1 /* 2 * Copyright (c) 2001, 2013, 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 #include "utilities/macros.hpp" 43 #if INCLUDE_ALL_GCS 44 #include "gc_implementation/concurrentMarkSweep/cmsAdaptiveSizePolicy.hpp" 45 #include "gc_implementation/concurrentMarkSweep/cmsGCAdaptivePolicyCounters.hpp" 46 #endif // INCLUDE_ALL_GCS 47 48 // CollectorPolicy methods. 49 50 CollectorPolicy::CollectorPolicy() : 51 _space_alignment(0), 52 _heap_alignment(0), 53 _initial_heap_byte_size(InitialHeapSize), 54 _max_heap_byte_size(MaxHeapSize), 55 _min_heap_byte_size(Arguments::min_heap_size()), 56 _max_heap_size_cmdline(false), 57 _size_policy(NULL), 58 _should_clear_all_soft_refs(false), 59 _all_soft_refs_clear(false) 60 {} 61 62 #ifdef ASSERT 63 void CollectorPolicy::assert_flags() { 64 assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes"); 65 assert(InitialHeapSize % _heap_alignment == 0, "InitialHeapSize alignment"); 66 assert(MaxHeapSize % _heap_alignment == 0, "MaxHeapSize alignment"); 67 } 68 69 void CollectorPolicy::assert_size_info() { 70 assert(InitialHeapSize == _initial_heap_byte_size, "Discrepancy between InitialHeapSize flag and local storage"); 71 assert(MaxHeapSize == _max_heap_byte_size, "Discrepancy between MaxHeapSize flag and local storage"); 72 assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes"); 73 assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes"); 74 assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes"); 75 assert(_min_heap_byte_size % _heap_alignment == 0, "min_heap_byte_size alignment"); 76 assert(_initial_heap_byte_size % _heap_alignment == 0, "initial_heap_byte_size alignment"); 77 assert(_max_heap_byte_size % _heap_alignment == 0, "max_heap_byte_size alignment"); 78 } 79 #endif // ASSERT 80 81 void CollectorPolicy::initialize_flags() { 82 assert(_space_alignment != 0, "Space alignment not set up properly"); 83 assert(_heap_alignment != 0, "Heap alignment not set up properly"); 84 assert(_heap_alignment >= _space_alignment, 85 err_msg("heap_alignment: " SIZE_FORMAT " less than space_alignment: " SIZE_FORMAT, 86 _heap_alignment, _space_alignment)); 87 assert(_heap_alignment % _space_alignment == 0, 88 err_msg("heap_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT, 89 _heap_alignment, _space_alignment)); 90 91 if (FLAG_IS_CMDLINE(MaxHeapSize)) { 92 if (FLAG_IS_CMDLINE(InitialHeapSize) && InitialHeapSize > MaxHeapSize) { 93 vm_exit_during_initialization("Initial heap size set to a larger value than the maximum heap size"); 94 } 95 if (_min_heap_byte_size != 0 && MaxHeapSize < _min_heap_byte_size) { 96 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified"); 97 } 98 _max_heap_size_cmdline = true; 99 } 100 101 // Check heap parameter properties 102 if (InitialHeapSize < M) { 103 vm_exit_during_initialization("Too small initial heap"); 104 } 105 if (_min_heap_byte_size < M) { 106 vm_exit_during_initialization("Too small minimum heap"); 107 } 108 109 // User inputs from -Xmx and -Xms must be aligned 110 _min_heap_byte_size = align_size_up(_min_heap_byte_size, _heap_alignment); 111 uintx aligned_initial_heap_size = align_size_up(InitialHeapSize, _heap_alignment); 112 uintx aligned_max_heap_size = align_size_up(MaxHeapSize, _heap_alignment); 113 114 // Write back to flags if the values changed 115 if (aligned_initial_heap_size != InitialHeapSize) { 116 FLAG_SET_ERGO(uintx, InitialHeapSize, aligned_initial_heap_size); 117 } 118 if (aligned_max_heap_size != MaxHeapSize) { 119 FLAG_SET_ERGO(uintx, MaxHeapSize, aligned_max_heap_size); 120 } 121 122 if (FLAG_IS_CMDLINE(InitialHeapSize) && _min_heap_byte_size != 0 && 123 InitialHeapSize < _min_heap_byte_size) { 124 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified"); 125 } 126 if (!FLAG_IS_DEFAULT(InitialHeapSize) && InitialHeapSize > MaxHeapSize) { 127 FLAG_SET_ERGO(uintx, MaxHeapSize, InitialHeapSize); 128 } else if (!FLAG_IS_DEFAULT(MaxHeapSize) && InitialHeapSize > MaxHeapSize) { 129 FLAG_SET_ERGO(uintx, InitialHeapSize, MaxHeapSize); 130 if (InitialHeapSize < _min_heap_byte_size) { 131 _min_heap_byte_size = InitialHeapSize; 132 } 133 } 134 135 _initial_heap_byte_size = InitialHeapSize; 136 _max_heap_byte_size = MaxHeapSize; 137 138 FLAG_SET_ERGO(uintx, MinHeapDeltaBytes, align_size_up(MinHeapDeltaBytes, _space_alignment)); 139 140 DEBUG_ONLY(CollectorPolicy::assert_flags();) 141 } 142 143 void CollectorPolicy::initialize_size_info() { 144 if (PrintGCDetails && Verbose) { 145 gclog_or_tty->print_cr("Minimum heap " SIZE_FORMAT " Initial heap " 146 SIZE_FORMAT " Maximum heap " SIZE_FORMAT, 147 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size); 148 } 149 150 DEBUG_ONLY(CollectorPolicy::assert_size_info();) 151 } 152 153 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) { 154 bool result = _should_clear_all_soft_refs; 155 set_should_clear_all_soft_refs(false); 156 return result; 157 } 158 159 GenRemSet* CollectorPolicy::create_rem_set(MemRegion whole_heap, 160 int max_covered_regions) { 161 return new CardTableRS(whole_heap, max_covered_regions); 162 } 163 164 void CollectorPolicy::cleared_all_soft_refs() { 165 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may 166 // have been cleared in the last collection but if the gc overhear 167 // limit continues to be near, SoftRefs should still be cleared. 168 if (size_policy() != NULL) { 169 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near(); 170 } 171 _all_soft_refs_clear = true; 172 } 173 174 size_t CollectorPolicy::compute_heap_alignment() { 175 // The card marking array and the offset arrays for old generations are 176 // committed in os pages as well. Make sure they are entirely full (to 177 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1 178 // byte entry and the os page size is 4096, the maximum heap size should 179 // be 512*4096 = 2MB aligned. 180 181 // There is only the GenRemSet in Hotspot and only the GenRemSet::CardTable 182 // is supported. 183 // Requirements of any new remembered set implementations must be added here. 184 size_t alignment = GenRemSet::max_alignment_constraint(GenRemSet::CardTable); 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 // GenCollectorPolicy methods. 200 201 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) { 202 return align_size_down_bounded(base_size / (NewRatio + 1), _gen_alignment); 203 } 204 205 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size, 206 size_t maximum_size) { 207 size_t max_minus = maximum_size - _gen_alignment; 208 return desired_size < max_minus ? desired_size : max_minus; 209 } 210 211 212 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size, 213 size_t init_promo_size, 214 size_t init_survivor_size) { 215 const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0; 216 _size_policy = new AdaptiveSizePolicy(init_eden_size, 217 init_promo_size, 218 init_survivor_size, 219 max_gc_pause_sec, 220 GCTimeRatio); 221 } 222 223 size_t GenCollectorPolicy::young_gen_size_lower_bound() { 224 // The young generation must be aligned and have room for eden + two survivors 225 return align_size_up(3 * _space_alignment, _gen_alignment); 226 } 227 228 #ifdef ASSERT 229 void GenCollectorPolicy::assert_flags() { 230 CollectorPolicy::assert_flags(); 231 assert(NewSize >= _min_gen0_size, "Ergonomics decided on a too small young gen size"); 232 assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes"); 233 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes"); 234 assert(NewSize % _gen_alignment == 0, "NewSize alignment"); 235 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _gen_alignment == 0, "MaxNewSize alignment"); 236 } 237 238 void TwoGenerationCollectorPolicy::assert_flags() { 239 GenCollectorPolicy::assert_flags(); 240 assert(OldSize + NewSize <= MaxHeapSize, "Ergonomics decided on incompatible generation and heap sizes"); 241 assert(OldSize % _gen_alignment == 0, "OldSize alignment"); 242 } 243 244 void GenCollectorPolicy::assert_size_info() { 245 CollectorPolicy::assert_size_info(); 246 // GenCollectorPolicy::initialize_size_info may update the MaxNewSize 247 assert(MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young and heap sizes"); 248 assert(NewSize == _initial_gen0_size, "Discrepancy between NewSize flag and local storage"); 249 assert(MaxNewSize == _max_gen0_size, "Discrepancy between MaxNewSize flag and local storage"); 250 assert(_min_gen0_size <= _initial_gen0_size, "Ergonomics decided on incompatible minimum and initial young gen sizes"); 251 assert(_initial_gen0_size <= _max_gen0_size, "Ergonomics decided on incompatible initial and maximum young gen sizes"); 252 assert(_min_gen0_size % _gen_alignment == 0, "_min_gen0_size alignment"); 253 assert(_initial_gen0_size % _gen_alignment == 0, "_initial_gen0_size alignment"); 254 assert(_max_gen0_size % _gen_alignment == 0, "_max_gen0_size alignment"); 255 } 256 257 void TwoGenerationCollectorPolicy::assert_size_info() { 258 GenCollectorPolicy::assert_size_info(); 259 assert(OldSize == _initial_gen1_size, "Discrepancy between OldSize flag and local storage"); 260 assert(_min_gen1_size <= _initial_gen1_size, "Ergonomics decided on incompatible minimum and initial old gen sizes"); 261 assert(_initial_gen1_size <= _max_gen1_size, "Ergonomics decided on incompatible initial and maximum old gen sizes"); 262 assert(_max_gen1_size % _gen_alignment == 0, "_max_gen1_size alignment"); 263 assert(_initial_gen1_size % _gen_alignment == 0, "_initial_gen1_size alignment"); 264 assert(_max_heap_byte_size <= (_max_gen0_size + _max_gen1_size), "Total maximum heap sizes must be sum of generation maximum sizes"); 265 } 266 #endif // ASSERT 267 268 void GenCollectorPolicy::initialize_flags() { 269 CollectorPolicy::initialize_flags(); 270 271 assert(_gen_alignment != 0, "Generation alignment not set up properly"); 272 assert(_heap_alignment >= _gen_alignment, 273 err_msg("heap_alignment: " SIZE_FORMAT " less than gen_alignment: " SIZE_FORMAT, 274 _heap_alignment, _gen_alignment)); 275 assert(_gen_alignment % _space_alignment == 0, 276 err_msg("gen_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT, 277 _gen_alignment, _space_alignment)); 278 assert(_heap_alignment % _gen_alignment == 0, 279 err_msg("heap_alignment: " SIZE_FORMAT " not aligned by gen_alignment: " SIZE_FORMAT, 280 _heap_alignment, _gen_alignment)); 281 282 // All generational heaps have a youngest gen; handle those flags here 283 284 // Make sure the heap is large enough for two generations 285 uintx smallest_new_size = young_gen_size_lower_bound(); 286 uintx smallest_heap_size = align_size_up(smallest_new_size + align_size_up(_space_alignment, _gen_alignment), 287 _heap_alignment); 288 if (MaxHeapSize < smallest_heap_size) { 289 FLAG_SET_ERGO(uintx, MaxHeapSize, smallest_heap_size); 290 _max_heap_byte_size = MaxHeapSize; 291 } 292 // If needed, synchronize _min_heap_byte size and _initial_heap_byte_size 293 if (_min_heap_byte_size < smallest_heap_size) { 294 _min_heap_byte_size = smallest_heap_size; 295 if (InitialHeapSize < _min_heap_byte_size) { 296 FLAG_SET_ERGO(uintx, InitialHeapSize, smallest_heap_size); 297 _initial_heap_byte_size = smallest_heap_size; 298 } 299 } 300 301 // Now take the actual NewSize into account. We will silently increase NewSize 302 // if the user specified a smaller value. 303 smallest_new_size = MAX2(smallest_new_size, (uintx)align_size_down(NewSize, _gen_alignment)); 304 if (smallest_new_size != NewSize) { 305 FLAG_SET_ERGO(uintx, NewSize, smallest_new_size); 306 } 307 _initial_gen0_size = NewSize; 308 309 if (!FLAG_IS_DEFAULT(MaxNewSize)) { 310 uintx min_new_size = MAX2(_gen_alignment, _min_gen0_size); 311 312 if (MaxNewSize >= MaxHeapSize) { 313 // Make sure there is room for an old generation 314 uintx smaller_max_new_size = MaxHeapSize - _gen_alignment; 315 if (FLAG_IS_CMDLINE(MaxNewSize)) { 316 warning("MaxNewSize (" SIZE_FORMAT "k) is equal to or greater than the entire " 317 "heap (" SIZE_FORMAT "k). A new max generation size of " SIZE_FORMAT "k will be used.", 318 MaxNewSize/K, MaxHeapSize/K, smaller_max_new_size/K); 319 } 320 FLAG_SET_ERGO(uintx, MaxNewSize, smaller_max_new_size); 321 if (NewSize > MaxNewSize) { 322 FLAG_SET_ERGO(uintx, NewSize, MaxNewSize); 323 _initial_gen0_size = NewSize; 324 } 325 } else if (MaxNewSize < min_new_size) { 326 FLAG_SET_ERGO(uintx, MaxNewSize, min_new_size); 327 } else if (!is_size_aligned(MaxNewSize, _gen_alignment)) { 328 FLAG_SET_ERGO(uintx, MaxNewSize, align_size_down(MaxNewSize, _gen_alignment)); 329 } 330 _max_gen0_size = MaxNewSize; 331 } 332 333 if (NewSize > MaxNewSize) { 334 // At this point this should only happen if the user specifies a large NewSize and/or 335 // a small (but not too small) MaxNewSize. 336 if (FLAG_IS_CMDLINE(MaxNewSize)) { 337 warning("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). " 338 "A new max generation size of " SIZE_FORMAT "k will be used.", 339 NewSize/K, MaxNewSize/K, NewSize/K); 340 } 341 FLAG_SET_ERGO(uintx, MaxNewSize, NewSize); 342 _max_gen0_size = MaxNewSize; 343 } 344 345 if (SurvivorRatio < 1 || NewRatio < 1) { 346 vm_exit_during_initialization("Invalid young gen ratio specified"); 347 } 348 349 DEBUG_ONLY(GenCollectorPolicy::assert_flags();) 350 } 351 352 void TwoGenerationCollectorPolicy::initialize_flags() { 353 GenCollectorPolicy::initialize_flags(); 354 355 if (!is_size_aligned(OldSize, _gen_alignment)) { 356 FLAG_SET_ERGO(uintx, OldSize, align_size_down(OldSize, _gen_alignment)); 357 } 358 359 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(MaxHeapSize)) { 360 // NewRatio will be used later to set the young generation size so we use 361 // it to calculate how big the heap should be based on the requested OldSize 362 // and NewRatio. 363 assert(NewRatio > 0, "NewRatio should have been set up earlier"); 364 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1); 365 366 calculated_heapsize = align_size_up(calculated_heapsize, _heap_alignment); 367 FLAG_SET_ERGO(uintx, MaxHeapSize, calculated_heapsize); 368 _max_heap_byte_size = MaxHeapSize; 369 FLAG_SET_ERGO(uintx, InitialHeapSize, calculated_heapsize); 370 _initial_heap_byte_size = InitialHeapSize; 371 } 372 373 // adjust max heap size if necessary 374 if (NewSize + OldSize > MaxHeapSize) { 375 if (_max_heap_size_cmdline) { 376 // somebody set a maximum heap size with the intention that we should not 377 // exceed it. Adjust New/OldSize as necessary. 378 uintx calculated_size = NewSize + OldSize; 379 double shrink_factor = (double) MaxHeapSize / calculated_size; 380 uintx smaller_new_size = align_size_down((uintx)(NewSize * shrink_factor), _gen_alignment); 381 FLAG_SET_ERGO(uintx, NewSize, MAX2(young_gen_size_lower_bound(), smaller_new_size)); 382 _initial_gen0_size = NewSize; 383 384 // OldSize is already aligned because above we aligned MaxHeapSize to 385 // _heap_alignment, and we just made sure that NewSize is aligned to 386 // _gen_alignment. In initialize_flags() we verified that _heap_alignment 387 // is a multiple of _gen_alignment. 388 FLAG_SET_ERGO(uintx, OldSize, MaxHeapSize - NewSize); 389 } else { 390 FLAG_SET_ERGO(uintx, MaxHeapSize, align_size_up(NewSize + OldSize, _heap_alignment)); 391 _max_heap_byte_size = MaxHeapSize; 392 } 393 } 394 395 always_do_update_barrier = UseConcMarkSweepGC; 396 397 DEBUG_ONLY(TwoGenerationCollectorPolicy::assert_flags();) 398 } 399 400 // Values set on the command line win over any ergonomically 401 // set command line parameters. 402 // Ergonomic choice of parameters are done before this 403 // method is called. Values for command line parameters such as NewSize 404 // and MaxNewSize feed those ergonomic choices into this method. 405 // This method makes the final generation sizings consistent with 406 // themselves and with overall heap sizings. 407 // In the absence of explicitly set command line flags, policies 408 // such as the use of NewRatio are used to size the generation. 409 void GenCollectorPolicy::initialize_size_info() { 410 CollectorPolicy::initialize_size_info(); 411 412 // _space_alignment is used for alignment within a generation. 413 // There is additional alignment done down stream for some 414 // collectors that sometimes causes unwanted rounding up of 415 // generations sizes. 416 417 // Determine maximum size of gen0 418 419 size_t max_new_size = 0; 420 if (!FLAG_IS_DEFAULT(MaxNewSize)) { 421 max_new_size = MaxNewSize; 422 } else { 423 max_new_size = scale_by_NewRatio_aligned(_max_heap_byte_size); 424 // Bound the maximum size by NewSize below (since it historically 425 // would have been NewSize and because the NewRatio calculation could 426 // yield a size that is too small) and bound it by MaxNewSize above. 427 // Ergonomics plays here by previously calculating the desired 428 // NewSize and MaxNewSize. 429 max_new_size = MIN2(MAX2(max_new_size, NewSize), MaxNewSize); 430 } 431 assert(max_new_size > 0, "All paths should set max_new_size"); 432 433 // Given the maximum gen0 size, determine the initial and 434 // minimum gen0 sizes. 435 436 if (_max_heap_byte_size == _min_heap_byte_size) { 437 // The maximum and minimum heap sizes are the same so 438 // the generations minimum and initial must be the 439 // same as its maximum. 440 _min_gen0_size = max_new_size; 441 _initial_gen0_size = max_new_size; 442 _max_gen0_size = max_new_size; 443 } else { 444 size_t desired_new_size = 0; 445 if (!FLAG_IS_DEFAULT(NewSize)) { 446 // If NewSize is set ergonomically (for example by cms), it 447 // would make sense to use it. If it is used, also use it 448 // to set the initial size. Although there is no reason 449 // the minimum size and the initial size have to be the same, 450 // the current implementation gets into trouble during the calculation 451 // of the tenured generation sizes if they are different. 452 // Note that this makes the initial size and the minimum size 453 // generally small compared to the NewRatio calculation. 454 _min_gen0_size = NewSize; 455 desired_new_size = NewSize; 456 max_new_size = MAX2(max_new_size, NewSize); 457 } else { 458 // For the case where NewSize is the default, use NewRatio 459 // to size the minimum and initial generation sizes. 460 // Use the default NewSize as the floor for these values. If 461 // NewRatio is overly large, the resulting sizes can be too 462 // small. 463 _min_gen0_size = MAX2(scale_by_NewRatio_aligned(_min_heap_byte_size), NewSize); 464 desired_new_size = 465 MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize); 466 } 467 468 assert(_min_gen0_size > 0, "Sanity check"); 469 _initial_gen0_size = desired_new_size; 470 _max_gen0_size = max_new_size; 471 472 // At this point the desirable initial and minimum sizes have been 473 // determined without regard to the maximum sizes. 474 475 // Bound the sizes by the corresponding overall heap sizes. 476 _min_gen0_size = bound_minus_alignment(_min_gen0_size, _min_heap_byte_size); 477 _initial_gen0_size = bound_minus_alignment(_initial_gen0_size, _initial_heap_byte_size); 478 _max_gen0_size = bound_minus_alignment(_max_gen0_size, _max_heap_byte_size); 479 480 // At this point all three sizes have been checked against the 481 // maximum sizes but have not been checked for consistency 482 // among the three. 483 484 // Final check min <= initial <= max 485 _min_gen0_size = MIN2(_min_gen0_size, _max_gen0_size); 486 _initial_gen0_size = MAX2(MIN2(_initial_gen0_size, _max_gen0_size), _min_gen0_size); 487 _min_gen0_size = MIN2(_min_gen0_size, _initial_gen0_size); 488 } 489 490 // Write back to flags if necessary 491 if (NewSize != _initial_gen0_size) { 492 FLAG_SET_ERGO(uintx, NewSize, _initial_gen0_size); 493 } 494 495 if (MaxNewSize != _max_gen0_size) { 496 FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size); 497 } 498 499 if (PrintGCDetails && Verbose) { 500 gclog_or_tty->print_cr("1: Minimum gen0 " SIZE_FORMAT " Initial gen0 " 501 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT, 502 _min_gen0_size, _initial_gen0_size, _max_gen0_size); 503 } 504 505 DEBUG_ONLY(GenCollectorPolicy::assert_size_info();) 506 } 507 508 // Call this method during the sizing of the gen1 to make 509 // adjustments to gen0 because of gen1 sizing policy. gen0 initially has 510 // the most freedom in sizing because it is done before the 511 // policy for gen1 is applied. Once gen1 policies have been applied, 512 // there may be conflicts in the shape of the heap and this method 513 // is used to make the needed adjustments. The application of the 514 // policies could be more sophisticated (iterative for example) but 515 // keeping it simple also seems a worthwhile goal. 516 bool TwoGenerationCollectorPolicy::adjust_gen0_sizes(size_t* gen0_size_ptr, 517 size_t* gen1_size_ptr, 518 const size_t heap_size, 519 const size_t min_gen1_size) { 520 bool result = false; 521 522 if ((*gen1_size_ptr + *gen0_size_ptr) > heap_size) { 523 uintx smallest_new_size = young_gen_size_lower_bound(); 524 if ((heap_size < (*gen0_size_ptr + min_gen1_size)) && 525 (heap_size >= min_gen1_size + smallest_new_size)) { 526 // Adjust gen0 down to accommodate min_gen1_size 527 *gen0_size_ptr = align_size_down_bounded(heap_size - min_gen1_size, _gen_alignment); 528 assert(*gen0_size_ptr > 0, "Min gen0 is too large"); 529 result = true; 530 } else { 531 *gen1_size_ptr = align_size_down_bounded(heap_size - *gen0_size_ptr, _gen_alignment); 532 } 533 } 534 return result; 535 } 536 537 // Minimum sizes of the generations may be different than 538 // the initial sizes. An inconsistently is permitted here 539 // in the total size that can be specified explicitly by 540 // command line specification of OldSize and NewSize and 541 // also a command line specification of -Xms. Issue a warning 542 // but allow the values to pass. 543 544 void TwoGenerationCollectorPolicy::initialize_size_info() { 545 GenCollectorPolicy::initialize_size_info(); 546 547 // At this point the minimum, initial and maximum sizes 548 // of the overall heap and of gen0 have been determined. 549 // The maximum gen1 size can be determined from the maximum gen0 550 // and maximum heap size since no explicit flags exits 551 // for setting the gen1 maximum. 552 _max_gen1_size = MAX2(_max_heap_byte_size - _max_gen0_size, _gen_alignment); 553 554 // If no explicit command line flag has been set for the 555 // gen1 size, use what is left for gen1. 556 if (!FLAG_IS_CMDLINE(OldSize)) { 557 // The user has not specified any value but the ergonomics 558 // may have chosen a value (which may or may not be consistent 559 // with the overall heap size). In either case make 560 // the minimum, maximum and initial sizes consistent 561 // with the gen0 sizes and the overall heap sizes. 562 _min_gen1_size = MAX2(_min_heap_byte_size - _min_gen0_size, _gen_alignment); 563 _initial_gen1_size = MAX2(_initial_heap_byte_size - _initial_gen0_size, _gen_alignment); 564 // _max_gen1_size has already been made consistent above 565 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size); 566 } else { 567 // It's been explicitly set on the command line. Use the 568 // OldSize and then determine the consequences. 569 _min_gen1_size = MIN2(OldSize, _min_heap_byte_size - _min_gen0_size); 570 _initial_gen1_size = OldSize; 571 572 // If the user has explicitly set an OldSize that is inconsistent 573 // with other command line flags, issue a warning. 574 // The generation minimums and the overall heap mimimum should 575 // be within one generation alignment. 576 if ((_min_gen1_size + _min_gen0_size + _gen_alignment) < _min_heap_byte_size) { 577 warning("Inconsistency between minimum heap size and minimum " 578 "generation sizes: using minimum heap = " SIZE_FORMAT, 579 _min_heap_byte_size); 580 } 581 if (OldSize > _max_gen1_size) { 582 warning("Inconsistency between maximum heap size and maximum " 583 "generation sizes: using maximum heap = " SIZE_FORMAT 584 " -XX:OldSize flag is being ignored", 585 _max_heap_byte_size); 586 } 587 // If there is an inconsistency between the OldSize and the minimum and/or 588 // initial size of gen0, since OldSize was explicitly set, OldSize wins. 589 if (adjust_gen0_sizes(&_min_gen0_size, &_min_gen1_size, 590 _min_heap_byte_size, _min_gen1_size)) { 591 if (PrintGCDetails && Verbose) { 592 gclog_or_tty->print_cr("2: Minimum gen0 " SIZE_FORMAT " Initial gen0 " 593 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT, 594 _min_gen0_size, _initial_gen0_size, _max_gen0_size); 595 } 596 } 597 // Initial size 598 if (adjust_gen0_sizes(&_initial_gen0_size, &_initial_gen1_size, 599 _initial_heap_byte_size, _initial_gen1_size)) { 600 if (PrintGCDetails && Verbose) { 601 gclog_or_tty->print_cr("3: Minimum gen0 " SIZE_FORMAT " Initial gen0 " 602 SIZE_FORMAT " Maximum gen0 " SIZE_FORMAT, 603 _min_gen0_size, _initial_gen0_size, _max_gen0_size); 604 } 605 } 606 } 607 // Enforce the maximum gen1 size. 608 _min_gen1_size = MIN2(_min_gen1_size, _max_gen1_size); 609 610 // Check that min gen1 <= initial gen1 <= max gen1 611 _initial_gen1_size = MAX2(_initial_gen1_size, _min_gen1_size); 612 _initial_gen1_size = MIN2(_initial_gen1_size, _max_gen1_size); 613 614 // Write back to flags if necessary 615 if (NewSize != _initial_gen0_size) { 616 FLAG_SET_ERGO(uintx, NewSize, _max_gen0_size); 617 } 618 619 if (MaxNewSize != _max_gen0_size) { 620 FLAG_SET_ERGO(uintx, MaxNewSize, _max_gen0_size); 621 } 622 623 if (OldSize != _initial_gen1_size) { 624 FLAG_SET_ERGO(uintx, OldSize, _initial_gen1_size); 625 } 626 627 if (PrintGCDetails && Verbose) { 628 gclog_or_tty->print_cr("Minimum gen1 " SIZE_FORMAT " Initial gen1 " 629 SIZE_FORMAT " Maximum gen1 " SIZE_FORMAT, 630 _min_gen1_size, _initial_gen1_size, _max_gen1_size); 631 } 632 633 DEBUG_ONLY(TwoGenerationCollectorPolicy::assert_size_info();) 634 } 635 636 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size, 637 bool is_tlab, 638 bool* gc_overhead_limit_was_exceeded) { 639 GenCollectedHeap *gch = GenCollectedHeap::heap(); 640 641 debug_only(gch->check_for_valid_allocation_state()); 642 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed"); 643 644 // In general gc_overhead_limit_was_exceeded should be false so 645 // set it so here and reset it to true only if the gc time 646 // limit is being exceeded as checked below. 647 *gc_overhead_limit_was_exceeded = false; 648 649 HeapWord* result = NULL; 650 651 // Loop until the allocation is satisified, 652 // or unsatisfied after GC. 653 for (int try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) { 654 HandleMark hm; // discard any handles allocated in each iteration 655 656 // First allocation attempt is lock-free. 657 Generation *gen0 = gch->get_gen(0); 658 assert(gen0->supports_inline_contig_alloc(), 659 "Otherwise, must do alloc within heap lock"); 660 if (gen0->should_allocate(size, is_tlab)) { 661 result = gen0->par_allocate(size, is_tlab); 662 if (result != NULL) { 663 assert(gch->is_in_reserved(result), "result not in heap"); 664 return result; 665 } 666 } 667 unsigned int gc_count_before; // read inside the Heap_lock locked region 668 { 669 MutexLocker ml(Heap_lock); 670 if (PrintGC && Verbose) { 671 gclog_or_tty->print_cr("TwoGenerationCollectorPolicy::mem_allocate_work:" 672 " attempting locked slow path allocation"); 673 } 674 // Note that only large objects get a shot at being 675 // allocated in later generations. 676 bool first_only = ! should_try_older_generation_allocation(size); 677 678 result = gch->attempt_allocation(size, is_tlab, first_only); 679 if (result != NULL) { 680 assert(gch->is_in_reserved(result), "result not in heap"); 681 return result; 682 } 683 684 if (GC_locker::is_active_and_needs_gc()) { 685 if (is_tlab) { 686 return NULL; // Caller will retry allocating individual object 687 } 688 if (!gch->is_maximal_no_gc()) { 689 // Try and expand heap to satisfy request 690 result = expand_heap_and_allocate(size, is_tlab); 691 // result could be null if we are out of space 692 if (result != NULL) { 693 return result; 694 } 695 } 696 697 if (gclocker_stalled_count > GCLockerRetryAllocationCount) { 698 return NULL; // we didn't get to do a GC and we didn't get any memory 699 } 700 701 // If this thread is not in a jni critical section, we stall 702 // the requestor until the critical section has cleared and 703 // GC allowed. When the critical section clears, a GC is 704 // initiated by the last thread exiting the critical section; so 705 // we retry the allocation sequence from the beginning of the loop, 706 // rather than causing more, now probably unnecessary, GC attempts. 707 JavaThread* jthr = JavaThread::current(); 708 if (!jthr->in_critical()) { 709 MutexUnlocker mul(Heap_lock); 710 // Wait for JNI critical section to be exited 711 GC_locker::stall_until_clear(); 712 gclocker_stalled_count += 1; 713 continue; 714 } else { 715 if (CheckJNICalls) { 716 fatal("Possible deadlock due to allocating while" 717 " in jni critical section"); 718 } 719 return NULL; 720 } 721 } 722 723 // Read the gc count while the heap lock is held. 724 gc_count_before = Universe::heap()->total_collections(); 725 } 726 727 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before); 728 VMThread::execute(&op); 729 if (op.prologue_succeeded()) { 730 result = op.result(); 731 if (op.gc_locked()) { 732 assert(result == NULL, "must be NULL if gc_locked() is true"); 733 continue; // retry and/or stall as necessary 734 } 735 736 // Allocation has failed and a collection 737 // has been done. If the gc time limit was exceeded the 738 // this time, return NULL so that an out-of-memory 739 // will be thrown. Clear gc_overhead_limit_exceeded 740 // so that the overhead exceeded does not persist. 741 742 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded(); 743 const bool softrefs_clear = all_soft_refs_clear(); 744 745 if (limit_exceeded && softrefs_clear) { 746 *gc_overhead_limit_was_exceeded = true; 747 size_policy()->set_gc_overhead_limit_exceeded(false); 748 if (op.result() != NULL) { 749 CollectedHeap::fill_with_object(op.result(), size); 750 } 751 return NULL; 752 } 753 assert(result == NULL || gch->is_in_reserved(result), 754 "result not in heap"); 755 return result; 756 } 757 758 // Give a warning if we seem to be looping forever. 759 if ((QueuedAllocationWarningCount > 0) && 760 (try_count % QueuedAllocationWarningCount == 0)) { 761 warning("TwoGenerationCollectorPolicy::mem_allocate_work retries %d times \n\t" 762 " size=%d %s", try_count, size, is_tlab ? "(TLAB)" : ""); 763 } 764 } 765 } 766 767 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size, 768 bool is_tlab) { 769 GenCollectedHeap *gch = GenCollectedHeap::heap(); 770 HeapWord* result = NULL; 771 for (int i = number_of_generations() - 1; i >= 0 && result == NULL; i--) { 772 Generation *gen = gch->get_gen(i); 773 if (gen->should_allocate(size, is_tlab)) { 774 result = gen->expand_and_allocate(size, is_tlab); 775 } 776 } 777 assert(result == NULL || gch->is_in_reserved(result), "result not in heap"); 778 return result; 779 } 780 781 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size, 782 bool is_tlab) { 783 GenCollectedHeap *gch = GenCollectedHeap::heap(); 784 GCCauseSetter x(gch, GCCause::_allocation_failure); 785 HeapWord* result = NULL; 786 787 assert(size != 0, "Precondition violated"); 788 if (GC_locker::is_active_and_needs_gc()) { 789 // GC locker is active; instead of a collection we will attempt 790 // to expand the heap, if there's room for expansion. 791 if (!gch->is_maximal_no_gc()) { 792 result = expand_heap_and_allocate(size, is_tlab); 793 } 794 return result; // could be null if we are out of space 795 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) { 796 // Do an incremental collection. 797 gch->do_collection(false /* full */, 798 false /* clear_all_soft_refs */, 799 size /* size */, 800 is_tlab /* is_tlab */, 801 number_of_generations() - 1 /* max_level */); 802 } else { 803 if (Verbose && PrintGCDetails) { 804 gclog_or_tty->print(" :: Trying full because partial may fail :: "); 805 } 806 // Try a full collection; see delta for bug id 6266275 807 // for the original code and why this has been simplified 808 // with from-space allocation criteria modified and 809 // such allocation moved out of the safepoint path. 810 gch->do_collection(true /* full */, 811 false /* clear_all_soft_refs */, 812 size /* size */, 813 is_tlab /* is_tlab */, 814 number_of_generations() - 1 /* max_level */); 815 } 816 817 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/); 818 819 if (result != NULL) { 820 assert(gch->is_in_reserved(result), "result not in heap"); 821 return result; 822 } 823 824 // OK, collection failed, try expansion. 825 result = expand_heap_and_allocate(size, is_tlab); 826 if (result != NULL) { 827 return result; 828 } 829 830 // If we reach this point, we're really out of memory. Try every trick 831 // we can to reclaim memory. Force collection of soft references. Force 832 // a complete compaction of the heap. Any additional methods for finding 833 // free memory should be here, especially if they are expensive. If this 834 // attempt fails, an OOM exception will be thrown. 835 { 836 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted 837 838 gch->do_collection(true /* full */, 839 true /* clear_all_soft_refs */, 840 size /* size */, 841 is_tlab /* is_tlab */, 842 number_of_generations() - 1 /* max_level */); 843 } 844 845 result = gch->attempt_allocation(size, is_tlab, false /* first_only */); 846 if (result != NULL) { 847 assert(gch->is_in_reserved(result), "result not in heap"); 848 return result; 849 } 850 851 assert(!should_clear_all_soft_refs(), 852 "Flag should have been handled and cleared prior to this point"); 853 854 // What else? We might try synchronous finalization later. If the total 855 // space available is large enough for the allocation, then a more 856 // complete compaction phase than we've tried so far might be 857 // appropriate. 858 return NULL; 859 } 860 861 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation( 862 ClassLoaderData* loader_data, 863 size_t word_size, 864 Metaspace::MetadataType mdtype) { 865 uint loop_count = 0; 866 uint gc_count = 0; 867 uint full_gc_count = 0; 868 869 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock"); 870 871 do { 872 MetaWord* result = NULL; 873 if (GC_locker::is_active_and_needs_gc()) { 874 // If the GC_locker is active, just expand and allocate. 875 // If that does not succeed, wait if this thread is not 876 // in a critical section itself. 877 result = 878 loader_data->metaspace_non_null()->expand_and_allocate(word_size, 879 mdtype); 880 if (result != NULL) { 881 return result; 882 } 883 JavaThread* jthr = JavaThread::current(); 884 if (!jthr->in_critical()) { 885 // Wait for JNI critical section to be exited 886 GC_locker::stall_until_clear(); 887 // The GC invoked by the last thread leaving the critical 888 // section will be a young collection and a full collection 889 // is (currently) needed for unloading classes so continue 890 // to the next iteration to get a full GC. 891 continue; 892 } else { 893 if (CheckJNICalls) { 894 fatal("Possible deadlock due to allocating while" 895 " in jni critical section"); 896 } 897 return NULL; 898 } 899 } 900 901 { // Need lock to get self consistent gc_count's 902 MutexLocker ml(Heap_lock); 903 gc_count = Universe::heap()->total_collections(); 904 full_gc_count = Universe::heap()->total_full_collections(); 905 } 906 907 // Generate a VM operation 908 VM_CollectForMetadataAllocation op(loader_data, 909 word_size, 910 mdtype, 911 gc_count, 912 full_gc_count, 913 GCCause::_metadata_GC_threshold); 914 VMThread::execute(&op); 915 916 // If GC was locked out, try again. Check 917 // before checking success because the prologue 918 // could have succeeded and the GC still have 919 // been locked out. 920 if (op.gc_locked()) { 921 continue; 922 } 923 924 if (op.prologue_succeeded()) { 925 return op.result(); 926 } 927 loop_count++; 928 if ((QueuedAllocationWarningCount > 0) && 929 (loop_count % QueuedAllocationWarningCount == 0)) { 930 warning("satisfy_failed_metadata_allocation() retries %d times \n\t" 931 " size=%d", loop_count, word_size); 932 } 933 } while (true); // Until a GC is done 934 } 935 936 // Return true if any of the following is true: 937 // . the allocation won't fit into the current young gen heap 938 // . gc locker is occupied (jni critical section) 939 // . heap memory is tight -- the most recent previous collection 940 // was a full collection because a partial collection (would 941 // have) failed and is likely to fail again 942 bool GenCollectorPolicy::should_try_older_generation_allocation( 943 size_t word_size) const { 944 GenCollectedHeap* gch = GenCollectedHeap::heap(); 945 size_t gen0_capacity = gch->get_gen(0)->capacity_before_gc(); 946 return (word_size > heap_word_size(gen0_capacity)) 947 || GC_locker::is_active_and_needs_gc() 948 || gch->incremental_collection_failed(); 949 } 950 951 952 // 953 // MarkSweepPolicy methods 954 // 955 956 void MarkSweepPolicy::initialize_alignments() { 957 _space_alignment = _gen_alignment = (uintx)Generation::GenGrain; 958 _heap_alignment = compute_heap_alignment(); 959 } 960 961 void MarkSweepPolicy::initialize_generations() { 962 _generations = NEW_C_HEAP_ARRAY3(GenerationSpecPtr, number_of_generations(), mtGC, 0, AllocFailStrategy::RETURN_NULL); 963 if (_generations == NULL) { 964 vm_exit_during_initialization("Unable to allocate gen spec"); 965 } 966 967 if (UseParNewGC) { 968 _generations[0] = new GenerationSpec(Generation::ParNew, _initial_gen0_size, _max_gen0_size); 969 } else { 970 _generations[0] = new GenerationSpec(Generation::DefNew, _initial_gen0_size, _max_gen0_size); 971 } 972 _generations[1] = new GenerationSpec(Generation::MarkSweepCompact, _initial_gen1_size, _max_gen1_size); 973 974 if (_generations[0] == NULL || _generations[1] == NULL) { 975 vm_exit_during_initialization("Unable to allocate gen spec"); 976 } 977 } 978 979 void MarkSweepPolicy::initialize_gc_policy_counters() { 980 // initialize the policy counters - 2 collectors, 3 generations 981 if (UseParNewGC) { 982 _gc_policy_counters = new GCPolicyCounters("ParNew:MSC", 2, 3); 983 } else { 984 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3); 985 } 986 }