Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright 2001-2008 Sun Microsystems, Inc.  All Rights Reserved.

  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

  *

  * This code is free software; you can redistribute it and/or modify it

  * under the terms of the GNU General Public License version 2 only, as

  * published by the Free Software Foundation.

  *

  * This code is distributed in the hope that it will be useful, but WITHOUT

  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

  * version 2 for more details (a copy is included in the LICENSE file that

  * accompanied this code).

  *

  * You should have received a copy of the GNU General Public License version

  * 2 along with this work; if not, write to the Free Software Foundation,

  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

  *

  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,

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

  * have any questions.

  *

  */

 # include "incls/_precompiled.incl"

 # include "incls/_parallelScavengeHeap.cpp.incl"

 PSYoungGen*  ParallelScavengeHeap::_young_gen = NULL;

 PSOldGen*    ParallelScavengeHeap::_old_gen = NULL;

 PSPermGen*   ParallelScavengeHeap::_perm_gen = NULL;

 PSAdaptiveSizePolicy* ParallelScavengeHeap::_size_policy = NULL;

 PSGCAdaptivePolicyCounters* ParallelScavengeHeap::_gc_policy_counters = NULL;

 ParallelScavengeHeap* ParallelScavengeHeap::_psh = NULL;

 GCTaskManager* ParallelScavengeHeap::_gc_task_manager = NULL;

 static void trace_gen_sizes(const char* const str,

                             size_t pg_min, size_t pg_max,

                             size_t og_min, size_t og_max,

                             size_t yg_min, size_t yg_max)

 {

   if (TracePageSizes) {

     tty->print_cr("%s:  " SIZE_FORMAT "," SIZE_FORMAT " "

                   SIZE_FORMAT "," SIZE_FORMAT " "

                   SIZE_FORMAT "," SIZE_FORMAT " "

                   SIZE_FORMAT,

                   str, pg_min / K, pg_max / K,

                   og_min / K, og_max / K,

                   yg_min / K, yg_max / K,

                   (pg_max + og_max + yg_max) / K);

   }

 }

 jint ParallelScavengeHeap::initialize() {

   // Cannot be initialized until after the flags are parsed

   GenerationSizer flag_parser;

   size_t yg_min_size = flag_parser.min_young_gen_size();

   size_t yg_max_size = flag_parser.max_young_gen_size();

   size_t og_min_size = flag_parser.min_old_gen_size();

   size_t og_max_size = flag_parser.max_old_gen_size();

   // Why isn't there a min_perm_gen_size()?

   size_t pg_min_size = flag_parser.perm_gen_size();

   size_t pg_max_size = flag_parser.max_perm_gen_size();

   trace_gen_sizes("ps heap raw",

                   pg_min_size, pg_max_size,

                   og_min_size, og_max_size,

                   yg_min_size, yg_max_size);

   // The ReservedSpace ctor used below requires that the page size for the perm

   // gen is <= the page size for the rest of the heap (young + old gens).

   const size_t og_page_sz = os::page_size_for_region(yg_min_size + og_min_size,

                                                      yg_max_size + og_max_size,

                                                      8);

   const size_t pg_page_sz = MIN2(os::page_size_for_region(pg_min_size,

                                                           pg_max_size, 16),

                                  og_page_sz);

   const size_t pg_align = set_alignment(_perm_gen_alignment,  pg_page_sz);

   const size_t og_align = set_alignment(_old_gen_alignment,   og_page_sz);

   const size_t yg_align = set_alignment(_young_gen_alignment, og_page_sz);

   // Update sizes to reflect the selected page size(s).

   //

   // NEEDS_CLEANUP.  The default TwoGenerationCollectorPolicy uses NewRatio; it

   // should check UseAdaptiveSizePolicy.  Changes from generationSizer could

   // move to the common code.

   yg_min_size = align_size_up(yg_min_size, yg_align);

   yg_max_size = align_size_up(yg_max_size, yg_align);

   size_t yg_cur_size = align_size_up(flag_parser.young_gen_size(), yg_align);

   yg_cur_size = MAX2(yg_cur_size, yg_min_size);

   og_min_size = align_size_up(og_min_size, og_align);

   og_max_size = align_size_up(og_max_size, og_align);

   size_t og_cur_size = align_size_up(flag_parser.old_gen_size(), og_align);

   og_cur_size = MAX2(og_cur_size, og_min_size);

   pg_min_size = align_size_up(pg_min_size, pg_align);

   pg_max_size = align_size_up(pg_max_size, pg_align);

   size_t pg_cur_size = pg_min_size;

   trace_gen_sizes("ps heap rnd",

                   pg_min_size, pg_max_size,

                   og_min_size, og_max_size,

                   yg_min_size, yg_max_size);

   // The main part of the heap (old gen + young gen) can often use a larger page

   // size than is needed or wanted for the perm gen.  Use the "compound

   // alignment" ReservedSpace ctor to avoid having to use the same page size for

   // all gens.

   ReservedSpace heap_rs(pg_max_size, pg_align, og_max_size + yg_max_size,

                         og_align);

   os::trace_page_sizes("ps perm", pg_min_size, pg_max_size, pg_page_sz,

                        heap_rs.base(), pg_max_size);

   os::trace_page_sizes("ps main", og_min_size + yg_min_size,

                        og_max_size + yg_max_size, og_page_sz,

                        heap_rs.base() + pg_max_size,

                        heap_rs.size() - pg_max_size);

   if (!heap_rs.is_reserved()) {

     vm_shutdown_during_initialization(

       "Could not reserve enough space for object heap");

     return JNI_ENOMEM;

   }

   _reserved = MemRegion((HeapWord*)heap_rs.base(),

                         (HeapWord*)(heap_rs.base() + heap_rs.size()));

   CardTableExtension* const barrier_set = new CardTableExtension(_reserved, 3);

   _barrier_set = barrier_set;

   oopDesc::set_bs(_barrier_set);

   if (_barrier_set == NULL) {

     vm_shutdown_during_initialization(

       "Could not reserve enough space for barrier set");

     return JNI_ENOMEM;

   }

   // Initial young gen size is 4 Mb

   //

   // XXX - what about flag_parser.young_gen_size()?

   const size_t init_young_size = align_size_up(4 * M, yg_align);

   yg_cur_size = MAX2(MIN2(init_young_size, yg_max_size), yg_cur_size);

   // Split the reserved space into perm gen and the main heap (everything else).

   // The main heap uses a different alignment.

   ReservedSpace perm_rs = heap_rs.first_part(pg_max_size);

   ReservedSpace main_rs = heap_rs.last_part(pg_max_size, og_align);

   // Make up the generations

   // Calculate the maximum size that a generation can grow.  This

   // includes growth into the other generation.  Note that the

   // parameter _max_gen_size is kept as the maximum

   // size of the generation as the boundaries currently stand.

   // _max_gen_size is still used as that value.

   double max_gc_pause_sec = ((double) MaxGCPauseMillis)/1000.0;

   double max_gc_minor_pause_sec = ((double) MaxGCMinorPauseMillis)/1000.0;

   _gens = new AdjoiningGenerations(main_rs,

                                    og_cur_size,

                                    og_min_size,

                                    og_max_size,

                                    yg_cur_size,

                                    yg_min_size,

                                    yg_max_size,

                                    yg_align);

   _old_gen = _gens->old_gen();

   _young_gen = _gens->young_gen();

   const size_t eden_capacity = _young_gen->eden_space()->capacity_in_bytes();

   const size_t old_capacity = _old_gen->capacity_in_bytes();

   const size_t initial_promo_size = MIN2(eden_capacity, old_capacity);

   _size_policy =

     new PSAdaptiveSizePolicy(eden_capacity,

                              initial_promo_size,

                              young_gen()->to_space()->capacity_in_bytes(),

                              intra_heap_alignment(),

                              max_gc_pause_sec,

                              max_gc_minor_pause_sec,

                              GCTimeRatio

                              );

   _perm_gen = new PSPermGen(perm_rs,

                             pg_align,

                             pg_cur_size,

                             pg_cur_size,

                             pg_max_size,

                             "perm", 2);

   assert(!UseAdaptiveGCBoundary ||

     (old_gen()->virtual_space()->high_boundary() ==

      young_gen()->virtual_space()->low_boundary()),

     "Boundaries must meet");

   // initialize the policy counters - 2 collectors, 3 generations

   _gc_policy_counters =

     new PSGCAdaptivePolicyCounters("ParScav:MSC", 2, 3, _size_policy);

   _psh = this;

   // Set up the GCTaskManager

   _gc_task_manager = GCTaskManager::create(ParallelGCThreads);

   if (UseParallelOldGC && !PSParallelCompact::initialize()) {

     return JNI_ENOMEM;

   }

   return JNI_OK;

 }

 void ParallelScavengeHeap::post_initialize() {

   // Need to init the tenuring threshold

   PSScavenge::initialize();

   if (UseParallelOldGC) {

     PSParallelCompact::post_initialize();

     if (VerifyParallelOldWithMarkSweep) {

       // Will be used for verification of par old.

       PSMarkSweep::initialize();

     }

   } else {

     PSMarkSweep::initialize();

   }

   PSPromotionManager::initialize();

 }

 void ParallelScavengeHeap::update_counters() {

   young_gen()->update_counters();

   old_gen()->update_counters();

   perm_gen()->update_counters();

 }

 size_t ParallelScavengeHeap::capacity() const {

   size_t value = young_gen()->capacity_in_bytes() + old_gen()->capacity_in_bytes();

   return value;

 }

 size_t ParallelScavengeHeap::used() const {

   size_t value = young_gen()->used_in_bytes() + old_gen()->used_in_bytes();

   return value;

 }

 bool ParallelScavengeHeap::is_maximal_no_gc() const {

   return old_gen()->is_maximal_no_gc() && young_gen()->is_maximal_no_gc();

 }

 size_t ParallelScavengeHeap::permanent_capacity() const {

   return perm_gen()->capacity_in_bytes();

 }

 size_t ParallelScavengeHeap::permanent_used() const {

   return perm_gen()->used_in_bytes();

 }

 size_t ParallelScavengeHeap::max_capacity() const {

   size_t estimated = reserved_region().byte_size();

   estimated -= perm_gen()->reserved().byte_size();

   if (UseAdaptiveSizePolicy) {

     estimated -= _size_policy->max_survivor_size(young_gen()->max_size());

   } else {

     estimated -= young_gen()->to_space()->capacity_in_bytes();

   }

   return MAX2(estimated, capacity());

 }

 bool ParallelScavengeHeap::is_in(const void* p) const {

   if (young_gen()->is_in(p)) {

     return true;

   }

   if (old_gen()->is_in(p)) {

     return true;

   }

   if (perm_gen()->is_in(p)) {

     return true;

   }

   return false;

 }

 bool ParallelScavengeHeap::is_in_reserved(const void* p) const {

   if (young_gen()->is_in_reserved(p)) {

     return true;

   }

   if (old_gen()->is_in_reserved(p)) {

     return true;

   }

   if (perm_gen()->is_in_reserved(p)) {

     return true;

   }

   return false;

 }

 // Static method

 bool ParallelScavengeHeap::is_in_young(oop* p) {

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

   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap,

                                             "Must be ParallelScavengeHeap");

   PSYoungGen* young_gen = heap->young_gen();

   if (young_gen->is_in_reserved(p)) {

     return true;

   }

   return false;

 }

 // Static method

 bool ParallelScavengeHeap::is_in_old_or_perm(oop* p) {

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

   assert(heap->kind() == CollectedHeap::ParallelScavengeHeap,

                                             "Must be ParallelScavengeHeap");

   PSOldGen* old_gen = heap->old_gen();

   PSPermGen* perm_gen = heap->perm_gen();

   if (old_gen->is_in_reserved(p)) {

     return true;

   }

   if (perm_gen->is_in_reserved(p)) {

     return true;

   }

   return false;

 }

 // There are two levels of allocation policy here.

 //

 // When an allocation request fails, the requesting thread must invoke a VM

 // operation, transfer control to the VM thread, and await the results of a

 // garbage collection. That is quite expensive, and we should avoid doing it

 // multiple times if possible.

 //

 // To accomplish this, we have a basic allocation policy, and also a

 // failed allocation policy.

 //

 // The basic allocation policy controls how you allocate memory without

 // attempting garbage collection. It is okay to grab locks and

 // expand the heap, if that can be done without coming to a safepoint.

 // It is likely that the basic allocation policy will not be very

 // aggressive.

 //

 // The failed allocation policy is invoked from the VM thread after

 // the basic allocation policy is unable to satisfy a mem_allocate

 // request. This policy needs to cover the entire range of collection,

 // heap expansion, and out-of-memory conditions. It should make every

 // attempt to allocate the requested memory.

 // Basic allocation policy. Should never be called at a safepoint, or

 // from the VM thread.

 //

 // This method must handle cases where many mem_allocate requests fail

 // simultaneously. When that happens, only one VM operation will succeed,

 // and the rest will not be executed. For that reason, this method loops

 // during failed allocation attempts. If the java heap becomes exhausted,

 // we rely on the size_policy object to force a bail out.

 HeapWord* ParallelScavengeHeap::mem_allocate(

                                      size_t size,

                                      bool is_noref,

                                      bool is_tlab,

                                      bool* gc_overhead_limit_was_exceeded) {

   assert(!SafepointSynchronize::is_at_safepoint(), "should not be at safepoint");

   assert(Thread::current() != (Thread*)VMThread::vm_thread(), "should not be in vm thread");

   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");

   HeapWord* result = young_gen()->allocate(size, is_tlab);

   uint loop_count = 0;

   uint gc_count = 0;

   while (result == NULL) {

     // We don't want to have multiple collections for a single filled generation.

     // To prevent this, each thread tracks the total_collections() value, and if

     // the count has changed, does not do a new collection.

     //

     // The collection count must be read only while holding the heap lock. VM

     // operations also hold the heap lock during collections. There is a lock

     // contention case where thread A blocks waiting on the Heap_lock, while

     // thread B is holding it doing a collection. When thread A gets the lock,

     // the collection count has already changed. To prevent duplicate collections,

     // The policy MUST attempt allocations during the same period it reads the

     // total_collections() value!

     {

       MutexLocker ml(Heap_lock);

       gc_count = Universe::heap()->total_collections();

       result = young_gen()->allocate(size, is_tlab);

       // (1) If the requested object is too large to easily fit in the

       //     young_gen, or

       // (2) If GC is locked out via GCLocker, young gen is full and

       //     the need for a GC already signalled to GCLocker (done

       //     at a safepoint),

       // ... then, rather than force a safepoint and (a potentially futile)

       // collection (attempt) for each allocation, try allocation directly

       // in old_gen. For case (2) above, we may in the future allow

       // TLAB allocation directly in the old gen.

       if (result != NULL) {

         return result;

       }

       if (!is_tlab &&

           size >= (young_gen()->eden_space()->capacity_in_words() / 2)) {

         result = old_gen()->allocate(size, is_tlab);

         if (result != NULL) {

           return result;

         }

       }

       if (GC_locker::is_active_and_needs_gc()) {

         // GC is locked out. If this is a TLAB allocation,

         // return NULL; the requestor will retry allocation

         // of an idividual object at a time.

         if (is_tlab) {

           return NULL;

         }

         // If this thread is not in a jni critical section, we stall

         // the requestor until the critical section has cleared and

         // GC allowed. When the critical section clears, a GC is

         // initiated by the last thread exiting the critical section; so

         // we retry the allocation sequence from the beginning of the loop,

         // rather than causing more, now probably unnecessary, GC attempts.

         JavaThread* jthr = JavaThread::current();

         if (!jthr->in_critical()) {

           MutexUnlocker mul(Heap_lock);

           GC_locker::stall_until_clear();

           continue;

         } else {

           if (CheckJNICalls) {

             fatal("Possible deadlock due to allocating while"

                   " in jni critical section");

           }

           return NULL;

         }

       }

     }

     if (result == NULL) {

       // Exit the loop if if the gc time limit has been exceeded.

       // The allocation must have failed above (result must be NULL),

       // and the most recent collection must have exceeded the

       // gc time limit.  Exit the loop so that an out-of-memory

       // will be thrown (returning a NULL will do that), but

       // clear gc_time_limit_exceeded so that the next collection

       // will succeeded if the applications decides to handle the

       // out-of-memory and tries to go on.

       *gc_overhead_limit_was_exceeded = size_policy()->gc_time_limit_exceeded();

       if (size_policy()->gc_time_limit_exceeded()) {

         size_policy()->set_gc_time_limit_exceeded(false);

         if (PrintGCDetails && Verbose) {

         gclog_or_tty->print_cr("ParallelScavengeHeap::mem_allocate: "

           "return NULL because gc_time_limit_exceeded is set");

         }

         return NULL;

       }

       // Generate a VM operation

       VM_ParallelGCFailedAllocation op(size, is_tlab, gc_count);

       VMThread::execute(&op);

       // Did the VM operation execute? If so, return the result directly.

       // This prevents us from looping until time out on requests that can

       // not be satisfied.

       if (op.prologue_succeeded()) {

         assert(Universe::heap()->is_in_or_null(op.result()),

           "result not in heap");

         // If GC was locked out during VM operation then retry allocation

         // and/or stall as necessary.

         if (op.gc_locked()) {

           assert(op.result() == NULL, "must be NULL if gc_locked() is true");

           continue;  // retry and/or stall as necessary

         }

         // If a NULL result is being returned, an out-of-memory

         // will be thrown now.  Clear the gc_time_limit_exceeded

         // flag to avoid the following situation.

         //      gc_time_limit_exceeded is set during a collection

         //      the collection fails to return enough space and an OOM is thrown

         //      the next GC is skipped because the gc_time_limit_exceeded

         //        flag is set and another OOM is thrown

         if (op.result() == NULL) {

           size_policy()->set_gc_time_limit_exceeded(false);

         }

         return op.result();

       }

     }

     // The policy object will prevent us from looping forever. If the

     // time spent in gc crosses a threshold, we will bail out.

     loop_count++;

     if ((result == NULL) && (QueuedAllocationWarningCount > 0) &&

         (loop_count % QueuedAllocationWarningCount == 0)) {

       warning("ParallelScavengeHeap::mem_allocate retries %d times \n\t"

               " size=%d %s", loop_count, size, is_tlab ? "(TLAB)" : "");

     }

   }

   return result;

 }

 // Failed allocation policy. Must be called from the VM thread, and

 // only at a safepoint! Note that this method has policy for allocation

 // flow, and NOT collection policy. So we do not check for gc collection

 // time over limit here, that is the responsibility of the heap specific

 // collection methods. This method decides where to attempt allocations,

 // and when to attempt collections, but no collection specific policy.

 HeapWord* ParallelScavengeHeap::failed_mem_allocate(size_t size, bool is_tlab) {

   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");

   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");

   assert(!Universe::heap()->is_gc_active(), "not reentrant");

   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");

   size_t mark_sweep_invocation_count = total_invocations();

   // We assume (and assert!) that an allocation at this point will fail

   // unless we collect.

   // First level allocation failure, scavenge and allocate in young gen.

   GCCauseSetter gccs(this, GCCause::_allocation_failure);

   PSScavenge::invoke();

   HeapWord* result = young_gen()->allocate(size, is_tlab);

   // Second level allocation failure.

   //   Mark sweep and allocate in young generation.

   if (result == NULL) {

     // There is some chance the scavenge method decided to invoke mark_sweep.

     // Don't mark sweep twice if so.

     if (mark_sweep_invocation_count == total_invocations()) {

       invoke_full_gc(false);

       result = young_gen()->allocate(size, is_tlab);

     }

   }

   // Third level allocation failure.

   //   After mark sweep and young generation allocation failure,

   //   allocate in old generation.

   if (result == NULL && !is_tlab) {

     result = old_gen()->allocate(size, is_tlab);

   }

   // Fourth level allocation failure. We're running out of memory.

   //   More complete mark sweep and allocate in young generation.

   if (result == NULL) {

     invoke_full_gc(true);

     result = young_gen()->allocate(size, is_tlab);

   }

   // Fifth level allocation failure.

   //   After more complete mark sweep, allocate in old generation.

   if (result == NULL && !is_tlab) {

     result = old_gen()->allocate(size, is_tlab);

   }

   return result;

 }

 //

 // This is the policy loop for allocating in the permanent generation.

 // If the initial allocation fails, we create a vm operation which will

 // cause a collection.

 HeapWord* ParallelScavengeHeap::permanent_mem_allocate(size_t size) {

   assert(!SafepointSynchronize::is_at_safepoint(), "should not be at safepoint");

   assert(Thread::current() != (Thread*)VMThread::vm_thread(), "should not be in vm thread");

   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");

   HeapWord* result;

   uint loop_count = 0;

   uint gc_count = 0;

   uint full_gc_count = 0;

   do {

     // We don't want to have multiple collections for a single filled generation.

     // To prevent this, each thread tracks the total_collections() value, and if

     // the count has changed, does not do a new collection.

     //

     // The collection count must be read only while holding the heap lock. VM

     // operations also hold the heap lock during collections. There is a lock

     // contention case where thread A blocks waiting on the Heap_lock, while

     // thread B is holding it doing a collection. When thread A gets the lock,

     // the collection count has already changed. To prevent duplicate collections,

     // The policy MUST attempt allocations during the same period it reads the

     // total_collections() value!

     {

       MutexLocker ml(Heap_lock);

       gc_count      = Universe::heap()->total_collections();

       full_gc_count = Universe::heap()->total_full_collections();

       result = perm_gen()->allocate_permanent(size);

       if (result != NULL) {

         return result;

       }

       if (GC_locker::is_active_and_needs_gc()) {

         // If this thread is not in a jni critical section, we stall

         // the requestor until the critical section has cleared and

         // GC allowed. When the critical section clears, a GC is

         // initiated by the last thread exiting the critical section; so

         // we retry the allocation sequence from the beginning of the loop,

         // rather than causing more, now probably unnecessary, GC attempts.

         JavaThread* jthr = JavaThread::current();

         if (!jthr->in_critical()) {

           MutexUnlocker mul(Heap_lock);

           GC_locker::stall_until_clear();

           continue;

         } else {

           if (CheckJNICalls) {

             fatal("Possible deadlock due to allocating while"

                   " in jni critical section");

           }

           return NULL;

         }

       }

     }

     if (result == NULL) {

       // Exit the loop if the gc time limit has been exceeded.

       // The allocation must have failed above (result must be NULL),

       // and the most recent collection must have exceeded the

       // gc time limit.  Exit the loop so that an out-of-memory

       // will be thrown (returning a NULL will do that), but

       // clear gc_time_limit_exceeded so that the next collection

       // will succeeded if the applications decides to handle the

       // out-of-memory and tries to go on.

       if (size_policy()->gc_time_limit_exceeded()) {

         size_policy()->set_gc_time_limit_exceeded(false);

         if (PrintGCDetails && Verbose) {

         gclog_or_tty->print_cr("ParallelScavengeHeap::permanent_mem_allocate: "

           "return NULL because gc_time_limit_exceeded is set");

         }

         assert(result == NULL, "Allocation did not fail");

         return NULL;

       }

       // Generate a VM operation

       VM_ParallelGCFailedPermanentAllocation op(size, gc_count, full_gc_count);

       VMThread::execute(&op);

       // Did the VM operation execute? If so, return the result directly.

       // This prevents us from looping until time out on requests that can

       // not be satisfied.

       if (op.prologue_succeeded()) {

         assert(Universe::heap()->is_in_permanent_or_null(op.result()),

           "result not in heap");

         // If GC was locked out during VM operation then retry allocation

         // and/or stall as necessary.

         if (op.gc_locked()) {

           assert(op.result() == NULL, "must be NULL if gc_locked() is true");

           continue;  // retry and/or stall as necessary

         }

         // If a NULL results is being returned, an out-of-memory

         // will be thrown now.  Clear the gc_time_limit_exceeded

         // flag to avoid the following situation.

         //      gc_time_limit_exceeded is set during a collection

         //      the collection fails to return enough space and an OOM is thrown

         //      the next GC is skipped because the gc_time_limit_exceeded

         //        flag is set and another OOM is thrown

         if (op.result() == NULL) {

           size_policy()->set_gc_time_limit_exceeded(false);

         }

         return op.result();

       }

     }

     // The policy object will prevent us from looping forever. If the

     // time spent in gc crosses a threshold, we will bail out.

     loop_count++;

     if ((QueuedAllocationWarningCount > 0) &&

         (loop_count % QueuedAllocationWarningCount == 0)) {

       warning("ParallelScavengeHeap::permanent_mem_allocate retries %d times \n\t"

               " size=%d", loop_count, size);

     }

   } while (result == NULL);

   return result;

 }

 //

 // This is the policy code for permanent allocations which have failed

 // and require a collection. Note that just as in failed_mem_allocate,

 // we do not set collection policy, only where & when to allocate and

 // collect.

 HeapWord* ParallelScavengeHeap::failed_permanent_mem_allocate(size_t size) {

   assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");

   assert(Thread::current() == (Thread*)VMThread::vm_thread(), "should be in vm thread");

   assert(!Universe::heap()->is_gc_active(), "not reentrant");

   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");

   assert(size > perm_gen()->free_in_words(), "Allocation should fail");

   // We assume (and assert!) that an allocation at this point will fail

   // unless we collect.

   // First level allocation failure.  Mark-sweep and allocate in perm gen.

   GCCauseSetter gccs(this, GCCause::_allocation_failure);

   invoke_full_gc(false);

   HeapWord* result = perm_gen()->allocate_permanent(size);

   // Second level allocation failure. We're running out of memory.

   if (result == NULL) {

     invoke_full_gc(true);

     result = perm_gen()->allocate_permanent(size);

   }

   return result;

 }

 void ParallelScavengeHeap::ensure_parsability(bool retire_tlabs) {

   CollectedHeap::ensure_parsability(retire_tlabs);

   young_gen()->eden_space()->ensure_parsability();

 }

 size_t ParallelScavengeHeap::unsafe_max_alloc() {

   return young_gen()->eden_space()->free_in_bytes();

 }

 size_t ParallelScavengeHeap::tlab_capacity(Thread* thr) const {

   return young_gen()->eden_space()->tlab_capacity(thr);

 }

 size_t ParallelScavengeHeap::unsafe_max_tlab_alloc(Thread* thr) const {

   return young_gen()->eden_space()->unsafe_max_tlab_alloc(thr);

 }

 HeapWord* ParallelScavengeHeap::allocate_new_tlab(size_t size) {

   return young_gen()->allocate(size, true);

 }

 void ParallelScavengeHeap::fill_all_tlabs(bool retire) {

   CollectedHeap::fill_all_tlabs(retire);

 }

 void ParallelScavengeHeap::accumulate_statistics_all_tlabs() {

   CollectedHeap::accumulate_statistics_all_tlabs();

 }

 void ParallelScavengeHeap::resize_all_tlabs() {

   CollectedHeap::resize_all_tlabs();

 }

 // This method is used by System.gc() and JVMTI.

 void ParallelScavengeHeap::collect(GCCause::Cause cause) {

   assert(!Heap_lock->owned_by_self(),

     "this thread should not own the Heap_lock");

   unsigned int gc_count      = 0;

   unsigned int full_gc_count = 0;

   {

     MutexLocker ml(Heap_lock);

     // This value is guarded by the Heap_lock

     gc_count      = Universe::heap()->total_collections();

     full_gc_count = Universe::heap()->total_full_collections();

   }

   VM_ParallelGCSystemGC op(gc_count, full_gc_count, cause);

   VMThread::execute(&op);

 }

 // This interface assumes that it's being called by the

 // vm thread. It collects the heap assuming that the

 // heap lock is already held and that we are executing in

 // the context of the vm thread.

 void ParallelScavengeHeap::collect_as_vm_thread(GCCause::Cause cause) {

   assert(Thread::current()->is_VM_thread(), "Precondition#1");

   assert(Heap_lock->is_locked(), "Precondition#2");

   GCCauseSetter gcs(this, cause);

   switch (cause) {

     case GCCause::_heap_inspection:

     case GCCause::_heap_dump: {

       HandleMark hm;

       invoke_full_gc(false);

       break;

     }

     default: // XXX FIX ME

       ShouldNotReachHere();

   }

 }

 void ParallelScavengeHeap::oop_iterate(OopClosure* cl) {

   Unimplemented();

 }

 void ParallelScavengeHeap::object_iterate(ObjectClosure* cl) {

   young_gen()->object_iterate(cl);

   old_gen()->object_iterate(cl);

   perm_gen()->object_iterate(cl);

 }

 void ParallelScavengeHeap::permanent_oop_iterate(OopClosure* cl) {

   Unimplemented();

 }

 void ParallelScavengeHeap::permanent_object_iterate(ObjectClosure* cl) {

   perm_gen()->object_iterate(cl);

 }

 HeapWord* ParallelScavengeHeap::block_start(const void* addr) const {

   if (young_gen()->is_in_reserved(addr)) {

     assert(young_gen()->is_in(addr),

            "addr should be in allocated part of young gen");

     Unimplemented();

   } else if (old_gen()->is_in_reserved(addr)) {

     assert(old_gen()->is_in(addr),

            "addr should be in allocated part of old gen");

     return old_gen()->start_array()->object_start((HeapWord*)addr);

   } else if (perm_gen()->is_in_reserved(addr)) {

     assert(perm_gen()->is_in(addr),

            "addr should be in allocated part of perm gen");

     return perm_gen()->start_array()->object_start((HeapWord*)addr);

   }

   return 0;

 }

 size_t ParallelScavengeHeap::block_size(const HeapWord* addr) const {

   return oop(addr)->size();

 }

 bool ParallelScavengeHeap::block_is_obj(const HeapWord* addr) const {

   return block_start(addr) == addr;

 }

 jlong ParallelScavengeHeap::millis_since_last_gc() {

   return UseParallelOldGC ?

     PSParallelCompact::millis_since_last_gc() :

     PSMarkSweep::millis_since_last_gc();

 }

 void ParallelScavengeHeap::prepare_for_verify() {

   ensure_parsability(false);  // no need to retire TLABs for verification

 }

 void ParallelScavengeHeap::print() const { print_on(tty); }

 void ParallelScavengeHeap::print_on(outputStream* st) const {

   young_gen()->print_on(st);

   old_gen()->print_on(st);

   perm_gen()->print_on(st);

 }

 void ParallelScavengeHeap::gc_threads_do(ThreadClosure* tc) const {

   PSScavenge::gc_task_manager()->threads_do(tc);

 }

 void ParallelScavengeHeap::print_gc_threads_on(outputStream* st) const {

   PSScavenge::gc_task_manager()->print_threads_on(st);

 }

 void ParallelScavengeHeap::print_tracing_info() const {

   if (TraceGen0Time) {

     double time = PSScavenge::accumulated_time()->seconds();

     tty->print_cr("[Accumulated GC generation 0 time %3.7f secs]", time);

   }

   if (TraceGen1Time) {

     double time = PSMarkSweep::accumulated_time()->seconds();

     tty->print_cr("[Accumulated GC generation 1 time %3.7f secs]", time);

   }

 }

 void ParallelScavengeHeap::verify(bool allow_dirty, bool silent) {

   // Why do we need the total_collections()-filter below?

   if (total_collections() > 0) {

     if (!silent) {

       gclog_or_tty->print("permanent ");

     }

     perm_gen()->verify(allow_dirty);

     if (!silent) {

       gclog_or_tty->print("tenured ");

     }

     old_gen()->verify(allow_dirty);

     if (!silent) {

       gclog_or_tty->print("eden ");

     }

     young_gen()->verify(allow_dirty);

   }

   if (!silent) {

     gclog_or_tty->print("ref_proc ");

   }

   ReferenceProcessor::verify();

 }

 void ParallelScavengeHeap::print_heap_change(size_t prev_used) {

   if (PrintGCDetails && Verbose) {

     gclog_or_tty->print(" "  SIZE_FORMAT

                         "->" SIZE_FORMAT

                         "("  SIZE_FORMAT ")",

                         prev_used, used(), capacity());

   } else {

     gclog_or_tty->print(" "  SIZE_FORMAT "K"

                         "->" SIZE_FORMAT "K"

                         "("  SIZE_FORMAT "K)",

                         prev_used / K, used() / K, capacity() / K);

   }

 }

 ParallelScavengeHeap* ParallelScavengeHeap::heap() {

   assert(_psh != NULL, "Uninitialized access to ParallelScavengeHeap::heap()");

   assert(_psh->kind() == CollectedHeap::ParallelScavengeHeap, "not a parallel scavenge heap");

   return _psh;

 }

 // Before delegating the resize to the young generation,

 // the reserved space for the young and old generations

 // may be changed to accomodate the desired resize.

 void ParallelScavengeHeap::resize_young_gen(size_t eden_size,

     size_t survivor_size) {

   if (UseAdaptiveGCBoundary) {

     if (size_policy()->bytes_absorbed_from_eden() != 0) {

       size_policy()->reset_bytes_absorbed_from_eden();

       return;  // The generation changed size already.

     }

     gens()->adjust_boundary_for_young_gen_needs(eden_size, survivor_size);

   }

   // Delegate the resize to the generation.

   _young_gen->resize(eden_size, survivor_size);

 }

 // Before delegating the resize to the old generation,

 // the reserved space for the young and old generations

 // may be changed to accomodate the desired resize.

 void ParallelScavengeHeap::resize_old_gen(size_t desired_free_space) {

   if (UseAdaptiveGCBoundary) {

     if (size_policy()->bytes_absorbed_from_eden() != 0) {

       size_policy()->reset_bytes_absorbed_from_eden();

       return;  // The generation changed size already.

     }

     gens()->adjust_boundary_for_old_gen_needs(desired_free_space);

   }

   // Delegate the resize to the generation.

   _old_gen->resize(desired_free_space);

 }