1 /* 2 * Copyright (c) 2016, 2018, Red Hat, Inc. All rights reserved. 3 * 4 * This code is free software; you can redistribute it and/or modify it 5 * under the terms of the GNU General Public License version 2 only, as 6 * published by the Free Software Foundation. 7 * 8 * This code is distributed in the hope that it will be useful, but WITHOUT 9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 11 * version 2 for more details (a copy is included in the LICENSE file that 12 * accompanied this code). 13 * 14 * You should have received a copy of the GNU General Public License version 15 * 2 along with this work; if not, write to the Free Software Foundation, 16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 17 * 18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 19 * or visit www.oracle.com if you need additional information or have any 20 * questions. 21 * 22 */ 23 24 #include "precompiled.hpp" 25 26 #include "gc/shenandoah/shenandoahCollectionSet.hpp" 27 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 28 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp" 29 #include "gc/shenandoah/shenandoahUtils.hpp" 30 #include "runtime/atomic.hpp" 31 #include "services/memTracker.hpp" 32 #include "utilities/copy.hpp" 33 34 ShenandoahCollectionSet::ShenandoahCollectionSet(ShenandoahHeap* heap, char* heap_base, size_t size) : 35 _map_size(heap->num_regions()), 36 _region_size_bytes_shift(ShenandoahHeapRegion::region_size_bytes_shift()), 37 _map_space(align_up(((uintx)heap_base + size) >> _region_size_bytes_shift, os::vm_allocation_granularity())), 38 _cset_map(_map_space.base() + ((uintx)heap_base >> _region_size_bytes_shift)), 39 _biased_cset_map(_map_space.base()), 40 _heap(heap), 41 _garbage(0), 42 _live_data(0), 43 _used(0), 44 _region_count(0), 45 _current_index(0) { 46 47 // The collection set map is reserved to cover the entire heap *and* zero addresses. 48 // This is needed to accept in-cset checks for both heap oops and NULLs, freeing 49 // high-performance code from checking for NULL first. 50 // 51 // Since heap_base can be far away, committing the entire map would waste memory. 52 // Therefore, we only commit the parts that are needed to operate: the heap view, 53 // and the zero page. 54 // 55 // Note: we could instead commit the entire map, and piggyback on OS virtual memory 56 // subsystem for mapping not-yet-written-to pages to a single physical backing page, 57 // but this is not guaranteed, and would confuse NMT and other memory accounting tools. 58 59 MemTracker::record_virtual_memory_type(_map_space.base(), mtGC); 60 61 size_t page_size = (size_t)os::vm_page_size(); 62 63 if (!_map_space.special()) { 64 // Commit entire pages that cover the heap cset map. 65 char* bot_addr = align_down(_cset_map, page_size); 66 char* top_addr = align_up(_cset_map + _map_size, page_size); 67 os::commit_memory_or_exit(bot_addr, pointer_delta(top_addr, bot_addr, 1), false, 68 "Unable to commit collection set bitmap: heap"); 69 70 // Commit the zero page, if not yet covered by heap cset map. 71 if (bot_addr != _biased_cset_map) { 72 os::commit_memory_or_exit(_biased_cset_map, page_size, false, 73 "Unable to commit collection set bitmap: zero page"); 74 } 75 } 76 77 Copy::zero_to_bytes(_cset_map, _map_size); 78 Copy::zero_to_bytes(_biased_cset_map, page_size); 79 } 80 81 void ShenandoahCollectionSet::add_region(ShenandoahHeapRegion* r) { 82 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 83 assert(Thread::current()->is_VM_thread(), "Must be VMThread"); 84 assert(!is_in(r), "Already in collection set"); 85 _cset_map[r->region_number()] = 1; 86 _region_count ++; 87 _garbage += r->garbage(); 88 _live_data += r->get_live_data_bytes(); 89 _used += r->used(); 90 } 91 92 bool ShenandoahCollectionSet::add_region_check_for_duplicates(ShenandoahHeapRegion* r) { 93 if (!is_in(r)) { 94 add_region(r); 95 return true; 96 } else { 97 return false; 98 } 99 } 100 101 void ShenandoahCollectionSet::remove_region(ShenandoahHeapRegion* r) { 102 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 103 assert(Thread::current()->is_VM_thread(), "Must be VMThread"); 104 assert(is_in(r), "Not in collection set"); 105 _cset_map[r->region_number()] = 0; 106 _region_count --; 107 } 108 109 void ShenandoahCollectionSet::update_region_status() { 110 for (size_t index = 0; index < _heap->num_regions(); index ++) { 111 ShenandoahHeapRegion* r = _heap->get_region(index); 112 if (is_in(r)) { 113 r->make_cset(); 114 } else { 115 assert (!r->is_cset(), "should not be cset"); 116 } 117 } 118 } 119 120 void ShenandoahCollectionSet::clear() { 121 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 122 Copy::zero_to_bytes(_cset_map, _map_size); 123 124 #ifdef ASSERT 125 for (size_t index = 0; index < _heap->num_regions(); index ++) { 126 assert (!_heap->get_region(index)->is_cset(), "should have been cleared before"); 127 } 128 #endif 129 130 _garbage = 0; 131 _live_data = 0; 132 _used = 0; 133 134 _region_count = 0; 135 _current_index = 0; 136 } 137 138 ShenandoahHeapRegion* ShenandoahCollectionSet::claim_next() { 139 size_t num_regions = _heap->num_regions(); 140 if (_current_index >= (jint)num_regions) { 141 return NULL; 142 } 143 144 jint saved_current = _current_index; 145 size_t index = (size_t)saved_current; 146 147 while(index < num_regions) { 148 if (is_in(index)) { 149 jint cur = Atomic::cmpxchg((jint)(index + 1), &_current_index, saved_current); 150 assert(cur >= (jint)saved_current, "Must move forward"); 151 if (cur == saved_current) { 152 assert(is_in(index), "Invariant"); 153 return _heap->get_region(index); 154 } else { 155 index = (size_t)cur; 156 saved_current = cur; 157 } 158 } else { 159 index ++; 160 } 161 } 162 return NULL; 163 } 164 165 ShenandoahHeapRegion* ShenandoahCollectionSet::next() { 166 assert(ShenandoahSafepoint::is_at_shenandoah_safepoint(), "Must be at a safepoint"); 167 assert(Thread::current()->is_VM_thread(), "Must be VMThread"); 168 size_t num_regions = _heap->num_regions(); 169 for (size_t index = (size_t)_current_index; index < num_regions; index ++) { 170 if (is_in(index)) { 171 _current_index = (jint)(index + 1); 172 return _heap->get_region(index); 173 } 174 } 175 176 return NULL; 177 } 178 179 void ShenandoahCollectionSet::print_on(outputStream* out) const { 180 out->print_cr("Collection Set : " SIZE_FORMAT "", count()); 181 182 debug_only(size_t regions = 0;) 183 for (size_t index = 0; index < _heap->num_regions(); index ++) { 184 if (is_in(index)) { 185 _heap->get_region(index)->print_on(out); 186 debug_only(regions ++;) 187 } 188 } 189 assert(regions == count(), "Must match"); 190 }