heap size");
}
if (_min_heap_byte_size != 0 && MaxHeapSize < _min_heap_byte_size) {
vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
}
_max_heap_size_cmdline = true;
}
// Check heap parameter properties
if (InitialHeapSize < M) {
vm_exit_during_initialization("Too small initial heap");
}
if (_min_heap_byte_size < M) {
vm_exit_during_initialization("Too small minimum heap");
}
// User inputs from -Xmx and -Xms must be aligned
_min_heap_byte_size = align_size_up(_min_heap_byte_size, _heap_alignment);
uintx aligned_initial_heap_size = align_size_up(InitialHeapSize, _heap_alignment);
uintx aligned_max_heap_size = align_size_up(MaxHeapSize, _heap_alignment);
// Write back to flags if the values changed
if (aligned_initial_heap_size != InitialHeapSize) {
FLAG_SET_ERGO(uintx, InitialHeapSize, aligned_initial_heap_size);
}
if (aligned_max_heap_size != MaxHeapSize) {
FLAG_SET_ERGO(uintx, MaxHeapSize, aligned_max_heap_size);
}
if (FLAG_IS_CMDLINE(InitialHeapSize) && _min_heap_byte_size != 0 &&
InitialHeapSize < _min_heap_byte_size) {
vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
}
if (!FLAG_IS_DEFAULT(InitialHeapSize) && InitialHeapSize > MaxHeapSize) {
FLAG_SET_ERGO(uintx, MaxHeapSize, InitialHeapSize);
} else if (!FLAG_IS_DEFAULT(MaxHeapSize) && InitialHeapSize > MaxHeapSize) {
FLAG_SET_ERGO(uintx, InitialHeapSize, MaxHeapSize);
if (InitialHeapSize < _min_heap_byte_size) {
_min_heap_byte_size = InitialHeapSize;
}
}
_initial_heap_byte_size = InitialHeapSize;
_max_heap_byte_size = MaxHeapSize;
FLAG_SET_ERGO(uintx, MinHeapDeltaBytes, align_size_up(MinHeapDeltaBytes, _space_alignment));
DEBUG_ONLY(CollectorPolicy::assert_flags();)
}
void CollectorPolicy::initialize_size_info() {
if (PrintGCDetails && Verbose) {
gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap "
SIZE_FORMAT " Maximum heap " SIZE_FORMAT,
_min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size);
}
DEBUG_ONLY(CollectorPolicy::assert_size_info();)
}
bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
bool result = _should_clear_all_soft_refs;
set_should_clear_all_soft_refs(false);
return result;
}
GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
int max_covered_regions) {
return new CardTableRS(whole_heap, max_covered_regions);
}
void CollectorPolicy::cleared_all_soft_refs() {
// If near gc overhear limit, continue to clear SoftRefs. SoftRefs may
// have been cleared in the last collection but if the gc overhear
// limit continues to be near, SoftRefs should still be cleared.
if (size_policy() != NULL) {
_should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
}
_all_soft_refs_clear = true;
}
size_t CollectorPolicy::compute_heap_alignment() {
// The card marking array and the offset arrays for old generations are
// committed in os pages as well. Make sure they are entirely full (to
// avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
// byte entry and the os page size is 4096, the maximum heap size should
// be 512*4096 = 2MB aligned.
// There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable
// is supported.
// Requirements of any new remembered set implementations must be added here.
size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable);
// Parallel GC does its own alignment of the generations to avoid requiring a
// large page (256M on some platforms) for the permanent generation. The
// other collectors should also be updated to do their own alignment and then
// this use of lcm() should be removed.
if (UseLargePages && !UseParallelGC) {
// in presence of large pages we have to make sure that our
// alignment is large page aware
alignment = lcm(os::large_page_size(), alignment);
}
return alignment;
}
// GenCollectorPolicy methods.
GenCollectorPolicy::GenCollectorPolicy() :
_min_gen0_size(0),
_initial_gen0_size(0),
_max_gen0_size(0),
_gen_alignment(0),
_generations(NULL)
{}
size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
return align_size_down_bounded(base_size / (NewRatio + 1), _gen_alignment);
}
size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
size_t maximum_size) {
size_t max_minus = maximum_size - _gen_alignment;
return desired_size < max_minus ? desired_size : max_minus;
}
void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
size_t init_promo_size,
size_t init_survivor_size) {
const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0;
_size_policy = new AdaptiveSizePolicy(init_eden_size,
init_promo_size,
init_survivor_size,
max_gc_pause_sec,
GCTimeRatio);
}
size_t GenCollectorPolicy::young_gen_size_lower_bound() {
// The young generation must be aligned and have room for eden + two survivors
return align_size_up(3 * _space_alignment, _gen_alignment);
}
#ifdef ASSERT
void GenCollectorPolicy::assert_flags() {
CollectorPolicy::assert_flags();
assert(NewSize >= _min_gen0_size, "Ergonomics decided on a too small young gen size");
assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes");
assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes");
assert(NewSize % _gen_alignment == 0, "NewSize alignment");
assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _gen_alignment == 0, "MaxNewSize alignment");
}
void TwoGenerationCollectorPolicy::assert_flags() {
GenCollectorPolicy::assert_flags();
assert(OldSize + NewSize <= MaxHeapSize, "Ergonomics decided on incompatible generation and heap sizes");
assert(OldSize % _gen_alignment == 0, "OldSize alignment");
}
void GenCollectorPolicy::assert_size_info() {
CollectorPolicy::assert_size_info();
// GenCollectorPolicy::initialize_size_info may update the MaxNewSize
assert(MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young and heap sizes");
assert(NewSize == _initial_gen0_size, "Discrepancy between NewSize flag and local storage");
assert(MaxNewSize == _max_gen0_size, "Discrepancy between MaxNewSize flag and local storage");
assert(_min_gen0_size <= _initial_gen0_size, "Ergonomics decided on incompatible minimum and initial young gen sizes");
assert(_initial_gen0_size <= _max_gen0_size, "Ergonomics decided on incompatible initial and maximum young gen sizes");
assert(_min_gen0_size % _gen_alignment == 0, "_min_gen0_size alignment");
assert(_initial_gen0_size % _gen_alignment == 0, "_initial_gen0_size alignment");
assert(_max_gen0_size % _gen_alignment == 0, "_max_gen0_size alignment");
}
void TwoGenerationCollectorPolicy::assert_size_info() {
GenCollectorPolicy::assert_size_info();
assert(OldSize == _initial_gen1_size, "Discrepancy between OldSize flag and local storage");
assert(_min_gen1_size <= _initial_gen1_size, "Ergonomics decided on incompatible minimum and initial old gen sizes");
assert(_initial_gen1_size <= _max_gen1_size, "Ergonomics decided on incompatible initial and maximum old gen sizes");
assert(_max_gen1_size % _gen_alignment == 0, "_max_gen1_size alignment");
assert(_initial_gen1_size % _gen_alignment == 0, "_initial_gen1_size alignment");
assert(_max_heap_byte_size <= (_max_gen0_size + _max_gen1_size), "Total maximum heap sizes must be sum of generation maximum sizes");
}
#endif // ASSERT
void GenCollectorPolicy::initialize_flags() {
CollectorPolicy::initialize_flags();
assert(_gen_alignment != 0, "Generation alignment not set up properly");
assert(_heap_alignment >= _gen_alignment,
err_msg("heap_alignment: " SIZE_FORMAT " less than gen_alignment: " SIZE_FORMAT,
_heap_alignment, _gen_alignment));
assert(_gen_alignment % _space_alignment == 0,
err_msg("gen_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT,
_gen_alignment, _space_alignment));
assert(_heap_alignment % _gen_alignment == 0,
err_msg("heap_alignment: " SIZE_FORMAT " not aligned by gen_alignment: " SIZE_FORMAT,
_heap_alignment, _gen_alignment));
// All generational heaps have a youngest gen; handle those flags here
// Make sure the heap is large enough for two generations
uintx smallest_new_size = young_gen_size_lower_bound();
uintx smallest_heap_size = align_size_up(smallest_new_size + align_size_up(_space_alignment, _gen_alignment),
_heap_alignment);
if (MaxHeapSize < smallest_heap_size) {
FLAG_SET_ERGO(uintx, MaxHeapSize, smallest_heap_size);
_max_heap_byte_size = MaxHeapSize;
}
// If needed, synchronize _min_heap_byte size and _initial_heap_byte_size
if (_min_heap_byte_size < smallest_heap_size) {
_min_heap_byte_size = smallest_heap_size;
if (InitialHeapSize < _min_heap_byte_size) {
FLAG_SET_ERGO(uintx, InitialHeapSize, smallest_heap_size);
_initial_heap_byte_size = smallest_heap_size;
}
}
// Now take the actual NewSize into account. We will silently increase NewSize
// if the user specified a smaller value.
smallest_new_size = MAX2(smallest_new_size, (uintx)align_size_down(NewSize, _gen_alignment));
if (smallest_new_size != NewSize) {
FLAG_SET_ERGO(uintx, NewSize, smallest_new_size);
}
_initial_gen0_size = NewSize;
if (!FLAG_IS_DEFAULT(MaxNewSize)) {
uintx min_new_size = MAX2(_gen_alignment, _min_gen0_size);
if (MaxNewSize >= MaxHeapSize) {
// Make sure there is room for an old generation
uintx smaller_max_new_size = MaxHeapSize - _gen_alignment;
if (FLAG_IS_CMDLINE(MaxNewSize)) {
warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or greater than the entire "
"heap (" SIZE_FORMAT "k). A new max generation size of " SIZE_FORMAT "k will be used.",
MaxNewSize/K, MaxHeapSize/K, smaller_max_new_size/K);
}
FLAG_SET_ERGO(uintx, MaxNewSize, smaller_max_new_size);
if (NewSize > MaxNewSize) {
FLAG_SET_ERGO(uintx, NewSize, MaxNewSize);
_initial_gen0_size = NewSize;
}
} else if (MaxNewSize < min_new_size) {
FLAG_SET_ERGO(uintx, MaxNewSize, min_new_size);
} else if (!is_size_aligned(MaxNewSize, _gen_alignment)) {
FLAG_SET_ERGO(uintx, MaxNewSize, align_size_down(MaxNewSize, _gen_alignment));
}
_max_gen0_size = MaxNewSize;
}
if (NewSize > MaxNewSize) {
// At this point this should only happen if the user specifies a large NewSize and/or
// a small (but not too small) MaxNewSize.
if (FLAG_IS_CMDLINE(MaxNewSize)) {
warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). "
"A new max generation size of " SIZE_FORMAT "k will be used.",
NewSize/K, MaxNewSize/K, NewSize/K);
}
FLAG_SET_ERGO(uintx, MaxNewSize, NewSize);
_max_gen0_size = MaxNewSize;
}
if (SurvivorRatio < 1 || NewRatio < 1) {
vm_exit_during_initialization("Invalid young gen ratio specified");
}
DEBUG_ONLY(GenCollectorPolicy::assert_flags();)
}
void TwoGenerationCollectorPolicy::initialize_flags() {
GenCollectorPolicy::initialize_flags();
if (!is_size_aligned(OldSize, _gen_alignment)) {
FLAG_SET_ERGO(uintx, OldSize, align_size_down(OldSize, _gen_alignment));
}
if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(MaxHeapSize)) {
// NewRatio will be used later to set the young generation size so we use
// it to calculate how big the heap should be based on the requested OldSize
// and NewRatio.
assert(NewRatio > 0, "NewRatio should have been set up earlier");
size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1);
calculated_heapsize = align_size_up(calculated_heapsize, _heap_alignment);
FLAG_SET_ERGO(uintx, MaxHeapSize, calculated_heapsize);
_max_heap_byte_size = MaxHeapSize;
FLAG_SET_ERGO(uintx, InitialHeapSize, calculated_heapsize);
_initial_heap_byte_size = InitialHeapSize;
}
// adjust max heap size if necessary
if (NewSize + OldSize > MaxHeapSize) {
if (_max_heap_size_cmdline) {
// somebody set a maximum heap size with the intention that we should not
// exceed it. Adjust New/OldSize as necessary.
uintx calculated_size = NewSize + OldSize;
double shrink_factor = (double) MaxHeapSize / calculated_size;
uintx smaller_new_size = align_size_down((uintx)(NewSize * shrink_factor), _gen_alignment);
FLAG_SET_ERGO(uintx, NewSize, MAX2(young_gen_size_lower_bound(), smaller_new_size));
_initial_gen0_size = NewSize;
// OldSize is already aligned because above we aligned MaxHeapSize to
// _heap_alignment, and we just made sure that NewSize is aligned to
// _gen_alignment. In initialize_flags() we verified that _heap_alignment
// is a multiple of _gen_alignment.
FLAG_SET_ERGO(uintx, OldSize, MaxHeapSize - NewSize);
} else {
FLAG_SET_ERGO(uintx, MaxHeapSize, align_size_up(NewSize + OldSize, _heap_alignment));
_max_heap_byte_size = MaxHeapSize;
}
}
always_do_update_barrier = UseConcMarkSweepGC;
DEBUG_ONLY(TwoGenerationCollectorPolicy::assert_flags();)
}
// Values set on the command line win over any ergonomically
// set command line parameters.
// Ergonomic choice of parameters are done before this
// method is called. Values for command line parameters such as NewSize
// and MaxNewSize feed those ergonomic choices into this method.
// This method makes the final generation sizings consistent with
// themselves and with overall heap sizings.
// In the absence of explicitly set command line flags, policies
// such as the use of NewRatio are used to size the generation.
void GenCollectorPolicy::initialize_size_info() {
CollectorPolicy::initialize_size_info();
// _space_alignment is used for alignment within a generation.
// There is additional alignment done down stream for some
// collectors that sometimes causes unwanted rounding up of
// generations sizes.
// Determine maximum size of gen0
size_t max_new_size = 0;
if (!FLAG_IS_DEFAULT(MaxNewSize)) {
max_new_size = MaxNewSize;
} else {
max_new_size = scale_by_NewRatio_aligned(_max_heap_byte_size);
// Bound the maximum size by NewSize below (since it historically
// would have been NewSize and because the NewRatio calculation could
// yield a size that is too small) and bound it by MaxNewSize above.
// Ergonomics plays here by previously calculating the desired
// NewSize and MaxNewSize.
max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
}
assert(max_new_size > 0, "All paths should set max_new_size");
// Given the maximum gen0 size, determine the initial and
// minimum gen0 sizes.
if (_max_heap_byte_size == _min_heap_byte_size) {
// The maximum and minimum heap sizes are the same so
// the generations minimum and initial must be the
// same as its maximum.
_min_gen0_size = max_new_size;
_initial_gen0_size = max_new_size;
_max_gen0_size = max_new_size;
} else {
size_t desired_new_size = 0;
if (!FLAG_IS_DEFAULT(NewSize)) {
// If NewSize is set ergonomically (for example by cms), it
// would make sense to use it. If it is used, also use it
// to set the initial size. Although there is no reason
// the minimum size and the initial size have to be the same,
// the current implementation gets into trouble during the calculation
// of the tenured generation sizes if they are different.
// Note that this makes the initial size and the minimum size
// generally small compared to the NewRatio calculation.
_min_gen0_size = NewSize;
desired_new_size = NewSize;
max_new_size = MAX2(max_new_size, NewSize);
} else {
// For the case where NewSize is the default, use NewRatio
// to size the minimum and initial generation sizes.
// Use the default NewSize as the floor for these values. If
// NewRatio is overly large, the resulting sizes can be too
// small.
_min_gen0_size = MAX2(scale_by_NewRatio_aligned(_min_heap_byte_size), NewSize);
desired_new_size =
MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize);
}
assert(_min_gen0_size > 0, "Sanity check");
_initial_gen0_size = desired_new_size;
_max_gen0_size = max_new_size;
// At this point the desirable initial and minimum sizes have been
// determined without regard to the maximum sizes.
// Bound the sizes by the corresponding overall heap sizes.
_min_gen0_size = bound_minus_alignment(_min_gen0_size, _min_heap_byte_size);
_initial_gen0_size = bound_minus_alignment(_initial_gen0_size, _initial_heap_byte_size);
_max_gen0_size = bound_minus_alignment(_max_gen0_size, _max_heap_byte_size);
// At this point all three sizes have been checked against the
// maximum sizes but have not been checked for consistency
// among the three.
// Final check min <= initial <= max
_min_gen0_size = MIN2(_min_gen0_size, _max_gen0_size);
_initial_gen0_size = MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size);
_min_gen0_size = MIN2(_min_gen0_size, _initial_gen0_size);
}
// Write back to flags if necessary
if (NewSize != _initial_gen0_size) {
FLAG_SET_ERGO(uintx, NewSize, _initial_gen0_size);
}
if (MaxNewSize != _max_gen0_size) {
FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size);
}
if (PrintGCDetails && Verbose) {
gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
_min_gen0_size, _initial_gen0_size, _max_gen0_size);
}
DEBUG_ONLY(GenCollectorPolicy::assert_size_info();)
}
// Call this method during the sizing of the gen1 to make
// adjustments to gen0 because of gen1 sizing policy. gen0 initially has
// the most freedom in sizing because it is done before the
// policy for gen1 is applied. Once gen1 policies have been applied,
// there may be conflicts in the shape of the heap and this method
// is used to make the needed adjustments. The application of the
// policies could be more sophisticated (iterative for example) but
// keeping it simple also seems a worthwhile goal.
bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
size_t* gen1_size_ptr,
const size_t heap_size) {
bool result = false;
if ((*gen0_size_ptr + *gen1_size_ptr) > heap_size) {
uintx smallest_new_size = young_gen_size_lower_bound();
if ((heap_size < (*gen0_size_ptr + _min_gen1_size)) &&
(heap_size >= _min_gen1_size + smallest_new_size)) {
// Adjust gen0 down to accommodate _min_gen1_size
*gen0_size_ptr = align_size_down_bounded(heap_size - _min_gen1_size, _gen_alignment);
result = true;
} else {
*gen1_size_ptr = align_size_down_bounded(heap_size - *gen0_size_ptr, _gen_alignment);
}
}
return result;
}
// Minimum sizes of the generations may be different than
// the initial sizes. An inconsistently is permitted here
// in the total size that can be specified explicitly by
// command line specification of OldSize and NewSize and
// also a command line specification of -Xms. Issue a warning
// but allow the values to pass.
void TwoGenerationCollectorPolicy::initialize_size_info() {
GenCollectorPolicy::initialize_size_info();
// At this point the minimum, initial and maximum sizes
// of the overall heap and of gen0 have been determined.
// The maximum gen1 size can be determined from the maximum gen0
// and maximum heap size since no explicit flags exits
// for setting the gen1 maximum.
_max_gen1_size = MAX2(_max_heap_byte_size - _max_gen0_size, _gen_alignment);
// If no explicit command line flag has been set for the
// gen1 size, use what is left for gen1.
if (!FLAG_IS_CMDLINE(OldSize)) {
// The user has not specified any value but the ergonomics
// may have chosen a value (which may or may not be consistent
// with the overall heap size). In either case make
// the minimum, maximum and initial sizes consistent
// with the gen0 sizes and the overall heap sizes.
_min_gen1_size = MAX2(_min_heap_byte_size - _min_gen0_size, _gen_alignment);
_initial_gen1_size = MAX2(_initial_heap_byte_size - _initial_gen0_size, _gen_alignment);
// _max_gen1_size has already been made consistent above
FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
} else {
// It's been explicitly set on the command line. Use the
// OldSize and then determine the consequences.
_min_gen1_size = MIN2(OldSize, _min_heap_byte_size - _min_gen0_size);
_initial_gen1_size = OldSize;
// If the user has explicitly set an OldSize that is inconsistent
// with other command line flags, issue a warning.
// The generation minimums and the overall heap mimimum should
// be within one generation alignment.
if ((_min_gen1_size + _min_gen0_size + _gen_alignment) < _min_heap_byte_size) {
warning("Inconsistency between minimum heap size and minimum "
"generation sizes: using minimum heap = " SIZE_FORMAT,
_min_heap_byte_size);
}
if (OldSize > _max_gen1_size) {
warning("Inconsistency between maximum heap size and maximum "
"generation sizes: using maximum heap = " SIZE_FORMAT
" -XX:OldSize flag is being ignored",
_max_heap_byte_size);
}
// If there is an inconsistency between the OldSize and the minimum and/or
// initial size of gen0, since OldSize was explicitly set, OldSize wins.
if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size, _min_heap_byte_size)) {
if (PrintGCDetails && Verbose) {
gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
_min_gen0_size, _initial_gen0_size, _max_gen0_size);
}
}
// Initial size
if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
_initial_heap_byte_size)) {
if (PrintGCDetails && Verbose) {
gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 "
SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT,
_min_gen0_size, _initial_gen0_size, _max_gen0_size);
}
}
}
// Enforce the maximum gen1 size.
_min_gen1_size = MIN2(_min_gen1_size, _max_gen1_size);
// Check that min gen1 <= initial gen1 <= max gen1
_initial_gen1_size = MAX2(_initial_gen1_size, _min_gen1_size);
_initial_gen1_size = MIN2(_initial_gen1_size, _max_gen1_size);
// Write back to flags if necessary
if (NewSize != _initial_gen0_size) {
FLAG_SET_ERGO(uintx, NewSize, _initial_gen0_size);
}
if (MaxNewSize != _max_gen0_size) {
FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size);
}
if (OldSize != _initial_gen1_size) {
FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size);
}
if (PrintGCDetails && Verbose) {
gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 "
SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT,
_min_gen1_size, _initial_gen1_size, _max_gen1_size);
}
DEBUG_ONLY(TwoGenerationCollectorPolicy::assert_size_info();)
}
HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
bool is_tlab,
bool* gc_overhead_limit_was_exceeded) {
GenCollectedHeap *gch = GenCollectedHeap::heap();
debug_only(gch->check_for_valid_allocation_state());
assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
// In general gc_overhead_limit_was_exceeded should be false so
// set it so here and reset it to true only if the gc time
// limit is being exceeded as checked below.
*gc_overhead_limit_was_exceeded = false;
HeapWord* result = NULL;
// Loop until the allocation is satisified,
// or unsatisfied after GC.
for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) {
HandleMark hm; // discard any handles allocated in each iteration
// First allocation attempt is lock-free.
Generation *gen0 = gch->get_gen(0);
assert(gen0->supports_inline_contig_alloc(),
"Otherwise, must do alloc within heap lock");
if (gen0->should_allocate(size, is_tlab)) {
result = gen0->par_allocate(size, is_tlab);
if (result != NULL) {
assert(gch->is_in_reserved(result), "result not in heap");
return result;
}
}
unsigned int gc_count_before; // read inside the Heap_lock locked region
{
MutexLocker ml(Heap_lock);
if (PrintGC && Verbose) {
gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
" attempting locked slow path allocation");
}
// Note that only large objects get a shot at being
// allocated in later generations.
bool first_only = ! should_try_older_generation_allocation(size);
result = gch->attempt_allocation(size, is_tlab, first_only);
if (result != NULL) {
assert(gch->is_in_reserved(result), "result not in heap");
return result;
}
if (GC_locker::is_active_and_needs_gc()) {
if (is_tlab) {
return NULL; // Caller will retry allocating individual object
}
if (!gch->is_maximal_no_gc()) {
// Try and expand heap to satisfy request
result = expand_heap_and_allocate(size, is_tlab);
// result could be null if we are out of space
if (result != NULL) {
return result;
}
}
if (gclocker_stalled_count > GCLockerRetryAllocationCount) {
return NULL; // we didn't get to do a GC and we didn't get any memory
}
// If this thread is not in a jni critical section, we stall
// the requestor until the critical section has cleared and
// GC allowed. When the critical section clears, a GC is
// initiated by the last thread exiting the critical section; so
// we retry the allocation sequence from the beginning of the loop,
// rather than causing more, now probably unnecessary, GC attempts.
JavaThread* jthr = JavaThread::current();
if (!jthr->in_critical()) {
MutexUnlocker mul(Heap_lock);
// Wait for JNI critical section to be exited
GC_locker::stall_until_clear();
gclocker_stalled_count += 1;
continue;
} else {
if (CheckJNICalls) {
fatal("Possible deadlock due to allocating while"
" in jni critical section");
}
return NULL;
}
}
// Read the gc count while the heap lock is held.
gc_count_before = Universe::heap()->total_collections();
}
VM_GenCollectForAllocation op(size, is_tlab, gc_count_before);
VMThread::execute(&op);
if (op.prologue_succeeded()) {
result = op.result();
if (op.gc_locked()) {
assert(result == NULL, "must be NULL if gc_locked() is true");
continue; // retry and/or stall as necessary
}
// Allocation has failed and a collection
// has been done. If the gc time limit was exceeded the
// this time, return NULL so that an out-of-memory
// will be thrown. Clear gc_overhead_limit_exceeded
// so that the overhead exceeded does not persist.
const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
const bool softrefs_clear = all_soft_refs_clear();
if (limit_exceeded && softrefs_clear) {
*gc_overhead_limit_was_exceeded = true;
size_policy()->set_gc_overhead_limit_exceeded(false);
if (op.result() != NULL) {
CollectedHeap::fill_with_object(op.result(), size);
}
return NULL;
}
assert(result == NULL || gch->is_in_reserved(result),
"result not in heap");
return result;
}
// Give a warning if we seem to be looping forever.
if ((QueuedAllocationWarningCount > 0) &&
(try_count % QueuedAllocationWarningCount == 0)) {
warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
" size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
}
}
}
HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
bool is_tlab) {
GenCollectedHeap *gch = GenCollectedHeap::heap();
HeapWord* result = NULL;
for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
Generation *gen = gch->get_gen(i);
if (gen->should_allocate(size, is_tlab)) {
result = gen->expand_and_allocate(size, is_tlab);
}
}
assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
return result;
}
HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
bool is_tlab) {
GenCollectedHeap *gch = GenCollectedHeap::heap();
GCCauseSetter x(gch, GCCause::_allocation_failure);
HeapWord* result = NULL;
assert(size != 0, "Precondition violated");
if (GC_locker::is_active_and_needs_gc()) {
// GC locker is active; instead of a collection we will attempt
// to expand the heap, if there's room for expansion.
if (!gch->is_maximal_no_gc()) {
result = expand_heap_and_allocate(size, is_tlab);
}
return result; // could be null if we are out of space
} else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
// Do an incremental collection.
gch->do_collection(false /* full */,
false /* clear_all_soft_refs */,
size /* size */,
is_tlab /* is_tlab */,
number_of_generations() - 1 /* max_level */);
} else {
if (Verbose && PrintGCDetails) {
gclog_or_tty->print(" :: Trying full because partial may fail :: ");
}
// Try a full collection; see delta for bug id 6266275
// for the original code and why this has been simplified
// with from-space allocation criteria modified and
// such allocation moved out of the safepoint path.
gch->do_collection(true /* full */,
false /* clear_all_soft_refs */,
size /* size */,
is_tlab /* is_tlab */,
number_of_generations() - 1 /* max_level */);
}
result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
if (result != NULL) {
assert(gch->is_in_reserved(result), "result not in heap");
return result;
}
// OK, collection failed, try expansion.
result = expand_heap_and_allocate(size, is_tlab);
if (result != NULL) {
return result;
}
// If we reach this point, we're really out of memory. Try every trick
// we can to reclaim memory. Force collection of soft references. Force
// a complete compaction of the heap. Any additional methods for finding
// free memory should be here, especially if they are expensive. If this
// attempt fails, an OOM exception will be thrown.
{
UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
gch->do_collection(true /* full */,
true /* clear_all_soft_refs */,
size /* size */,
is_tlab /* is_tlab */,
number_of_generations() - 1 /* max_level */);
}
result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
if (result != NULL) {
assert(gch->is_in_reserved(result), "result not in heap");
return result;
}
assert(!should_clear_all_soft_refs(),
"Flag should have been handled and cleared prior to this point");
// What else? We might try synchronous finalization later. If the total
// space available is large enough for the allocation, then a more
// complete compaction phase than we've tried so far might be
// appropriate.
return NULL;
}
MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
ClassLoaderData* loader_data,
size_t word_size,
Metaspace::MetadataType mdtype) {
uint loop_count = 0;
uint gc_count = 0;
uint full_gc_count = 0;
assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
do {
MetaWord* result = NULL;
if (GC_locker::is_active_and_needs_gc()) {
// If the GC_locker is active, just expand and allocate.
// If that does not succeed, wait if this thread is not
// in a critical section itself.
result =
loader_data->metaspace_non_null()->expand_and_allocate(word_size,
mdtype);
if (result != NULL) {
return result;
}
JavaThread* jthr = JavaThread::current();
if (!jthr->in_critical()) {
// Wait for JNI critical section to be exited
GC_locker::stall_until_clear();
// The GC invoked by the last thread leaving the critical
// section will be a young collection and a full collection
// is (currently) needed for unloading classes so continue
// to the next iteration to get a full GC.
continue;
} else {
if (CheckJNICalls) {
fatal("Possible deadlock due to allocating while"
" in jni critical section");
}
return NULL;
}
}
{ // Need lock to get self consistent gc_count's
MutexLocker ml(Heap_lock);
gc_count = Universe::heap()->total_collections();
full_gc_count = Universe::heap()->total_full_collections();
}
// Generate a VM operation
VM_CollectForMetadataAllocation op(loader_data,
word_size,
mdtype,
gc_count,
full_gc_count,
GCCause::_metadata_GC_threshold);
VMThread::execute(&op);
// If GC was locked out, try again. Check
// before checking success because the prologue
// could have succeeded and the GC still have
// been locked out.
if (op.gc_locked()) {
continue;
}
if (op.prologue_succeeded()) {
return op.result();
}
loop_count++;
if ((QueuedAllocationWarningCount > 0) &&
(loop_count % QueuedAllocationWarningCount == 0)) {
warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
" size=%d", loop_count, word_size);
}
} while (true); // Until a GC is done
}
// Return true if any of the following is true:
// . the allocation won't fit into the current young gen heap
// . gc locker is occupied (jni critical section)
// . heap memory is tight -- the most recent previous collection
// was a full collection because a partial collection (would
// have) failed and is likely to fail again
bool GenCollectorPolicy::should_try_older_generation_allocation(
size_t word_size) const {
GenCollectedHeap* gch = GenCollectedHeap::heap();
size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
return (word_size > heap_word_size(gen0_capacity))
|| GC_locker::is_active_and_needs_gc()
|| gch->incremental_collection_failed();
}
//
// MarkSweepPolicy methods
//
void MarkSweepPolicy::initialize_alignments() {
_space_alignment = _gen_alignment = (uintx)Generation::GenGrain;
_heap_alignment = compute_heap_alignment();
}
void MarkSweepPolicy::initialize_generations() {
_generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL);
if (_generations == NULL) {
vm_exit_during_initialization("Unable to allocate gen spec");
}
if (UseParNewGC) {
_generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
} else {
_generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
}
_generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
if (_generations[0] == NULL || _generations[1] == NULL) {
vm_exit_during_initialization("Unable to allocate gen spec");
}
}
void MarkSweepPolicy::initialize_gc_policy_counters() {
// initialize the policy counters - 2 collectors, 3 generations
if (UseParNewGC) {
_gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
} else {
_gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
}
}
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