1 /*
   2  * Copyright (c) 2001, 2012, 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/shared/adaptiveSizePolicy.hpp"
  27 #include "gc_implementation/shared/gcPolicyCounters.hpp"
  28 #include "gc_implementation/shared/vmGCOperations.hpp"
  29 #include "memory/cardTableRS.hpp"
  30 #include "memory/collectorPolicy.hpp"
  31 #include "memory/gcLocker.inline.hpp"
  32 #include "memory/genCollectedHeap.hpp"
  33 #include "memory/generationSpec.hpp"
  34 #include "memory/space.hpp"
  35 #include "memory/universe.hpp"
  36 #include "runtime/arguments.hpp"
  37 #include "runtime/globals_extension.hpp"
  38 #include "runtime/handles.inline.hpp"
  39 #include "runtime/java.hpp"
  40 #include "runtime/thread.inline.hpp"
  41 #include "runtime/vmThread.hpp"
  42 #ifndef SERIALGC
  43 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp"
  44 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp"
  45 #endif
  46 
  47 // CollectorPolicy methods.
  48 
  49 void CollectorPolicy::initialize_flags() {
  50   if (MetaspaceSize > MaxMetaspaceSize) {
  51     MaxMetaspaceSize = MetaspaceSize;
  52   }
  53   MetaspaceSize = MAX2(min_alignment(), align_size_down_(MetaspaceSize, min_alignment()));
  54   // Don't increase Metaspace size limit above specified.
  55   MaxMetaspaceSize = align_size_down(MaxMetaspaceSize, max_alignment());
  56   if (MetaspaceSize > MaxMetaspaceSize) {
  57     MetaspaceSize = MaxMetaspaceSize;
  58   }
  59 
  60   MinMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MinMetaspaceExpansion, min_alignment()));
  61   MaxMetaspaceExpansion = MAX2(min_alignment(), align_size_down_(MaxMetaspaceExpansion, min_alignment()));
  62 
  63   MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment());
  64 
  65   assert(MetaspaceSize    % min_alignment() == 0, "metapace alignment");
  66   assert(MaxMetaspaceSize % max_alignment() == 0, "maximum metaspace alignment");
  67   if (MetaspaceSize < 256*K) {
  68     vm_exit_during_initialization("Too small initial Metaspace size");
  69   }
  70 }
  71 
  72 void CollectorPolicy::initialize_size_info() {
  73   // User inputs from -mx and ms are aligned
  74   set_initial_heap_byte_size(InitialHeapSize);
  75   if (initial_heap_byte_size() == 0) {
  76     set_initial_heap_byte_size(NewSize + OldSize);
  77   }
  78   set_initial_heap_byte_size(align_size_up(_initial_heap_byte_size,
  79                                            min_alignment()));
  80 
  81   set_min_heap_byte_size(Arguments::min_heap_size());
  82   if (min_heap_byte_size() == 0) {
  83     set_min_heap_byte_size(NewSize + OldSize);
  84   }
  85   set_min_heap_byte_size(align_size_up(_min_heap_byte_size,
  86                                        min_alignment()));
  87 
  88   set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment()));
  89 
  90   // Check heap parameter properties
  91   if (initial_heap_byte_size() < M) {
  92     vm_exit_during_initialization("Too small initial heap");
  93   }
  94   // Check heap parameter properties
  95   if (min_heap_byte_size() < M) {
  96     vm_exit_during_initialization("Too small minimum heap");
  97   }
  98   if (initial_heap_byte_size() <= NewSize) {
  99      // make sure there is at least some room in old space
 100     vm_exit_during_initialization("Too small initial heap for new size specified");
 101   }
 102   if (max_heap_byte_size() < min_heap_byte_size()) {
 103     vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified");
 104   }
 105   if (initial_heap_byte_size() < min_heap_byte_size()) {
 106     vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified");
 107   }
 108   if (max_heap_byte_size() < initial_heap_byte_size()) {
 109     vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified");
 110   }
 111 
 112   if (PrintGCDetails && Verbose) {
 113     gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT "  Initial heap "
 114       SIZE_FORMAT "  Maximum heap " SIZE_FORMAT,
 115       min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size());
 116   }
 117 }
 118 
 119 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) {
 120   bool result = _should_clear_all_soft_refs;
 121   set_should_clear_all_soft_refs(false);
 122   return result;
 123 }
 124 
 125 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap,
 126                                            int max_covered_regions) {
 127   switch (rem_set_name()) {
 128   case GenRemSet::CardTable: {
 129     CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions);
 130     return res;
 131   }
 132   default:
 133     guarantee(false, "unrecognized GenRemSet::Name");
 134     return NULL;
 135   }
 136 }
 137 
 138 void CollectorPolicy::cleared_all_soft_refs() {
 139   // If near gc overhear limit, continue to clear SoftRefs.  SoftRefs may
 140   // have been cleared in the last collection but if the gc overhear
 141   // limit continues to be near, SoftRefs should still be cleared.
 142   if (size_policy() != NULL) {
 143     _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near();
 144   }
 145   _all_soft_refs_clear = true;
 146 }
 147 
 148 
 149 // GenCollectorPolicy methods.
 150 
 151 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) {
 152   size_t x = base_size / (NewRatio+1);
 153   size_t new_gen_size = x > min_alignment() ?
 154                      align_size_down(x, min_alignment()) :
 155                      min_alignment();
 156   return new_gen_size;
 157 }
 158 
 159 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size,
 160                                                  size_t maximum_size) {
 161   size_t alignment = min_alignment();
 162   size_t max_minus = maximum_size - alignment;
 163   return desired_size < max_minus ? desired_size : max_minus;
 164 }
 165 
 166 
 167 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size,
 168                                                 size_t init_promo_size,
 169                                                 size_t init_survivor_size) {
 170   const double max_gc_minor_pause_sec = ((double) MaxGCMinorPauseMillis)/1000.0;
 171   _size_policy = new AdaptiveSizePolicy(init_eden_size,
 172                                         init_promo_size,
 173                                         init_survivor_size,
 174                                         max_gc_minor_pause_sec,
 175                                         GCTimeRatio);
 176 }
 177 
 178 size_t GenCollectorPolicy::compute_max_alignment() {
 179   // The card marking array and the offset arrays for old generations are
 180   // committed in os pages as well. Make sure they are entirely full (to
 181   // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1
 182   // byte entry and the os page size is 4096, the maximum heap size should
 183   // be 512*4096 = 2MB aligned.
 184   size_t alignment = GenRemSet::max_alignment_constraint(rem_set_name());
 185 
 186   // Parallel GC does its own alignment of the generations to avoid requiring a
 187   // large page (256M on some platforms) for the permanent generation.  The
 188   // other collectors should also be updated to do their own alignment and then
 189   // this use of lcm() should be removed.
 190   if (UseLargePages && !UseParallelGC) {
 191       // in presence of large pages we have to make sure that our
 192       // alignment is large page aware
 193       alignment = lcm(os::large_page_size(), alignment);
 194   }
 195 
 196   return alignment;
 197 }
 198 
 199 void GenCollectorPolicy::initialize_flags() {
 200   // All sizes must be multiples of the generation granularity.
 201   set_min_alignment((uintx) Generation::GenGrain);
 202   set_max_alignment(compute_max_alignment());
 203   assert(max_alignment() >= min_alignment() &&
 204          max_alignment() % min_alignment() == 0,
 205          "invalid alignment constraints");
 206 
 207   CollectorPolicy::initialize_flags();
 208 
 209   // All generational heaps have a youngest gen; handle those flags here.
 210 
 211   // Adjust max size parameters
 212   if (NewSize > MaxNewSize) {
 213     MaxNewSize = NewSize;
 214   }
 215   NewSize = align_size_down(NewSize, min_alignment());
 216   MaxNewSize = align_size_down(MaxNewSize, min_alignment());
 217 
 218   // Check validity of heap flags
 219   assert(NewSize     % min_alignment() == 0, "eden space alignment");
 220   assert(MaxNewSize  % min_alignment() == 0, "survivor space alignment");
 221 
 222   if (NewSize < 3*min_alignment()) {
 223      // make sure there room for eden and two survivor spaces
 224     vm_exit_during_initialization("Too small new size specified");
 225   }
 226   if (SurvivorRatio < 1 || NewRatio < 1) {
 227     vm_exit_during_initialization("Invalid heap ratio specified");
 228   }
 229 }
 230 
 231 void TwoGenerationCollectorPolicy::initialize_flags() {
 232   GenCollectorPolicy::initialize_flags();
 233 
 234   OldSize = align_size_down(OldSize, min_alignment());
 235   if (NewSize + OldSize > MaxHeapSize) {
 236     MaxHeapSize = NewSize + OldSize;
 237   }
 238   MaxHeapSize = align_size_up(MaxHeapSize, max_alignment());
 239 
 240   always_do_update_barrier = UseConcMarkSweepGC;
 241 
 242   // Check validity of heap flags
 243   assert(OldSize     % min_alignment() == 0, "old space alignment");
 244   assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment");
 245 }
 246 
 247 // Values set on the command line win over any ergonomically
 248 // set command line parameters.
 249 // Ergonomic choice of parameters are done before this
 250 // method is called.  Values for command line parameters such as NewSize
 251 // and MaxNewSize feed those ergonomic choices into this method.
 252 // This method makes the final generation sizings consistent with
 253 // themselves and with overall heap sizings.
 254 // In the absence of explicitly set command line flags, policies
 255 // such as the use of NewRatio are used to size the generation.
 256 void GenCollectorPolicy::initialize_size_info() {
 257   CollectorPolicy::initialize_size_info();
 258 
 259   // min_alignment() is used for alignment within a generation.
 260   // There is additional alignment done down stream for some
 261   // collectors that sometimes causes unwanted rounding up of
 262   // generations sizes.
 263 
 264   // Determine maximum size of gen0
 265 
 266   size_t max_new_size = 0;
 267   if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) {
 268     if (MaxNewSize < min_alignment()) {
 269       max_new_size = min_alignment();
 270     }
 271     if (MaxNewSize >= max_heap_byte_size()) {
 272       max_new_size = align_size_down(max_heap_byte_size() - min_alignment(),
 273                                      min_alignment());
 274       warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or "
 275         "greater than the entire heap (" SIZE_FORMAT "k).  A "
 276         "new generation size of " SIZE_FORMAT "k will be used.",
 277         MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K);
 278     } else {
 279       max_new_size = align_size_down(MaxNewSize, min_alignment());
 280     }
 281 
 282   // The case for FLAG_IS_ERGO(MaxNewSize) could be treated
 283   // specially at this point to just use an ergonomically set
 284   // MaxNewSize to set max_new_size.  For cases with small
 285   // heaps such a policy often did not work because the MaxNewSize
 286   // was larger than the entire heap.  The interpretation given
 287   // to ergonomically set flags is that the flags are set
 288   // by different collectors for their own special needs but
 289   // are not allowed to badly shape the heap.  This allows the
 290   // different collectors to decide what's best for themselves
 291   // without having to factor in the overall heap shape.  It
 292   // can be the case in the future that the collectors would
 293   // only make "wise" ergonomics choices and this policy could
 294   // just accept those choices.  The choices currently made are
 295   // not always "wise".
 296   } else {
 297     max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size());
 298     // Bound the maximum size by NewSize below (since it historically
 299     // would have been NewSize and because the NewRatio calculation could
 300     // yield a size that is too small) and bound it by MaxNewSize above.
 301     // Ergonomics plays here by previously calculating the desired
 302     // NewSize and MaxNewSize.
 303     max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize);
 304   }
 305   assert(max_new_size > 0, "All paths should set max_new_size");
 306 
 307   // Given the maximum gen0 size, determine the initial and
 308   // minimum gen0 sizes.
 309 
 310   if (max_heap_byte_size() == min_heap_byte_size()) {
 311     // The maximum and minimum heap sizes are the same so
 312     // the generations minimum and initial must be the
 313     // same as its maximum.
 314     set_min_gen0_size(max_new_size);
 315     set_initial_gen0_size(max_new_size);
 316     set_max_gen0_size(max_new_size);
 317   } else {
 318     size_t desired_new_size = 0;
 319     if (!FLAG_IS_DEFAULT(NewSize)) {
 320       // If NewSize is set ergonomically (for example by cms), it
 321       // would make sense to use it.  If it is used, also use it
 322       // to set the initial size.  Although there is no reason
 323       // the minimum size and the initial size have to be the same,
 324       // the current implementation gets into trouble during the calculation
 325       // of the tenured generation sizes if they are different.
 326       // Note that this makes the initial size and the minimum size
 327       // generally small compared to the NewRatio calculation.
 328       _min_gen0_size = NewSize;
 329       desired_new_size = NewSize;
 330       max_new_size = MAX2(max_new_size, NewSize);
 331     } else {
 332       // For the case where NewSize is the default, use NewRatio
 333       // to size the minimum and initial generation sizes.
 334       // Use the default NewSize as the floor for these values.  If
 335       // NewRatio is overly large, the resulting sizes can be too
 336       // small.
 337       _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()),
 338                           NewSize);
 339       desired_new_size =
 340         MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()),
 341              NewSize);
 342     }
 343 
 344     assert(_min_gen0_size > 0, "Sanity check");
 345     set_initial_gen0_size(desired_new_size);
 346     set_max_gen0_size(max_new_size);
 347 
 348     // At this point the desirable initial and minimum sizes have been
 349     // determined without regard to the maximum sizes.
 350 
 351     // Bound the sizes by the corresponding overall heap sizes.
 352     set_min_gen0_size(
 353       bound_minus_alignment(_min_gen0_size, min_heap_byte_size()));
 354     set_initial_gen0_size(
 355       bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size()));
 356     set_max_gen0_size(
 357       bound_minus_alignment(_max_gen0_size, max_heap_byte_size()));
 358 
 359     // At this point all three sizes have been checked against the
 360     // maximum sizes but have not been checked for consistency
 361     // among the three.
 362 
 363     // Final check min <= initial <= max
 364     set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size));
 365     set_initial_gen0_size(
 366       MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size));
 367     set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size));
 368   }
 369 
 370   if (PrintGCDetails && Verbose) {
 371     gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT "  Initial gen0 "
 372       SIZE_FORMAT "  Maximum gen0 " SIZE_FORMAT,
 373       min_gen0_size(), initial_gen0_size(), max_gen0_size());
 374   }
 375 }
 376 
 377 // Call this method during the sizing of the gen1 to make
 378 // adjustments to gen0 because of gen1 sizing policy.  gen0 initially has
 379 // the most freedom in sizing because it is done before the
 380 // policy for gen1 is applied.  Once gen1 policies have been applied,
 381 // there may be conflicts in the shape of the heap and this method
 382 // is used to make the needed adjustments.  The application of the
 383 // policies could be more sophisticated (iterative for example) but
 384 // keeping it simple also seems a worthwhile goal.
 385 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr,
 386                                                      size_t* gen1_size_ptr,
 387                                                      size_t heap_size,
 388                                                      size_t min_gen0_size) {
 389   bool result = false;
 390   if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) {
 391     if (((*gen0_size_ptr + OldSize) > heap_size) &&
 392        (heap_size - min_gen0_size) >= min_alignment()) {
 393       // Adjust gen0 down to accomodate OldSize
 394       *gen0_size_ptr = heap_size - min_gen0_size;
 395       *gen0_size_ptr =
 396         MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()),
 397              min_alignment());
 398       assert(*gen0_size_ptr > 0, "Min gen0 is too large");
 399       result = true;
 400     } else {
 401       *gen1_size_ptr = heap_size - *gen0_size_ptr;
 402       *gen1_size_ptr =
 403         MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()),
 404                        min_alignment());
 405     }
 406   }
 407   return result;
 408 }
 409 
 410 // Minimum sizes of the generations may be different than
 411 // the initial sizes.  An inconsistently is permitted here
 412 // in the total size that can be specified explicitly by
 413 // command line specification of OldSize and NewSize and
 414 // also a command line specification of -Xms.  Issue a warning
 415 // but allow the values to pass.
 416 
 417 void TwoGenerationCollectorPolicy::initialize_size_info() {
 418   GenCollectorPolicy::initialize_size_info();
 419 
 420   // At this point the minimum, initial and maximum sizes
 421   // of the overall heap and of gen0 have been determined.
 422   // The maximum gen1 size can be determined from the maximum gen0
 423   // and maximum heap size since no explicit flags exits
 424   // for setting the gen1 maximum.
 425   _max_gen1_size = max_heap_byte_size() - _max_gen0_size;
 426   _max_gen1_size =
 427     MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()),
 428          min_alignment());
 429   // If no explicit command line flag has been set for the
 430   // gen1 size, use what is left for gen1.
 431   if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) {
 432     // The user has not specified any value or ergonomics
 433     // has chosen a value (which may or may not be consistent
 434     // with the overall heap size).  In either case make
 435     // the minimum, maximum and initial sizes consistent
 436     // with the gen0 sizes and the overall heap sizes.
 437     assert(min_heap_byte_size() > _min_gen0_size,
 438       "gen0 has an unexpected minimum size");
 439     set_min_gen1_size(min_heap_byte_size() - min_gen0_size());
 440     set_min_gen1_size(
 441       MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()),
 442            min_alignment()));
 443     set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size());
 444     set_initial_gen1_size(
 445       MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()),
 446            min_alignment()));
 447 
 448   } else {
 449     // It's been explicitly set on the command line.  Use the
 450     // OldSize and then determine the consequences.
 451     set_min_gen1_size(OldSize);
 452     set_initial_gen1_size(OldSize);
 453 
 454     // If the user has explicitly set an OldSize that is inconsistent
 455     // with other command line flags, issue a warning.
 456     // The generation minimums and the overall heap mimimum should
 457     // be within one heap alignment.
 458     if ((_min_gen1_size + _min_gen0_size + min_alignment()) <
 459            min_heap_byte_size()) {
 460       warning("Inconsistency between minimum heap size and minimum "
 461           "generation sizes: using minimum heap = " SIZE_FORMAT,
 462           min_heap_byte_size());
 463     }
 464     if ((OldSize > _max_gen1_size)) {
 465       warning("Inconsistency between maximum heap size and maximum "
 466           "generation sizes: using maximum heap = " SIZE_FORMAT
 467           " -XX:OldSize flag is being ignored",
 468           max_heap_byte_size());
 469     }
 470     // If there is an inconsistency between the OldSize and the minimum and/or
 471     // initial size of gen0, since OldSize was explicitly set, OldSize wins.
 472     if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size,
 473                           min_heap_byte_size(), OldSize)) {
 474       if (PrintGCDetails && Verbose) {
 475         gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT "  Initial gen0 "
 476               SIZE_FORMAT "  Maximum gen0 " SIZE_FORMAT,
 477               min_gen0_size(), initial_gen0_size(), max_gen0_size());
 478       }
 479     }
 480     // Initial size
 481     if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size,
 482                          initial_heap_byte_size(), OldSize)) {
 483       if (PrintGCDetails && Verbose) {
 484         gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT "  Initial gen0 "
 485           SIZE_FORMAT "  Maximum gen0 " SIZE_FORMAT,
 486           min_gen0_size(), initial_gen0_size(), max_gen0_size());
 487       }
 488     }
 489   }
 490   // Enforce the maximum gen1 size.
 491   set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size));
 492 
 493   // Check that min gen1 <= initial gen1 <= max gen1
 494   set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size));
 495   set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size));
 496 
 497   if (PrintGCDetails && Verbose) {
 498     gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT "  Initial gen1 "
 499       SIZE_FORMAT "  Maximum gen1 " SIZE_FORMAT,
 500       min_gen1_size(), initial_gen1_size(), max_gen1_size());
 501   }
 502 }
 503 
 504 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size,
 505                                         bool is_tlab,
 506                                         bool* gc_overhead_limit_was_exceeded) {
 507   GenCollectedHeap *gch = GenCollectedHeap::heap();
 508 
 509   debug_only(gch->check_for_valid_allocation_state());
 510   assert(gch->no_gc_in_progress(), "Allocation during gc not allowed");
 511 
 512   // In general gc_overhead_limit_was_exceeded should be false so
 513   // set it so here and reset it to true only if the gc time
 514   // limit is being exceeded as checked below.
 515   *gc_overhead_limit_was_exceeded = false;
 516 
 517   HeapWord* result = NULL;
 518 
 519   // Loop until the allocation is satisified,
 520   // or unsatisfied after GC.
 521   for (int try_count = 1; /* return or throw */; try_count += 1) {
 522     HandleMark hm; // discard any handles allocated in each iteration
 523 
 524     // First allocation attempt is lock-free.
 525     Generation *gen0 = gch->get_gen(0);
 526     assert(gen0->supports_inline_contig_alloc(),
 527       "Otherwise, must do alloc within heap lock");
 528     if (gen0->should_allocate(size, is_tlab)) {
 529       result = gen0->par_allocate(size, is_tlab);
 530       if (result != NULL) {
 531         assert(gch->is_in_reserved(result), "result not in heap");
 532         return result;
 533       }
 534     }
 535     unsigned int gc_count_before;  // read inside the Heap_lock locked region
 536     {
 537       MutexLocker ml(Heap_lock);
 538       if (PrintGC && Verbose) {
 539         gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:"
 540                       " attempting locked slow path allocation");
 541       }
 542       // Note that only large objects get a shot at being
 543       // allocated in later generations.
 544       bool first_only = ! should_try_older_generation_allocation(size);
 545 
 546       result = gch->attempt_allocation(size, is_tlab, first_only);
 547       if (result != NULL) {
 548         assert(gch->is_in_reserved(result), "result not in heap");
 549         return result;
 550       }
 551 
 552       if (GC_locker::is_active_and_needs_gc()) {
 553         if (is_tlab) {
 554           return NULL;  // Caller will retry allocating individual object
 555         }
 556         if (!gch->is_maximal_no_gc()) {
 557           // Try and expand heap to satisfy request
 558           result = expand_heap_and_allocate(size, is_tlab);
 559           // result could be null if we are out of space
 560           if (result != NULL) {
 561             return result;
 562           }
 563         }
 564 
 565         // If this thread is not in a jni critical section, we stall
 566         // the requestor until the critical section has cleared and
 567         // GC allowed. When the critical section clears, a GC is
 568         // initiated by the last thread exiting the critical section; so
 569         // we retry the allocation sequence from the beginning of the loop,
 570         // rather than causing more, now probably unnecessary, GC attempts.
 571         JavaThread* jthr = JavaThread::current();
 572         if (!jthr->in_critical()) {
 573           MutexUnlocker mul(Heap_lock);
 574           // Wait for JNI critical section to be exited
 575           GC_locker::stall_until_clear();
 576           continue;
 577         } else {
 578           if (CheckJNICalls) {
 579             fatal("Possible deadlock due to allocating while"
 580                   " in jni critical section");
 581           }
 582           return NULL;
 583         }
 584       }
 585 
 586       // Read the gc count while the heap lock is held.
 587       gc_count_before = Universe::heap()->total_collections();
 588     }
 589 
 590     VM_GenCollectForAllocation op(size,
 591                                   is_tlab,
 592                                   gc_count_before);
 593     VMThread::execute(&op);
 594     if (op.prologue_succeeded()) {
 595       result = op.result();
 596       if (op.gc_locked()) {
 597          assert(result == NULL, "must be NULL if gc_locked() is true");
 598          continue;  // retry and/or stall as necessary
 599       }
 600 
 601       // Allocation has failed and a collection
 602       // has been done.  If the gc time limit was exceeded the
 603       // this time, return NULL so that an out-of-memory
 604       // will be thrown.  Clear gc_overhead_limit_exceeded
 605       // so that the overhead exceeded does not persist.
 606 
 607       const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded();
 608       const bool softrefs_clear = all_soft_refs_clear();
 609       assert(!limit_exceeded || softrefs_clear, "Should have been cleared");
 610       if (limit_exceeded && softrefs_clear) {
 611         *gc_overhead_limit_was_exceeded = true;
 612         size_policy()->set_gc_overhead_limit_exceeded(false);
 613         if (op.result() != NULL) {
 614           CollectedHeap::fill_with_object(op.result(), size);
 615         }
 616         return NULL;
 617       }
 618       assert(result == NULL || gch->is_in_reserved(result),
 619              "result not in heap");
 620       return result;
 621     }
 622 
 623     // Give a warning if we seem to be looping forever.
 624     if ((QueuedAllocationWarningCount > 0) &&
 625         (try_count % QueuedAllocationWarningCount == 0)) {
 626           warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t"
 627                   " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : "");
 628     }
 629   }
 630 }
 631 
 632 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size,
 633                                                        bool   is_tlab) {
 634   GenCollectedHeap *gch = GenCollectedHeap::heap();
 635   HeapWord* result = NULL;
 636   for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) {
 637     Generation *gen = gch->get_gen(i);
 638     if (gen->should_allocate(size, is_tlab)) {
 639       result = gen->expand_and_allocate(size, is_tlab);
 640     }
 641   }
 642   assert(result == NULL || gch->is_in_reserved(result), "result not in heap");
 643   return result;
 644 }
 645 
 646 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size,
 647                                                         bool   is_tlab) {
 648   GenCollectedHeap *gch = GenCollectedHeap::heap();
 649   GCCauseSetter x(gch, GCCause::_allocation_failure);
 650   HeapWord* result = NULL;
 651 
 652   assert(size != 0, "Precondition violated");
 653   if (GC_locker::is_active_and_needs_gc()) {
 654     // GC locker is active; instead of a collection we will attempt
 655     // to expand the heap, if there's room for expansion.
 656     if (!gch->is_maximal_no_gc()) {
 657       result = expand_heap_and_allocate(size, is_tlab);
 658     }
 659     return result;   // could be null if we are out of space
 660   } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) {
 661     // Do an incremental collection.
 662     gch->do_collection(false            /* full */,
 663                        false            /* clear_all_soft_refs */,
 664                        size             /* size */,
 665                        is_tlab          /* is_tlab */,
 666                        number_of_generations() - 1 /* max_level */);
 667   } else {
 668     if (Verbose && PrintGCDetails) {
 669       gclog_or_tty->print(" :: Trying full because partial may fail :: ");
 670     }
 671     // Try a full collection; see delta for bug id 6266275
 672     // for the original code and why this has been simplified
 673     // with from-space allocation criteria modified and
 674     // such allocation moved out of the safepoint path.
 675     gch->do_collection(true             /* full */,
 676                        false            /* clear_all_soft_refs */,
 677                        size             /* size */,
 678                        is_tlab          /* is_tlab */,
 679                        number_of_generations() - 1 /* max_level */);
 680   }
 681 
 682   result = gch->attempt_allocation(size, is_tlab, false /*first_only*/);
 683 
 684   if (result != NULL) {
 685     assert(gch->is_in_reserved(result), "result not in heap");
 686     return result;
 687   }
 688 
 689   // OK, collection failed, try expansion.
 690   result = expand_heap_and_allocate(size, is_tlab);
 691   if (result != NULL) {
 692     return result;
 693   }
 694 
 695   // If we reach this point, we're really out of memory. Try every trick
 696   // we can to reclaim memory. Force collection of soft references. Force
 697   // a complete compaction of the heap. Any additional methods for finding
 698   // free memory should be here, especially if they are expensive. If this
 699   // attempt fails, an OOM exception will be thrown.
 700   {
 701     IntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted
 702 
 703     gch->do_collection(true             /* full */,
 704                        true             /* clear_all_soft_refs */,
 705                        size             /* size */,
 706                        is_tlab          /* is_tlab */,
 707                        number_of_generations() - 1 /* max_level */);
 708   }
 709 
 710   result = gch->attempt_allocation(size, is_tlab, false /* first_only */);
 711   if (result != NULL) {
 712     assert(gch->is_in_reserved(result), "result not in heap");
 713     return result;
 714   }
 715 
 716   assert(!should_clear_all_soft_refs(),
 717     "Flag should have been handled and cleared prior to this point");
 718 
 719   // What else?  We might try synchronous finalization later.  If the total
 720   // space available is large enough for the allocation, then a more
 721   // complete compaction phase than we've tried so far might be
 722   // appropriate.
 723   return NULL;
 724 }
 725 
 726 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation(
 727                                                  ClassLoaderData* loader_data,
 728                                                  size_t word_size,
 729                                                  Metaspace::MetadataType mdtype) {
 730   uint loop_count = 0;
 731   uint gc_count = 0;
 732   uint full_gc_count = 0;
 733 
 734   assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock");
 735 
 736   do {
 737     MetaWord* result = NULL;
 738     if (GC_locker::is_active_and_needs_gc()) {
 739       // If the GC_locker is active, just expand and allocate.
 740       // If that does not succeed, wait if this thread is not
 741       // in a critical section itself.
 742       result =
 743         loader_data->metaspace_non_null()->expand_and_allocate(word_size,
 744                                                                mdtype);
 745       if (result != NULL) {
 746         return result;
 747       }
 748       JavaThread* jthr = JavaThread::current();
 749       if (!jthr->in_critical()) {
 750         // Wait for JNI critical section to be exited
 751         GC_locker::stall_until_clear();
 752         // The GC invoked by the last thread leaving the critical
 753         // section will be a young collection and a full collection
 754         // is (currently) needed for unloading classes so continue
 755         // to the next iteration to get a full GC.
 756         continue;
 757       } else {
 758         if (CheckJNICalls) {
 759           fatal("Possible deadlock due to allocating while"
 760                 " in jni critical section");
 761         }
 762         return NULL;
 763       }
 764     }
 765 
 766     {  // Need lock to get self consistent gc_count's
 767       MutexLocker ml(Heap_lock);
 768       gc_count      = Universe::heap()->total_collections();
 769       full_gc_count = Universe::heap()->total_full_collections();
 770     }
 771 
 772     // Generate a VM operation
 773     VM_CollectForMetadataAllocation op(loader_data,
 774                                        word_size,
 775                                        mdtype,
 776                                        gc_count,
 777                                        full_gc_count,
 778                                        GCCause::_metadata_GC_threshold);
 779     VMThread::execute(&op);
 780 
 781     // If GC was locked out, try again.  Check
 782     // before checking success because the prologue
 783     // could have succeeded and the GC still have
 784     // been locked out.
 785     if (op.gc_locked()) {
 786       continue;
 787     }
 788 
 789     if (op.prologue_succeeded()) {
 790       return op.result();
 791     }
 792     loop_count++;
 793     if ((QueuedAllocationWarningCount > 0) &&
 794         (loop_count % QueuedAllocationWarningCount == 0)) {
 795       warning("satisfy_failed_metadata_allocation() retries %d times \n\t"
 796               " size=%d", loop_count, word_size);
 797     }
 798   } while (true);  // Until a GC is done
 799 }
 800 
 801 // Return true if any of the following is true:
 802 // . the allocation won't fit into the current young gen heap
 803 // . gc locker is occupied (jni critical section)
 804 // . heap memory is tight -- the most recent previous collection
 805 //   was a full collection because a partial collection (would
 806 //   have) failed and is likely to fail again
 807 bool GenCollectorPolicy::should_try_older_generation_allocation(
 808         size_t word_size) const {
 809   GenCollectedHeap* gch = GenCollectedHeap::heap();
 810   size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc();
 811   return    (word_size > heap_word_size(gen0_capacity))
 812          || GC_locker::is_active_and_needs_gc()
 813          || gch->incremental_collection_failed();
 814 }
 815 
 816 
 817 //
 818 // MarkSweepPolicy methods
 819 //
 820 
 821 MarkSweepPolicy::MarkSweepPolicy() {
 822   initialize_all();
 823 }
 824 
 825 void MarkSweepPolicy::initialize_generations() {
 826   _generations = new GenerationSpecPtr[number_of_generations()];
 827   if (_generations == NULL)
 828     vm_exit_during_initialization("Unable to allocate gen spec");
 829 
 830   if (UseParNewGC && ParallelGCThreads > 0) {
 831     _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size);
 832   } else {
 833     _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size);
 834   }
 835   _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size);
 836 
 837   if (_generations[0] == NULL || _generations[1] == NULL)
 838     vm_exit_during_initialization("Unable to allocate gen spec");
 839 }
 840 
 841 void MarkSweepPolicy::initialize_gc_policy_counters() {
 842   // initialize the policy counters - 2 collectors, 3 generations
 843   if (UseParNewGC && ParallelGCThreads > 0) {
 844     _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3);
 845   }
 846   else {
 847     _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3);
 848   }
 849 }