1 /* 2 * Copyright (c) 2016, 2023, Red Hat, Inc. All rights reserved. 3 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13 * version 2 for more details (a copy is included in the LICENSE file that 14 * accompanied this code). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 * 24 */ 25 26 #include "precompiled.hpp" 27 28 #include "gc/shenandoah/shenandoahAgeCensus.hpp" 29 #include "gc/shenandoah/shenandoahCollectionSet.hpp" 30 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 31 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp" 32 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp" 33 #include "gc/shenandoah/shenandoahUtils.hpp" 34 #include "runtime/atomic.hpp" 35 #include "services/memTracker.hpp" 36 #include "utilities/copy.hpp" 37 38 ShenandoahCollectionSet::ShenandoahCollectionSet(ShenandoahHeap* heap, ReservedSpace space, char* heap_base) : 39 _map_size(heap->num_regions()), 40 _region_size_bytes_shift(ShenandoahHeapRegion::region_size_bytes_shift()), 41 _map_space(space), 42 _cset_map(_map_space.base() + ((uintx)heap_base >> _region_size_bytes_shift)), 43 _biased_cset_map(_map_space.base()), 44 _heap(heap), 45 _has_old_regions(false), 46 _garbage(0), 47 _used(0), 48 _live(0), 49 _region_count(0), 50 _old_garbage(0), 51 _preselected_regions(nullptr), 52 _current_index(0) { 53 54 // The collection set map is reserved to cover the entire heap *and* zero addresses. 55 // This is needed to accept in-cset checks for both heap oops and nulls, freeing 56 // high-performance code from checking for null first. 57 // 58 // Since heap_base can be far away, committing the entire map would waste memory. 59 // Therefore, we only commit the parts that are needed to operate: the heap view, 60 // and the zero page. 61 // 62 // Note: we could instead commit the entire map, and piggyback on OS virtual memory 63 // subsystem for mapping not-yet-written-to pages to a single physical backing page, 64 // but this is not guaranteed, and would confuse NMT and other memory accounting tools. 65 66 MemTracker::record_virtual_memory_type(_map_space.base(), mtGC); 67 68 size_t page_size = os::vm_page_size(); 69 70 if (!_map_space.special()) { 71 // Commit entire pages that cover the heap cset map. 72 char* bot_addr = align_down(_cset_map, page_size); 73 char* top_addr = align_up(_cset_map + _map_size, page_size); 74 os::commit_memory_or_exit(bot_addr, pointer_delta(top_addr, bot_addr, 1), false, 75 "Unable to commit collection set bitmap: heap"); 76 77 // Commit the zero page, if not yet covered by heap cset map. 78 if (bot_addr != _biased_cset_map) { 79 os::commit_memory_or_exit(_biased_cset_map, page_size, false, 80 "Unable to commit collection set bitmap: zero page"); 81 } 82 } 83 84 Copy::zero_to_bytes(_cset_map, _map_size); 85 Copy::zero_to_bytes(_biased_cset_map, page_size); 86 } 87 88 void ShenandoahCollectionSet::add_region(ShenandoahHeapRegion* r) { 89 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 90 assert(Thread::current()->is_VM_thread(), "Must be VMThread"); 91 assert(!is_in(r), "Already in collection set"); 92 assert(!r->is_humongous(), "Only add regular regions to the collection set"); 93 94 _cset_map[r->index()] = 1; 95 size_t live = r->get_live_data_bytes(); 96 size_t garbage = r->garbage(); 97 size_t free = r->free(); 98 if (r->is_young()) { 99 _young_bytes_to_evacuate += live; 100 _young_available_bytes_collected += free; 101 if (ShenandoahHeap::heap()->mode()->is_generational() && r->age() >= ShenandoahGenerationalHeap::heap()->age_census()->tenuring_threshold()) { 102 _young_bytes_to_promote += live; 103 } 104 } else if (r->is_old()) { 105 _old_bytes_to_evacuate += live; 106 _old_garbage += garbage; 107 } 108 109 _region_count++; 110 _has_old_regions |= r->is_old(); 111 _garbage += garbage; 112 _used += r->used(); 113 _live += live; 114 // Update the region status too. State transition would be checked internally. 115 r->make_cset(); 116 } 117 118 void ShenandoahCollectionSet::clear() { 119 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 120 121 Copy::zero_to_bytes(_cset_map, _map_size); 122 123 #ifdef ASSERT 124 for (size_t index = 0; index < _heap->num_regions(); index ++) { 125 assert (!_heap->get_region(index)->is_cset(), "should have been cleared before"); 126 } 127 #endif 128 129 _garbage = 0; 130 _old_garbage = 0; 131 _used = 0; 132 _live = 0; 133 134 _region_count = 0; 135 _current_index = 0; 136 137 _young_bytes_to_evacuate = 0; 138 _young_bytes_to_promote = 0; 139 _old_bytes_to_evacuate = 0; 140 141 _young_available_bytes_collected = 0; 142 143 _has_old_regions = false; 144 } 145 146 ShenandoahHeapRegion* ShenandoahCollectionSet::claim_next() { 147 // This code is optimized for the case when collection set contains only 148 // a few regions. In this case, it is more constructive to check for is_in 149 // before hitting the (potentially contended) atomic index. 150 151 size_t max = _heap->num_regions(); 152 size_t old = Atomic::load(&_current_index); 153 154 for (size_t index = old; index < max; index++) { 155 if (is_in(index)) { 156 size_t cur = Atomic::cmpxchg(&_current_index, old, index + 1, memory_order_relaxed); 157 assert(cur >= old, "Always move forward"); 158 if (cur == old) { 159 // Successfully moved the claim index, this is our region. 160 return _heap->get_region(index); 161 } else { 162 // Somebody else moved the claim index, restart from there. 163 index = cur - 1; // adjust for loop post-increment 164 old = cur; 165 } 166 } 167 } 168 return nullptr; 169 } 170 171 ShenandoahHeapRegion* ShenandoahCollectionSet::next() { 172 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 173 assert(Thread::current()->is_VM_thread(), "Must be VMThread"); 174 175 size_t max = _heap->num_regions(); 176 for (size_t index = _current_index; index < max; index++) { 177 if (is_in(index)) { 178 _current_index = index + 1; 179 return _heap->get_region(index); 180 } 181 } 182 183 return nullptr; 184 } 185 186 void ShenandoahCollectionSet::print_on(outputStream* out) const { 187 out->print_cr("Collection Set: Regions: " 188 SIZE_FORMAT ", Garbage: " SIZE_FORMAT "%s, Live: " SIZE_FORMAT "%s, Used: " SIZE_FORMAT "%s", count(), 189 byte_size_in_proper_unit(garbage()), proper_unit_for_byte_size(garbage()), 190 byte_size_in_proper_unit(live()), proper_unit_for_byte_size(live()), 191 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used())); 192 193 debug_only(size_t regions = 0;) 194 for (size_t index = 0; index < _heap->num_regions(); index ++) { 195 if (is_in(index)) { 196 _heap->get_region(index)->print_on(out); 197 debug_only(regions ++;) 198 } 199 } 200 assert(regions == count(), "Must match"); 201 } --- EOF ---