| /* |
| * Copyright (c) 2018, Red Hat, Inc. All rights reserved. |
| * |
| * 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 |
| * or visit www.oracle.com if you need additional information or have any |
| * questions. |
| * |
| */ |
| |
| #include "precompiled.hpp" |
| |
| #include "gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.hpp" |
| #include "gc/shenandoah/shenandoahCollectionSet.hpp" |
| #include "gc/shenandoah/shenandoahFreeSet.hpp" |
| #include "gc/shenandoah/shenandoahHeap.inline.hpp" |
| #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp" |
| #include "logging/log.hpp" |
| #include "logging/logTag.hpp" |
| #include "utilities/quickSort.hpp" |
| |
| ShenandoahAdaptiveHeuristics::ShenandoahAdaptiveHeuristics() : |
| ShenandoahHeuristics() {} |
| |
| ShenandoahAdaptiveHeuristics::~ShenandoahAdaptiveHeuristics() {} |
| |
| void ShenandoahAdaptiveHeuristics::choose_collection_set_from_regiondata(ShenandoahCollectionSet* cset, |
| RegionData* data, size_t size, |
| size_t actual_free) { |
| size_t garbage_threshold = ShenandoahHeapRegion::region_size_bytes() * ShenandoahGarbageThreshold / 100; |
| |
| // The logic for cset selection in adaptive is as follows: |
| // |
| // 1. We cannot get cset larger than available free space. Otherwise we guarantee OOME |
| // during evacuation, and thus guarantee full GC. In practice, we also want to let |
| // application to allocate something. This is why we limit CSet to some fraction of |
| // available space. In non-overloaded heap, max_cset would contain all plausible candidates |
| // over garbage threshold. |
| // |
| // 2. We should not get cset too low so that free threshold would not be met right |
| // after the cycle. Otherwise we get back-to-back cycles for no reason if heap is |
| // too fragmented. In non-overloaded non-fragmented heap min_garbage would be around zero. |
| // |
| // Therefore, we start by sorting the regions by garbage. Then we unconditionally add the best candidates |
| // before we meet min_garbage. Then we add all candidates that fit with a garbage threshold before |
| // we hit max_cset. When max_cset is hit, we terminate the cset selection. Note that in this scheme, |
| // ShenandoahGarbageThreshold is the soft threshold which would be ignored until min_garbage is hit. |
| |
| size_t capacity = ShenandoahHeap::heap()->soft_max_capacity(); |
| size_t max_cset = (size_t)((1.0 * capacity / 100 * ShenandoahEvacReserve) / ShenandoahEvacWaste); |
| size_t free_target = (capacity / 100 * ShenandoahMinFreeThreshold) + max_cset; |
| size_t min_garbage = (free_target > actual_free ? (free_target - actual_free) : 0); |
| |
| log_info(gc, ergo)("Adaptive CSet Selection. Target Free: " SIZE_FORMAT "%s, Actual Free: " |
| SIZE_FORMAT "%s, Max CSet: " SIZE_FORMAT "%s, Min Garbage: " SIZE_FORMAT "%s", |
| byte_size_in_proper_unit(free_target), proper_unit_for_byte_size(free_target), |
| byte_size_in_proper_unit(actual_free), proper_unit_for_byte_size(actual_free), |
| byte_size_in_proper_unit(max_cset), proper_unit_for_byte_size(max_cset), |
| byte_size_in_proper_unit(min_garbage), proper_unit_for_byte_size(min_garbage)); |
| |
| // Better select garbage-first regions |
| QuickSort::sort<RegionData>(data, (int)size, compare_by_garbage, false); |
| |
| size_t cur_cset = 0; |
| size_t cur_garbage = 0; |
| |
| for (size_t idx = 0; idx < size; idx++) { |
| ShenandoahHeapRegion* r = data[idx]._region; |
| |
| size_t new_cset = cur_cset + r->get_live_data_bytes(); |
| size_t new_garbage = cur_garbage + r->garbage(); |
| |
| if (new_cset > max_cset) { |
| break; |
| } |
| |
| if ((new_garbage < min_garbage) || (r->garbage() > garbage_threshold)) { |
| cset->add_region(r); |
| cur_cset = new_cset; |
| cur_garbage = new_garbage; |
| } |
| } |
| } |
| |
| void ShenandoahAdaptiveHeuristics::record_cycle_start() { |
| ShenandoahHeuristics::record_cycle_start(); |
| } |
| |
| bool ShenandoahAdaptiveHeuristics::should_start_gc() const { |
| ShenandoahHeap* heap = ShenandoahHeap::heap(); |
| size_t max_capacity = heap->max_capacity(); |
| size_t capacity = heap->soft_max_capacity(); |
| size_t available = heap->free_set()->available(); |
| |
| // Make sure the code below treats available without the soft tail. |
| size_t soft_tail = max_capacity - capacity; |
| available = (available > soft_tail) ? (available - soft_tail) : 0; |
| |
| // Check if we are falling below the worst limit, time to trigger the GC, regardless of |
| // anything else. |
| size_t min_threshold = capacity / 100 * ShenandoahMinFreeThreshold; |
| if (available < min_threshold) { |
| log_info(gc)("Trigger: Free (" SIZE_FORMAT "%s) is below minimum threshold (" SIZE_FORMAT "%s)", |
| byte_size_in_proper_unit(available), proper_unit_for_byte_size(available), |
| byte_size_in_proper_unit(min_threshold), proper_unit_for_byte_size(min_threshold)); |
| return true; |
| } |
| |
| // Check if are need to learn a bit about the application |
| const size_t max_learn = ShenandoahLearningSteps; |
| if (_gc_times_learned < max_learn) { |
| size_t init_threshold = capacity / 100 * ShenandoahInitFreeThreshold; |
| if (available < init_threshold) { |
| log_info(gc)("Trigger: Learning " SIZE_FORMAT " of " SIZE_FORMAT ". Free (" SIZE_FORMAT "%s) is below initial threshold (" SIZE_FORMAT "%s)", |
| _gc_times_learned + 1, max_learn, |
| byte_size_in_proper_unit(available), proper_unit_for_byte_size(available), |
| byte_size_in_proper_unit(init_threshold), proper_unit_for_byte_size(init_threshold)); |
| return true; |
| } |
| } |
| |
| // Check if allocation headroom is still okay. This also factors in: |
| // 1. Some space to absorb allocation spikes |
| // 2. Accumulated penalties from Degenerated and Full GC |
| |
| size_t allocation_headroom = available; |
| |
| size_t spike_headroom = capacity / 100 * ShenandoahAllocSpikeFactor; |
| size_t penalties = capacity / 100 * _gc_time_penalties; |
| |
| allocation_headroom -= MIN2(allocation_headroom, spike_headroom); |
| allocation_headroom -= MIN2(allocation_headroom, penalties); |
| |
| // TODO: Allocation rate is way too averaged to be useful during state changes |
| |
| double average_gc = _gc_time_history->avg(); |
| double time_since_last = time_since_last_gc(); |
| double allocation_rate = heap->bytes_allocated_since_gc_start() / time_since_last; |
| |
| if (average_gc > allocation_headroom / allocation_rate) { |
| log_info(gc)("Trigger: Average GC time (%.2f ms) is above the time for allocation rate (%.0f %sB/s) to deplete free headroom (" SIZE_FORMAT "%s)", |
| average_gc * 1000, |
| byte_size_in_proper_unit(allocation_rate), proper_unit_for_byte_size(allocation_rate), |
| byte_size_in_proper_unit(allocation_headroom), proper_unit_for_byte_size(allocation_headroom)); |
| log_info(gc, ergo)("Free headroom: " SIZE_FORMAT "%s (free) - " SIZE_FORMAT "%s (spike) - " SIZE_FORMAT "%s (penalties) = " SIZE_FORMAT "%s", |
| byte_size_in_proper_unit(available), proper_unit_for_byte_size(available), |
| byte_size_in_proper_unit(spike_headroom), proper_unit_for_byte_size(spike_headroom), |
| byte_size_in_proper_unit(penalties), proper_unit_for_byte_size(penalties), |
| byte_size_in_proper_unit(allocation_headroom), proper_unit_for_byte_size(allocation_headroom)); |
| return true; |
| } |
| |
| return ShenandoahHeuristics::should_start_gc(); |
| } |