1 /*

     2  * Copyright 2002-2006 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

    20  * CA 95054 USA or visit www.sun.com if you need additional information or

    21  * have any questions.

    22  *

    23  */

    24 

    25 #include "incls/_precompiled.incl"

    26 #include "incls/_psPromotionManager.cpp.incl"

    27 

    28 PSPromotionManager**         PSPromotionManager::_manager_array = NULL;

    29 OopStarTaskQueueSet*         PSPromotionManager::_stack_array_depth = NULL;

    30 OopTaskQueueSet*             PSPromotionManager::_stack_array_breadth = NULL;

    31 PSOldGen*                    PSPromotionManager::_old_gen = NULL;

    32 MutableSpace*                PSPromotionManager::_young_space = NULL;

    33 

    34 void PSPromotionManager::initialize() {

    35   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

    36   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

    37 

    38   _old_gen = heap->old_gen();

    39   _young_space = heap->young_gen()->to_space();

    40 

    41   assert(_manager_array == NULL, "Attempt to initialize twice");

    42   _manager_array = NEW_C_HEAP_ARRAY(PSPromotionManager*, ParallelGCThreads+1 );

    43   guarantee(_manager_array != NULL, "Could not initialize promotion manager");

    44 

    45   if (UseDepthFirstScavengeOrder) {

    46     _stack_array_depth = new OopStarTaskQueueSet(ParallelGCThreads);

    47     guarantee(_stack_array_depth != NULL, "Count not initialize promotion manager");

    48   } else {

    49     _stack_array_breadth = new OopTaskQueueSet(ParallelGCThreads);

    50     guarantee(_stack_array_breadth != NULL, "Count not initialize promotion manager");

    51   }

    52 

    53   // Create and register the PSPromotionManager(s) for the worker threads.

    54   for(uint i=0; i<ParallelGCThreads; i++) {

    55     _manager_array[i] = new PSPromotionManager();

    56     guarantee(_manager_array[i] != NULL, "Could not create PSPromotionManager");

    57     if (UseDepthFirstScavengeOrder) {

    58       stack_array_depth()->register_queue(i, _manager_array[i]->claimed_stack_depth());

    59     } else {

    60       stack_array_breadth()->register_queue(i, _manager_array[i]->claimed_stack_breadth());

    61     }

    62   }

    63 

    64   // The VMThread gets its own PSPromotionManager, which is not available

    65   // for work stealing.

    66   _manager_array[ParallelGCThreads] = new PSPromotionManager();

    67   guarantee(_manager_array[ParallelGCThreads] != NULL, "Could not create PSPromotionManager");

    68 }

    69 

    70 PSPromotionManager* PSPromotionManager::gc_thread_promotion_manager(int index) {

    71   assert(index >= 0 && index < (int)ParallelGCThreads, "index out of range");

    72   assert(_manager_array != NULL, "Sanity");

    73   return _manager_array[index];

    74 }

    75 

    76 PSPromotionManager* PSPromotionManager::vm_thread_promotion_manager() {

    77   assert(_manager_array != NULL, "Sanity");

    78   return _manager_array[ParallelGCThreads];

    79 }

    80 

    81 void PSPromotionManager::pre_scavenge() {

    82   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

    83   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

    84 

    85   _young_space = heap->young_gen()->to_space();

    86 

    87   for(uint i=0; i<ParallelGCThreads+1; i++) {

    88     manager_array(i)->reset();

    89   }

    90 }

    91 

    92 void PSPromotionManager::post_scavenge() {

    93 #if PS_PM_STATS

    94   print_stats();

    95 #endif // PS_PM_STATS

    96 

    97   for(uint i=0; i<ParallelGCThreads+1; i++) {

    98     PSPromotionManager* manager = manager_array(i);

    99 

   100     // the guarantees are a bit gratuitous but, if one fires, we'll

   101     // have a better idea of what went wrong

   102     if (i < ParallelGCThreads) {

   103       guarantee((!UseDepthFirstScavengeOrder ||

   104                  manager->overflow_stack_depth()->length() <= 0),

   105                 "promotion manager overflow stack must be empty");

   106       guarantee((UseDepthFirstScavengeOrder ||

   107                  manager->overflow_stack_breadth()->length() <= 0),

   108                 "promotion manager overflow stack must be empty");

   109 

   110       guarantee((!UseDepthFirstScavengeOrder ||

   111                  manager->claimed_stack_depth()->size() <= 0),

   112                 "promotion manager claimed stack must be empty");

   113       guarantee((UseDepthFirstScavengeOrder ||

   114                  manager->claimed_stack_breadth()->size() <= 0),

   115                 "promotion manager claimed stack must be empty");

   116     } else {

   117       guarantee((!UseDepthFirstScavengeOrder ||

   118                  manager->overflow_stack_depth()->length() <= 0),

   119                 "VM Thread promotion manager overflow stack "

   120                 "must be empty");

   121       guarantee((UseDepthFirstScavengeOrder ||

   122                  manager->overflow_stack_breadth()->length() <= 0),

   123                 "VM Thread promotion manager overflow stack "

   124                 "must be empty");

   125 

   126       guarantee((!UseDepthFirstScavengeOrder ||

   127                  manager->claimed_stack_depth()->size() <= 0),

   128                 "VM Thread promotion manager claimed stack "

   129                 "must be empty");

   130       guarantee((UseDepthFirstScavengeOrder ||

   131                  manager->claimed_stack_breadth()->size() <= 0),

   132                 "VM Thread promotion manager claimed stack "

   133                 "must be empty");

   134     }

   135 

   136     manager->flush_labs();

   137   }

   138 }

   139 

   140 #if PS_PM_STATS

   141 

   142 void

   143 PSPromotionManager::print_stats(uint i) {

   144   tty->print_cr("---- GC Worker %2d Stats", i);

   145   tty->print_cr("    total pushes            %8d", _total_pushes);

   146   tty->print_cr("    masked pushes           %8d", _masked_pushes);

   147   tty->print_cr("    overflow pushes         %8d", _overflow_pushes);

   148   tty->print_cr("    max overflow length     %8d", _max_overflow_length);

   149   tty->print_cr("");

   150   tty->print_cr("    arrays chunked          %8d", _arrays_chunked);

   151   tty->print_cr("    array chunks processed  %8d", _array_chunks_processed);

   152   tty->print_cr("");

   153   tty->print_cr("    total steals            %8d", _total_steals);

   154   tty->print_cr("    masked steals           %8d", _masked_steals);

   155   tty->print_cr("");

   156 }

   157 

   158 void

   159 PSPromotionManager::print_stats() {

   160   tty->print_cr("== GC Tasks Stats (%s), GC %3d",

   161                 (UseDepthFirstScavengeOrder) ? "Depth-First" : "Breadth-First",

   162                 Universe::heap()->total_collections());

   163 

   164   for (uint i = 0; i < ParallelGCThreads+1; ++i) {

   165     PSPromotionManager* manager = manager_array(i);

   166     manager->print_stats(i);

   167   }

   168 }

   169 

   170 #endif // PS_PM_STATS

   171 

   172 PSPromotionManager::PSPromotionManager() {

   173   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   174   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   175   _depth_first = UseDepthFirstScavengeOrder;

   176 

   177   // We set the old lab's start array.

   178   _old_lab.set_start_array(old_gen()->start_array());

   179 

   180   uint queue_size;

   181   if (depth_first()) {

   182     claimed_stack_depth()->initialize();

   183     queue_size = claimed_stack_depth()->max_elems();

   184     // We want the overflow stack to be permanent

   185     _overflow_stack_depth = new (ResourceObj::C_HEAP) GrowableArray<oop*>(10, true);

   186     _overflow_stack_breadth = NULL;

   187   } else {

   188     claimed_stack_breadth()->initialize();

   189     queue_size = claimed_stack_breadth()->max_elems();

   190     // We want the overflow stack to be permanent

   191     _overflow_stack_breadth = new (ResourceObj::C_HEAP) GrowableArray<oop>(10, true);

   192     _overflow_stack_depth = NULL;

   193   }

   194 

   195   _totally_drain = (ParallelGCThreads == 1) || (GCDrainStackTargetSize == 0);

   196   if (_totally_drain) {

   197     _target_stack_size = 0;

   198   } else {

   199     // don't let the target stack size to be more than 1/4 of the entries

   200     _target_stack_size = (uint) MIN2((uint) GCDrainStackTargetSize,

   201                                      (uint) (queue_size / 4));

   202   }

   203 

   204   _array_chunk_size = ParGCArrayScanChunk;

   205   // let's choose 1.5x the chunk size

   206   _min_array_size_for_chunking = 3 * _array_chunk_size / 2;

   207 

   208   reset();

   209 }

   210 

   211 void PSPromotionManager::reset() {

   212   assert(claimed_stack_empty(), "reset of non-empty claimed stack");

   213   assert(overflow_stack_empty(), "reset of non-empty overflow stack");

   214 

   215   // We need to get an assert in here to make sure the labs are always flushed.

   216 

   217   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   218   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   219 

   220   // Do not prefill the LAB's, save heap wastage!

   221   HeapWord* lab_base = young_space()->top();

   222   _young_lab.initialize(MemRegion(lab_base, (size_t)0));

   223   _young_gen_is_full = false;

   224 

   225   lab_base = old_gen()->object_space()->top();

   226   _old_lab.initialize(MemRegion(lab_base, (size_t)0));

   227   _old_gen_is_full = false;

   228 

   229   _prefetch_queue.clear();

   230 

   231 #if PS_PM_STATS

   232   _total_pushes = 0;

   233   _masked_pushes = 0;

   234   _overflow_pushes = 0;

   235   _max_overflow_length = 0;

   236   _arrays_chunked = 0;

   237   _array_chunks_processed = 0;

   238   _total_steals = 0;

   239   _masked_steals = 0;

   240 #endif // PS_PM_STATS

   241 }

   242 

   243 void PSPromotionManager::drain_stacks_depth(bool totally_drain) {

   244   assert(depth_first(), "invariant");

   245   assert(overflow_stack_depth() != NULL, "invariant");

   246   totally_drain = totally_drain || _totally_drain;

   247 

   248 #ifdef ASSERT

   249   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   250   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   251   MutableSpace* to_space = heap->young_gen()->to_space();

   252   MutableSpace* old_space = heap->old_gen()->object_space();

   253   MutableSpace* perm_space = heap->perm_gen()->object_space();

   254 #endif /* ASSERT */

   255 

   256   do {

   257     oop* p;

   258 

   259     // Drain overflow stack first, so other threads can steal from

   260     // claimed stack while we work.

   261     while(!overflow_stack_depth()->is_empty()) {

   262       p = overflow_stack_depth()->pop();

   263       process_popped_location_depth(p);

   264     }

   265 

   266     if (totally_drain) {

   267       while (claimed_stack_depth()->pop_local(p)) {

   268         process_popped_location_depth(p);

   269       }

   270     } else {

   271       while (claimed_stack_depth()->size() > _target_stack_size &&

   272              claimed_stack_depth()->pop_local(p)) {

   273         process_popped_location_depth(p);

   274       }

   275     }

   276   } while( (totally_drain && claimed_stack_depth()->size() > 0) ||

   277            (overflow_stack_depth()->length() > 0) );

   278 

   279   assert(!totally_drain || claimed_stack_empty(), "Sanity");

   280   assert(totally_drain ||

   281          claimed_stack_depth()->size() <= _target_stack_size,

   282          "Sanity");

   283   assert(overflow_stack_empty(), "Sanity");

   284 }

   285 

   286 void PSPromotionManager::drain_stacks_breadth(bool totally_drain) {

   287   assert(!depth_first(), "invariant");

   288   assert(overflow_stack_breadth() != NULL, "invariant");

   289   totally_drain = totally_drain || _totally_drain;

   290 

   291 #ifdef ASSERT

   292   ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();

   293   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");

   294   MutableSpace* to_space = heap->young_gen()->to_space();

   295   MutableSpace* old_space = heap->old_gen()->object_space();

   296   MutableSpace* perm_space = heap->perm_gen()->object_space();

   297 #endif /* ASSERT */

   298 

   299   do {

   300     oop obj;

   301 

   302     // Drain overflow stack first, so other threads can steal from

   303     // claimed stack while we work.

   304     while(!overflow_stack_breadth()->is_empty()) {

   305       obj = overflow_stack_breadth()->pop();

   306       obj->copy_contents(this);

   307     }

   308 

   309     if (totally_drain) {

   310       // obj is a reference!!!

   311       while (claimed_stack_breadth()->pop_local(obj)) {

   312         // It would be nice to assert about the type of objects we might

   313         // pop, but they can come from anywhere, unfortunately.

   314         obj->copy_contents(this);

   315       }

   316     } else {

   317       // obj is a reference!!!

   318       while (claimed_stack_breadth()->size() > _target_stack_size &&

   319              claimed_stack_breadth()->pop_local(obj)) {

   320         // It would be nice to assert about the type of objects we might

   321         // pop, but they can come from anywhere, unfortunately.

   322         obj->copy_contents(this);

   323       }

   324     }

   325 

   326     // If we could not find any other work, flush the prefetch queue

   327     if (claimed_stack_breadth()->size() == 0 &&

   328         (overflow_stack_breadth()->length() == 0)) {

   329       flush_prefetch_queue();

   330     }

   331   } while((totally_drain && claimed_stack_breadth()->size() > 0) ||

   332           (overflow_stack_breadth()->length() > 0));

   333 

   334   assert(!totally_drain || claimed_stack_empty(), "Sanity");

   335   assert(totally_drain ||

   336          claimed_stack_breadth()->size() <= _target_stack_size,

   337          "Sanity");

   338   assert(overflow_stack_empty(), "Sanity");

   339 }

   340 

   341 void PSPromotionManager::flush_labs() {

   342   assert(claimed_stack_empty(), "Attempt to flush lab with live stack");

   343   assert(overflow_stack_empty(), "Attempt to flush lab with live overflow stack");

   344 

   345   // If either promotion lab fills up, we can flush the

   346   // lab but not refill it, so check first.

   347   assert(!_young_lab.is_flushed() || _young_gen_is_full, "Sanity");

   348   if (!_young_lab.is_flushed())

   349     _young_lab.flush();

   350 

   351   assert(!_old_lab.is_flushed() || _old_gen_is_full, "Sanity");

   352   if (!_old_lab.is_flushed())

   353     _old_lab.flush();

   354 

   355   // Let PSScavenge know if we overflowed

   356   if (_young_gen_is_full) {

   357     PSScavenge::set_survivor_overflow(true);

   358   }

   359 }

   360 

   361 //

   362 // This method is pretty bulky. It would be nice to split it up

   363 // into smaller submethods, but we need to be careful not to hurt

   364 // performance.

   365 //

   366 

   367 oop PSPromotionManager::copy_to_survivor_space(oop o, bool depth_first) {

   368   assert(PSScavenge::should_scavenge(o), "Sanity");

   369 

   370   oop new_obj = NULL;

   371 

   372   // NOTE! We must be very careful with any methods that access the mark

   373   // in o. There may be multiple threads racing on it, and it may be forwarded

   374   // at any time. Do not use oop methods for accessing the mark!

   375   markOop test_mark = o->mark();

   376 

   377   // The same test as "o->is_forwarded()"

   378   if (!test_mark->is_marked()) {

   379     bool new_obj_is_tenured = false;

   380     size_t new_obj_size = o->size();

   381 

   382     // Find the objects age, MT safe.

   383     int age = (test_mark->has_displaced_mark_helper() /* o->has_displaced_mark() */) ?

   384       test_mark->displaced_mark_helper()->age() : test_mark->age();

   385 

   386     // Try allocating obj in to-space (unless too old)

   387     if (age < PSScavenge::tenuring_threshold()) {

   388       new_obj = (oop) _young_lab.allocate(new_obj_size);

   389       if (new_obj == NULL && !_young_gen_is_full) {

   390         // Do we allocate directly, or flush and refill?

   391         if (new_obj_size > (YoungPLABSize / 2)) {

   392           // Allocate this object directly

   393           new_obj = (oop)young_space()->cas_allocate(new_obj_size);

   394         } else {

   395           // Flush and fill

   396           _young_lab.flush();

   397 

   398           HeapWord* lab_base = young_space()->cas_allocate(YoungPLABSize);

   399           if (lab_base != NULL) {

   400             _young_lab.initialize(MemRegion(lab_base, YoungPLABSize));

   401             // Try the young lab allocation again.

   402             new_obj = (oop) _young_lab.allocate(new_obj_size);

   403           } else {

   404             _young_gen_is_full = true;

   405           }

   406         }

   407       }

   408     }

   409 

   410     // Otherwise try allocating obj tenured

   411     if (new_obj == NULL) {

   412 #ifndef PRODUCT

   413       if (Universe::heap()->promotion_should_fail()) {

   414         return oop_promotion_failed(o, test_mark);

   415       }

   416 #endif  // #ifndef PRODUCT

   417 

   418       new_obj = (oop) _old_lab.allocate(new_obj_size);

   419       new_obj_is_tenured = true;

   420 

   421       if (new_obj == NULL) {

   422         if (!_old_gen_is_full) {

   423           // Do we allocate directly, or flush and refill?

   424           if (new_obj_size > (OldPLABSize / 2)) {

   425             // Allocate this object directly

   426             new_obj = (oop)old_gen()->cas_allocate(new_obj_size);

   427           } else {

   428             // Flush and fill

   429             _old_lab.flush();

   430 

   431             HeapWord* lab_base = old_gen()->cas_allocate(OldPLABSize);

   432             if(lab_base != NULL) {

   433               _old_lab.initialize(MemRegion(lab_base, OldPLABSize));

   434               // Try the old lab allocation again.

   435               new_obj = (oop) _old_lab.allocate(new_obj_size);

   436             }

   437           }

   438         }

   439 

   440         // This is the promotion failed test, and code handling.

   441         // The code belongs here for two reasons. It is slightly

   442         // different thatn the code below, and cannot share the

   443         // CAS testing code. Keeping the code here also minimizes

   444         // the impact on the common case fast path code.

   445 

   446         if (new_obj == NULL) {

   447           _old_gen_is_full = true;

   448           return oop_promotion_failed(o, test_mark);

   449         }

   450       }

   451     }

   452 

   453     assert(new_obj != NULL, "allocation should have succeeded");

   454 

   455     // Copy obj

   456     Copy::aligned_disjoint_words((HeapWord*)o, (HeapWord*)new_obj, new_obj_size);

   457 

   458     // Now we have to CAS in the header.

   459     if (o->cas_forward_to(new_obj, test_mark)) {

   460       // We won any races, we "own" this object.

   461       assert(new_obj == o->forwardee(), "Sanity");

   462 

   463       // Increment age if obj still in new generation. Now that

   464       // we're dealing with a markOop that cannot change, it is

   465       // okay to use the non mt safe oop methods.

   466       if (!new_obj_is_tenured) {

   467         new_obj->incr_age();

   468         assert(young_space()->contains(new_obj), "Attempt to push non-promoted obj");

   469       }

   470 

   471       if (depth_first) {

   472         // Do the size comparison first with new_obj_size, which we

   473         // already have. Hopefully, only a few objects are larger than

   474         // _min_array_size_for_chunking, and most of them will be arrays.

   475         // So, the is->objArray() test would be very infrequent.

   476         if (new_obj_size > _min_array_size_for_chunking &&

   477             new_obj->is_objArray() &&

   478             PSChunkLargeArrays) {

   479           // we'll chunk it

   480 #if PS_PM_STATS

   481           ++_arrays_chunked;

   482 #endif // PS_PM_STATS

   483           oop* const masked_o = mask_chunked_array_oop(o);

   484           push_depth(masked_o);

   485 #if PS_PM_STATS

   486           ++_masked_pushes;

   487 #endif // PS_PM_STATS

   488         } else {

   489           // we'll just push its contents

   490           new_obj->push_contents(this);

   491         }

   492       } else {

   493         push_breadth(new_obj);

   494       }

   495     }  else {

   496       // We lost, someone else "owns" this object

   497       guarantee(o->is_forwarded(), "Object must be forwarded if the cas failed.");

   498 

   499       // Unallocate the space used. NOTE! We may have directly allocated

   500       // the object. If so, we cannot deallocate it, so we have to test!

   501       if (new_obj_is_tenured) {

   502         if (!_old_lab.unallocate_object(new_obj)) {

   503           // The promotion lab failed to unallocate the object.

   504           // We need to overwrite the object with a filler that

   505           // contains no interior pointers.

   506           MemRegion mr((HeapWord*)new_obj, new_obj_size);

   507           // Clean this up and move to oopFactory (see bug 4718422)

   508           SharedHeap::fill_region_with_object(mr);

   509         }

   510       } else {

   511         if (!_young_lab.unallocate_object(new_obj)) {

   512           // The promotion lab failed to unallocate the object.

   513           // We need to overwrite the object with a filler that

   514           // contains no interior pointers.

   515           MemRegion mr((HeapWord*)new_obj, new_obj_size);

   516           // Clean this up and move to oopFactory (see bug 4718422)

   517           SharedHeap::fill_region_with_object(mr);

   518         }

   519       }

   520 

   521       // don't update this before the unallocation!

   522       new_obj = o->forwardee();

   523     }

   524   } else {

   525     assert(o->is_forwarded(), "Sanity");

   526     new_obj = o->forwardee();

   527   }

   528 

   529 #ifdef DEBUG

   530   // This code must come after the CAS test, or it will print incorrect

   531   // information.

   532   if (TraceScavenge) {

   533     gclog_or_tty->print_cr("{%s %s 0x%x -> 0x%x (%d)}",

   534        PSScavenge::should_scavenge(new_obj) ? "copying" : "tenuring",

   535        new_obj->blueprint()->internal_name(), o, new_obj, new_obj->size());

   536 

   537   }

   538 #endif

   539 

   540   return new_obj;

   541 }

   542 

   543 void PSPromotionManager::process_array_chunk(oop old) {

   544   assert(PSChunkLargeArrays, "invariant");

   545   assert(old->is_objArray(), "invariant");

   546   assert(old->is_forwarded(), "invariant");

   547 

   548 #if PS_PM_STATS

   549   ++_array_chunks_processed;

   550 #endif // PS_PM_STATS

   551 

   552   oop const obj = old->forwardee();

   553 

   554   int start;

   555   int const end = arrayOop(old)->length();

   556   if (end > (int) _min_array_size_for_chunking) {

   557     // we'll chunk more

   558     start = end - _array_chunk_size;

   559     assert(start > 0, "invariant");

   560     arrayOop(old)->set_length(start);

   561     push_depth(mask_chunked_array_oop(old));

   562 #if PS_PM_STATS

   563     ++_masked_pushes;

   564 #endif // PS_PM_STATS

   565   } else {

   566     // this is the final chunk for this array

   567     start = 0;

   568     int const actual_length = arrayOop(obj)->length();

   569     arrayOop(old)->set_length(actual_length);

   570   }

   571 

   572   assert(start < end, "invariant");

   573   oop* const base      = objArrayOop(obj)->base();

   574   oop* p               = base + start;

   575   oop* const chunk_end = base + end;

   576   while (p < chunk_end) {

   577     if (PSScavenge::should_scavenge(*p)) {

   578       claim_or_forward_depth(p);

   579     }

   580     ++p;

   581   }

   582 }

   583 

   584 oop PSPromotionManager::oop_promotion_failed(oop obj, markOop obj_mark) {

   585   assert(_old_gen_is_full || PromotionFailureALot, "Sanity");

   586 

   587   // Attempt to CAS in the header.

   588   // This tests if the header is still the same as when

   589   // this started.  If it is the same (i.e., no forwarding

   590   // pointer has been installed), then this thread owns

   591   // it.

   592   if (obj->cas_forward_to(obj, obj_mark)) {

   593     // We won any races, we "own" this object.

   594     assert(obj == obj->forwardee(), "Sanity");

   595 

   596     if (depth_first()) {

   597       obj->push_contents(this);

   598     } else {

   599       // Don't bother incrementing the age, just push

   600       // onto the claimed_stack..

   601       push_breadth(obj);

   602     }

   603 

   604     // Save the mark if needed

   605     PSScavenge::oop_promotion_failed(obj, obj_mark);

   606   }  else {

   607     // We lost, someone else "owns" this object

   608     guarantee(obj->is_forwarded(), "Object must be forwarded if the cas failed.");

   609 

   610     // No unallocation to worry about.

   611     obj = obj->forwardee();

   612   }

   613 

   614 #ifdef DEBUG

   615   if (TraceScavenge) {

   616     gclog_or_tty->print_cr("{%s %s 0x%x (%d)}",

   617                            "promotion-failure",

   618                            obj->blueprint()->internal_name(),

   619                            obj, obj->size());

   620 

   621   }

   622 #endif

   623 

   624   return obj;

   625 }