1 /* 2 * Copyright (c) 2016, 2019, Red Hat, Inc. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 27 #include "gc/shenandoah/shenandoahCollectionSet.hpp" 28 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 29 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp" 30 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp" 31 #include "gc/shenandoah/shenandoahUtils.hpp" 32 #include "runtime/atomic.hpp" 33 #include "services/memTracker.hpp" 34 #include "utilities/copy.hpp" 35 36 ShenandoahCollectionSet::ShenandoahCollectionSet(ShenandoahHeap* heap, ReservedSpace space, char* heap_base) : 37 _map_size(heap->num_regions()), 38 _region_size_bytes_shift(ShenandoahHeapRegion::region_size_bytes_shift()), 39 _map_space(space), 40 _cset_map(_map_space.base() + ((uintx)heap_base >> _region_size_bytes_shift)), 41 _biased_cset_map(_map_space.base()), 42 _heap(heap), 43 _garbage(0), 44 _used(0), 45 _region_count(0), 46 _current_index(0) { 47 48 // The collection set map is reserved to cover the entire heap *and* zero addresses. 49 // This is needed to accept in-cset checks for both heap oops and NULLs, freeing 50 // high-performance code from checking for NULL first. 51 // 52 // Since heap_base can be far away, committing the entire map would waste memory. 53 // Therefore, we only commit the parts that are needed to operate: the heap view, 54 // and the zero page. 55 // 56 // Note: we could instead commit the entire map, and piggyback on OS virtual memory 57 // subsystem for mapping not-yet-written-to pages to a single physical backing page, 58 // but this is not guaranteed, and would confuse NMT and other memory accounting tools. 59 60 MemTracker::record_virtual_memory_type(_map_space.base(), mtGC); 61 62 size_t page_size = (size_t)os::vm_page_size(); 63 64 if (!_map_space.special()) { 65 // Commit entire pages that cover the heap cset map. 66 char* bot_addr = align_down(_cset_map, page_size); 67 char* top_addr = align_up(_cset_map + _map_size, page_size); 68 os::commit_memory_or_exit(bot_addr, pointer_delta(top_addr, bot_addr, 1), false, 69 "Unable to commit collection set bitmap: heap"); 70 71 // Commit the zero page, if not yet covered by heap cset map. 72 if (bot_addr != _biased_cset_map) { 73 os::commit_memory_or_exit(_biased_cset_map, page_size, false, 74 "Unable to commit collection set bitmap: zero page"); 75 } 76 } 77 78 Copy::zero_to_bytes(_cset_map, _map_size); 79 Copy::zero_to_bytes(_biased_cset_map, page_size); 80 } 81 82 void ShenandoahCollectionSet::add_region(ShenandoahHeapRegion* r) { 83 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 84 assert(Thread::current()->is_VM_thread(), "Must be VMThread"); 85 assert(!is_in(r), "Already in collection set"); 86 _cset_map[r->index()] = 1; 87 _region_count++; 88 _garbage += r->garbage(); 89 _used += r->used(); 90 91 // Update the region status too. State transition would be checked internally. 92 r->make_cset(); 93 } 94 95 void ShenandoahCollectionSet::clear() { 96 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 97 Copy::zero_to_bytes(_cset_map, _map_size); 98 99 #ifdef ASSERT 100 for (size_t index = 0; index < _heap->num_regions(); index ++) { 101 assert (!_heap->get_region(index)->is_cset(), "should have been cleared before"); 102 } 103 #endif 104 105 _garbage = 0; 106 _used = 0; 107 108 _region_count = 0; 109 _current_index = 0; 110 } 111 112 ShenandoahHeapRegion* ShenandoahCollectionSet::claim_next() { 113 size_t num_regions = _heap->num_regions(); 114 if (_current_index >= (jint)num_regions) { 115 return NULL; 116 } 117 118 jint saved_current = _current_index; 119 size_t index = (size_t)saved_current; 120 121 while(index < num_regions) { 122 if (is_in(index)) { 123 jint cur = Atomic::cmpxchg(&_current_index, saved_current, (jint)(index + 1)); 124 assert(cur >= (jint)saved_current, "Must move forward"); 125 if (cur == saved_current) { 126 assert(is_in(index), "Invariant"); 127 return _heap->get_region(index); 128 } else { 129 index = (size_t)cur; 130 saved_current = cur; 131 } 132 } else { 133 index ++; 134 } 135 } 136 return NULL; 137 } 138 139 ShenandoahHeapRegion* ShenandoahCollectionSet::next() { 140 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 141 assert(Thread::current()->is_VM_thread(), "Must be VMThread"); 142 size_t num_regions = _heap->num_regions(); 143 for (size_t index = (size_t)_current_index; index < num_regions; index ++) { 144 if (is_in(index)) { 145 _current_index = (jint)(index + 1); 146 return _heap->get_region(index); 147 } 148 } 149 150 return NULL; 151 } 152 153 void ShenandoahCollectionSet::print_on(outputStream* out) const { 154 out->print_cr("Collection Set : " SIZE_FORMAT "", count()); 155 156 debug_only(size_t regions = 0;) 157 for (size_t index = 0; index < _heap->num_regions(); index ++) { 158 if (is_in(index)) { 159 _heap->get_region(index)->print_on(out); 160 debug_only(regions ++;) 161 } 162 } 163 assert(regions == count(), "Must match"); 164 }