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 if (op.prologue_succeeded()) { 781 return op.result(); 782 } 783 loop_count++; 784 if ((QueuedAllocationWarningCount > 0) && 785 (loop_count % QueuedAllocationWarningCount == 0)) { 786 warning("satisfy_failed_metadata_allocation() retries %d times \n\t" 787 " size=%d", loop_count, word_size); 788 } 789 } while (true); // Until a GC is done 790 } 791 792 // Return true if any of the following is true: 793 // . the allocation won't fit into the current young gen heap 794 // . gc locker is occupied (jni critical section) 795 // . heap memory is tight -- the most recent previous collection 796 // was a full collection because a partial collection (would 797 // have) failed and is likely to fail again 798 bool GenCollectorPolicy::should_try_older_generation_allocation( 799 size_t word_size) const { 800 GenCollectedHeap* gch = GenCollectedHeap::heap(); 801 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc(); 802 return (word_size > heap_word_size(gen0_capacity)) 803 || GC_locker::is_active_and_needs_gc() 804 || gch->incremental_collection_failed(); 805 } 806 807 808 // 809 // MarkSweepPolicy methods 810 // 811 812 MarkSweepPolicy::MarkSweepPolicy() { 813 initialize_all(); 814 } 815 816 void MarkSweepPolicy::initialize_generations() { 817 _generations = new GenerationSpecPtr[number_of_generations()]; 818 if (_generations == NULL) 819 vm_exit_during_initialization("Unable to allocate gen spec"); 820 821 if (UseParNewGC && ParallelGCThreads > 0) { 822 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size); 823 } else { 824 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size); 825 } 826 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size); 827 828 if (_generations[0] == NULL || _generations[1] == NULL) 829 vm_exit_during_initialization("Unable to allocate gen spec"); 830 } 831 832 void MarkSweepPolicy::initialize_gc_policy_counters() { 833 // initialize the policy counters - 2 collectors, 3 generations 834 if (UseParNewGC && ParallelGCThreads > 0) { 835 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3); 836 } 837 else { 838 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3); 839 } 840 }