1 /* 2 * Copyright (c) 2000, 2018, 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/shared/collectedHeap.hpp" 29 #include "gc/shared/generation.hpp" 30 #include "gc/shared/space.hpp" 31 #include "gc/shared/spaceDecorator.hpp" 32 #include "memory/universe.hpp" 33 #include "oops/oopsHierarchy.hpp" 34 #include "oops/oop.inline.hpp" 35 #include "runtime/prefetch.inline.hpp" 36 #include "runtime/safepoint.hpp" 37 #if INCLUDE_SERIALGC 38 #include "gc/serial/markSweep.inline.hpp" 39 #endif 40 41 inline HeapWord* Space::block_start(const void* p) { 42 return block_start_const(p); 43 } 44 45 inline HeapWord* OffsetTableContigSpace::allocate(size_t size) { 46 HeapWord* res = ContiguousSpace::allocate(size); 47 if (res != NULL) { 48 _offsets.alloc_block(res, size); 49 } 50 return res; 51 } 52 53 // Because of the requirement of keeping "_offsets" up to date with the 54 // allocations, we sequentialize these with a lock. Therefore, best if 55 // this is used for larger LAB allocations only. 56 inline HeapWord* OffsetTableContigSpace::par_allocate(size_t size) { 57 MutexLocker x(&_par_alloc_lock); 58 // This ought to be just "allocate", because of the lock above, but that 59 // ContiguousSpace::allocate asserts that either the allocating thread 60 // holds the heap lock or it is the VM thread and we're at a safepoint. 61 // The best I (dld) could figure was to put a field in ContiguousSpace 62 // meaning "locking at safepoint taken care of", and set/reset that 63 // here. But this will do for now, especially in light of the comment 64 // above. Perhaps in the future some lock-free manner of keeping the 65 // coordination. 66 HeapWord* res = ContiguousSpace::par_allocate(size); 67 if (res != NULL) { 68 _offsets.alloc_block(res, size); 69 } 70 return res; 71 } 72 73 inline HeapWord* 74 OffsetTableContigSpace::block_start_const(const void* p) const { 75 return _offsets.block_start(p); 76 } 77 78 size_t CompactibleSpace::obj_size(const HeapWord* addr) const { 79 return oop(addr)->size(); 80 } 81 82 #if INCLUDE_SERIALGC 83 84 class DeadSpacer : StackObj { 85 size_t _allowed_deadspace_words; 86 bool _active; 87 CompactibleSpace* _space; 88 89 public: 90 DeadSpacer(CompactibleSpace* space) : _space(space), _allowed_deadspace_words(0) { 91 size_t ratio = _space->allowed_dead_ratio(); 92 _active = ratio > 0; 93 94 if (_active) { 95 assert(!UseG1GC, "G1 should not be using dead space"); 96 97 // We allow some amount of garbage towards the bottom of the space, so 98 // we don't start compacting before there is a significant gain to be made. 99 // Occasionally, we want to ensure a full compaction, which is determined 100 // by the MarkSweepAlwaysCompactCount parameter. 101 if ((MarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0) { 102 _allowed_deadspace_words = (space->capacity() * ratio / 100) / HeapWordSize; 103 } else { 104 _active = false; 105 } 106 } 107 } 108 109 110 bool insert_deadspace(HeapWord* dead_start, HeapWord* dead_end) { 111 if (!_active) { 112 return false; 113 } 114 115 size_t dead_length = pointer_delta(dead_end, dead_start); 116 if (_allowed_deadspace_words >= dead_length) { 117 _allowed_deadspace_words -= dead_length; 118 CollectedHeap::fill_with_object(dead_start, dead_length); 119 oop obj = oop(dead_start); 120 obj->set_mark_raw(obj->mark_raw()->set_marked()); 121 122 assert(dead_length == (size_t)obj->size(), "bad filler object size"); 123 log_develop_trace(gc, compaction)("Inserting object to dead space: " PTR_FORMAT ", " PTR_FORMAT ", " SIZE_FORMAT "b", 124 p2i(dead_start), p2i(dead_end), dead_length * HeapWordSize); 125 126 return true; 127 } else { 128 _active = false; 129 return false; 130 } 131 } 132 133 }; 134 135 template <class SpaceType> 136 inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp) { 137 // Compute the new addresses for the live objects and store it in the mark 138 // Used by universe::mark_sweep_phase2() 139 140 // We're sure to be here before any objects are compacted into this 141 // space, so this is a good time to initialize this: 142 space->set_compaction_top(space->bottom()); 143 144 if (cp->space == NULL) { 145 assert(cp->gen != NULL, "need a generation"); 146 assert(cp->threshold == NULL, "just checking"); 147 assert(cp->gen->first_compaction_space() == space, "just checking"); 148 cp->space = cp->gen->first_compaction_space(); 149 cp->threshold = cp->space->initialize_threshold(); 150 cp->space->set_compaction_top(cp->space->bottom()); 151 } 152 153 HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to. 154 155 DeadSpacer dead_spacer(space); 156 157 HeapWord* end_of_live = space->bottom(); // One byte beyond the last byte of the last live object. 158 HeapWord* first_dead = NULL; // The first dead object. 159 160 const intx interval = PrefetchScanIntervalInBytes; 161 162 HeapWord* cur_obj = space->bottom(); 163 HeapWord* scan_limit = space->scan_limit(); 164 165 while (cur_obj < scan_limit) { 166 assert(!space->scanned_block_is_obj(cur_obj) || 167 oop(cur_obj)->mark_raw()->is_marked() || oop(cur_obj)->mark_raw()->is_unlocked() || 168 oop(cur_obj)->mark_raw()->has_bias_pattern(), 169 "these are the only valid states during a mark sweep"); 170 if (space->scanned_block_is_obj(cur_obj) && oop(cur_obj)->is_gc_marked()) { 171 // prefetch beyond cur_obj 172 Prefetch::write(cur_obj, interval); 173 size_t size = space->scanned_block_size(cur_obj); 174 compact_top = cp->space->forward(oop(cur_obj), size, cp, compact_top); 175 cur_obj += size; 176 end_of_live = cur_obj; 177 } else { 178 // run over all the contiguous dead objects 179 HeapWord* end = cur_obj; 180 do { 181 // prefetch beyond end 182 Prefetch::write(end, interval); 183 end += space->scanned_block_size(end); 184 } while (end < scan_limit && (!space->scanned_block_is_obj(end) || !oop(end)->is_gc_marked())); 185 186 // see if we might want to pretend this object is alive so that 187 // we don't have to compact quite as often. 188 if (cur_obj == compact_top && dead_spacer.insert_deadspace(cur_obj, end)) { 189 oop obj = oop(cur_obj); 190 compact_top = cp->space->forward(obj, obj->size(), cp, compact_top); 191 end_of_live = end; 192 } else { 193 // otherwise, it really is a free region. 194 195 // cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object. 196 *(HeapWord**)cur_obj = end; 197 198 // see if this is the first dead region. 199 if (first_dead == NULL) { 200 first_dead = cur_obj; 201 } 202 } 203 204 // move on to the next object 205 cur_obj = end; 206 } 207 } 208 209 assert(cur_obj == scan_limit, "just checking"); 210 space->_end_of_live = end_of_live; 211 if (first_dead != NULL) { 212 space->_first_dead = first_dead; 213 } else { 214 space->_first_dead = end_of_live; 215 } 216 217 // save the compaction_top of the compaction space. 218 cp->space->set_compaction_top(compact_top); 219 } 220 221 template <class SpaceType> 222 inline void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space) { 223 // adjust all the interior pointers to point at the new locations of objects 224 // Used by MarkSweep::mark_sweep_phase3() 225 226 HeapWord* cur_obj = space->bottom(); 227 HeapWord* const end_of_live = space->_end_of_live; // Established by "scan_and_forward". 228 HeapWord* const first_dead = space->_first_dead; // Established by "scan_and_forward". 229 230 assert(first_dead <= end_of_live, "Stands to reason, no?"); 231 232 const intx interval = PrefetchScanIntervalInBytes; 233 234 debug_only(HeapWord* prev_obj = NULL); 235 while (cur_obj < end_of_live) { 236 Prefetch::write(cur_obj, interval); 237 if (cur_obj < first_dead || oop(cur_obj)->is_gc_marked()) { 238 // cur_obj is alive 239 // point all the oops to the new location 240 size_t size = MarkSweep::adjust_pointers(oop(cur_obj)); 241 size = space->adjust_obj_size(size); 242 debug_only(prev_obj = cur_obj); 243 cur_obj += size; 244 } else { 245 debug_only(prev_obj = cur_obj); 246 // cur_obj is not a live object, instead it points at the next live object 247 cur_obj = *(HeapWord**)cur_obj; 248 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)); 249 } 250 } 251 252 assert(cur_obj == end_of_live, "just checking"); 253 } 254 255 #ifdef ASSERT 256 template <class SpaceType> 257 inline void CompactibleSpace::verify_up_to_first_dead(SpaceType* space) { 258 HeapWord* cur_obj = space->bottom(); 259 260 if (cur_obj < space->_end_of_live && space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) { 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* prev_obj = NULL; 265 266 while (cur_obj < space->_first_dead) { 267 size_t size = space->obj_size(cur_obj); 268 assert(!oop(cur_obj)->is_gc_marked(), "should be unmarked (special dense prefix handling)"); 269 prev_obj = cur_obj; 270 cur_obj += size; 271 } 272 } 273 } 274 #endif 275 276 template <class SpaceType> 277 inline void CompactibleSpace::clear_empty_region(SpaceType* space) { 278 // Let's remember if we were empty before we did the compaction. 279 bool was_empty = space->used_region().is_empty(); 280 // Reset space after compaction is complete 281 space->reset_after_compaction(); 282 // We do this clear, below, since it has overloaded meanings for some 283 // space subtypes. For example, OffsetTableContigSpace's that were 284 // compacted into will have had their offset table thresholds updated 285 // continuously, but those that weren't need to have their thresholds 286 // re-initialized. Also mangles unused area for debugging. 287 if (space->used_region().is_empty()) { 288 if (!was_empty) space->clear(SpaceDecorator::Mangle); 289 } else { 290 if (ZapUnusedHeapArea) space->mangle_unused_area(); 291 } 292 } 293 294 template <class SpaceType> 295 inline void CompactibleSpace::scan_and_compact(SpaceType* space) { 296 // Copy all live objects to their new location 297 // Used by MarkSweep::mark_sweep_phase4() 298 299 verify_up_to_first_dead(space); 300 301 HeapWord* const bottom = space->bottom(); 302 HeapWord* const end_of_live = space->_end_of_live; 303 304 assert(space->_first_dead <= end_of_live, "Invariant. _first_dead: " PTR_FORMAT " <= end_of_live: " PTR_FORMAT, p2i(space->_first_dead), p2i(end_of_live)); 305 if (space->_first_dead == end_of_live && (bottom == end_of_live || !oop(bottom)->is_gc_marked())) { 306 // Nothing to compact. The space is either empty or all live object should be left in place. 307 clear_empty_region(space); 308 return; 309 } 310 311 const intx scan_interval = PrefetchScanIntervalInBytes; 312 const intx copy_interval = PrefetchCopyIntervalInBytes; 313 314 assert(bottom < end_of_live, "bottom: " PTR_FORMAT " should be < end_of_live: " PTR_FORMAT, p2i(bottom), p2i(end_of_live)); 315 HeapWord* cur_obj = bottom; 316 if (space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) { 317 // All object before _first_dead can be skipped. They should not be moved. 318 // A pointer to the first live object is stored at the memory location for _first_dead. 319 cur_obj = *(HeapWord**)(space->_first_dead); 320 } 321 322 debug_only(HeapWord* prev_obj = NULL); 323 while (cur_obj < end_of_live) { 324 if (!oop(cur_obj)->is_gc_marked()) { 325 debug_only(prev_obj = cur_obj); 326 // The first word of the dead object contains a pointer to the next live object or end of space. 327 cur_obj = *(HeapWord**)cur_obj; 328 assert(cur_obj > prev_obj, "we should be moving forward through memory"); 329 } else { 330 // prefetch beyond q 331 Prefetch::read(cur_obj, scan_interval); 332 333 // size and destination 334 size_t size = space->obj_size(cur_obj); 335 HeapWord* compaction_top = (HeapWord*)oop(cur_obj)->forwardee(); 336 337 // prefetch beyond compaction_top 338 Prefetch::write(compaction_top, copy_interval); 339 340 // copy object and reinit its mark 341 assert(cur_obj != compaction_top, "everything in this pass should be moving"); 342 Copy::aligned_conjoint_words(cur_obj, compaction_top, size); 343 oop(compaction_top)->init_mark_raw(); 344 assert(oop(compaction_top)->klass() != NULL, "should have a class"); 345 346 debug_only(prev_obj = cur_obj); 347 cur_obj += size; 348 } 349 } 350 351 clear_empty_region(space); 352 } 353 354 #endif // INCLUDE_SERIALGC 355 356 size_t ContiguousSpace::scanned_block_size(const HeapWord* addr) const { 357 return oop(addr)->size(); 358 } 359 360 template <typename OopClosureType> 361 void ContiguousSpace::oop_since_save_marks_iterate(OopClosureType* blk) { 362 HeapWord* t; 363 HeapWord* p = saved_mark_word(); 364 assert(p != NULL, "expected saved mark"); 365 366 const intx interval = PrefetchScanIntervalInBytes; 367 do { 368 t = top(); 369 while (p < t) { 370 Prefetch::write(p, interval); 371 debug_only(HeapWord* prev = p); 372 oop m = oop(p); 373 p += m->oop_iterate_size(blk); 374 } 375 } while (t < top()); 376 377 set_saved_mark_word(p); 378 } 379 380 #endif // SHARE_VM_GC_SHARED_SPACE_INLINE_HPP