1 /*
   2  * Copyright (c) 2011, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  27 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  28 #include "runtime/orderAccess.inline.hpp"
  29 
  30 G1CollectedHeap* G1AllocRegion::_g1h = NULL;
  31 HeapRegion* G1AllocRegion::_dummy_region = NULL;
  32 
  33 void G1AllocRegion::setup(G1CollectedHeap* g1h, HeapRegion* dummy_region) {
  34   assert(_dummy_region == NULL, "should be set once");
  35   assert(dummy_region != NULL, "pre-condition");
  36   assert(dummy_region->free() == 0, "pre-condition");
  37 
  38   // Make sure that any allocation attempt on this region will fail
  39   // and will not trigger any asserts.
  40   assert(allocate(dummy_region, 1, false) == NULL, "should fail");
  41   assert(par_allocate(dummy_region, 1, false) == NULL, "should fail");
  42   assert(allocate(dummy_region, 1, true) == NULL, "should fail");
  43   assert(par_allocate(dummy_region, 1, true) == NULL, "should fail");
  44 
  45   _g1h = g1h;
  46   _dummy_region = dummy_region;
  47 }
  48 
  49 void G1AllocRegion::fill_up_remaining_space(HeapRegion* alloc_region,
  50                                             bool bot_updates) {
  51   assert(alloc_region != NULL && alloc_region != _dummy_region,
  52          "pre-condition");
  53 
  54   // Other threads might still be trying to allocate using a CAS out
  55   // of the region we are trying to retire, as they can do so without
  56   // holding the lock. So, we first have to make sure that noone else
  57   // can allocate out of it by doing a maximal allocation. Even if our
  58   // CAS attempt fails a few times, we'll succeed sooner or later
  59   // given that failed CAS attempts mean that the region is getting
  60   // closed to being full.
  61   size_t free_word_size = alloc_region->free() / HeapWordSize;
  62 
  63   // This is the minimum free chunk we can turn into a dummy
  64   // object. If the free space falls below this, then noone can
  65   // allocate in this region anyway (all allocation requests will be
  66   // of a size larger than this) so we won't have to perform the dummy
  67   // allocation.
  68   size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
  69 
  70   while (free_word_size >= min_word_size_to_fill) {
  71     HeapWord* dummy = par_allocate(alloc_region, free_word_size, bot_updates);
  72     if (dummy != NULL) {
  73       // If the allocation was successful we should fill in the space.
  74       CollectedHeap::fill_with_object(dummy, free_word_size);
  75       alloc_region->set_pre_dummy_top(dummy);
  76       break;
  77     }
  78 
  79     free_word_size = alloc_region->free() / HeapWordSize;
  80     // It's also possible that someone else beats us to the
  81     // allocation and they fill up the region. In that case, we can
  82     // just get out of the loop.
  83   }
  84   assert(alloc_region->free() / HeapWordSize < min_word_size_to_fill,
  85          "post-condition");
  86 }
  87 
  88 void G1AllocRegion::retire(bool fill_up) {
  89   assert(_alloc_region != NULL, ar_ext_msg(this, "not initialized properly"));
  90 
  91   trace("retiring");
  92   HeapRegion* alloc_region = _alloc_region;
  93   if (alloc_region != _dummy_region) {
  94     // We never have to check whether the active region is empty or not,
  95     // and potentially free it if it is, given that it's guaranteed that
  96     // it will never be empty.
  97     assert(!alloc_region->is_empty(),
  98            ar_ext_msg(this, "the alloc region should never be empty"));
  99 
 100     if (fill_up) {
 101       fill_up_remaining_space(alloc_region, _bot_updates);
 102     }
 103 
 104     assert(alloc_region->used() >= _used_bytes_before,
 105            ar_ext_msg(this, "invariant"));
 106     size_t allocated_bytes = alloc_region->used() - _used_bytes_before;
 107     retire_region(alloc_region, allocated_bytes);
 108     _used_bytes_before = 0;
 109     _alloc_region = _dummy_region;
 110   }
 111   trace("retired");
 112 }
 113 
 114 HeapWord* G1AllocRegion::new_alloc_region_and_allocate(size_t word_size,
 115                                                        bool force) {
 116   assert(_alloc_region == _dummy_region, ar_ext_msg(this, "pre-condition"));
 117   assert(_used_bytes_before == 0, ar_ext_msg(this, "pre-condition"));
 118 
 119   trace("attempting region allocation");
 120   HeapRegion* new_alloc_region = allocate_new_region(word_size, force);
 121   if (new_alloc_region != NULL) {
 122     new_alloc_region->reset_pre_dummy_top();
 123     // Need to do this before the allocation
 124     _used_bytes_before = new_alloc_region->used();
 125     HeapWord* result = allocate(new_alloc_region, word_size, _bot_updates);
 126     assert(result != NULL, ar_ext_msg(this, "the allocation should succeeded"));
 127 
 128     OrderAccess::storestore();
 129     // Note that we first perform the allocation and then we store the
 130     // region in _alloc_region. This is the reason why an active region
 131     // can never be empty.
 132     update_alloc_region(new_alloc_region);
 133     trace("region allocation successful");
 134     return result;
 135   } else {
 136     trace("region allocation failed");
 137     return NULL;
 138   }
 139   ShouldNotReachHere();
 140 }
 141 
 142 void G1AllocRegion::fill_in_ext_msg(ar_ext_msg* msg, const char* message) {
 143   msg->append("[%s] %s c: %u b: %s r: "PTR_FORMAT" u: "SIZE_FORMAT,
 144               _name, message, _count, BOOL_TO_STR(_bot_updates),
 145               p2i(_alloc_region), _used_bytes_before);
 146 }
 147 
 148 void G1AllocRegion::init() {
 149   trace("initializing");
 150   assert(_alloc_region == NULL && _used_bytes_before == 0,
 151          ar_ext_msg(this, "pre-condition"));
 152   assert(_dummy_region != NULL, ar_ext_msg(this, "should have been set"));
 153   _alloc_region = _dummy_region;
 154   _count = 0;
 155   trace("initialized");
 156 }
 157 
 158 void G1AllocRegion::set(HeapRegion* alloc_region) {
 159   trace("setting");
 160   // We explicitly check that the region is not empty to make sure we
 161   // maintain the "the alloc region cannot be empty" invariant.
 162   assert(alloc_region != NULL && !alloc_region->is_empty(),
 163          ar_ext_msg(this, "pre-condition"));
 164   assert(_alloc_region == _dummy_region &&
 165          _used_bytes_before == 0 && _count == 0,
 166          ar_ext_msg(this, "pre-condition"));
 167 
 168   _used_bytes_before = alloc_region->used();
 169   _alloc_region = alloc_region;
 170   _count += 1;
 171   trace("set");
 172 }
 173 
 174 void G1AllocRegion::update_alloc_region(HeapRegion* alloc_region) {
 175   trace("update");
 176   // We explicitly check that the region is not empty to make sure we
 177   // maintain the "the alloc region cannot be empty" invariant.
 178   assert(alloc_region != NULL && !alloc_region->is_empty(),
 179          ar_ext_msg(this, "pre-condition"));
 180 
 181   _alloc_region = alloc_region;
 182   _alloc_region->set_allocation_context(allocation_context());
 183   _count += 1;
 184   trace("updated");
 185 }
 186 
 187 HeapRegion* G1AllocRegion::release() {
 188   trace("releasing");
 189   HeapRegion* alloc_region = _alloc_region;
 190   retire(false /* fill_up */);
 191   assert(_alloc_region == _dummy_region,
 192          ar_ext_msg(this, "post-condition of retire()"));
 193   _alloc_region = NULL;
 194   trace("released");
 195   return (alloc_region == _dummy_region) ? NULL : alloc_region;
 196 }
 197 
 198 #if G1_ALLOC_REGION_TRACING
 199 void G1AllocRegion::trace(const char* str, size_t word_size, HeapWord* result) {
 200   // All the calls to trace that set either just the size or the size
 201   // and the result are considered part of level 2 tracing and are
 202   // skipped during level 1 tracing.
 203   if ((word_size == 0 && result == NULL) || (G1_ALLOC_REGION_TRACING > 1)) {
 204     const size_t buffer_length = 128;
 205     char hr_buffer[buffer_length];
 206     char rest_buffer[buffer_length];
 207 
 208     HeapRegion* alloc_region = _alloc_region;
 209     if (alloc_region == NULL) {
 210       jio_snprintf(hr_buffer, buffer_length, "NULL");
 211     } else if (alloc_region == _dummy_region) {
 212       jio_snprintf(hr_buffer, buffer_length, "DUMMY");
 213     } else {
 214       jio_snprintf(hr_buffer, buffer_length,
 215                    HR_FORMAT, HR_FORMAT_PARAMS(alloc_region));
 216     }
 217 
 218     if (G1_ALLOC_REGION_TRACING > 1) {
 219       if (result != NULL) {
 220         jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT" "PTR_FORMAT,
 221                      word_size, result);
 222       } else if (word_size != 0) {
 223         jio_snprintf(rest_buffer, buffer_length, SIZE_FORMAT, word_size);
 224       } else {
 225         jio_snprintf(rest_buffer, buffer_length, "");
 226       }
 227     } else {
 228       jio_snprintf(rest_buffer, buffer_length, "");
 229     }
 230 
 231     tty->print_cr("[%s] %u %s : %s %s",
 232                   _name, _count, hr_buffer, str, rest_buffer);
 233   }
 234 }
 235 #endif // G1_ALLOC_REGION_TRACING
 236 
 237 G1AllocRegion::G1AllocRegion(const char* name,
 238                              bool bot_updates)
 239   : _name(name), _bot_updates(bot_updates),
 240     _alloc_region(NULL), _count(0), _used_bytes_before(0),
 241     _allocation_context(AllocationContext::system()) { }
 242 
 243 
 244 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
 245                                                     bool force) {
 246   return _g1h->new_mutator_alloc_region(word_size, force);
 247 }
 248 
 249 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
 250                                        size_t allocated_bytes) {
 251   _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
 252 }
 253 
 254 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
 255                                                        bool force) {
 256   assert(!force, "not supported for GC alloc regions");
 257   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
 258 }
 259 
 260 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
 261                                           size_t allocated_bytes) {
 262   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
 263                                GCAllocForSurvived);
 264 }
 265 
 266 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
 267                                                   bool force) {
 268   assert(!force, "not supported for GC alloc regions");
 269   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
 270 }
 271 
 272 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
 273                                      size_t allocated_bytes) {
 274   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
 275                                GCAllocForTenured);
 276 }
 277 
 278 HeapRegion* OldGCAllocRegion::release() {
 279   HeapRegion* cur = get();
 280   if (cur != NULL) {
 281     // Determine how far we are from the next card boundary. If it is smaller than
 282     // the minimum object size we can allocate into, expand into the next card.
 283     HeapWord* top = cur->top();
 284     HeapWord* aligned_top = (HeapWord*)align_ptr_up(top, G1BlockOffsetSharedArray::N_bytes);
 285 
 286     size_t to_allocate_words = pointer_delta(aligned_top, top, HeapWordSize);
 287 
 288     if (to_allocate_words != 0) {
 289       // We are not at a card boundary. Fill up, possibly into the next, taking the
 290       // end of the region and the minimum object size into account.
 291       to_allocate_words = MIN2(pointer_delta(cur->end(), cur->top(), HeapWordSize),
 292                                MAX2(to_allocate_words, G1CollectedHeap::min_fill_size()));
 293 
 294       // Skip allocation if there is not enough space to allocate even the smallest
 295       // possible object. In this case this region will not be retained, so the
 296       // original problem cannot occur.
 297       if (to_allocate_words >= G1CollectedHeap::min_fill_size()) {
 298         HeapWord* dummy = attempt_allocation(to_allocate_words, true /* bot_updates */);
 299         CollectedHeap::fill_with_object(dummy, to_allocate_words);
 300       }
 301     }
 302   }
 303   return G1AllocRegion::release();
 304 }
 305 
 306