1 /*

     2  * Copyright (c) 2010, 2015, 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 //////////////////////////////////////////////////////////////////////////////

    38 // We go over the list of promoted objects, removing each from the list,

    39 // and applying the closure (this may, in turn, add more elements to

    40 // the tail of the promoted list, and these newly added objects will

    41 // also be processed) until the list is empty.

    42 // To aid verification and debugging, in the non-product builds

    43 // we actually forward _promoHead each time we process a promoted oop.

    44 // Note that this is not necessary in general (i.e. when we don't need to

    45 // call PromotionInfo::verify()) because oop_iterate can only add to the

    46 // end of _promoTail, and never needs to look at _promoHead.

    47 

    48 #define PROMOTED_OOPS_ITERATE_DEFN(OopClosureType, nv_suffix)               \

    49                                                                             \

    50 void PromotionInfo::promoted_oops_iterate##nv_suffix(OopClosureType* cl) {  \

    51   NOT_PRODUCT(verify());                                                    \

    52   PromotedObject *curObj, *nextObj;                                         \

    53   for (curObj = _promoHead; curObj != NULL; curObj = nextObj) {             \

    54     if ((nextObj = curObj->next()) == NULL) {                               \

    55       /* protect ourselves against additions due to closure application     \

    56          below by resetting the list.  */                                   \

    57       assert(_promoTail == curObj, "Should have been the tail");            \

    58       _promoHead = _promoTail = NULL;                                       \

    59     }                                                                       \

    60     if (curObj->hasDisplacedMark()) {                                       \

    61       /* restore displaced header */                                        \

    62       oop(curObj)->set_mark(nextDisplacedHeader());                         \

    63     } else {                                                                \

    64       /* restore prototypical header */                                     \

    65       oop(curObj)->init_mark();                                             \

    66     }                                                                       \

    67     /* The "promoted_mark" should now not be set */                         \

    68     assert(!curObj->hasPromotedMark(),                                      \

    69            "Should have been cleared by restoring displaced mark-word");    \

    70     NOT_PRODUCT(_promoHead = nextObj);                                      \

    71     if (cl != NULL) oop(curObj)->oop_iterate(cl);                           \

    72     if (nextObj == NULL) { /* start at head of list reset above */          \

    73       nextObj = _promoHead;                                                 \

    74     }                                                                       \

    75   }                                                                         \

    76   assert(noPromotions(), "post-condition violation");                       \

    77   assert(_promoHead == NULL && _promoTail == NULL, "emptied promoted list");\

    78   assert(_spoolHead == _spoolTail, "emptied spooling buffers");             \

    79   assert(_firstIndex == _nextIndex, "empty buffer");                        \

    80 }

    81 

    82 // This should have been ALL_SINCE_...() just like the others,

    83 // but, because the body of the method above is somehwat longer,

    84 // the MSVC compiler cannot cope; as a workaround, we split the

    85 // macro into its 3 constituent parts below (see original macro

    86 // definition in specializedOopClosures.hpp).

    87 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES_YOUNG(PROMOTED_OOPS_ITERATE_DEFN)

    88 PROMOTED_OOPS_ITERATE_DEFN(OopsInGenClosure,_v)

    89 

    90 

    91 // Return the next displaced header, incrementing the pointer and

    92 // recycling spool area as necessary.

    93 markOop PromotionInfo::nextDisplacedHeader() {

    94   assert(_spoolHead != NULL, "promotionInfo inconsistency");

    95   assert(_spoolHead != _spoolTail || _firstIndex < _nextIndex,

    96          "Empty spool space: no displaced header can be fetched");

    97   assert(_spoolHead->bufferSize > _firstIndex, "Off by one error at head?");

    98   markOop hdr = _spoolHead->displacedHdr[_firstIndex];

    99   // Spool forward

   100   if (++_firstIndex == _spoolHead->bufferSize) { // last location in this block

   101     // forward to next block, recycling this block into spare spool buffer

   102     SpoolBlock* tmp = _spoolHead->nextSpoolBlock;

   103     assert(_spoolHead != _spoolTail, "Spooling storage mix-up");

   104     _spoolHead->nextSpoolBlock = _spareSpool;

   105     _spareSpool = _spoolHead;

   106     _spoolHead = tmp;

   107     _firstIndex = 1;

   108     NOT_PRODUCT(

   109       if (_spoolHead == NULL) {  // all buffers fully consumed

   110         assert(_spoolTail == NULL && _nextIndex == 1,

   111                "spool buffers processing inconsistency");

   112       }

   113     )

   114   }

   115   return hdr;

   116 }

   117 

   118 void PromotionInfo::track(PromotedObject* trackOop) {

   119   track(trackOop, oop(trackOop)->klass());

   120 }

   121 

   122 void PromotionInfo::track(PromotedObject* trackOop, Klass* klassOfOop) {

   123   // make a copy of header as it may need to be spooled

   124   markOop mark = oop(trackOop)->mark();

   125   trackOop->clear_next();

   126   if (mark->must_be_preserved_for_cms_scavenge(klassOfOop)) {

   127     // save non-prototypical header, and mark oop

   128     saveDisplacedHeader(mark);

   129     trackOop->setDisplacedMark();

   130   } else {

   131     // we'd like to assert something like the following:

   132     // assert(mark == markOopDesc::prototype(), "consistency check");

   133     // ... but the above won't work because the age bits have not (yet) been

   134     // cleared. The remainder of the check would be identical to the

   135     // condition checked in must_be_preserved() above, so we don't really

   136     // have anything useful to check here!

   137   }

   138   if (_promoTail != NULL) {

   139     assert(_promoHead != NULL, "List consistency");

   140     _promoTail->setNext(trackOop);

   141     _promoTail = trackOop;

   142   } else {

   143     assert(_promoHead == NULL, "List consistency");

   144     _promoHead = _promoTail = trackOop;

   145   }

   146   // Mask as newly promoted, so we can skip over such objects

   147   // when scanning dirty cards

   148   assert(!trackOop->hasPromotedMark(), "Should not have been marked");

   149   trackOop->setPromotedMark();

   150 }

   151 

   152 // Save the given displaced header, incrementing the pointer and

   153 // obtaining more spool area as necessary.

   154 void PromotionInfo::saveDisplacedHeader(markOop hdr) {

   155   assert(_spoolHead != NULL && _spoolTail != NULL,

   156          "promotionInfo inconsistency");

   157   assert(_spoolTail->bufferSize > _nextIndex, "Off by one error at tail?");

   158   _spoolTail->displacedHdr[_nextIndex] = hdr;

   159   // Spool forward

   160   if (++_nextIndex == _spoolTail->bufferSize) { // last location in this block

   161     // get a new spooling block

   162     assert(_spoolTail->nextSpoolBlock == NULL, "tail should terminate spool list");

   163     _splice_point = _spoolTail;                   // save for splicing

   164     _spoolTail->nextSpoolBlock = getSpoolBlock(); // might fail

   165     _spoolTail = _spoolTail->nextSpoolBlock;      // might become NULL ...

   166     // ... but will attempt filling before next promotion attempt

   167     _nextIndex = 1;

   168   }

   169 }

   170 

   171 // Ensure that spooling space exists. Return false if spooling space

   172 // could not be obtained.

   173 bool PromotionInfo::ensure_spooling_space_work() {

   174   assert(!has_spooling_space(), "Only call when there is no spooling space");

   175   // Try and obtain more spooling space

   176   SpoolBlock* newSpool = getSpoolBlock();

   177   assert(newSpool == NULL ||

   178          (newSpool->bufferSize != 0 && newSpool->nextSpoolBlock == NULL),

   179         "getSpoolBlock() sanity check");

   180   if (newSpool == NULL) {

   181     return false;

   182   }

   183   _nextIndex = 1;

   184   if (_spoolTail == NULL) {

   185     _spoolTail = newSpool;

   186     if (_spoolHead == NULL) {

   187       _spoolHead = newSpool;

   188       _firstIndex = 1;

   189     } else {

   190       assert(_splice_point != NULL && _splice_point->nextSpoolBlock == NULL,

   191              "Splice point invariant");

   192       // Extra check that _splice_point is connected to list

   193       #ifdef ASSERT

   194       {

   195         SpoolBlock* blk = _spoolHead;

   196         for (; blk->nextSpoolBlock != NULL;

   197              blk = blk->nextSpoolBlock);

   198         assert(blk != NULL && blk == _splice_point,

   199                "Splice point incorrect");

   200       }

   201       #endif // ASSERT

   202       _splice_point->nextSpoolBlock = newSpool;

   203     }

   204   } else {

   205     assert(_spoolHead != NULL, "spool list consistency");

   206     _spoolTail->nextSpoolBlock = newSpool;

   207     _spoolTail = newSpool;

   208   }

   209   return true;

   210 }

   211 

   212 // Get a free spool buffer from the free pool, getting a new block

   213 // from the heap if necessary.

   214 SpoolBlock* PromotionInfo::getSpoolBlock() {

   215   SpoolBlock* res;

   216   if ((res = _spareSpool) != NULL) {

   217     _spareSpool = _spareSpool->nextSpoolBlock;

   218     res->nextSpoolBlock = NULL;

   219   } else {  // spare spool exhausted, get some from heap

   220     res = (SpoolBlock*)(space()->allocateScratch(refillSize()));

   221     if (res != NULL) {

   222       res->init();

   223     }

   224   }

   225   assert(res == NULL || res->nextSpoolBlock == NULL, "postcondition");

   226   return res;

   227 }

   228 

   229 void PromotionInfo::startTrackingPromotions() {

   230   assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,

   231          "spooling inconsistency?");

   232   _firstIndex = _nextIndex = 1;

   233   _tracking = true;

   234 }

   235 

   236 #define CMSPrintPromoBlockInfo 1

   237 

   238 void PromotionInfo::stopTrackingPromotions(uint worker_id) {

   239   assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,

   240          "spooling inconsistency?");

   241   _firstIndex = _nextIndex = 1;

   242   _tracking = false;

   243   if (CMSPrintPromoBlockInfo > 1) {

   244     print_statistics(worker_id);

   245   }

   246 }

   247 

   248 void PromotionInfo::print_statistics(uint worker_id) const {

   249   assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,

   250          "Else will undercount");

   251   assert(CMSPrintPromoBlockInfo > 0, "Else unnecessary call");

   252   // Count the number of blocks and slots in the free pool

   253   size_t slots  = 0;

   254   size_t blocks = 0;

   255   for (SpoolBlock* cur_spool = _spareSpool;

   256        cur_spool != NULL;

   257        cur_spool = cur_spool->nextSpoolBlock) {

   258     // the first entry is just a self-pointer; indices 1 through

   259     // bufferSize - 1 are occupied (thus, bufferSize - 1 slots).

   260     assert((void*)cur_spool->displacedHdr == (void*)&cur_spool->displacedHdr,

   261            "first entry of displacedHdr should be self-referential");

   262     slots += cur_spool->bufferSize - 1;

   263     blocks++;

   264   }

   265   if (_spoolHead != NULL) {

   266     slots += _spoolHead->bufferSize - 1;

   267     blocks++;

   268   }

   269   gclog_or_tty->print_cr(" [worker %d] promo_blocks = " SIZE_FORMAT ", promo_slots = " SIZE_FORMAT,

   270                          worker_id, blocks, slots);

   271 }

   272 

   273 // When _spoolTail is not NULL, then the slot <_spoolTail, _nextIndex>

   274 // points to the next slot available for filling.

   275 // The set of slots holding displaced headers are then all those in the

   276 // right-open interval denoted by:

   277 //

   278 //    [ <_spoolHead, _firstIndex>, <_spoolTail, _nextIndex> )

   279 //

   280 // When _spoolTail is NULL, then the set of slots with displaced headers

   281 // is all those starting at the slot <_spoolHead, _firstIndex> and

   282 // going up to the last slot of last block in the linked list.

   283 // In this latter case, _splice_point points to the tail block of

   284 // this linked list of blocks holding displaced headers.

   285 void PromotionInfo::verify() const {

   286   // Verify the following:

   287   // 1. the number of displaced headers matches the number of promoted

   288   //    objects that have displaced headers

   289   // 2. each promoted object lies in this space

   290   debug_only(

   291     PromotedObject* junk = NULL;

   292     assert(junk->next_addr() == (void*)(oop(junk)->mark_addr()),

   293            "Offset of PromotedObject::_next is expected to align with "

   294            "  the OopDesc::_mark within OopDesc");

   295   )

   296   // FIXME: guarantee????

   297   guarantee(_spoolHead == NULL || _spoolTail != NULL ||

   298             _splice_point != NULL, "list consistency");

   299   guarantee(_promoHead == NULL || _promoTail != NULL, "list consistency");

   300   // count the number of objects with displaced headers

   301   size_t numObjsWithDisplacedHdrs = 0;

   302   for (PromotedObject* curObj = _promoHead; curObj != NULL; curObj = curObj->next()) {

   303     guarantee(space()->is_in_reserved((HeapWord*)curObj), "Containment");

   304     // the last promoted object may fail the mark() != NULL test of is_oop().

   305     guarantee(curObj->next() == NULL || oop(curObj)->is_oop(), "must be an oop");

   306     if (curObj->hasDisplacedMark()) {

   307       numObjsWithDisplacedHdrs++;

   308     }

   309   }

   310   // Count the number of displaced headers

   311   size_t numDisplacedHdrs = 0;

   312   for (SpoolBlock* curSpool = _spoolHead;

   313        curSpool != _spoolTail && curSpool != NULL;

   314        curSpool = curSpool->nextSpoolBlock) {

   315     // the first entry is just a self-pointer; indices 1 through

   316     // bufferSize - 1 are occupied (thus, bufferSize - 1 slots).

   317     guarantee((void*)curSpool->displacedHdr == (void*)&curSpool->displacedHdr,

   318               "first entry of displacedHdr should be self-referential");

   319     numDisplacedHdrs += curSpool->bufferSize - 1;

   320   }

   321   guarantee((_spoolHead == _spoolTail) == (numDisplacedHdrs == 0),

   322             "internal consistency");

   323   guarantee(_spoolTail != NULL || _nextIndex == 1,

   324             "Inconsistency between _spoolTail and _nextIndex");

   325   // We overcounted (_firstIndex-1) worth of slots in block

   326   // _spoolHead and we undercounted (_nextIndex-1) worth of

   327   // slots in block _spoolTail. We make an appropriate

   328   // adjustment by subtracting the first and adding the

   329   // second:  - (_firstIndex - 1) + (_nextIndex - 1)

   330   numDisplacedHdrs += (_nextIndex - _firstIndex);

   331   guarantee(numDisplacedHdrs == numObjsWithDisplacedHdrs, "Displaced hdr count");

   332 }

   333 

   334 void PromotionInfo::print_on(outputStream* st) const {

   335   SpoolBlock* curSpool = NULL;

   336   size_t i = 0;

   337   st->print_cr(" start & end indices: [" SIZE_FORMAT ", " SIZE_FORMAT ")",

   338                _firstIndex, _nextIndex);

   339   for (curSpool = _spoolHead; curSpool != _spoolTail && curSpool != NULL;

   340        curSpool = curSpool->nextSpoolBlock) {

   341     curSpool->print_on(st);

   342     st->print_cr(" active ");

   343     i++;

   344   }

   345   for (curSpool = _spoolTail; curSpool != NULL;

   346        curSpool = curSpool->nextSpoolBlock) {

   347     curSpool->print_on(st);

   348     st->print_cr(" inactive ");

   349     i++;

   350   }

   351   for (curSpool = _spareSpool; curSpool != NULL;

   352        curSpool = curSpool->nextSpoolBlock) {

   353     curSpool->print_on(st);

   354     st->print_cr(" free ");

   355     i++;

   356   }

   357   st->print_cr("  " SIZE_FORMAT " header spooling blocks", i);

   358 }

   359 

   360 void SpoolBlock::print_on(outputStream* st) const {

   361   st->print("[" PTR_FORMAT "," PTR_FORMAT "), " SIZE_FORMAT " HeapWords -> " PTR_FORMAT,

   362             p2i(this), p2i((HeapWord*)displacedHdr + bufferSize),

   363             bufferSize, p2i(nextSpoolBlock));

   364 }