1 /*

     2  * Copyright (c) 2010, 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 #include "precompiled.hpp"

    26 #include "gc/cms/compactibleFreeListSpace.hpp"

    27 #include "gc/cms/promotionInfo.hpp"

    28 #include "gc/shared/genOopClosures.hpp"

    29 #include "oops/compressedOops.inline.hpp"

    30 #include "oops/markWord.inline.hpp"

    31 #include "oops/oop.inline.hpp"

    32 

    33 /////////////////////////////////////////////////////////////////////////

    34 //// PromotionInfo

    35 /////////////////////////////////////////////////////////////////////////

    36 

    37 

    38 PromotedObject* PromotedObject::next() const {

    39   assert(!((FreeChunk*)this)->is_free(), "Error");

    40   PromotedObject* res;

    41   if (UseCompressedOops) {

    42     // The next pointer is a compressed oop stored in the top 32 bits

    43     res = (PromotedObject*)CompressedOops::decode(_data._narrow_next);

    44   } else {

    45     res = (PromotedObject*)(_next & next_mask);

    46   }

    47   assert(oopDesc::is_oop_or_null(oop(res), true /* ignore mark word */), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(res)));

    48   return res;

    49 }

    50 

    51 inline void PromotedObject::setNext(PromotedObject* x) {

    52   assert(((intptr_t)x & ~next_mask) == 0, "Conflict in bit usage, "

    53          "or insufficient alignment of objects");

    54   if (UseCompressedOops) {

    55     assert(_data._narrow_next == 0, "Overwrite?");

    56     _data._narrow_next = CompressedOops::encode(oop(x));

    57   } else {

    58     _next |= (intptr_t)x;

    59   }

    60   assert(!((FreeChunk*)this)->is_free(), "Error");

    61 }

    62 

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

    64 // recycling spool area as necessary.

    65 markWord PromotionInfo::nextDisplacedHeader() {

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

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

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

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

    70   markWord hdr = _spoolHead->displacedHdr[_firstIndex];

    71   // Spool forward

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

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

    74     SpoolBlock* tmp = _spoolHead->nextSpoolBlock;

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

    76     _spoolHead->nextSpoolBlock = _spareSpool;

    77     _spareSpool = _spoolHead;

    78     _spoolHead = tmp;

    79     _firstIndex = 1;

    80     NOT_PRODUCT(

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

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

    83                "spool buffers processing inconsistency");

    84       }

    85     )

    86   }

    87   return hdr;

    88 }

    89 

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

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

    92 }

    93 

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

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

    96   markWord mark = oop(trackOop)->mark_raw();

    97   trackOop->clear_next();

    98   if (mark.must_be_preserved_for_cms_scavenge(klassOfOop)) {

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

   100     saveDisplacedHeader(mark);

   101     trackOop->setDisplacedMark();

   102   } else {

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

   104     // assert(mark == markWord::prototype(), "consistency check");

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

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

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

   108     // have anything useful to check here!

   109   }

   110   if (_promoTail != NULL) {

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

   112     _promoTail->setNext(trackOop);

   113     _promoTail = trackOop;

   114   } else {

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

   116     _promoHead = _promoTail = trackOop;

   117   }

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

   119   // when scanning dirty cards

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

   121   trackOop->setPromotedMark();

   122 }

   123 

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

   125 // obtaining more spool area as necessary.

   126 void PromotionInfo::saveDisplacedHeader(markWord hdr) {

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

   128          "promotionInfo inconsistency");

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

   130   _spoolTail->displacedHdr[_nextIndex] = hdr;

   131   // Spool forward

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

   133     // get a new spooling block

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

   135     _splice_point = _spoolTail;                   // save for splicing

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

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

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

   139     _nextIndex = 1;

   140   }

   141 }

   142 

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

   144 // could not be obtained.

   145 bool PromotionInfo::ensure_spooling_space_work() {

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

   147   // Try and obtain more spooling space

   148   SpoolBlock* newSpool = getSpoolBlock();

   149   assert(newSpool == NULL ||

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

   151         "getSpoolBlock() sanity check");

   152   if (newSpool == NULL) {

   153     return false;

   154   }

   155   _nextIndex = 1;

   156   if (_spoolTail == NULL) {

   157     _spoolTail = newSpool;

   158     if (_spoolHead == NULL) {

   159       _spoolHead = newSpool;

   160       _firstIndex = 1;

   161     } else {

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

   163              "Splice point invariant");

   164       // Extra check that _splice_point is connected to list

   165       #ifdef ASSERT

   166       {

   167         SpoolBlock* blk = _spoolHead;

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

   169              blk = blk->nextSpoolBlock);

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

   171                "Splice point incorrect");

   172       }

   173       #endif // ASSERT

   174       _splice_point->nextSpoolBlock = newSpool;

   175     }

   176   } else {

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

   178     _spoolTail->nextSpoolBlock = newSpool;

   179     _spoolTail = newSpool;

   180   }

   181   return true;

   182 }

   183 

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

   185 // from the heap if necessary.

   186 SpoolBlock* PromotionInfo::getSpoolBlock() {

   187   SpoolBlock* res;

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

   189     _spareSpool = _spareSpool->nextSpoolBlock;

   190     res->nextSpoolBlock = NULL;

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

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

   193     if (res != NULL) {

   194       res->init();

   195     }

   196   }

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

   198   return res;

   199 }

   200 

   201 void PromotionInfo::startTrackingPromotions() {

   202   assert(noPromotions(), "sanity");

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

   204          "spooling inconsistency?");

   205   _firstIndex = _nextIndex = 1;

   206   _tracking = true;

   207 }

   208 

   209 void PromotionInfo::stopTrackingPromotions() {

   210   assert(noPromotions(), "we should have torn down the lists by now");

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

   212          "spooling inconsistency?");

   213   _firstIndex = _nextIndex = 1;

   214   _tracking = false;

   215 }

   216 

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

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

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

   220 // right-open interval denoted by:

   221 //

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

   223 //

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

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

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

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

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

   229 void PromotionInfo::verify() const {

   230   // Verify the following:

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

   232   //    objects that have displaced headers

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

   234   debug_only(

   235     PromotedObject* junk = NULL;

   236     assert(junk->next_addr() == (void*)(oop(junk)->mark_addr_raw()),

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

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

   239   )

   240   // FIXME: guarantee????

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

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

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

   244   // count the number of objects with displaced headers

   245   size_t numObjsWithDisplacedHdrs = 0;

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

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

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

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

   250     if (curObj->hasDisplacedMark()) {

   251       numObjsWithDisplacedHdrs++;

   252     }

   253   }

   254   // Count the number of displaced headers

   255   size_t numDisplacedHdrs = 0;

   256   for (SpoolBlock* curSpool = _spoolHead;

   257        curSpool != _spoolTail && curSpool != NULL;

   258        curSpool = curSpool->nextSpoolBlock) {

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

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

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

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

   263     numDisplacedHdrs += curSpool->bufferSize - 1;

   264   }

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

   266             "internal consistency");

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

   268             "Inconsistency between _spoolTail and _nextIndex");

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

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

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

   272   // adjustment by subtracting the first and adding the

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

   274   numDisplacedHdrs += (_nextIndex - _firstIndex);

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

   276 }

   277 

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

   279   SpoolBlock* curSpool = NULL;

   280   size_t i = 0;

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

   282                _firstIndex, _nextIndex);

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

   284        curSpool = curSpool->nextSpoolBlock) {

   285     curSpool->print_on(st);

   286     st->print_cr(" active ");

   287     i++;

   288   }

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

   290        curSpool = curSpool->nextSpoolBlock) {

   291     curSpool->print_on(st);

   292     st->print_cr(" inactive ");

   293     i++;

   294   }

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

   296        curSpool = curSpool->nextSpoolBlock) {

   297     curSpool->print_on(st);

   298     st->print_cr(" free ");

   299     i++;

   300   }

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

   302 }

   303 

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

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

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

   307             bufferSize, p2i(nextSpoolBlock));

   308 }