1 /* 2 * Copyright (c) 2010, 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 #include "precompiled.hpp" 26 #include "gc/cms/compactibleFreeListSpace.hpp" 27 #include "gc/cms/promotionInfo.hpp" 28 #include "gc/shared/genOopClosures.hpp" 29 #include "oops/markOop.inline.hpp" 30 #include "oops/oop.inline.hpp" 31 32 ///////////////////////////////////////////////////////////////////////// 33 //// PromotionInfo 34 ///////////////////////////////////////////////////////////////////////// 35 36 37 PromotedObject* PromotedObject::next() const { 38 assert(!((FreeChunk*)this)->is_free(), "Error"); 39 PromotedObject* res; 40 if (UseCompressedOops) { 41 // The next pointer is a compressed oop stored in the top 32 bits 42 res = (PromotedObject*)oopDesc::decode_heap_oop(_data._narrow_next); 43 } else { 44 res = (PromotedObject*)(_next & next_mask); 45 } 46 assert(oopDesc::is_oop_or_null(oop(res), true /* ignore mark word */), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(res))); 47 return res; 48 } 49 50 inline void PromotedObject::setNext(PromotedObject* x) { 51 assert(((intptr_t)x & ~next_mask) == 0, "Conflict in bit usage, " 52 "or insufficient alignment of objects"); 53 if (UseCompressedOops) { 54 assert(_data._narrow_next == 0, "Overwrite?"); 55 _data._narrow_next = oopDesc::encode_heap_oop(oop(x)); 56 } else { 57 _next |= (intptr_t)x; 58 } 59 assert(!((FreeChunk*)this)->is_free(), "Error"); 60 } 61 62 ////////////////////////////////////////////////////////////////////////////// 63 // We go over the list of promoted objects, removing each from the list, 64 // and applying the closure (this may, in turn, add more elements to 65 // the tail of the promoted list, and these newly added objects will 66 // also be processed) until the list is empty. 67 // To aid verification and debugging, in the non-product builds 68 // we actually forward _promoHead each time we process a promoted oop. 69 // Note that this is not necessary in general (i.e. when we don't need to 70 // call PromotionInfo::verify()) because oop_iterate can only add to the 71 // end of _promoTail, and never needs to look at _promoHead. 72 73 #define PROMOTED_OOPS_ITERATE_DEFN(OopClosureType, nv_suffix) \ 74 \ 75 void PromotionInfo::promoted_oops_iterate##nv_suffix(OopClosureType* cl) { \ 76 NOT_PRODUCT(verify()); \ 77 PromotedObject *curObj, *nextObj; \ 78 for (curObj = _promoHead; curObj != NULL; curObj = nextObj) { \ 79 if ((nextObj = curObj->next()) == NULL) { \ 80 /* protect ourselves against additions due to closure application \ 81 below by resetting the list. */ \ 82 assert(_promoTail == curObj, "Should have been the tail"); \ 83 _promoHead = _promoTail = NULL; \ 84 } \ 85 if (curObj->hasDisplacedMark()) { \ 86 /* restore displaced header */ \ 87 oop(curObj)->set_mark(nextDisplacedHeader()); \ 88 } else { \ 89 /* restore prototypical header */ \ 90 oop(curObj)->init_mark(); \ 91 } \ 92 /* The "promoted_mark" should now not be set */ \ 93 assert(!curObj->hasPromotedMark(), \ 94 "Should have been cleared by restoring displaced mark-word"); \ 95 NOT_PRODUCT(_promoHead = nextObj); \ 96 if (cl != NULL) oop(curObj)->oop_iterate(cl); \ 97 if (nextObj == NULL) { /* start at head of list reset above */ \ 98 nextObj = _promoHead; \ 99 } \ 100 } \ 101 assert(noPromotions(), "post-condition violation"); \ 102 assert(_promoHead == NULL && _promoTail == NULL, "emptied promoted list");\ 103 assert(_spoolHead == _spoolTail, "emptied spooling buffers"); \ 104 assert(_firstIndex == _nextIndex, "empty buffer"); \ 105 } 106 107 // This should have been ALL_SINCE_...() just like the others, 108 // but, because the body of the method above is somehwat longer, 109 // the MSVC compiler cannot cope; as a workaround, we split the 110 // macro into its 3 constituent parts below (see original macro 111 // definition in specializedOopClosures.hpp). 112 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES_YOUNG(PROMOTED_OOPS_ITERATE_DEFN) 113 PROMOTED_OOPS_ITERATE_DEFN(OopsInGenClosure,_v) 114 115 116 // Return the next displaced header, incrementing the pointer and 117 // recycling spool area as necessary. 118 markOop PromotionInfo::nextDisplacedHeader() { 119 assert(_spoolHead != NULL, "promotionInfo inconsistency"); 120 assert(_spoolHead != _spoolTail || _firstIndex < _nextIndex, 121 "Empty spool space: no displaced header can be fetched"); 122 assert(_spoolHead->bufferSize > _firstIndex, "Off by one error at head?"); 123 markOop hdr = _spoolHead->displacedHdr[_firstIndex]; 124 // Spool forward 125 if (++_firstIndex == _spoolHead->bufferSize) { // last location in this block 126 // forward to next block, recycling this block into spare spool buffer 127 SpoolBlock* tmp = _spoolHead->nextSpoolBlock; 128 assert(_spoolHead != _spoolTail, "Spooling storage mix-up"); 129 _spoolHead->nextSpoolBlock = _spareSpool; 130 _spareSpool = _spoolHead; 131 _spoolHead = tmp; 132 _firstIndex = 1; 133 NOT_PRODUCT( 134 if (_spoolHead == NULL) { // all buffers fully consumed 135 assert(_spoolTail == NULL && _nextIndex == 1, 136 "spool buffers processing inconsistency"); 137 } 138 ) 139 } 140 return hdr; 141 } 142 143 void PromotionInfo::track(PromotedObject* trackOop) { 144 track(trackOop, oop(trackOop)->klass()); 145 } 146 147 void PromotionInfo::track(PromotedObject* trackOop, Klass* klassOfOop) { 148 // make a copy of header as it may need to be spooled 149 markOop mark = oop(trackOop)->mark(); 150 trackOop->clear_next(); 151 if (mark->must_be_preserved_for_cms_scavenge(klassOfOop)) { 152 // save non-prototypical header, and mark oop 153 saveDisplacedHeader(mark); 154 trackOop->setDisplacedMark(); 155 } else { 156 // we'd like to assert something like the following: 157 // assert(mark == markOopDesc::prototype(), "consistency check"); 158 // ... but the above won't work because the age bits have not (yet) been 159 // cleared. The remainder of the check would be identical to the 160 // condition checked in must_be_preserved() above, so we don't really 161 // have anything useful to check here! 162 } 163 if (_promoTail != NULL) { 164 assert(_promoHead != NULL, "List consistency"); 165 _promoTail->setNext(trackOop); 166 _promoTail = trackOop; 167 } else { 168 assert(_promoHead == NULL, "List consistency"); 169 _promoHead = _promoTail = trackOop; 170 } 171 // Mask as newly promoted, so we can skip over such objects 172 // when scanning dirty cards 173 assert(!trackOop->hasPromotedMark(), "Should not have been marked"); 174 trackOop->setPromotedMark(); 175 } 176 177 // Save the given displaced header, incrementing the pointer and 178 // obtaining more spool area as necessary. 179 void PromotionInfo::saveDisplacedHeader(markOop hdr) { 180 assert(_spoolHead != NULL && _spoolTail != NULL, 181 "promotionInfo inconsistency"); 182 assert(_spoolTail->bufferSize > _nextIndex, "Off by one error at tail?"); 183 _spoolTail->displacedHdr[_nextIndex] = hdr; 184 // Spool forward 185 if (++_nextIndex == _spoolTail->bufferSize) { // last location in this block 186 // get a new spooling block 187 assert(_spoolTail->nextSpoolBlock == NULL, "tail should terminate spool list"); 188 _splice_point = _spoolTail; // save for splicing 189 _spoolTail->nextSpoolBlock = getSpoolBlock(); // might fail 190 _spoolTail = _spoolTail->nextSpoolBlock; // might become NULL ... 191 // ... but will attempt filling before next promotion attempt 192 _nextIndex = 1; 193 } 194 } 195 196 // Ensure that spooling space exists. Return false if spooling space 197 // could not be obtained. 198 bool PromotionInfo::ensure_spooling_space_work() { 199 assert(!has_spooling_space(), "Only call when there is no spooling space"); 200 // Try and obtain more spooling space 201 SpoolBlock* newSpool = getSpoolBlock(); 202 assert(newSpool == NULL || 203 (newSpool->bufferSize != 0 && newSpool->nextSpoolBlock == NULL), 204 "getSpoolBlock() sanity check"); 205 if (newSpool == NULL) { 206 return false; 207 } 208 _nextIndex = 1; 209 if (_spoolTail == NULL) { 210 _spoolTail = newSpool; 211 if (_spoolHead == NULL) { 212 _spoolHead = newSpool; 213 _firstIndex = 1; 214 } else { 215 assert(_splice_point != NULL && _splice_point->nextSpoolBlock == NULL, 216 "Splice point invariant"); 217 // Extra check that _splice_point is connected to list 218 #ifdef ASSERT 219 { 220 SpoolBlock* blk = _spoolHead; 221 for (; blk->nextSpoolBlock != NULL; 222 blk = blk->nextSpoolBlock); 223 assert(blk != NULL && blk == _splice_point, 224 "Splice point incorrect"); 225 } 226 #endif // ASSERT 227 _splice_point->nextSpoolBlock = newSpool; 228 } 229 } else { 230 assert(_spoolHead != NULL, "spool list consistency"); 231 _spoolTail->nextSpoolBlock = newSpool; 232 _spoolTail = newSpool; 233 } 234 return true; 235 } 236 237 // Get a free spool buffer from the free pool, getting a new block 238 // from the heap if necessary. 239 SpoolBlock* PromotionInfo::getSpoolBlock() { 240 SpoolBlock* res; 241 if ((res = _spareSpool) != NULL) { 242 _spareSpool = _spareSpool->nextSpoolBlock; 243 res->nextSpoolBlock = NULL; 244 } else { // spare spool exhausted, get some from heap 245 res = (SpoolBlock*)(space()->allocateScratch(refillSize())); 246 if (res != NULL) { 247 res->init(); 248 } 249 } 250 assert(res == NULL || res->nextSpoolBlock == NULL, "postcondition"); 251 return res; 252 } 253 254 void PromotionInfo::startTrackingPromotions() { 255 assert(noPromotions(), "sanity"); 256 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex, 257 "spooling inconsistency?"); 258 _firstIndex = _nextIndex = 1; 259 _tracking = true; 260 } 261 262 void PromotionInfo::stopTrackingPromotions() { 263 assert(noPromotions(), "we should have torn down the lists by now"); 264 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex, 265 "spooling inconsistency?"); 266 _firstIndex = _nextIndex = 1; 267 _tracking = false; 268 } 269 270 // When _spoolTail is not NULL, then the slot <_spoolTail, _nextIndex> 271 // points to the next slot available for filling. 272 // The set of slots holding displaced headers are then all those in the 273 // right-open interval denoted by: 274 // 275 // [ <_spoolHead, _firstIndex>, <_spoolTail, _nextIndex> ) 276 // 277 // When _spoolTail is NULL, then the set of slots with displaced headers 278 // is all those starting at the slot <_spoolHead, _firstIndex> and 279 // going up to the last slot of last block in the linked list. 280 // In this latter case, _splice_point points to the tail block of 281 // this linked list of blocks holding displaced headers. 282 void PromotionInfo::verify() const { 283 // Verify the following: 284 // 1. the number of displaced headers matches the number of promoted 285 // objects that have displaced headers 286 // 2. each promoted object lies in this space 287 debug_only( 288 PromotedObject* junk = NULL; 289 assert(junk->next_addr() == (void*)(oop(junk)->mark_addr()), 290 "Offset of PromotedObject::_next is expected to align with " 291 " the OopDesc::_mark within OopDesc"); 292 ) 293 // FIXME: guarantee???? 294 guarantee(_spoolHead == NULL || _spoolTail != NULL || 295 _splice_point != NULL, "list consistency"); 296 guarantee(_promoHead == NULL || _promoTail != NULL, "list consistency"); 297 // count the number of objects with displaced headers 298 size_t numObjsWithDisplacedHdrs = 0; 299 for (PromotedObject* curObj = _promoHead; curObj != NULL; curObj = curObj->next()) { 300 guarantee(space()->is_in_reserved((HeapWord*)curObj), "Containment"); 301 // the last promoted object may fail the mark() != NULL test of is_oop(). 302 guarantee(curObj->next() == NULL || oopDesc::is_oop(oop(curObj)), "must be an oop"); 303 if (curObj->hasDisplacedMark()) { 304 numObjsWithDisplacedHdrs++; 305 } 306 } 307 // Count the number of displaced headers 308 size_t numDisplacedHdrs = 0; 309 for (SpoolBlock* curSpool = _spoolHead; 310 curSpool != _spoolTail && curSpool != NULL; 311 curSpool = curSpool->nextSpoolBlock) { 312 // the first entry is just a self-pointer; indices 1 through 313 // bufferSize - 1 are occupied (thus, bufferSize - 1 slots). 314 guarantee((void*)curSpool->displacedHdr == (void*)&curSpool->displacedHdr, 315 "first entry of displacedHdr should be self-referential"); 316 numDisplacedHdrs += curSpool->bufferSize - 1; 317 } 318 guarantee((_spoolHead == _spoolTail) == (numDisplacedHdrs == 0), 319 "internal consistency"); 320 guarantee(_spoolTail != NULL || _nextIndex == 1, 321 "Inconsistency between _spoolTail and _nextIndex"); 322 // We overcounted (_firstIndex-1) worth of slots in block 323 // _spoolHead and we undercounted (_nextIndex-1) worth of 324 // slots in block _spoolTail. We make an appropriate 325 // adjustment by subtracting the first and adding the 326 // second: - (_firstIndex - 1) + (_nextIndex - 1) 327 numDisplacedHdrs += (_nextIndex - _firstIndex); 328 guarantee(numDisplacedHdrs == numObjsWithDisplacedHdrs, "Displaced hdr count"); 329 } 330 331 void PromotionInfo::print_on(outputStream* st) const { 332 SpoolBlock* curSpool = NULL; 333 size_t i = 0; 334 st->print_cr(" start & end indices: [" SIZE_FORMAT ", " SIZE_FORMAT ")", 335 _firstIndex, _nextIndex); 336 for (curSpool = _spoolHead; curSpool != _spoolTail && curSpool != NULL; 337 curSpool = curSpool->nextSpoolBlock) { 338 curSpool->print_on(st); 339 st->print_cr(" active "); 340 i++; 341 } 342 for (curSpool = _spoolTail; curSpool != NULL; 343 curSpool = curSpool->nextSpoolBlock) { 344 curSpool->print_on(st); 345 st->print_cr(" inactive "); 346 i++; 347 } 348 for (curSpool = _spareSpool; curSpool != NULL; 349 curSpool = curSpool->nextSpoolBlock) { 350 curSpool->print_on(st); 351 st->print_cr(" free "); 352 i++; 353 } 354 st->print_cr(" " SIZE_FORMAT " header spooling blocks", i); 355 } 356 357 void SpoolBlock::print_on(outputStream* st) const { 358 st->print("[" PTR_FORMAT "," PTR_FORMAT "), " SIZE_FORMAT " HeapWords -> " PTR_FORMAT, 359 p2i(this), p2i((HeapWord*)displacedHdr + bufferSize), 360 bufferSize, p2i(nextSpoolBlock)); 361 }