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/shenandoahCollectionSet.hpp" 29 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 30 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp" 31 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp" 32 #include "gc/shenandoah/shenandoahUtils.hpp" 33 #include "runtime/atomic.hpp" 34 #include "nmt/memTracker.hpp" 35 #include "utilities/copy.hpp" 36 37 ShenandoahCollectionSet::ShenandoahCollectionSet(ShenandoahHeap* heap, ReservedSpace space, char* heap_base) : 38 _map_size(heap->num_regions()), 39 _region_size_bytes_shift(ShenandoahHeapRegion::region_size_bytes_shift()), 40 _map_space(space), 41 _cset_map(_map_space.base() + ((uintx)heap_base >> _region_size_bytes_shift)), 42 _biased_cset_map(_map_space.base()), 43 _heap(heap), 44 _has_old_regions(false), 45 _garbage(0), 46 _used(0), 47 _live(0), 48 _region_count(0), 49 _old_garbage(0), 50 _preselected_regions(nullptr), 51 _current_index(0) { 52 53 // The collection set map is reserved to cover the entire heap *and* zero addresses. 54 // This is needed to accept in-cset checks for both heap oops and nulls, freeing 55 // high-performance code from checking for null first. 56 // 57 // Since heap_base can be far away, committing the entire map would waste memory. 58 // Therefore, we only commit the parts that are needed to operate: the heap view, 59 // and the zero page. 60 // 61 // Note: we could instead commit the entire map, and piggyback on OS virtual memory 62 // subsystem for mapping not-yet-written-to pages to a single physical backing page, 63 // but this is not guaranteed, and would confuse NMT and other memory accounting tools. 64 65 MemTracker::record_virtual_memory_type(_map_space.base(), mtGC); 66 67 size_t page_size = os::vm_page_size(); 68 69 if (!_map_space.special()) { 70 // Commit entire pages that cover the heap cset map. 71 char* bot_addr = align_down(_cset_map, page_size); 72 char* top_addr = align_up(_cset_map + _map_size, page_size); 73 os::commit_memory_or_exit(bot_addr, pointer_delta(top_addr, bot_addr, 1), false, 74 "Unable to commit collection set bitmap: heap"); 75 76 // Commit the zero page, if not yet covered by heap cset map. 77 if (bot_addr != _biased_cset_map) { 78 os::commit_memory_or_exit(_biased_cset_map, page_size, false, 79 "Unable to commit collection set bitmap: zero page"); 80 } 81 } 82 83 Copy::zero_to_bytes(_cset_map, _map_size); 84 Copy::zero_to_bytes(_biased_cset_map, page_size); 85 } 86 87 void ShenandoahCollectionSet::add_region(ShenandoahHeapRegion* r) { 88 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 89 assert(Thread::current()->is_VM_thread(), "Must be VMThread"); 90 assert(!is_in(r), "Already in collection set"); 91 assert(!r->is_humongous(), "Only add regular regions to the collection set"); 92 93 _cset_map[r->index()] = 1; 94 size_t live = r->get_live_data_bytes(); 95 size_t garbage = r->garbage(); 96 size_t free = r->free(); 97 if (r->is_young()) { 98 _young_bytes_to_evacuate += live; 99 _young_available_bytes_collected += free; 100 if (ShenandoahHeap::heap()->mode()->is_generational() && r->age() >= ShenandoahHeap::heap()->age_census()->tenuring_threshold()) { 101 _young_bytes_to_promote += live; 102 } 103 } else if (r->is_old()) { 104 _old_bytes_to_evacuate += live; 105 _old_garbage += garbage; 106 } 107 108 _region_count++; 109 _has_old_regions |= r->is_old(); 110 _garbage += garbage; 111 _used += r->used(); 112 _live += live; 113 // Update the region status too. State transition would be checked internally. 114 r->make_cset(); 115 } 116 117 void ShenandoahCollectionSet::clear() { 118 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 119 120 Copy::zero_to_bytes(_cset_map, _map_size); 121 122 #ifdef ASSERT 123 for (size_t index = 0; index < _heap->num_regions(); index ++) { 124 assert (!_heap->get_region(index)->is_cset(), "should have been cleared before"); 125 } 126 #endif 127 128 _garbage = 0; 129 _old_garbage = 0; 130 _used = 0; 131 _live = 0; 132 133 _region_count = 0; 134 _current_index = 0; 135 136 _young_bytes_to_evacuate = 0; 137 _young_bytes_to_promote = 0; 138 _old_bytes_to_evacuate = 0; 139 140 _young_available_bytes_collected = 0; 141 142 _has_old_regions = false; 143 } 144 145 ShenandoahHeapRegion* ShenandoahCollectionSet::claim_next() { 146 // This code is optimized for the case when collection set contains only 147 // a few regions. In this case, it is more constructive to check for is_in 148 // before hitting the (potentially contended) atomic index. 149 150 size_t max = _heap->num_regions(); 151 size_t old = Atomic::load(&_current_index); 152 153 for (size_t index = old; index < max; index++) { 154 if (is_in(index)) { 155 size_t cur = Atomic::cmpxchg(&_current_index, old, index + 1, memory_order_relaxed); 156 assert(cur >= old, "Always move forward"); 157 if (cur == old) { 158 // Successfully moved the claim index, this is our region. 159 return _heap->get_region(index); 160 } else { 161 // Somebody else moved the claim index, restart from there. 162 index = cur - 1; // adjust for loop post-increment 163 old = cur; 164 } 165 } 166 } 167 return nullptr; 168 } 169 170 ShenandoahHeapRegion* ShenandoahCollectionSet::next() { 171 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 172 assert(Thread::current()->is_VM_thread(), "Must be VMThread"); 173 174 size_t max = _heap->num_regions(); 175 for (size_t index = _current_index; index < max; index++) { 176 if (is_in(index)) { 177 _current_index = index + 1; 178 return _heap->get_region(index); 179 } 180 } 181 182 return nullptr; 183 } 184 185 void ShenandoahCollectionSet::print_on(outputStream* out) const { 186 out->print_cr("Collection Set: Regions: " 187 SIZE_FORMAT ", Garbage: " SIZE_FORMAT "%s, Live: " SIZE_FORMAT "%s, Used: " SIZE_FORMAT "%s", count(), 188 byte_size_in_proper_unit(garbage()), proper_unit_for_byte_size(garbage()), 189 byte_size_in_proper_unit(live()), proper_unit_for_byte_size(live()), 190 byte_size_in_proper_unit(used()), proper_unit_for_byte_size(used())); 191 192 debug_only(size_t regions = 0;) 193 for (size_t index = 0; index < _heap->num_regions(); index ++) { 194 if (is_in(index)) { 195 _heap->get_region(index)->print_on(out); 196 debug_only(regions ++;) 197 } 198 } 199 assert(regions == count(), "Must match"); 200 }