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_young_size, "Discrepancy between NewSize flag and local storage"); assert(MaxNewSize == _max_young_size, "Discrepancy between MaxNewSize flag and local storage"); assert(OldSize == _initial_old_size, "Discrepancy between OldSize flag and local storage"); assert(_min_young_size <= _initial_young_size, "Ergonomics decided on incompatible minimum and initial young gen sizes"); assert(_initial_young_size <= _max_young_size, "Ergonomics decided on incompatible initial and maximum young gen sizes"); assert(_min_young_size % _gen_alignment == 0, "_min_young_size alignment"); assert(_initial_young_size % _gen_alignment == 0, "_initial_young_size alignment"); assert(_max_young_size % _gen_alignment == 0, "_max_young_size alignment"); assert(_min_young_size <= bound_minus_alignment(_min_young_size, _min_heap_byte_size), "Ergonomics made minimum young generation larger than minimum heap"); assert(_initial_young_size <= bound_minus_alignment(_initial_young_size, _initial_heap_byte_size), "Ergonomics made initial young generation larger than initial heap"); assert(_max_young_size <= bound_minus_alignment(_max_young_size, _max_heap_byte_size), "Ergonomics made maximum young generation lager than maximum heap"); assert(_min_old_size <= _initial_old_size, "Ergonomics decided on incompatible minimum and initial old gen sizes"); assert(_initial_old_size <= _max_old_size, "Ergonomics decided on incompatible initial and maximum old gen sizes"); assert(_max_old_size % _gen_alignment == 0, "_max_old_size alignment"); assert(_initial_old_size % _gen_alignment == 0, "_initial_old_size alignment"); assert(_max_heap_byte_size <= (_max_young_size + _max_old_size), "Total maximum heap sizes must be sum of generation maximum sizes"); assert(_min_young_size + _min_old_size <= _min_heap_byte_size, "Minimum generation sizes exceed minimum heap size"); assert(_initial_young_size + _initial_old_size == _initial_heap_byte_size, "Initial generation sizes should match initial heap size"); assert(_max_young_size + _max_old_size == _max_heap_byte_size, "Maximum generation sizes should match maximum heap size"); }
// 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_CMDLINE(NewSize)) { // If NewSize is set on the command line, we must use it as // the initial size and it also makes sense to use it as the // lower limit. _min_gen0_size = NewSize; desired_new_size = NewSize; max_new_size = MAX2(max_new_size, NewSize); } else if (FLAG_IS_ERGO(NewSize)) { // If NewSize is set ergonomically, we should use it as a lower // limit, but use NewRatio to calculate the initial size. _min_gen0_size = NewSize; desired_new_size = MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_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();) }
// 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(); // min_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_CMDLINE(MaxNewSize)) { if (MaxNewSize < min_alignment()) { max_new_size = min_alignment(); } else if (MaxNewSize >= max_heap_byte_size()) { max_new_size = align_size_down(max_heap_byte_size() - min_alignment(), min_alignment()); warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or " "greater than the entire heap (" SIZE_FORMAT "k). A " "new generation size of " SIZE_FORMAT "k will be used.", MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K); } else { max_new_size = align_size_down(MaxNewSize, min_alignment()); } // The case for FLAG_IS_ERGO(MaxNewSize) could be treated // specially at this point to just use an ergonomically set // MaxNewSize to set max_new_size. For cases with small // heaps such a policy often did not work because the MaxNewSize // was larger than the entire heap. The interpretation given // to ergonomically set flags is that the flags are set // by different collectors for their own special needs but // are not allowed to badly shape the heap. This allows the // different collectors to decide what's best for themselves // without having to factor in the overall heap shape. It // can be the case in the future that the collectors would // only make "wise" ergonomics choices and this policy could // just accept those choices. The choices currently made are // not always "wise". } 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, (size_t)NewSize), (size_t)MaxNewSize); } assert(max_new_size > 0, "All paths should set max_new_size"); // Given the maximum gen0 size, determine the initial and // minimum 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. set_min_gen0_size(max_new_size); set_initial_gen0_size(max_new_size); set_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, (size_t) 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()), (size_t) NewSize); desired_new_size = MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()), (size_t) NewSize); } assert(_min_gen0_size > 0, "Sanity check"); set_initial_gen0_size(desired_new_size); set_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. set_min_gen0_size( bound_minus_alignment(_min_gen0_size, min_heap_byte_size())); set_initial_gen0_size( bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size())); set_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 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size)); set_initial_gen0_size( MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size)); set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size)); } if (PrintGCDetails && Verbose) { gclog_or_tty->print_cr("Minimum gen0 " SIZE_FORMAT " Initial gen0 " SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT, min_gen0_size(), initial_gen0_size(), max_gen0_size()); } }
// Minimum sizes of the generations may be different than // the initial sizes. An inconsistency 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 GenCollectorPolicy::initialize_size_info() { CollectorPolicy::initialize_size_info(); _initial_young_size = NewSize; _max_young_size = MaxNewSize; _initial_old_size = OldSize; // Determine maximum size of the young generation. if (FLAG_IS_DEFAULT(MaxNewSize)) { _max_young_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_young_size = MIN2(MAX2(_max_young_size, _initial_young_size), MaxNewSize); } // Given the maximum young size, determine the initial and // minimum young sizes. if (_max_heap_byte_size == _initial_heap_byte_size) { // The maximum and initial heap sizes are the same so the generation's // initial size must be the same as it maximum size. Use NewSize as the // size if set on command line. _max_young_size = FLAG_IS_CMDLINE(NewSize) ? NewSize : _max_young_size; _initial_young_size = _max_young_size; // Also update the minimum size if min == initial == max. if (_max_heap_byte_size == _min_heap_byte_size) { _min_young_size = _max_young_size; } } else { if (FLAG_IS_CMDLINE(NewSize)) { // If NewSize is set on the command line, we should use it as // the initial size, but make sure it is within the heap bounds. _initial_young_size = MIN2(_max_young_size, bound_minus_alignment(NewSize, _initial_heap_byte_size)); _min_young_size = bound_minus_alignment(_initial_young_size, _min_heap_byte_size); } else { // For the case where NewSize is not set on the command line, use // NewRatio to size the initial generation size. Use the current // NewSize as the floor, because if NewRatio is overly large, the resulting // size can be too small. _initial_young_size = MIN2(_max_young_size, MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize)); } } log_trace(gc, heap)("1: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT, _min_young_size, _initial_young_size, _max_young_size); // At this point the minimum, initial and maximum sizes // of the overall heap and of the young generation have been determined. // The maximum old size can be determined from the maximum young // and maximum heap size since no explicit flags exist // for setting the old generation maximum. _max_old_size = MAX2(_max_heap_byte_size - _max_young_size, _gen_alignment); // If no explicit command line flag has been set for the // old generation size, use what is left. 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 young sizes and the overall heap sizes. _min_old_size = _gen_alignment; _initial_old_size = MIN2(_max_old_size, MAX2(_initial_heap_byte_size - _initial_young_size, _min_old_size)); // _max_old_size has already been made consistent above. } else { // OldSize has been explicitly set on the command line. Use it // for the initial size but make sure the minimum allow a young // generation to fit as well. // 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 minimum should // be within one generation alignment. if (_initial_old_size > _max_old_size) { log_warning(gc, ergo)("Inconsistency between maximum heap size and maximum " "generation sizes: using maximum heap = " SIZE_FORMAT ", -XX:OldSize flag is being ignored", _max_heap_byte_size); _initial_old_size = _max_old_size; } _min_old_size = MIN2(_initial_old_size, _min_heap_byte_size - _min_young_size); } // The initial generation sizes should match the initial heap size, // if not issue a warning and resize the generations. This behavior // differs from JDK8 where the generation sizes have higher priority // than the initial heap size. if ((_initial_old_size + _initial_young_size) != _initial_heap_byte_size) { log_warning(gc, ergo)("Inconsistency between generation sizes and heap size, resizing " "the generations to fit the heap."); size_t desired_young_size = _initial_heap_byte_size - _initial_old_size; if (_initial_heap_byte_size < _initial_old_size) { // Old want all memory, use minimum for young and rest for old _initial_young_size = _min_young_size; _initial_old_size = _initial_heap_byte_size - _min_young_size; } else if (desired_young_size > _max_young_size) { // Need to increase both young and old generation _initial_young_size = _max_young_size; _initial_old_size = _initial_heap_byte_size - _max_young_size; } else if (desired_young_size < _min_young_size) { // Need to decrease both young and old generation _initial_young_size = _min_young_size; _initial_old_size = _initial_heap_byte_size - _min_young_size; } else { // The young generation boundaries allow us to only update the // young generation. _initial_young_size = desired_young_size; } log_trace(gc, heap)("2: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT, _min_young_size, _initial_young_size, _max_young_size); } // Write back to flags if necessary. if (NewSize != _initial_young_size) { FLAG_SET_ERGO(size_t, NewSize, _initial_young_size); } if (MaxNewSize != _max_young_size) { FLAG_SET_ERGO(size_t, MaxNewSize, _max_young_size); } if (OldSize != _initial_old_size) { FLAG_SET_ERGO(size_t, OldSize, _initial_old_size); } log_trace(gc, heap)("Minimum old " SIZE_FORMAT " Initial old " SIZE_FORMAT " Maximum old " SIZE_FORMAT, _min_old_size, _initial_old_size, _max_old_size); DEBUG_ONLY(GenCollectorPolicy::assert_size_info();) }
void GenCollectorPolicy::initialize_flags() { CollectorPolicy::initialize_flags(); assert(_gen_alignment != 0, "Generation alignment not set up properly"); assert(_heap_alignment >= _gen_alignment, "heap_alignment: " SIZE_FORMAT " less than gen_alignment: " SIZE_FORMAT, _heap_alignment, _gen_alignment); assert(_gen_alignment % _space_alignment == 0, "gen_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT, _gen_alignment, _space_alignment); assert(_heap_alignment % _gen_alignment == 0, "heap_alignment: " SIZE_FORMAT " not aligned by gen_alignment: " SIZE_FORMAT, _heap_alignment, _gen_alignment); // All generational heaps have a young gen; handle those flags here // Make sure the heap is large enough for two generations size_t smallest_new_size = young_gen_size_lower_bound(); size_t smallest_heap_size = align_size_up(smallest_new_size + old_gen_size_lower_bound(), _heap_alignment); if (MaxHeapSize < smallest_heap_size) { FLAG_SET_ERGO(size_t, 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(size_t, InitialHeapSize, smallest_heap_size); _initial_heap_byte_size = smallest_heap_size; } } // Make sure NewSize allows an old generation to fit even if set on the command line if (FLAG_IS_CMDLINE(NewSize) && NewSize >= _initial_heap_byte_size) { log_warning(gc, ergo)("NewSize was set larger than initial heap size, will use initial heap size."); FLAG_SET_ERGO(size_t, NewSize, bound_minus_alignment(NewSize, _initial_heap_byte_size)); } // Now take the actual NewSize into account. We will silently increase NewSize // if the user specified a smaller or unaligned value. size_t bounded_new_size = bound_minus_alignment(NewSize, MaxHeapSize); bounded_new_size = MAX2(smallest_new_size, (size_t)align_size_down(bounded_new_size, _gen_alignment)); if (bounded_new_size != NewSize) { FLAG_SET_ERGO(size_t, NewSize, bounded_new_size); } _min_young_size = smallest_new_size; _initial_young_size = NewSize; if (!FLAG_IS_DEFAULT(MaxNewSize)) { if (MaxNewSize >= MaxHeapSize) { // Make sure there is room for an old generation size_t smaller_max_new_size = MaxHeapSize - _gen_alignment; if (FLAG_IS_CMDLINE(MaxNewSize)) { log_warning(gc, ergo)("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(size_t, MaxNewSize, smaller_max_new_size); if (NewSize > MaxNewSize) { FLAG_SET_ERGO(size_t, NewSize, MaxNewSize); _initial_young_size = NewSize; } } else if (MaxNewSize < _initial_young_size) { FLAG_SET_ERGO(size_t, MaxNewSize, _initial_young_size); } else if (!is_size_aligned(MaxNewSize, _gen_alignment)) { FLAG_SET_ERGO(size_t, MaxNewSize, align_size_down(MaxNewSize, _gen_alignment)); } _max_young_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)) { log_warning(gc, ergo)("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(size_t, MaxNewSize, NewSize); _max_young_size = MaxNewSize; } if (SurvivorRatio < 1 || NewRatio < 1) { vm_exit_during_initialization("Invalid young gen ratio specified"); } if (OldSize < old_gen_size_lower_bound()) { FLAG_SET_ERGO(size_t, OldSize, old_gen_size_lower_bound()); } if (!is_size_aligned(OldSize, _gen_alignment)) { FLAG_SET_ERGO(size_t, 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(size_t, MaxHeapSize, calculated_heapsize); _max_heap_byte_size = MaxHeapSize; FLAG_SET_ERGO(size_t, InitialHeapSize, calculated_heapsize); _initial_heap_byte_size = InitialHeapSize; } // Adjust NewSize and OldSize or MaxHeapSize to match each other if (NewSize + OldSize > MaxHeapSize) { if (FLAG_IS_CMDLINE(MaxHeapSize)) { // Somebody has set a maximum heap size with the intention that we should not // exceed it. Adjust New/OldSize as necessary. size_t calculated_size = NewSize + OldSize; double shrink_factor = (double) MaxHeapSize / calculated_size; size_t smaller_new_size = align_size_down((size_t)(NewSize * shrink_factor), _gen_alignment); FLAG_SET_ERGO(size_t, NewSize, MAX2(young_gen_size_lower_bound(), smaller_new_size)); _initial_young_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(size_t, OldSize, MaxHeapSize - NewSize); } else { FLAG_SET_ERGO(size_t, MaxHeapSize, align_size_up(NewSize + OldSize, _heap_alignment)); _max_heap_byte_size = MaxHeapSize; } } // Update NewSize, if possible, to avoid sizing the young gen too small when only // OldSize is set on the command line. if (FLAG_IS_CMDLINE(OldSize) && !FLAG_IS_CMDLINE(NewSize)) { if (OldSize < _initial_heap_byte_size) { size_t new_size = _initial_heap_byte_size - OldSize; // Need to compare against the flag value for max since _max_young_size // might not have been set yet. if (new_size >= _min_young_size && new_size <= MaxNewSize) { FLAG_SET_ERGO(size_t, NewSize, new_size); _initial_young_size = NewSize; } } } always_do_update_barrier = UseConcMarkSweepGC; DEBUG_ONLY(GenCollectorPolicy::assert_flags();) }