src/share/vm/gc_implementation/g1/g1AllocRegion.cpp - platform/external/jetbrains/jdk8u_hotspot - Git at Google

 /*
  * Copyright (c) 2011, 2014, 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
  * questions.
  *
  */

 #include "precompiled.hpp"
 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
 #include "runtime/orderAccess.inline.hpp"

 G1CollectedHeap* G1AllocRegion::_g1h = NULL;
 HeapRegion* G1AllocRegion::_dummy_region = NULL;

 void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
   assert(_dummy_region == NULL, "should be set once");
   assert(dummy_region != NULL, "pre-condition");
   assert(dummy_region->free() == 0, "pre-condition");

   // Make sure that any allocation attempt on this region will fail
   // and will not trigger any asserts.
   assert(allocate(dummy_region, 1, false) == NULL, "should fail");
   assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
   assert(allocate(dummy_region, 1, true) == NULL, "should fail");
   assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");

   _g1h = g1h;
   _dummy_region = dummy_region;
 }

 void G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
                                             bool bot_updates) {
   assert(alloc_region != NULL && alloc_region != _dummy_region,
          "pre-condition");

   // Other threads might still be trying to allocate using a CAS out
   // of the region we are trying to retire, as they can do so without
   // holding the lock. So, we first have to make sure that noone else
   // can allocate out of it by doing a maximal allocation. Even if our
   // CAS attempt fails a few times, we'll succeed sooner or later
   // given that failed CAS attempts mean that the region is getting
   // closed to being full.
   size_t free_word_size = alloc_region->free() / HeapWordSize;

   // This is the minimum free chunk we can turn into a dummy
   // object. If the free space falls below this, then noone can
   // allocate in this region anyway (all allocation requests will be
   // of a size larger than this) so we won't have to perform the dummy
   // allocation.
   size_t min_word_size_to_fill = CollectedHeap::min_fill_size();

   while (free_word_size >= min_word_size_to_fill) {
     HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
     if (dummy != NULL) {
       // If the allocation was successful we should fill in the space.
       CollectedHeap::fill_with_object(dummy, free_word_size);
       alloc_region->set_pre_dummy_top(dummy);
       break;
     }

     free_word_size = alloc_region->free() / HeapWordSize;
     // It's also possible that someone else beats us to the
     // allocation and they fill up the region. In that case, we can
     // just get out of the loop.
   }
   assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
          "post-condition");
 }

 void G1AllocRegion::retire(bool fill_up) {
   assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));

   trace("retiring");
   HeapRegion* alloc_region = _alloc_region;
   if (alloc_region != _dummy_region) {
     // We never have to check whether the active region is empty or not,
     // and potentially free it if it is, given that it's guaranteed that
     // it will never be empty.
     assert(!alloc_region->is_empty(),
            ar_ext_msg(this, "the alloc region should never be empty"));

     if (fill_up) {
       fill_up_remaining_space(alloc_region, _bot_updates);
     }

     assert(alloc_region->used() >= _used_bytes_before,
            ar_ext_msg(this, "invariant"));
     size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
     retire_region(alloc_region, allocated_bytes);
     _used_bytes_before = 0;
     _alloc_region = _dummy_region;
   }
   trace("retired");
 }

 HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
                                                        bool force) {
   assert(_alloc_region == _dummy_region, ar_ext_msg(this, "pre-condition"));
   assert(_used_bytes_before == 0, ar_ext_msg(this, "pre-condition"));

   trace("attempting region allocation");
   HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
   if (new_alloc_region != NULL) {
     new_alloc_region->reset_pre_dummy_top();
     // Need to do this before the allocation
     _used_bytes_before = new_alloc_region->used();
     HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
     assert(result != NULL, ar_ext_msg(this, "the allocation should succeeded"));

     OrderAccess::storestore();
     // Note that we first perform the allocation and then we store the
     // region in _alloc_region. This is the reason why an active region
     // can never be empty.
     update_alloc_region(new_alloc_region);
     trace("region allocation successful");
     return result;
   } else {
     trace("region allocation failed");
     return NULL;
   }
   ShouldNotReachHere();
 }

 void G1AllocRegion::fill_in_ext_msg(ar_ext_msg* msg, const char* message) {
   msg->append("[%s] %s c: %u b: %s r: "PTR_FORMAT" u: "SIZE_FORMAT,
               _name, message, _count, BOOL_TO_STR(_bot_updates),
               p2i(_alloc_region), _used_bytes_before);
 }

 void G1AllocRegion::init() {
   trace("initializing");
   assert(_alloc_region == NULL && _used_bytes_before == 0,
          ar_ext_msg(this, "pre-condition"));
   assert(_dummy_region != NULL, ar_ext_msg(this, "should have been set"));
   _alloc_region = _dummy_region;
   _count = 0;
   trace("initialized");
 }

 void G1AllocRegion::set(HeapRegion* alloc_region) {
   trace("setting");
   // We explicitly check that the region is not empty to make sure we
   // maintain the "the alloc region cannot be empty" invariant.
   assert(alloc_region != NULL && !alloc_region->is_empty(),
          ar_ext_msg(this, "pre-condition"));
   assert(_alloc_region == _dummy_region &&
          _used_bytes_before == 0 && _count == 0,
          ar_ext_msg(this, "pre-condition"));

   _used_bytes_before = alloc_region->used();
   _alloc_region = alloc_region;
   _count += 1;
   trace("set");
 }

 void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
   trace("update");
   // We explicitly check that the region is not empty to make sure we
   // maintain the "the alloc region cannot be empty" invariant.
   assert(alloc_region != NULL && !alloc_region->is_empty(),
          ar_ext_msg(this, "pre-condition"));

   _alloc_region = alloc_region;
   _alloc_region->set_allocation_context(allocation_context());
   _count += 1;
   trace("updated");
 }

 HeapRegion* G1AllocRegion::release() {
   trace("releasing");
   HeapRegion* alloc_region = _alloc_region;
   retire(false /* fill_up */);
   assert(_alloc_region == _dummy_region,
          ar_ext_msg(this, "post-condition of retire()"));
   _alloc_region = NULL;
   trace("released");
   return (alloc_region == _dummy_region) ? NULL : alloc_region;
 }

 #if G1_ALLOC_REGION_TRACING
 void G1AllocRegion::trace(const char* str, size_t word_size, HeapWord* result) {
   // All the calls to trace that set either just the size or the size
   // and the result are considered part of level 2 tracing and are
   // skipped during level 1 tracing.
   if ((word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) {
     const size_t buffer_length = 128;
     char hr_buffer[buffer_length];
     char rest_buffer[buffer_length];

     HeapRegion* alloc_region = _alloc_region;
     if (alloc_region == NULL) {
       jio_snprintf(hr_buffer, buffer_length, "NULL");
     } else if (alloc_region == _dummy_region) {
       jio_snprintf(hr_buffer, buffer_length, "DUMMY");
     } else {
       jio_snprintf(hr_buffer, buffer_length,
                    HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));
     }

     if (G1_ALLOC_REGION_TRACING > 1) {
       if (result != NULL) {
         jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT" "PTR_FORMAT,
                      word_size, result);
       } else if (word_size != 0) {
         jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT, word_size);
       } else {
         jio_snprintf(rest_buffer, buffer_length, "");
       }
     } else {
       jio_snprintf(rest_buffer, buffer_length, "");
     }

     tty->print_cr("[%s] %u %s : %s %s",
                   _name, _count, hr_buffer, str, rest_buffer);
   }
 }
 #endif // G1_ALLOC_REGION_TRACING

 G1AllocRegion::G1AllocRegion(const char* name,
                              bool bot_updates)
   : _name(name), _bot_updates(bot_updates),
     _alloc_region(NULL), _count(0), _used_bytes_before(0),
     _allocation_context(AllocationContext::system()) { }


 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
                                                     bool force) {
   return _g1h->new_mutator_alloc_region(word_size, force);
 }

 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
                                        size_t allocated_bytes) {
   _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
 }

 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
                                                        bool force) {
   assert(!force, "not supported for GC alloc regions");
   return _g1h->new_gc_alloc_region(word_size, count(), InCSetState::Young);
 }

 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
                                           size_t allocated_bytes) {
   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, InCSetState::Young);
 }

 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
                                                   bool force) {
   assert(!force, "not supported for GC alloc regions");
   return _g1h->new_gc_alloc_region(word_size, count(), InCSetState::Old);
 }

 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
                                      size_t allocated_bytes) {
   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, InCSetState::Old);
 }

 HeapRegion* OldGCAllocRegion::release() {
   HeapRegion* cur = get();
   if (cur != NULL) {
     // Determine how far we are from the next card boundary. If it is smaller than
     // the minimum object size we can allocate into, expand into the next card.
     HeapWord* top = cur->top();
     HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, G1BlockOffsetSharedArray::N_bytes);

     size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);

     if (to_allocate_words != 0) {
       // We are not at a card boundary. Fill up, possibly into the next, taking the
       // end of the region and the minimum object size into account.
       to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
                                MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));

       // Skip allocation if there is not enough space to allocate even the smallest
       // possible object. In this case this region will not be retained, so the
       // original problem cannot occur.
       if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
         HeapWord* dummy = attempt_allocation(to_allocate_words, true /* bot_updates */);
         CollectedHeap::fill_with_object(dummy, to_allocate_words);
       }
     }
   }
   return G1AllocRegion::release();
 }
	/*
	* Copyright (c) 2011, 2014, 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
	* questions.
	*
	*/

	#include "precompiled.hpp"
	#include "gc_implementation/g1/g1AllocRegion.inline.hpp"
	#include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
	#include "runtime/orderAccess.inline.hpp"

	G1CollectedHeap* G1AllocRegion::_g1h = NULL;
	HeapRegion* G1AllocRegion::_dummy_region = NULL;

	void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
	assert(_dummy_region == NULL, "should be set once");
	assert(dummy_region != NULL, "pre-condition");
	assert(dummy_region->free() == 0, "pre-condition");

	// Make sure that any allocation attempt on this region will fail
	// and will not trigger any asserts.
	assert(allocate(dummy_region, 1, false) == NULL, "should fail");
	assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
	assert(allocate(dummy_region, 1, true) == NULL, "should fail");
	assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");

	_g1h = g1h;
	_dummy_region = dummy_region;
	}

	void G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
	bool bot_updates) {
	assert(alloc_region != NULL && alloc_region != _dummy_region,
	"pre-condition");

	// Other threads might still be trying to allocate using a CAS out
	// of the region we are trying to retire, as they can do so without
	// holding the lock. So, we first have to make sure that noone else
	// can allocate out of it by doing a maximal allocation. Even if our
	// CAS attempt fails a few times, we'll succeed sooner or later
	// given that failed CAS attempts mean that the region is getting
	// closed to being full.
	size_t free_word_size = alloc_region->free() / HeapWordSize;

	// This is the minimum free chunk we can turn into a dummy
	// object. If the free space falls below this, then noone can
	// allocate in this region anyway (all allocation requests will be
	// of a size larger than this) so we won't have to perform the dummy
	// allocation.
	size_t min_word_size_to_fill = CollectedHeap::min_fill_size();

	while (free_word_size >= min_word_size_to_fill) {
	HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
	if (dummy != NULL) {
	// If the allocation was successful we should fill in the space.
	CollectedHeap::fill_with_object(dummy, free_word_size);
	alloc_region->set_pre_dummy_top(dummy);
	break;
	}

	free_word_size = alloc_region->free() / HeapWordSize;
	// It's also possible that someone else beats us to the
	// allocation and they fill up the region. In that case, we can
	// just get out of the loop.
	}
	assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
	"post-condition");
	}

	void G1AllocRegion::retire(bool fill_up) {
	assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));

	trace("retiring");
	HeapRegion* alloc_region = _alloc_region;
	if (alloc_region != _dummy_region) {
	// We never have to check whether the active region is empty or not,
	// and potentially free it if it is, given that it's guaranteed that
	// it will never be empty.
	assert(!alloc_region->is_empty(),
	ar_ext_msg(this, "the alloc region should never be empty"));

	if (fill_up) {
	fill_up_remaining_space(alloc_region, _bot_updates);
	}

	assert(alloc_region->used() >= _used_bytes_before,
	ar_ext_msg(this, "invariant"));
	size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
	retire_region(alloc_region, allocated_bytes);
	_used_bytes_before = 0;
	_alloc_region = _dummy_region;
	}
	trace("retired");
	}

	HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
	bool force) {
	assert(_alloc_region == _dummy_region, ar_ext_msg(this, "pre-condition"));
	assert(_used_bytes_before == 0, ar_ext_msg(this, "pre-condition"));

	trace("attempting region allocation");
	HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
	if (new_alloc_region != NULL) {
	new_alloc_region->reset_pre_dummy_top();
	// Need to do this before the allocation
	_used_bytes_before = new_alloc_region->used();
	HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
	assert(result != NULL, ar_ext_msg(this, "the allocation should succeeded"));

	OrderAccess::storestore();
	// Note that we first perform the allocation and then we store the
	// region in _alloc_region. This is the reason why an active region
	// can never be empty.
	update_alloc_region(new_alloc_region);
	trace("region allocation successful");
	return result;
	} else {
	trace("region allocation failed");
	return NULL;
	}
	ShouldNotReachHere();
	}

	void G1AllocRegion::fill_in_ext_msg(ar_ext_msg* msg, const char* message) {
	msg->append("[%s] %s c: %u b: %s r: "PTR_FORMAT" u: "SIZE_FORMAT,
	_name, message, _count, BOOL_TO_STR(_bot_updates),
	p2i(_alloc_region), _used_bytes_before);
	}

	void G1AllocRegion::init() {
	trace("initializing");
	assert(_alloc_region == NULL && _used_bytes_before == 0,
	ar_ext_msg(this, "pre-condition"));
	assert(_dummy_region != NULL, ar_ext_msg(this, "should have been set"));
	_alloc_region = _dummy_region;
	_count = 0;
	trace("initialized");
	}

	void G1AllocRegion::set(HeapRegion* alloc_region) {
	trace("setting");
	// We explicitly check that the region is not empty to make sure we
	// maintain the "the alloc region cannot be empty" invariant.
	assert(alloc_region != NULL && !alloc_region->is_empty(),
	ar_ext_msg(this, "pre-condition"));
	assert(_alloc_region == _dummy_region &&
	_used_bytes_before == 0 && _count == 0,
	ar_ext_msg(this, "pre-condition"));

	_used_bytes_before = alloc_region->used();
	_alloc_region = alloc_region;
	_count += 1;
	trace("set");
	}

	void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
	trace("update");
	// We explicitly check that the region is not empty to make sure we
	// maintain the "the alloc region cannot be empty" invariant.
	assert(alloc_region != NULL && !alloc_region->is_empty(),
	ar_ext_msg(this, "pre-condition"));

	_alloc_region = alloc_region;
	_alloc_region->set_allocation_context(allocation_context());
	_count += 1;
	trace("updated");
	}

	HeapRegion* G1AllocRegion::release() {
	trace("releasing");
	HeapRegion* alloc_region = _alloc_region;
	retire(false /* fill_up */);
	assert(_alloc_region == _dummy_region,
	ar_ext_msg(this, "post-condition of retire()"));
	_alloc_region = NULL;
	trace("released");
	return (alloc_region == _dummy_region) ? NULL : alloc_region;
	}

	#if G1_ALLOC_REGION_TRACING
	void G1AllocRegion::trace(const char* str, size_t word_size, HeapWord* result) {
	// All the calls to trace that set either just the size or the size
	// and the result are considered part of level 2 tracing and are
	// skipped during level 1 tracing.
	if ((word_size == 0 && result == NULL) \|\| (G1_ALLOC_REGION_TRACING > 1)) {
	const size_t buffer_length = 128;
	char hr_buffer[buffer_length];
	char rest_buffer[buffer_length];

	HeapRegion* alloc_region = _alloc_region;
	if (alloc_region == NULL) {
	jio_snprintf(hr_buffer, buffer_length, "NULL");
	} else if (alloc_region == _dummy_region) {
	jio_snprintf(hr_buffer, buffer_length, "DUMMY");
	} else {
	jio_snprintf(hr_buffer, buffer_length,
	HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));
	}

	if (G1_ALLOC_REGION_TRACING > 1) {
	if (result != NULL) {
	jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT" "PTR_FORMAT,
	word_size, result);
	} else if (word_size != 0) {
	jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT, word_size);
	} else {
	jio_snprintf(rest_buffer, buffer_length, "");
	}
	} else {
	jio_snprintf(rest_buffer, buffer_length, "");
	}

	tty->print_cr("[%s] %u %s : %s %s",
	_name, _count, hr_buffer, str, rest_buffer);
	}
	}
	#endif // G1_ALLOC_REGION_TRACING

	G1AllocRegion::G1AllocRegion(const char* name,
	bool bot_updates)
	: _name(name), _bot_updates(bot_updates),
	_alloc_region(NULL), _count(0), _used_bytes_before(0),
	_allocation_context(AllocationContext::system()) { }


	HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
	bool force) {
	return _g1h->new_mutator_alloc_region(word_size, force);
	}

	void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
	size_t allocated_bytes) {
	_g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
	}

	HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
	bool force) {
	assert(!force, "not supported for GC alloc regions");
	return _g1h->new_gc_alloc_region(word_size, count(), InCSetState::Young);
	}

	void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
	size_t allocated_bytes) {
	_g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, InCSetState::Young);
	}

	HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
	bool force) {
	assert(!force, "not supported for GC alloc regions");
	return _g1h->new_gc_alloc_region(word_size, count(), InCSetState::Old);
	}

	void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
	size_t allocated_bytes) {
	_g1h->retire_gc_alloc_region(alloc_region, allocated_bytes, InCSetState::Old);
	}

	HeapRegion* OldGCAllocRegion::release() {
	HeapRegion* cur = get();
	if (cur != NULL) {
	// Determine how far we are from the next card boundary. If it is smaller than
	// the minimum object size we can allocate into, expand into the next card.
	HeapWord* top = cur->top();
	HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, G1BlockOffsetSharedArray::N_bytes);

	size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);

	if (to_allocate_words != 0) {
	// We are not at a card boundary. Fill up, possibly into the next, taking the
	// end of the region and the minimum object size into account.
	to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
	MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));

	// Skip allocation if there is not enough space to allocate even the smallest
	// possible object. In this case this region will not be retained, so the
	// original problem cannot occur.
	if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
	HeapWord* dummy = attempt_allocation(to_allocate_words, true /* bot_updates */);
	CollectedHeap::fill_with_object(dummy, to_allocate_words);
	}
	}
	}
	return G1AllocRegion::release();
	}