1 /* 2 * Copyright (c) 2000, 2016, Oracle and/or its affiliates. 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 #ifndef SHARE_VM_GC_SHARED_SPACE_INLINE_HPP 26 #define SHARE_VM_GC_SHARED_SPACE_INLINE_HPP 27 28 #include "gc/serial/markSweep.inline.hpp" 29 #include "gc/shared/collectedHeap.hpp" 30 #include "gc/shared/generation.hpp" 31 #include "gc/shared/space.hpp" 32 #include "gc/shared/spaceDecorator.hpp" 33 #include "memory/universe.hpp" 34 #include "oops/oopsHierarchy.hpp" 35 #include "runtime/prefetch.inline.hpp" 36 #include "runtime/safepoint.hpp" 37 38 inline HeapWord* Space::block_start(const void* p) { 39 return block_start_const(p); 40 } 41 42 inline HeapWord* OffsetTableContigSpace::allocate(size_t size) { 43 HeapWord* res = ContiguousSpace::allocate(size); 44 if (res != NULL) { 45 _offsets.alloc_block(res, size); 46 } 47 return res; 48 } 49 50 // Because of the requirement of keeping "_offsets" up to date with the 51 // allocations, we sequentialize these with a lock. Therefore, best if 52 // this is used for larger LAB allocations only. 53 inline HeapWord* OffsetTableContigSpace::par_allocate(size_t size) { 54 MutexLocker x(&_par_alloc_lock); 55 // This ought to be just "allocate", because of the lock above, but that 56 // ContiguousSpace::allocate asserts that either the allocating thread 57 // holds the heap lock or it is the VM thread and we're at a safepoint. 58 // The best I (dld) could figure was to put a field in ContiguousSpace 59 // meaning "locking at safepoint taken care of", and set/reset that 60 // here. But this will do for now, especially in light of the comment 61 // above. Perhaps in the future some lock-free manner of keeping the 62 // coordination. 63 HeapWord* res = ContiguousSpace::par_allocate(size); 64 if (res != NULL) { 65 _offsets.alloc_block(res, size); 66 } 67 return res; 68 } 69 70 inline HeapWord* 71 OffsetTableContigSpace::block_start_const(const void* p) const { 72 return _offsets.block_start(p); 73 } 74 75 size_t CompactibleSpace::obj_size(const HeapWord* addr) const { 76 return oop(addr)->size(); 77 } 78 79 class DeadSpacer : StackObj { 80 size_t _allowed_deadspace_words; 81 bool _active; 82 CompactibleSpace* _space; 83 84 public: 85 DeadSpacer(CompactibleSpace* space) : _space(space), _allowed_deadspace_words(0) { 86 size_t ratio = _space->allowed_dead_ratio(); 87 _active = ratio > 0; 88 89 if (_active) { 90 assert(!UseG1GC, "G1 should not be using dead space"); 91 92 // We allow some amount of garbage towards the bottom of the space, so 93 // we don't start compacting before there is a significant gain to be made. 94 // Occasionally, we want to ensure a full compaction, which is determined 95 // by the MarkSweepAlwaysCompactCount parameter. 96 if ((MarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0) { 97 _allowed_deadspace_words = (space->capacity() * ratio / 100) / HeapWordSize; 98 } else { 99 _active = false; 100 } 101 } 102 } 103 104 105 bool insert_deadspace(HeapWord* dead_start, HeapWord* dead_end) { 106 if (!_active) { 107 return false; 108 } 109 110 size_t dead_length = pointer_delta(dead_end, dead_start); 111 if (_allowed_deadspace_words >= dead_length) { 112 _allowed_deadspace_words -= dead_length; 113 CollectedHeap::fill_with_object(dead_start, dead_length); 114 oop obj = oop(dead_start); 115 obj->set_mark(obj->mark()->set_marked()); 116 117 assert(dead_length == (size_t)obj->size(), "bad filler object size"); 118 log_develop_trace(gc, compaction)("Inserting object to dead space: " PTR_FORMAT ", " PTR_FORMAT ", " SIZE_FORMAT "b", 119 p2i(dead_start), p2i(dead_end), dead_length * HeapWordSize); 120 121 return true; 122 } else { 123 _active = false; 124 return false; 125 } 126 } 127 128 }; 129 130 template <class SpaceType> 131 inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp) { 132 // Compute the new addresses for the live objects and store it in the mark 133 // Used by universe::mark_sweep_phase2() 134 135 // We're sure to be here before any objects are compacted into this 136 // space, so this is a good time to initialize this: 137 space->set_compaction_top(space->bottom()); 138 139 if (cp->space == NULL) { 140 assert(cp->gen != NULL, "need a generation"); 141 assert(cp->threshold == NULL, "just checking"); 142 assert(cp->gen->first_compaction_space() == space, "just checking"); 143 cp->space = cp->gen->first_compaction_space(); 144 cp->threshold = cp->space->initialize_threshold(); 145 cp->space->set_compaction_top(cp->space->bottom()); 146 } 147 148 HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to. 149 150 DeadSpacer dead_spacer(space); 151 152 HeapWord* end_of_live = space->bottom(); // One byte beyond the last byte of the last live object. 153 HeapWord* first_dead = NULL; // The first dead object. 154 155 const intx interval = PrefetchScanIntervalInBytes; 156 157 HeapWord* cur_obj = space->bottom(); 158 HeapWord* scan_limit = space->scan_limit(); 159 160 while (cur_obj < scan_limit) { 161 assert(!space->scanned_block_is_obj(cur_obj) || 162 oop(cur_obj)->mark()->is_marked() || oop(cur_obj)->mark()->is_unlocked() || 163 oop(cur_obj)->mark()->has_bias_pattern(), 164 "these are the only valid states during a mark sweep"); 165 if (space->scanned_block_is_obj(cur_obj) && oop(cur_obj)->is_gc_marked()) { 166 // prefetch beyond cur_obj 167 Prefetch::write(cur_obj, interval); 168 size_t size = space->scanned_block_size(cur_obj); 169 compact_top = cp->space->forward(oop(cur_obj), size, cp, compact_top); 170 cur_obj += size; 171 end_of_live = cur_obj; 172 } else { 173 // run over all the contiguous dead objects 174 HeapWord* end = cur_obj; 175 do { 176 // prefetch beyond end 177 Prefetch::write(end, interval); 178 end += space->scanned_block_size(end); 179 } while (end < scan_limit && (!space->scanned_block_is_obj(end) || !oop(end)->is_gc_marked())); 180 181 // see if we might want to pretend this object is alive so that 182 // we don't have to compact quite as often. 183 if (cur_obj == compact_top && dead_spacer.insert_deadspace(cur_obj, end)) { 184 oop obj = oop(cur_obj); 185 compact_top = cp->space->forward(obj, obj->size(), cp, compact_top); 186 end_of_live = end; 187 } else { 188 // otherwise, it really is a free region. 189 190 // cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object. 191 *(HeapWord**)cur_obj = end; 192 193 // see if this is the first dead region. 194 if (first_dead == NULL) { 195 first_dead = cur_obj; 196 } 197 } 198 199 // move on to the next object 200 cur_obj = end; 201 } 202 } 203 204 assert(cur_obj == scan_limit, "just checking"); 205 space->_end_of_live = end_of_live; 206 if (first_dead != NULL) { 207 space->_first_dead = first_dead; 208 } else { 209 space->_first_dead = end_of_live; 210 } 211 212 // save the compaction_top of the compaction space. 213 cp->space->set_compaction_top(compact_top); 214 } 215 216 template <class SpaceType> 217 inline void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space) { 218 // adjust all the interior pointers to point at the new locations of objects 219 // Used by MarkSweep::mark_sweep_phase3() 220 221 HeapWord* cur_obj = space->bottom(); 222 HeapWord* const end_of_live = space->_end_of_live; // Established by "scan_and_forward". 223 HeapWord* const first_dead = space->_first_dead; // Established by "scan_and_forward". 224 225 assert(first_dead <= end_of_live, "Stands to reason, no?"); 226 227 const intx interval = PrefetchScanIntervalInBytes; 228 229 debug_only(HeapWord* prev_obj = NULL); 230 while (cur_obj < end_of_live) { 231 Prefetch::write(cur_obj, interval); 232 if (cur_obj < first_dead || oop(cur_obj)->is_gc_marked()) { 233 // cur_obj is alive 234 // point all the oops to the new location 235 size_t size = MarkSweep::adjust_pointers(oop(cur_obj)); 236 size = space->adjust_obj_size(size); 237 debug_only(prev_obj = cur_obj); 238 cur_obj += size; 239 } else { 240 debug_only(prev_obj = cur_obj); 241 // cur_obj is not a live object, instead it points at the next live object 242 cur_obj = *(HeapWord**)cur_obj; 243 assert(cur_obj > prev_obj, "we should be moving forward through memory, cur_obj: " PTR_FORMAT ", prev_obj: " PTR_FORMAT, p2i(cur_obj), p2i(prev_obj)); 244 } 245 } 246 247 assert(cur_obj == end_of_live, "just checking"); 248 } 249 250 template <class SpaceType> 251 inline void CompactibleSpace::scan_and_compact(SpaceType* space) { 252 // Copy all live objects to their new location 253 // Used by MarkSweep::mark_sweep_phase4() 254 255 HeapWord* q = space->bottom(); 256 HeapWord* const t = space->_end_of_live; 257 debug_only(HeapWord* prev_q = NULL); 258 259 if (q < t && space->_first_dead > q && !oop(q)->is_gc_marked()) { 260 #ifdef ASSERT // Debug only 261 // we have a chunk of the space which hasn't moved and we've reinitialized 262 // the mark word during the previous pass, so we can't use is_gc_marked for 263 // the traversal. 264 HeapWord* const end = space->_first_dead; 265 266 while (q < end) { 267 size_t size = space->obj_size(q); 268 assert(!oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)"); 269 prev_q = q; 270 q += size; 271 } 272 #endif 273 274 if (space->_first_dead == t) { 275 q = t; 276 } else { 277 // $$$ Funky 278 q = (HeapWord*) oop(space->_first_dead)->mark()->decode_pointer(); 279 } 280 } 281 282 const intx scan_interval = PrefetchScanIntervalInBytes; 283 const intx copy_interval = PrefetchCopyIntervalInBytes; 284 while (q < t) { 285 if (!oop(q)->is_gc_marked()) { 286 // mark is pointer to next marked oop 287 debug_only(prev_q = q); 288 q = (HeapWord*) oop(q)->mark()->decode_pointer(); 289 assert(q > prev_q, "we should be moving forward through memory"); 290 } else { 291 // prefetch beyond q 292 Prefetch::read(q, scan_interval); 293 294 // size and destination 295 size_t size = space->obj_size(q); 296 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee(); 297 298 // prefetch beyond compaction_top 299 Prefetch::write(compaction_top, copy_interval); 300 301 // copy object and reinit its mark 302 assert(q != compaction_top, "everything in this pass should be moving"); 303 Copy::aligned_conjoint_words(q, compaction_top, size); 304 oop(compaction_top)->init_mark(); 305 assert(oop(compaction_top)->klass() != NULL, "should have a class"); 306 307 debug_only(prev_q = q); 308 q += size; 309 } 310 } 311 312 // Let's remember if we were empty before we did the compaction. 313 bool was_empty = space->used_region().is_empty(); 314 // Reset space after compaction is complete 315 space->reset_after_compaction(); 316 // We do this clear, below, since it has overloaded meanings for some 317 // space subtypes. For example, OffsetTableContigSpace's that were 318 // compacted into will have had their offset table thresholds updated 319 // continuously, but those that weren't need to have their thresholds 320 // re-initialized. Also mangles unused area for debugging. 321 if (space->used_region().is_empty()) { 322 if (!was_empty) space->clear(SpaceDecorator::Mangle); 323 } else { 324 if (ZapUnusedHeapArea) space->mangle_unused_area(); 325 } 326 } 327 328 size_t ContiguousSpace::scanned_block_size(const HeapWord* addr) const { 329 return oop(addr)->size(); 330 } 331 332 #endif // SHARE_VM_GC_SHARED_SPACE_INLINE_HPP