1 /* 2 * Copyright (c) 2001, 2011, 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/vmThread.hpp" 41 #ifdef TARGET_OS_FAMILY_linux 42 # include "thread_linux.inline.hpp" 43 #endif 44 #ifdef TARGET_OS_FAMILY_solaris 45 # include "thread_solaris.inline.hpp" 46 #endif 47 #ifdef TARGET_OS_FAMILY_windows 48 # include "thread_windows.inline.hpp" 49 #endif 50 #ifdef TARGET_OS_FAMILY_bsd 51 # include "thread_bsd.inline.hpp" 52 #endif 53 #ifndef SERIALGC 54 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp" 55 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp" 56 #endif 57 58 // CollectorPolicy methods. 59 60 void CollectorPolicy::initialize_flags() { 61 if (PermSize > MaxPermSize) { 62 MaxPermSize = PermSize; 63 } 64 PermSize = MAX2(min_alignment(), align_size_down_(PermSize, min_alignment())); 65 // Don't increase Perm size limit above specified. 66 MaxPermSize = align_size_down(MaxPermSize, max_alignment()); 67 if (PermSize > MaxPermSize) { 68 PermSize = MaxPermSize; 69 } 70 71 MinPermHeapExpansion = MAX2(min_alignment(), align_size_down_(MinPermHeapExpansion, min_alignment())); 72 MaxPermHeapExpansion = MAX2(min_alignment(), align_size_down_(MaxPermHeapExpansion, min_alignment())); 73 74 MinHeapDeltaBytes = align_size_up(MinHeapDeltaBytes, min_alignment()); 75 76 SharedReadOnlySize = align_size_up(SharedReadOnlySize, max_alignment()); 77 SharedReadWriteSize = align_size_up(SharedReadWriteSize, max_alignment()); 78 SharedMiscDataSize = align_size_up(SharedMiscDataSize, max_alignment()); 79 80 assert(PermSize % min_alignment() == 0, "permanent space alignment"); 81 assert(MaxPermSize % max_alignment() == 0, "maximum permanent space alignment"); 82 assert(SharedReadOnlySize % max_alignment() == 0, "read-only space alignment"); 83 assert(SharedReadWriteSize % max_alignment() == 0, "read-write space alignment"); 84 assert(SharedMiscDataSize % max_alignment() == 0, "misc-data space alignment"); 85 if (PermSize < M) { 86 vm_exit_during_initialization("Too small initial permanent heap"); 87 } 88 } 89 90 void CollectorPolicy::initialize_size_info() { 91 // User inputs from -mx and ms are aligned 92 set_initial_heap_byte_size(InitialHeapSize); 93 if (initial_heap_byte_size() == 0) { 94 set_initial_heap_byte_size(NewSize + OldSize); 95 } 96 set_initial_heap_byte_size(align_size_up(_initial_heap_byte_size, 97 min_alignment())); 98 99 set_min_heap_byte_size(Arguments::min_heap_size()); 100 if (min_heap_byte_size() == 0) { 101 set_min_heap_byte_size(NewSize + OldSize); 102 } 103 set_min_heap_byte_size(align_size_up(_min_heap_byte_size, 104 min_alignment())); 105 106 set_max_heap_byte_size(align_size_up(MaxHeapSize, max_alignment())); 107 108 // Check heap parameter properties 109 if (initial_heap_byte_size() < M) { 110 vm_exit_during_initialization("Too small initial heap"); 111 } 112 // Check heap parameter properties 113 if (min_heap_byte_size() < M) { 114 vm_exit_during_initialization("Too small minimum heap"); 115 } 116 if (initial_heap_byte_size() <= NewSize) { 117 // make sure there is at least some room in old space 118 vm_exit_during_initialization("Too small initial heap for new size specified"); 119 } 120 if (max_heap_byte_size() < min_heap_byte_size()) { 121 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified"); 122 } 123 if (initial_heap_byte_size() < min_heap_byte_size()) { 124 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified"); 125 } 126 if (max_heap_byte_size() < initial_heap_byte_size()) { 127 vm_exit_during_initialization("Incompatible initial and maximum heap sizes specified"); 128 } 129 130 if (PrintGCDetails && Verbose) { 131 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap " 132 SIZE_FORMAT " Maximum heap " SIZE_FORMAT, 133 min_heap_byte_size(), initial_heap_byte_size(), max_heap_byte_size()); 134 } 135 } 136 137 void CollectorPolicy::initialize_perm_generation(PermGen::Name pgnm) { 138 _permanent_generation = 139 new PermanentGenerationSpec(pgnm, PermSize, MaxPermSize, 140 SharedReadOnlySize, 141 SharedReadWriteSize, 142 SharedMiscDataSize, 143 SharedMiscCodeSize); 144 if (_permanent_generation == NULL) { 145 vm_exit_during_initialization("Unable to allocate gen spec"); 146 } 147 } 148 149 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) { 150 bool result = _should_clear_all_soft_refs; 151 set_should_clear_all_soft_refs(false); 152 return result; 153 } 154 155 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap, 156 int max_covered_regions) { 157 switch (rem_set_name()) { 158 case GenRemSet::CardTable: { 159 CardTableRS* res = new CardTableRS(whole_heap, max_covered_regions); 160 return res; 161 } 162 default: 163 guarantee(false, "unrecognized GenRemSet::Name"); 164 return NULL; 165 } 166 } 167 168 void CollectorPolicy::cleared_all_soft_refs() { 169 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may 170 // have been cleared in the last collection but if the gc overhear 171 // limit continues to be near, SoftRefs should still be cleared. 172 if (size_policy() != NULL) { 173 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near(); 174 } 175 _all_soft_refs_clear = true; 176 } 177 178 179 // GenCollectorPolicy methods. 180 181 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) { 182 size_t x = base_size / (NewRatio+1); 183 size_t new_gen_size = x > min_alignment() ? 184 align_size_down(x, min_alignment()) : 185 min_alignment(); 186 return new_gen_size; 187 } 188 189 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size, 190 size_t maximum_size) { 191 size_t alignment = min_alignment(); 192 size_t max_minus = maximum_size - alignment; 193 return desired_size < max_minus ? desired_size : max_minus; 194 } 195 196 197 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size, 198 size_t init_promo_size, 199 size_t init_survivor_size) { 200 const double max_gc_minor_pause_sec = ((double) MaxGCMinorPauseMillis)/1000.0; 201 _size_policy = new AdaptiveSizePolicy(init_eden_size, 202 init_promo_size, 203 init_survivor_size, 204 max_gc_minor_pause_sec, 205 GCTimeRatio); 206 } 207 208 size_t GenCollectorPolicy::compute_max_alignment() { 209 // The card marking array and the offset arrays for old generations are 210 // committed in os pages as well. Make sure they are entirely full (to 211 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1 212 // byte entry and the os page size is 4096, the maximum heap size should 213 // be 512*4096 = 2MB aligned. 214 size_t alignment = GenRemSet::max_alignment_constraint(rem_set_name()); 215 216 // Parallel GC does its own alignment of the generations to avoid requiring a 217 // large page (256M on some platforms) for the permanent generation. The 218 // other collectors should also be updated to do their own alignment and then 219 // this use of lcm() should be removed. 220 if (UseLargePages && !UseParallelGC) { 221 // in presence of large pages we have to make sure that our 222 // alignment is large page aware 223 alignment = lcm(os::large_page_size(), alignment); 224 } 225 226 return alignment; 227 } 228 229 void GenCollectorPolicy::initialize_flags() { 230 // All sizes must be multiples of the generation granularity. 231 set_min_alignment((uintx) Generation::GenGrain); 232 set_max_alignment(compute_max_alignment()); 233 assert(max_alignment() >= min_alignment() && 234 max_alignment() % min_alignment() == 0, 235 "invalid alignment constraints"); 236 237 CollectorPolicy::initialize_flags(); 238 239 // All generational heaps have a youngest gen; handle those flags here. 240 241 // Adjust max size parameters 242 if (NewSize > MaxNewSize) { 243 MaxNewSize = NewSize; 244 } 245 NewSize = align_size_down(NewSize, min_alignment()); 246 MaxNewSize = align_size_down(MaxNewSize, min_alignment()); 247 248 // Check validity of heap flags 249 assert(NewSize % min_alignment() == 0, "eden space alignment"); 250 assert(MaxNewSize % min_alignment() == 0, "survivor space alignment"); 251 252 if (NewSize < 3*min_alignment()) { 253 // make sure there room for eden and two survivor spaces 254 vm_exit_during_initialization("Too small new size specified"); 255 } 256 if (SurvivorRatio < 1 || NewRatio < 1) { 257 vm_exit_during_initialization("Invalid heap ratio specified"); 258 } 259 } 260 261 void TwoGenerationCollectorPolicy::initialize_flags() { 262 GenCollectorPolicy::initialize_flags(); 263 264 OldSize = align_size_down(OldSize, min_alignment()); 265 if (NewSize + OldSize > MaxHeapSize) { 266 MaxHeapSize = NewSize + OldSize; 267 } 268 MaxHeapSize = align_size_up(MaxHeapSize, max_alignment()); 269 270 always_do_update_barrier = UseConcMarkSweepGC; 271 272 // Check validity of heap flags 273 assert(OldSize % min_alignment() == 0, "old space alignment"); 274 assert(MaxHeapSize % max_alignment() == 0, "maximum heap alignment"); 275 } 276 277 // Values set on the command line win over any ergonomically 278 // set command line parameters. 279 // Ergonomic choice of parameters are done before this 280 // method is called. Values for command line parameters such as NewSize 281 // and MaxNewSize feed those ergonomic choices into this method. 282 // This method makes the final generation sizings consistent with 283 // themselves and with overall heap sizings. 284 // In the absence of explicitly set command line flags, policies 285 // such as the use of NewRatio are used to size the generation. 286 void GenCollectorPolicy::initialize_size_info() { 287 CollectorPolicy::initialize_size_info(); 288 289 // min_alignment() is used for alignment within a generation. 290 // There is additional alignment done down stream for some 291 // collectors that sometimes causes unwanted rounding up of 292 // generations sizes. 293 294 // Determine maximum size of gen0 295 296 size_t max_new_size = 0; 297 if (FLAG_IS_CMDLINE(MaxNewSize) || FLAG_IS_ERGO(MaxNewSize)) { 298 if (MaxNewSize < min_alignment()) { 299 max_new_size = min_alignment(); 300 } 301 if (MaxNewSize >= max_heap_byte_size()) { 302 max_new_size = align_size_down(max_heap_byte_size() - min_alignment(), 303 min_alignment()); 304 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or " 305 "greater than the entire heap (" SIZE_FORMAT "k). A " 306 "new generation size of " SIZE_FORMAT "k will be used.", 307 MaxNewSize/K, max_heap_byte_size()/K, max_new_size/K); 308 } else { 309 max_new_size = align_size_down(MaxNewSize, min_alignment()); 310 } 311 312 // The case for FLAG_IS_ERGO(MaxNewSize) could be treated 313 // specially at this point to just use an ergonomically set 314 // MaxNewSize to set max_new_size. For cases with small 315 // heaps such a policy often did not work because the MaxNewSize 316 // was larger than the entire heap. The interpretation given 317 // to ergonomically set flags is that the flags are set 318 // by different collectors for their own special needs but 319 // are not allowed to badly shape the heap. This allows the 320 // different collectors to decide what's best for themselves 321 // without having to factor in the overall heap shape. It 322 // can be the case in the future that the collectors would 323 // only make "wise" ergonomics choices and this policy could 324 // just accept those choices. The choices currently made are 325 // not always "wise". 326 } else { 327 max_new_size = scale_by_NewRatio_aligned(max_heap_byte_size()); 328 // Bound the maximum size by NewSize below (since it historically 329 // would have been NewSize and because the NewRatio calculation could 330 // yield a size that is too small) and bound it by MaxNewSize above. 331 // Ergonomics plays here by previously calculating the desired 332 // NewSize and MaxNewSize. 333 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize); 334 } 335 assert(max_new_size > 0, "All paths should set max_new_size"); 336 337 // Given the maximum gen0 size, determine the initial and 338 // minimum gen0 sizes. 339 340 if (max_heap_byte_size() == min_heap_byte_size()) { 341 // The maximum and minimum heap sizes are the same so 342 // the generations minimum and initial must be the 343 // same as its maximum. 344 set_min_gen0_size(max_new_size); 345 set_initial_gen0_size(max_new_size); 346 set_max_gen0_size(max_new_size); 347 } else { 348 size_t desired_new_size = 0; 349 if (!FLAG_IS_DEFAULT(NewSize)) { 350 // If NewSize is set ergonomically (for example by cms), it 351 // would make sense to use it. If it is used, also use it 352 // to set the initial size. Although there is no reason 353 // the minimum size and the initial size have to be the same, 354 // the current implementation gets into trouble during the calculation 355 // of the tenured generation sizes if they are different. 356 // Note that this makes the initial size and the minimum size 357 // generally small compared to the NewRatio calculation. 358 _min_gen0_size = NewSize; 359 desired_new_size = NewSize; 360 max_new_size = MAX2(max_new_size, NewSize); 361 } else { 362 // For the case where NewSize is the default, use NewRatio 363 // to size the minimum and initial generation sizes. 364 // Use the default NewSize as the floor for these values. If 365 // NewRatio is overly large, the resulting sizes can be too 366 // small. 367 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(min_heap_byte_size()), 368 NewSize); 369 desired_new_size = 370 MAX2(scale_by_NewRatio_aligned(initial_heap_byte_size()), 371 NewSize); 372 } 373 374 assert(_min_gen0_size > 0, "Sanity check"); 375 set_initial_gen0_size(desired_new_size); 376 set_max_gen0_size(max_new_size); 377 378 // At this point the desirable initial and minimum sizes have been 379 // determined without regard to the maximum sizes. 380 381 // Bound the sizes by the corresponding overall heap sizes. 382 set_min_gen0_size( 383 bound_minus_alignment(_min_gen0_size, min_heap_byte_size())); 384 set_initial_gen0_size( 385 bound_minus_alignment(_initial_gen0_size, initial_heap_byte_size())); 386 set_max_gen0_size( 387 bound_minus_alignment(_max_gen0_size, max_heap_byte_size())); 388 389 // At this point all three sizes have been checked against the 390 // maximum sizes but have not been checked for consistency 391 // among the three. 392 393 // Final check min <= initial <= max 394 set_min_gen0_size(MIN2(_min_gen0_size, _max_gen0_size)); 395 set_initial_gen0_size( 396 MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size)); 397 set_min_gen0_size(MIN2(_min_gen0_size, _initial_gen0_size)); 398 } 399 400 if (PrintGCDetails && Verbose) { 401 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 " 402 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT, 403 min_gen0_size(), initial_gen0_size(), max_gen0_size()); 404 } 405 } 406 407 // Call this method during the sizing of the gen1 to make 408 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has 409 // the most freedom in sizing because it is done before the 410 // policy for gen1 is applied. Once gen1 policies have been applied, 411 // there may be conflicts in the shape of the heap and this method 412 // is used to make the needed adjustments. The application of the 413 // policies could be more sophisticated (iterative for example) but 414 // keeping it simple also seems a worthwhile goal. 415 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr, 416 size_t* gen1_size_ptr, 417 size_t heap_size, 418 size_t min_gen0_size) { 419 bool result = false; 420 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) { 421 if (((*gen0_size_ptr + OldSize) > heap_size) && 422 (heap_size - min_gen0_size) >= min_alignment()) { 423 // Adjust gen0 down to accomodate OldSize 424 *gen0_size_ptr = heap_size - min_gen0_size; 425 *gen0_size_ptr = 426 MAX2((uintx)align_size_down(*gen0_size_ptr, min_alignment()), 427 min_alignment()); 428 assert(*gen0_size_ptr > 0, "Min gen0 is too large"); 429 result = true; 430 } else { 431 *gen1_size_ptr = heap_size - *gen0_size_ptr; 432 *gen1_size_ptr = 433 MAX2((uintx)align_size_down(*gen1_size_ptr, min_alignment()), 434 min_alignment()); 435 } 436 } 437 return result; 438 } 439 440 // Minimum sizes of the generations may be different than 441 // the initial sizes. An inconsistently is permitted here 442 // in the total size that can be specified explicitly by 443 // command line specification of OldSize and NewSize and 444 // also a command line specification of -Xms. Issue a warning 445 // but allow the values to pass. 446 447 void TwoGenerationCollectorPolicy::initialize_size_info() { 448 GenCollectorPolicy::initialize_size_info(); 449 450 // At this point the minimum, initial and maximum sizes 451 // of the overall heap and of gen0 have been determined. 452 // The maximum gen1 size can be determined from the maximum gen0 453 // and maximum heap size since no explicit flags exits 454 // for setting the gen1 maximum. 455 _max_gen1_size = max_heap_byte_size() - _max_gen0_size; 456 _max_gen1_size = 457 MAX2((uintx)align_size_down(_max_gen1_size, min_alignment()), 458 min_alignment()); 459 // If no explicit command line flag has been set for the 460 // gen1 size, use what is left for gen1. 461 if (FLAG_IS_DEFAULT(OldSize) || FLAG_IS_ERGO(OldSize)) { 462 // The user has not specified any value or ergonomics 463 // has chosen a value (which may or may not be consistent 464 // with the overall heap size). In either case make 465 // the minimum, maximum and initial sizes consistent 466 // with the gen0 sizes and the overall heap sizes. 467 assert(min_heap_byte_size() > _min_gen0_size, 468 "gen0 has an unexpected minimum size"); 469 set_min_gen1_size(min_heap_byte_size() - min_gen0_size()); 470 set_min_gen1_size( 471 MAX2((uintx)align_size_down(_min_gen1_size, min_alignment()), 472 min_alignment())); 473 set_initial_gen1_size(initial_heap_byte_size() - initial_gen0_size()); 474 set_initial_gen1_size( 475 MAX2((uintx)align_size_down(_initial_gen1_size, min_alignment()), 476 min_alignment())); 477 478 } else { 479 // It's been explicitly set on the command line. Use the 480 // OldSize and then determine the consequences. 481 set_min_gen1_size(OldSize); 482 set_initial_gen1_size(OldSize); 483 484 // If the user has explicitly set an OldSize that is inconsistent 485 // with other command line flags, issue a warning. 486 // The generation minimums and the overall heap mimimum should 487 // be within one heap alignment. 488 if ((_min_gen1_size + _min_gen0_size + min_alignment()) < 489 min_heap_byte_size()) { 490 warning("Inconsistency between minimum heap size and minimum " 491 "generation sizes: using minimum heap = " SIZE_FORMAT, 492 min_heap_byte_size()); 493 } 494 if ((OldSize > _max_gen1_size)) { 495 warning("Inconsistency between maximum heap size and maximum " 496 "generation sizes: using maximum heap = " SIZE_FORMAT 497 " -XX:OldSize flag is being ignored", 498 max_heap_byte_size()); 499 } 500 // If there is an inconsistency between the OldSize and the minimum and/or 501 // initial size of gen0, since OldSize was explicitly set, OldSize wins. 502 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size, 503 min_heap_byte_size(), OldSize)) { 504 if (PrintGCDetails && Verbose) { 505 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 " 506 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT, 507 min_gen0_size(), initial_gen0_size(), max_gen0_size()); 508 } 509 } 510 // Initial size 511 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size, 512 initial_heap_byte_size(), OldSize)) { 513 if (PrintGCDetails && Verbose) { 514 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 " 515 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT, 516 min_gen0_size(), initial_gen0_size(), max_gen0_size()); 517 } 518 } 519 } 520 // Enforce the maximum gen1 size. 521 set_min_gen1_size(MIN2(_min_gen1_size, _max_gen1_size)); 522 523 // Check that min gen1 <= initial gen1 <= max gen1 524 set_initial_gen1_size(MAX2(_initial_gen1_size, _min_gen1_size)); 525 set_initial_gen1_size(MIN2(_initial_gen1_size, _max_gen1_size)); 526 527 if (PrintGCDetails && Verbose) { 528 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 " 529 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT, 530 min_gen1_size(), initial_gen1_size(), max_gen1_size()); 531 } 532 } 533 534 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size, 535 bool is_tlab, 536 bool* gc_overhead_limit_was_exceeded) { 537 GenCollectedHeap *gch = GenCollectedHeap::heap(); 538 539 debug_only(gch->check_for_valid_allocation_state()); 540 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed"); 541 542 // In general gc_overhead_limit_was_exceeded should be false so 543 // set it so here and reset it to true only if the gc time 544 // limit is being exceeded as checked below. 545 *gc_overhead_limit_was_exceeded = false; 546 547 HeapWord* result = NULL; 548 549 // Loop until the allocation is satisified, 550 // or unsatisfied after GC. 551 for (int try_count = 1; /* return or throw */; try_count += 1) { 552 HandleMark hm; // discard any handles allocated in each iteration 553 554 // First allocation attempt is lock-free. 555 Generation *gen0 = gch->get_gen(0); 556 assert(gen0->supports_inline_contig_alloc(), 557 "Otherwise, must do alloc within heap lock"); 558 if (gen0->should_allocate(size, is_tlab)) { 559 result = gen0->par_allocate(size, is_tlab); 560 if (result != NULL) { 561 assert(gch->is_in_reserved(result), "result not in heap"); 562 return result; 563 } 564 } 565 unsigned int gc_count_before; // read inside the Heap_lock locked region 566 { 567 MutexLocker ml(Heap_lock); 568 if (PrintGC && Verbose) { 569 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:" 570 " attempting locked slow path allocation"); 571 } 572 // Note that only large objects get a shot at being 573 // allocated in later generations. 574 bool first_only = ! should_try_older_generation_allocation(size); 575 576 result = gch->attempt_allocation(size, is_tlab, first_only); 577 if (result != NULL) { 578 assert(gch->is_in_reserved(result), "result not in heap"); 579 return result; 580 } 581 582 if (GC_locker::is_active_and_needs_gc()) { 583 if (is_tlab) { 584 return NULL; // Caller will retry allocating individual object 585 } 586 if (!gch->is_maximal_no_gc()) { 587 // Try and expand heap to satisfy request 588 result = expand_heap_and_allocate(size, is_tlab); 589 // result could be null if we are out of space 590 if (result != NULL) { 591 return result; 592 } 593 } 594 595 // If this thread is not in a jni critical section, we stall 596 // the requestor until the critical section has cleared and 597 // GC allowed. When the critical section clears, a GC is 598 // initiated by the last thread exiting the critical section; so 599 // we retry the allocation sequence from the beginning of the loop, 600 // rather than causing more, now probably unnecessary, GC attempts. 601 JavaThread* jthr = JavaThread::current(); 602 if (!jthr->in_critical()) { 603 MutexUnlocker mul(Heap_lock); 604 // Wait for JNI critical section to be exited 605 GC_locker::stall_until_clear(); 606 continue; 607 } else { 608 if (CheckJNICalls) { 609 fatal("Possible deadlock due to allocating while" 610 " in jni critical section"); 611 } 612 return NULL; 613 } 614 } 615 616 // Read the gc count while the heap lock is held. 617 gc_count_before = Universe::heap()->total_collections(); 618 } 619 620 VM_GenCollectForAllocation op(size, 621 is_tlab, 622 gc_count_before); 623 VMThread::execute(&op); 624 if (op.prologue_succeeded()) { 625 result = op.result(); 626 if (op.gc_locked()) { 627 assert(result == NULL, "must be NULL if gc_locked() is true"); 628 continue; // retry and/or stall as necessary 629 } 630 631 // Allocation has failed and a collection 632 // has been done. If the gc time limit was exceeded the 633 // this time, return NULL so that an out-of-memory 634 // will be thrown. Clear gc_overhead_limit_exceeded 635 // so that the overhead exceeded does not persist. 636 637 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded(); 638 const bool softrefs_clear = all_soft_refs_clear(); 639 assert(!limit_exceeded || softrefs_clear, "Should have been cleared"); 640 if (limit_exceeded && softrefs_clear) { 641 *gc_overhead_limit_was_exceeded = true; 642 size_policy()->set_gc_overhead_limit_exceeded(false); 643 if (op.result() != NULL) { 644 CollectedHeap::fill_with_object(op.result(), size); 645 } 646 return NULL; 647 } 648 assert(result == NULL || gch->is_in_reserved(result), 649 "result not in heap"); 650 return result; 651 } 652 653 // Give a warning if we seem to be looping forever. 654 if ((QueuedAllocationWarningCount > 0) && 655 (try_count % QueuedAllocationWarningCount == 0)) { 656 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t" 657 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : ""); 658 } 659 } 660 } 661 662 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size, 663 bool is_tlab) { 664 GenCollectedHeap *gch = GenCollectedHeap::heap(); 665 HeapWord* result = NULL; 666 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) { 667 Generation *gen = gch->get_gen(i); 668 if (gen->should_allocate(size, is_tlab)) { 669 result = gen->expand_and_allocate(size, is_tlab); 670 } 671 } 672 assert(result == NULL || gch->is_in_reserved(result), "result not in heap"); 673 return result; 674 } 675 676 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size, 677 bool is_tlab) { 678 GenCollectedHeap *gch = GenCollectedHeap::heap(); 679 GCCauseSetter x(gch, GCCause::_allocation_failure); 680 HeapWord* result = NULL; 681 682 assert(size != 0, "Precondition violated"); 683 if (GC_locker::is_active_and_needs_gc()) { 684 // GC locker is active; instead of a collection we will attempt 685 // to expand the heap, if there's room for expansion. 686 if (!gch->is_maximal_no_gc()) { 687 result = expand_heap_and_allocate(size, is_tlab); 688 } 689 return result; // could be null if we are out of space 690 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) { 691 // Do an incremental collection. 692 gch->do_collection(false /* full */, 693 false /* clear_all_soft_refs */, 694 size /* size */, 695 is_tlab /* is_tlab */, 696 number_of_generations() - 1 /* max_level */); 697 } else { 698 if (Verbose && PrintGCDetails) { 699 gclog_or_tty->print(" :: Trying full because partial may fail :: "); 700 } 701 // Try a full collection; see delta for bug id 6266275 702 // for the original code and why this has been simplified 703 // with from-space allocation criteria modified and 704 // such allocation moved out of the safepoint path. 705 gch->do_collection(true /* full */, 706 false /* clear_all_soft_refs */, 707 size /* size */, 708 is_tlab /* is_tlab */, 709 number_of_generations() - 1 /* max_level */); 710 } 711 712 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/); 713 714 if (result != NULL) { 715 assert(gch->is_in_reserved(result), "result not in heap"); 716 return result; 717 } 718 719 // OK, collection failed, try expansion. 720 result = expand_heap_and_allocate(size, is_tlab); 721 if (result != NULL) { 722 return result; 723 } 724 725 // If we reach this point, we're really out of memory. Try every trick 726 // we can to reclaim memory. Force collection of soft references. Force 727 // a complete compaction of the heap. Any additional methods for finding 728 // free memory should be here, especially if they are expensive. If this 729 // attempt fails, an OOM exception will be thrown. 730 { 731 IntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted 732 733 gch->do_collection(true /* full */, 734 true /* clear_all_soft_refs */, 735 size /* size */, 736 is_tlab /* is_tlab */, 737 number_of_generations() - 1 /* max_level */); 738 } 739 740 result = gch->attempt_allocation(size, is_tlab, false /* first_only */); 741 if (result != NULL) { 742 assert(gch->is_in_reserved(result), "result not in heap"); 743 return result; 744 } 745 746 assert(!should_clear_all_soft_refs(), 747 "Flag should have been handled and cleared prior to this point"); 748 749 // What else? We might try synchronous finalization later. If the total 750 // space available is large enough for the allocation, then a more 751 // complete compaction phase than we've tried so far might be 752 // appropriate. 753 return NULL; 754 } 755 756 // Return true if any of the following is true: 757 // . the allocation won't fit into the current young gen heap 758 // . gc locker is occupied (jni critical section) 759 // . heap memory is tight -- the most recent previous collection 760 // was a full collection because a partial collection (would 761 // have) failed and is likely to fail again 762 bool GenCollectorPolicy::should_try_older_generation_allocation( 763 size_t word_size) const { 764 GenCollectedHeap* gch = GenCollectedHeap::heap(); 765 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc(); 766 return (word_size > heap_word_size(gen0_capacity)) 767 || GC_locker::is_active_and_needs_gc() 768 || gch->incremental_collection_failed(); 769 } 770 771 772 // 773 // MarkSweepPolicy methods 774 // 775 776 MarkSweepPolicy::MarkSweepPolicy() { 777 initialize_all(); 778 } 779 780 void MarkSweepPolicy::initialize_generations() { 781 initialize_perm_generation(PermGen::MarkSweepCompact); 782 _generations = new GenerationSpecPtr[number_of_generations()]; 783 if (_generations == NULL) 784 vm_exit_during_initialization("Unable to allocate gen spec"); 785 786 if (UseParNewGC && ParallelGCThreads > 0) { 787 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size); 788 } else { 789 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size); 790 } 791 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size); 792 793 if (_generations[0] == NULL || _generations[1] == NULL) 794 vm_exit_during_initialization("Unable to allocate gen spec"); 795 } 796 797 void MarkSweepPolicy::initialize_gc_policy_counters() { 798 // initialize the policy counters - 2 collectors, 3 generations 799 if (UseParNewGC && ParallelGCThreads > 0) { 800 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3); 801 } 802 else { 803 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3); 804 } 805 }