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

 /*

  * Copyright (c) 2001, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

  * or visit www.oracle.com if you need additional information or have any

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  */

 #include "precompiled.hpp"

 #include "gc_implementation/shared/adaptiveSizePolicy.hpp"

 #include "gc_implementation/shared/gcPolicyCounters.hpp"

 #include "gc_implementation/shared/vmGCOperations.hpp"

 #include "memory/cardTableRS.hpp"

 #include "memory/collectorPolicy.hpp"

 #include "memory/gcLocker.inline.hpp"

 #include "memory/genCollectedHeap.hpp"

 #include "memory/generationSpec.hpp"

 #include "memory/space.hpp"

 #include "memory/universe.hpp"

 #include "runtime/arguments.hpp"

 #include "runtime/globals_extension.hpp"

 #include "runtime/handles.inline.hpp"

 #include "runtime/java.hpp"

 #include "runtime/vmThread.hpp"

 #ifdef TARGET_OS_FAMILY_linux

 # include "thread_linux.inline.hpp"

 #endif

 #ifdef TARGET_OS_FAMILY_solaris

 # include "thread_solaris.inline.hpp"

 #endif

 #ifdef TARGET_OS_FAMILY_windows

 # include "thread_windows.inline.hpp"

 #endif

 #ifndef SERIALGC

 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp"

 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp"

 #endif

 // CollectorPolicy methods.

 void CollectorPolicy::initialize_flags() {

   if (PermSize > MaxPermSize) {

     MaxPermSize = PermSize;

   }

   PermSize = MAX2(min_alignment(), align_size_down_(PermSize, min_alignment()));

   // Don't increase Perm size limit above specified.

   MaxPermSize = align_size_down(MaxPermSize, max_alignment());

   if (PermSize > MaxPermSize) {

     PermSize = MaxPermSize;

   }

   MinPermHeapExpansion = MAX2(min_alignment(), align_size_down_(MinPermHeapExpansion, min_alignment()));

   MaxPermHeapExpansion = MAX2(min_alignment(), align_size_down_(MaxPermHeapExpansion, min_alignment()));

   MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());

   SharedReadOnlySize = align_size_up(SharedReadOnlySize, max_alignment());

   SharedReadWriteSize = align_size_up(SharedReadWriteSize, max_alignment());

   SharedMiscDataSize = align_size_up(SharedMiscDataSize, max_alignment());

   assert(PermSize    % min_alignment() == 0, "permanent space alignment");

   assert(MaxPermSize % max_alignment() == 0, "maximum permanent space alignment");

   assert(SharedReadOnlySize % max_alignment() == 0, "read-only space alignment");

   assert(SharedReadWriteSize % max_alignment() == 0, "read-write space alignment");

   assert(SharedMiscDataSize % max_alignment() == 0, "misc-data space alignment");

   if (PermSize < M) {

     vm_exit_during_initialization("Too small initial permanent heap");

   }

 }

 void CollectorPolicy::initialize_size_info() {

   // User inputs from -mx and ms are aligned

   set_initial_heap_byte_size(InitialHeapSize);

   if (initial_heap_byte_size() == 0) {

     set_initial_heap_byte_size(NewSize + OldSize);

   }

   set_initial_heap_byte_size(align_size_up(_initial_heap_byte_size,

                                            min_alignment()));

   set_min_heap_byte_size(Arguments::min_heap_size());

   if (min_heap_byte_size() == 0) {

     set_min_heap_byte_size(NewSize + OldSize);

   }

   set_min_heap_byte_size(align_size_up(_min_heap_byte_size,

                                        min_alignment()));

   set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));

   // Check heap parameter properties

   if (initial_heap_byte_size() < M) {

     vm_exit_during_initialization("Too small initial heap");

   }

   // Check heap parameter properties

   if (min_heap_byte_size() < M) {

     vm_exit_during_initialization("Too small minimum heap");

   }

   if (initial_heap_byte_size() <= NewSize) {

      // make sure there is at least some room in old space

     vm_exit_during_initialization("Too small initial heap for new size specified");

   }

   if (max_heap_byte_size() < min_heap_byte_size()) {

     vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");

   }

   if (initial_heap_byte_size() < min_heap_byte_size()) {

     vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");

   }

   if (max_heap_byte_size() < initial_heap_byte_size()) {

     vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");

   }

   if (PrintGCDetails && Verbose) {

     gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT "  Initial heap "

       SIZE_FORMAT "  Maximum heap " SIZE_FORMAT,

       min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());

   }

 }

 void CollectorPolicy::initialize_perm_generation(PermGen::Name pgnm) {

   _permanent_generation =

     new PermanentGenerationSpec(pgnm, PermSize, MaxPermSize,

                                 SharedReadOnlySize,

                                 SharedReadWriteSize,

                                 SharedMiscDataSize,

                                 SharedMiscCodeSize);

   if (_permanent_generation == NULL) {

     vm_exit_during_initialization("Unable to allocate gen spec");

   }

 }

 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {

   bool result = _should_clear_all_soft_refs;

   set_should_clear_all_soft_refs(false);

   return result;

 }

 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,

                                            int max_covered_regions) {

   switch (rem_set_name()) {

   case GenRemSet::CardTable: {

     CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);

     return res;

   }

   default:

     guarantee(false, "unrecognized GenRemSet::Name");

     return NULL;

   }

 }

 void CollectorPolicy::cleared_all_soft_refs() {

   // If near gc overhear limit, continue to clear SoftRefs.  SoftRefs may

   // have been cleared in the last collection but if the gc overhear

   // limit continues to be near, SoftRefs should still be cleared.

   if (size_policy() != NULL) {

     _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();

   }

   _all_soft_refs_clear = true;

 }

 // GenCollectorPolicy methods.

 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {

   size_t x = base_size / (NewRatio+1);

   size_t new_gen_size = x > min_alignment() ?

                      align_size_down(x, min_alignment()) :

                      min_alignment();

   return new_gen_size;

 }

 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,

                                                  size_t maximum_size) {

   size_t alignment = min_alignment();

   size_t max_minus = maximum_size - alignment;

   return desired_size < max_minus ? desired_size : max_minus;

 }

 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,

                                                 size_t init_promo_size,

                                                 size_t init_survivor_size) {

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

   _size_policy = new AdaptiveSizePolicy(init_eden_size,

                                         init_promo_size,

                                         init_survivor_size,

                                         max_gc_minor_pause_sec,

                                         GCTimeRatio);

 }

 size_t GenCollectorPolicy::compute_max_alignment() {

   // The card marking array and the offset arrays for old generations are

   // committed in os pages as well. Make sure they are entirely full (to

   // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1

   // byte entry and the os page size is 4096, the maximum heap size should

   // be 512*4096 = 2MB aligned.

   size_t alignment = GenRemSet::max_alignment_constraint(rem_set_name());

   // Parallel GC does its own alignment of the generations to avoid requiring a

   // large page (256M on some platforms) for the permanent generation.  The

   // other collectors should also be updated to do their own alignment and then

   // this use of lcm() should be removed.

   if (UseLargePages && !UseParallelGC) {

       // in presence of large pages we have to make sure that our

       // alignment is large page aware

       alignment = lcm(os::large_page_size(), alignment);

   }

   return alignment;

 }

 void GenCollectorPolicy::initialize_flags() {

   // All sizes must be multiples of the generation granularity.

   set_min_alignment((uintx) Generation::GenGrain);

   set_max_alignment(compute_max_alignment());

   assert(max_alignment() >= min_alignment() &&

          max_alignment() % min_alignment() == 0,

          "invalid alignment constraints");

   CollectorPolicy::initialize_flags();

   // All generational heaps have a youngest gen; handle those flags here.

   // Adjust max size parameters

   if (NewSize > MaxNewSize) {

     MaxNewSize = NewSize;

   }

   NewSize = align_size_down(NewSize, min_alignment());

   MaxNewSize = align_size_down(MaxNewSize, min_alignment());

   // Check validity of heap flags

   assert(NewSize     % min_alignment() == 0, "eden space alignment");

   assert(MaxNewSize  % min_alignment() == 0, "survivor space alignment");

   if (NewSize < 3*min_alignment()) {

      // make sure there room for eden and two survivor spaces

     vm_exit_during_initialization("Too small new size specified");

   }

   if (SurvivorRatio < 1 || NewRatio < 1) {

     vm_exit_during_initialization("Invalid heap ratio specified");

   }

 }

 void TwoGenerationCollectorPolicy::initialize_flags() {

   GenCollectorPolicy::initialize_flags();

   OldSize = align_size_down(OldSize, min_alignment());

   if (NewSize + OldSize > MaxHeapSize) {

     MaxHeapSize = NewSize + OldSize;

   }

   MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());

   always_do_update_barrier = UseConcMarkSweepGC;

   BlockOffsetArrayUseUnallocatedBlock =

       BlockOffsetArrayUseUnallocatedBlock || ParallelGCThreads > 0;

   // Check validity of heap flags

   assert(OldSize     % min_alignment() == 0, "old space alignment");

   assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");

 }

 // Values set on the command line win over any ergonomically

 // set command line parameters.

 // Ergonomic choice of parameters are done before this

 // method is called.  Values for command line parameters such as NewSize

 // and MaxNewSize feed those ergonomic choices into this method.

 // This method makes the final generation sizings consistent with

 // themselves and with overall heap sizings.

 // In the absence of explicitly set command line flags, policies

 // such as the use of NewRatio are used to size the generation.

 void GenCollectorPolicy::initialize_size_info() {

   CollectorPolicy::initialize_size_info();

   // min_alignment() is used for alignment within a generation.

   // There is additional alignment done down stream for some

   // collectors that sometimes causes unwanted rounding up of

   // generations sizes.

   // Determine maximum size of gen0

   size_t max_new_size = 0;

   if (FLAG_IS_CMDLINE(MaxNewSize)) {

     if (MaxNewSize < min_alignment()) {

       max_new_size = min_alignment();

     } else if (MaxNewSize >= max_heap_byte_size()) {

       max_new_size = align_size_down(max_heap_byte_size() - min_alignment(),

                                      min_alignment());

       warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "

         "greater than the entire heap (" SIZE_FORMAT "k).  A "

         "new generation size of " SIZE_FORMAT "k will be used.",

         MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K);

     } else {

       max_new_size = align_size_down(MaxNewSize, min_alignment());

     }

   // The case for FLAG_IS_ERGO(MaxNewSize) could be treated

   // specially at this point to just use an ergonomically set

   // MaxNewSize to set max_new_size.  For cases with small

   // heaps such a policy often did not work because the MaxNewSize

   // was larger than the entire heap.  The interpretation given

   // to ergonomically set flags is that the flags are set

   // by different collectors for their own special needs but

   // are not allowed to badly shape the heap.  This allows the

   // different collectors to decide what's best for themselves

   // without having to factor in the overall heap shape.  It

   // can be the case in the future that the collectors would

   // only make "wise" ergonomics choices and this policy could

   // just accept those choices.  The choices currently made are

   // not always "wise".

   } else {

     max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size());

     // Bound the maximum size by NewSize below (since it historically

     // would have been NewSize and because the NewRatio calculation could

     // yield a size that is too small) and bound it by MaxNewSize above.

     // Ergonomics plays here by previously calculating the desired

     // NewSize and MaxNewSize.

     max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);

   }

   assert(max_new_size > 0, "All paths should set max_new_size");

   // Given the maximum gen0 size, determine the initial and

   // minimum sizes.

   if (max_heap_byte_size() == min_heap_byte_size()) {

     // The maximum and minimum heap sizes are the same so

     // the generations minimum and initial must be the

     // same as its maximum.

     set_min_gen0_size(max_new_size);

     set_initial_gen0_size(max_new_size);

     set_max_gen0_size(max_new_size);

   } else {

     size_t desired_new_size = 0;

     if (!FLAG_IS_DEFAULT(NewSize)) {

       // If NewSize is set ergonomically (for example by cms), it

       // would make sense to use it.  If it is used, also use it

       // to set the initial size.  Although there is no reason

       // the minimum size and the initial size have to be the same,

       // the current implementation gets into trouble during the calculation

       // of the tenured generation sizes if they are different.

       // Note that this makes the initial size and the minimum size

       // generally small compared to the NewRatio calculation.

       _min_gen0_size = NewSize;

       desired_new_size = NewSize;

       max_new_size = MAX2(max_new_size, NewSize);

     } else {

       // For the case where NewSize is the default, use NewRatio

       // to size the minimum and initial generation sizes.

       // Use the default NewSize as the floor for these values.  If

       // NewRatio is overly large, the resulting sizes can be too

       // small.

       _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()),

                           NewSize);

       desired_new_size =

         MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),

              NewSize);

     }

     assert(_min_gen0_size > 0, "Sanity check");

     set_initial_gen0_size(desired_new_size);

     set_max_gen0_size(max_new_size);

     // At this point the desirable initial and minimum sizes have been

     // determined without regard to the maximum sizes.

     // Bound the sizes by the corresponding overall heap sizes.

     set_min_gen0_size(

       bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));

     set_initial_gen0_size(

       bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));

     set_max_gen0_size(

       bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));

     // At this point all three sizes have been checked against the

     // maximum sizes but have not been checked for consistency

     // among the three.

     // Final check min <= initial <= max

     set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));

     set_initial_gen0_size(

       MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));

     set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));

   }

   if (PrintGCDetails && Verbose) {

     gclog_or_tty->print_cr("Minimum gen0 " SIZE_FORMAT "  Initial gen0 "

       SIZE_FORMAT "  Maximum gen0 " SIZE_FORMAT,

       min_gen0_size(), initial_gen0_size(), max_gen0_size());

   }

 }

 // Call this method during the sizing of the gen1 to make

 // adjustments to gen0 because of gen1 sizing policy.  gen0 initially has

 // the most freedom in sizing because it is done before the

 // policy for gen1 is applied.  Once gen1 policies have been applied,

 // there may be conflicts in the shape of the heap and this method

 // is used to make the needed adjustments.  The application of the

 // policies could be more sophisticated (iterative for example) but

 // keeping it simple also seems a worthwhile goal.

 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,

                                                      size_t* gen1_size_ptr,

                                                      size_t heap_size,

                                                      size_t min_gen0_size) {

   bool result = false;

   if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {

     if (((*gen0_size_ptr + OldSize) > heap_size) &&

        (heap_size - min_gen0_size) >= min_alignment()) {

       // Adjust gen0 down to accomodate OldSize

       *gen0_size_ptr = heap_size - min_gen0_size;

       *gen0_size_ptr =

         MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),

              min_alignment());

       assert(*gen0_size_ptr > 0, "Min gen0 is too large");

       result = true;

     } else {

       *gen1_size_ptr = heap_size - *gen0_size_ptr;

       *gen1_size_ptr =

         MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),

                        min_alignment());

     }

   }

   return result;

 }

 // Minimum sizes of the generations may be different than

 // the initial sizes.  An inconsistently is permitted here

 // in the total size that can be specified explicitly by

 // command line specification of OldSize and NewSize and

 // also a command line specification of -Xms.  Issue a warning

 // but allow the values to pass.

 void TwoGenerationCollectorPolicy::initialize_size_info() {

   GenCollectorPolicy::initialize_size_info();

   // At this point the minimum, initial and maximum sizes

   // of the overall heap and of gen0 have been determined.

   // The maximum gen1 size can be determined from the maximum gen0

   // and maximum heap size since not explicit flags exits

   // for setting the gen1 maximum.

   _max_gen1_size = max_heap_byte_size() - _max_gen0_size;

   _max_gen1_size =

     MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),

          min_alignment());

   // If no explicit command line flag has been set for the

   // gen1 size, use what is left for gen1.

   if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {

     // The user has not specified any value or ergonomics

     // has chosen a value (which may or may not be consistent

     // with the overall heap size).  In either case make

     // the minimum, maximum and initial sizes consistent

     // with the gen0 sizes and the overall heap sizes.

     assert(min_heap_byte_size() > _min_gen0_size,

       "gen0 has an unexpected minimum size");

     set_min_gen1_size(min_heap_byte_size() - min_gen0_size());

     set_min_gen1_size(

       MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),

            min_alignment()));

     set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());

     set_initial_gen1_size(

       MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),

            min_alignment()));

   } else {

     // It's been explicitly set on the command line.  Use the

     // OldSize and then determine the consequences.

     set_min_gen1_size(OldSize);

     set_initial_gen1_size(OldSize);

     // If the user has explicitly set an OldSize that is inconsistent

     // with other command line flags, issue a warning.

     // The generation minimums and the overall heap mimimum should

     // be within one heap alignment.

     if ((_min_gen1_size + _min_gen0_size + min_alignment()) <

            min_heap_byte_size()) {

       warning("Inconsistency between minimum heap size and minimum "

           "generation sizes: using minimum heap = " SIZE_FORMAT,

           min_heap_byte_size());

     }

     if ((OldSize > _max_gen1_size)) {

       warning("Inconsistency between maximum heap size and maximum "

           "generation sizes: using maximum heap = " SIZE_FORMAT

           " -XX:OldSize flag is being ignored",

           max_heap_byte_size());

   }

     // If there is an inconsistency between the OldSize and the minimum and/or

     // initial size of gen0, since OldSize was explicitly set, OldSize wins.

     if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,

                           min_heap_byte_size(), OldSize)) {

       if (PrintGCDetails && Verbose) {

         gclog_or_tty->print_cr("Minimum gen0 " SIZE_FORMAT "  Initial gen0 "

               SIZE_FORMAT "  Maximum gen0 " SIZE_FORMAT,

               min_gen0_size(), initial_gen0_size(), max_gen0_size());

       }

     }

     // Initial size

     if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,

                          initial_heap_byte_size(), OldSize)) {

       if (PrintGCDetails && Verbose) {

         gclog_or_tty->print_cr("Minimum gen0 " SIZE_FORMAT "  Initial gen0 "

           SIZE_FORMAT "  Maximum gen0 " SIZE_FORMAT,

           min_gen0_size(), initial_gen0_size(), max_gen0_size());

       }

     }

   }

   // Enforce the maximum gen1 size.

   set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));

   // Check that min gen1 <= initial gen1 <= max gen1

   set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));

   set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));

   if (PrintGCDetails && Verbose) {

     gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT "  Initial gen1 "

       SIZE_FORMAT "  Maximum gen1 " SIZE_FORMAT,

       min_gen1_size(), initial_gen1_size(), max_gen1_size());

   }

 }

 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,

                                         bool is_tlab,

                                         bool* gc_overhead_limit_was_exceeded) {

   GenCollectedHeap *gch = GenCollectedHeap::heap();

   debug_only(gch->check_for_valid_allocation_state());

   assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");

   // In general gc_overhead_limit_was_exceeded should be false so

   // set it so here and reset it to true only if the gc time

   // limit is being exceeded as checked below.

   *gc_overhead_limit_was_exceeded = false;

   HeapWord* result = NULL;

   // Loop until the allocation is satisified,

   // or unsatisfied after GC.

   for (int try_count = 1; /* return or throw */; try_count += 1) {

     HandleMark hm; // discard any handles allocated in each iteration

     // First allocation attempt is lock-free.

     Generation *gen0 = gch->get_gen(0);

     assert(gen0->supports_inline_contig_alloc(),

       "Otherwise, must do alloc within heap lock");

     if (gen0->should_allocate(size, is_tlab)) {

       result = gen0->par_allocate(size, is_tlab);

       if (result != NULL) {

         assert(gch->is_in_reserved(result), "result not in heap");

         return result;

       }

     }

     unsigned int gc_count_before;  // read inside the Heap_lock locked region

     {

       MutexLocker ml(Heap_lock);

       if (PrintGC && Verbose) {

         gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"

                       " attempting locked slow path allocation");

       }

       // Note that only large objects get a shot at being

       // allocated in later generations.

       bool first_only = ! should_try_older_generation_allocation(size);

       result = gch->attempt_allocation(size, is_tlab, first_only);

       if (result != NULL) {

         assert(gch->is_in_reserved(result), "result not in heap");

         return result;

       }

       if (GC_locker::is_active_and_needs_gc()) {

         if (is_tlab) {

           return NULL;  // Caller will retry allocating individual object

         }

         if (!gch->is_maximal_no_gc()) {

           // Try and expand heap to satisfy request

           result = expand_heap_and_allocate(size, is_tlab);

           // result could be null if we are out of space

           if (result != NULL) {

             return result;

           }

         }

         // 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);

           // Wait for JNI critical section to be exited

           GC_locker::stall_until_clear();

           continue;

         } else {

           if (CheckJNICalls) {

             fatal("Possible deadlock due to allocating while"

                   " in jni critical section");

           }

           return NULL;

         }

       }

       // Read the gc count while the heap lock is held.

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

     }

     VM_GenCollectForAllocation op(size,

                                   is_tlab,

                                   gc_count_before);

     VMThread::execute(&op);

     if (op.prologue_succeeded()) {

       result = op.result();

       if (op.gc_locked()) {

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

          continue;  // retry and/or stall as necessary

       }

       // Allocation has failed and a collection

       // has been done.  If the gc time limit was exceeded the

       // this time, return NULL so that an out-of-memory

       // will be thrown.  Clear gc_overhead_limit_exceeded

       // so that the overhead exceeded does not persist.

       const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();

       const bool softrefs_clear = all_soft_refs_clear();

       assert(!limit_exceeded || softrefs_clear, "Should have been cleared");

       if (limit_exceeded && softrefs_clear) {

         *gc_overhead_limit_was_exceeded = true;

         size_policy()->set_gc_overhead_limit_exceeded(false);

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

           CollectedHeap::fill_with_object(op.result(), size);

         }

         return NULL;

       }

       assert(result == NULL || gch->is_in_reserved(result),

              "result not in heap");

       return result;

     }

     // Give a warning if we seem to be looping forever.

     if ((QueuedAllocationWarningCount > 0) &&

         (try_count % QueuedAllocationWarningCount == 0)) {

           warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"

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

     }

   }

 }

 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,

                                                        bool   is_tlab) {

   GenCollectedHeap *gch = GenCollectedHeap::heap();

   HeapWord* result = NULL;

   for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {

     Generation *gen = gch->get_gen(i);

     if (gen->should_allocate(size, is_tlab)) {

       result = gen->expand_and_allocate(size, is_tlab);

     }

   }

   assert(result == NULL || gch->is_in_reserved(result), "result not in heap");

   return result;

 }

 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,

                                                         bool   is_tlab) {

   GenCollectedHeap *gch = GenCollectedHeap::heap();

   GCCauseSetter x(gch, GCCause::_allocation_failure);

   HeapWord* result = NULL;

   assert(size != 0, "Precondition violated");

   if (GC_locker::is_active_and_needs_gc()) {

     // GC locker is active; instead of a collection we will attempt

     // to expand the heap, if there's room for expansion.

     if (!gch->is_maximal_no_gc()) {

       result = expand_heap_and_allocate(size, is_tlab);

     }

     return result;   // could be null if we are out of space

   } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {

     // Do an incremental collection.

     gch->do_collection(false            /* full */,

                        false            /* clear_all_soft_refs */,

                        size             /* size */,

                        is_tlab          /* is_tlab */,

                        number_of_generations() - 1 /* max_level */);

   } else {

     if (Verbose && PrintGCDetails) {

       gclog_or_tty->print(" :: Trying full because partial may fail :: ");

     }

     // Try a full collection; see delta for bug id 6266275

     // for the original code and why this has been simplified

     // with from-space allocation criteria modified and

     // such allocation moved out of the safepoint path.

     gch->do_collection(true             /* full */,

                        false            /* clear_all_soft_refs */,

                        size             /* size */,

                        is_tlab          /* is_tlab */,

                        number_of_generations() - 1 /* max_level */);

   }

   result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);

   if (result != NULL) {

     assert(gch->is_in_reserved(result), "result not in heap");

     return result;

   }

   // OK, collection failed, try expansion.

   result = expand_heap_and_allocate(size, is_tlab);

   if (result != NULL) {

     return result;

   }

   // If we reach this point, we're really out of memory. Try every trick

   // we can to reclaim memory. Force collection of soft references. Force

   // a complete compaction of the heap. Any additional methods for finding

   // free memory should be here, especially if they are expensive. If this

   // attempt fails, an OOM exception will be thrown.

   {

     IntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted

     gch->do_collection(true             /* full */,

                        true             /* clear_all_soft_refs */,

                        size             /* size */,

                        is_tlab          /* is_tlab */,

                        number_of_generations() - 1 /* max_level */);

   }

   result = gch->attempt_allocation(size, is_tlab, false /* first_only */);

   if (result != NULL) {

     assert(gch->is_in_reserved(result), "result not in heap");

     return result;

   }

   assert(!should_clear_all_soft_refs(),

     "Flag should have been handled and cleared prior to this point");

   // What else?  We might try synchronous finalization later.  If the total

   // space available is large enough for the allocation, then a more

   // complete compaction phase than we've tried so far might be

   // appropriate.

   return NULL;

 }

 size_t GenCollectorPolicy::large_typearray_limit() {

   return FastAllocateSizeLimit;

 }

 // Return true if any of the following is true:

 // . the allocation won't fit into the current young gen heap

 // . gc locker is occupied (jni critical section)

 // . heap memory is tight -- the most recent previous collection

 //   was a full collection because a partial collection (would

 //   have) failed and is likely to fail again

 bool GenCollectorPolicy::should_try_older_generation_allocation(

         size_t word_size) const {

   GenCollectedHeap* gch = GenCollectedHeap::heap();

   size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();

   return    (word_size > heap_word_size(gen0_capacity))

          || GC_locker::is_active_and_needs_gc()

          || gch->incremental_collection_failed();

 }

 //

 // MarkSweepPolicy methods

 //

 MarkSweepPolicy::MarkSweepPolicy() {

   initialize_all();

 }

 void MarkSweepPolicy::initialize_generations() {

   initialize_perm_generation(PermGen::MarkSweepCompact);

   _generations = new GenerationSpecPtr[number_of_generations()];

   if (_generations == NULL)

     vm_exit_during_initialization("Unable to allocate gen spec");

   if (UseParNewGC && ParallelGCThreads > 0) {

     _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);

   } else {

     _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);

   }

   _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);

   if (_generations[0] == NULL || _generations[1] == NULL)

     vm_exit_during_initialization("Unable to allocate gen spec");

 }

 void MarkSweepPolicy::initialize_gc_policy_counters() {

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

   if (UseParNewGC && ParallelGCThreads > 0) {

     _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);

   }

   else {

     _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);

   }

 }