1 /* 2 * Copyright (c) 2001, 2016, 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/shared/adaptiveSizePolicy.hpp" 27 #include "gc/shared/cardTableRS.hpp" 28 #include "gc/shared/collectorPolicy.hpp" 29 #include "gc/shared/gcLocker.inline.hpp" 30 #include "gc/shared/gcPolicyCounters.hpp" 31 #include "gc/shared/genCollectedHeap.hpp" 32 #include "gc/shared/generationSpec.hpp" 33 #include "gc/shared/space.hpp" 34 #include "gc/shared/vmGCOperations.hpp" 35 #include "logging/log.hpp" 36 #include "memory/universe.hpp" 37 #include "runtime/arguments.hpp" 38 #include "runtime/globals_extension.hpp" 39 #include "runtime/handles.inline.hpp" 40 #include "runtime/java.hpp" 41 #include "runtime/thread.inline.hpp" 42 #include "runtime/vmThread.hpp" 43 #include "utilities/align.hpp" 44 #include "utilities/macros.hpp" 45 46 // CollectorPolicy methods 47 48 CollectorPolicy::CollectorPolicy() : 49 _space_alignment(0), 50 _heap_alignment(0), 51 _initial_heap_byte_size(InitialHeapSize), 52 _max_heap_byte_size(MaxHeapSize), 53 _min_heap_byte_size(Arguments::min_heap_size()), 54 _size_policy(NULL), 55 _should_clear_all_soft_refs(false), 56 _all_soft_refs_clear(false) 57 {} 58 59 #ifdef ASSERT 60 void CollectorPolicy::assert_flags() { 61 assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes"); 62 assert(InitialHeapSize % _heap_alignment == 0, "InitialHeapSize alignment"); 63 assert(MaxHeapSize % _heap_alignment == 0, "MaxHeapSize alignment"); 64 } 65 66 void CollectorPolicy::assert_size_info() { 67 assert(InitialHeapSize == _initial_heap_byte_size, "Discrepancy between InitialHeapSize flag and local storage"); 68 assert(MaxHeapSize == _max_heap_byte_size, "Discrepancy between MaxHeapSize flag and local storage"); 69 assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes"); 70 assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes"); 71 assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes"); 72 assert(_min_heap_byte_size % _heap_alignment == 0, "min_heap_byte_size alignment"); 73 assert(_initial_heap_byte_size % _heap_alignment == 0, "initial_heap_byte_size alignment"); 74 assert(_max_heap_byte_size % _heap_alignment == 0, "max_heap_byte_size alignment"); 75 } 76 #endif // ASSERT 77 78 void CollectorPolicy::initialize_flags() { 79 assert(_space_alignment != 0, "Space alignment not set up properly"); 80 assert(_heap_alignment != 0, "Heap alignment not set up properly"); 81 assert(_heap_alignment >= _space_alignment, 82 "heap_alignment: " SIZE_FORMAT " less than space_alignment: " SIZE_FORMAT, 83 _heap_alignment, _space_alignment); 84 assert(_heap_alignment % _space_alignment == 0, 85 "heap_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT, 86 _heap_alignment, _space_alignment); 87 88 if (FLAG_IS_CMDLINE(MaxHeapSize)) { 89 if (FLAG_IS_CMDLINE(InitialHeapSize) && InitialHeapSize > MaxHeapSize) { 90 vm_exit_during_initialization("Initial heap size set to a larger value than the maximum heap size"); 91 } 92 if (_min_heap_byte_size != 0 && MaxHeapSize < _min_heap_byte_size) { 93 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified"); 94 } 95 } 96 97 // Check heap parameter properties 98 if (MaxHeapSize < 2 * M) { 99 vm_exit_during_initialization("Too small maximum heap"); 100 } 101 if (InitialHeapSize < M) { 102 vm_exit_during_initialization("Too small initial heap"); 103 } 104 if (_min_heap_byte_size < M) { 105 vm_exit_during_initialization("Too small minimum heap"); 106 } 107 108 // User inputs from -Xmx and -Xms must be aligned 109 _min_heap_byte_size = align_up(_min_heap_byte_size, _heap_alignment); 110 size_t aligned_initial_heap_size = align_up(InitialHeapSize, _heap_alignment); 111 size_t aligned_max_heap_size = align_up(MaxHeapSize, _heap_alignment); 112 113 // Write back to flags if the values changed 114 if (aligned_initial_heap_size != InitialHeapSize) { 115 FLAG_SET_ERGO(size_t, InitialHeapSize, aligned_initial_heap_size); 116 } 117 if (aligned_max_heap_size != MaxHeapSize) { 118 FLAG_SET_ERGO(size_t, MaxHeapSize, aligned_max_heap_size); 119 } 120 121 if (FLAG_IS_CMDLINE(InitialHeapSize) && _min_heap_byte_size != 0 && 122 InitialHeapSize < _min_heap_byte_size) { 123 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified"); 124 } 125 if (!FLAG_IS_DEFAULT(InitialHeapSize) && InitialHeapSize > MaxHeapSize) { 126 FLAG_SET_ERGO(size_t, MaxHeapSize, InitialHeapSize); 127 } else if (!FLAG_IS_DEFAULT(MaxHeapSize) && InitialHeapSize > MaxHeapSize) { 128 FLAG_SET_ERGO(size_t, InitialHeapSize, MaxHeapSize); 129 if (InitialHeapSize < _min_heap_byte_size) { 130 _min_heap_byte_size = InitialHeapSize; 131 } 132 } 133 134 _initial_heap_byte_size = InitialHeapSize; 135 _max_heap_byte_size = MaxHeapSize; 136 137 FLAG_SET_ERGO(size_t, MinHeapDeltaBytes, align_up(MinHeapDeltaBytes, _space_alignment)); 138 139 DEBUG_ONLY(CollectorPolicy::assert_flags();) 140 } 141 142 void CollectorPolicy::initialize_size_info() { 143 log_debug(gc, heap)("Minimum heap " SIZE_FORMAT " Initial heap " SIZE_FORMAT " Maximum heap " SIZE_FORMAT, 144 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size); 145 146 DEBUG_ONLY(CollectorPolicy::assert_size_info();) 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 CardTableRS* CollectorPolicy::create_rem_set(MemRegion whole_heap) { 156 return new CardTableRS(whole_heap); 157 } 158 159 void CollectorPolicy::cleared_all_soft_refs() { 160 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may 161 // have been cleared in the last collection but if the gc overhear 162 // limit continues to be near, SoftRefs should still be cleared. 163 if (size_policy() != NULL) { 164 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near(); 165 } 166 _all_soft_refs_clear = true; 167 } 168 169 size_t CollectorPolicy::compute_heap_alignment() { 170 // The card marking array and the offset arrays for old generations are 171 // committed in os pages as well. Make sure they are entirely full (to 172 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1 173 // byte entry and the os page size is 4096, the maximum heap size should 174 // be 512*4096 = 2MB aligned. 175 176 size_t alignment = CardTableRS::ct_max_alignment_constraint(); 177 178 if (UseLargePages) { 179 // In presence of large pages we have to make sure that our 180 // alignment is large page aware. 181 alignment = lcm(os::large_page_size(), alignment); 182 } 183 184 return alignment; 185 } 186 187 // GenCollectorPolicy methods 188 189 GenCollectorPolicy::GenCollectorPolicy() : 190 _min_young_size(0), 191 _initial_young_size(0), 192 _max_young_size(0), 193 _min_old_size(0), 194 _initial_old_size(0), 195 _max_old_size(0), 196 _gen_alignment(0), 197 _young_gen_spec(NULL), 198 _old_gen_spec(NULL) 199 {} 200 201 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) { 202 return align_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_up(3 * _space_alignment, _gen_alignment); 226 } 227 228 size_t GenCollectorPolicy::old_gen_size_lower_bound() { 229 return align_up(_space_alignment, _gen_alignment); 230 } 231 232 #ifdef ASSERT 233 void GenCollectorPolicy::assert_flags() { 234 CollectorPolicy::assert_flags(); 235 assert(NewSize >= _min_young_size, "Ergonomics decided on a too small young gen size"); 236 assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes"); 237 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes"); 238 assert(NewSize % _gen_alignment == 0, "NewSize alignment"); 239 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _gen_alignment == 0, "MaxNewSize alignment"); 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_young_size, "Discrepancy between NewSize flag and local storage"); 249 assert(MaxNewSize == _max_young_size, "Discrepancy between MaxNewSize flag and local storage"); 250 assert(OldSize == _initial_old_size, "Discrepancy between OldSize flag and local storage"); 251 assert(_min_young_size <= _initial_young_size, "Ergonomics decided on incompatible minimum and initial young gen sizes"); 252 assert(_initial_young_size <= _max_young_size, "Ergonomics decided on incompatible initial and maximum young gen sizes"); 253 assert(_min_young_size % _gen_alignment == 0, "_min_young_size alignment"); 254 assert(_initial_young_size % _gen_alignment == 0, "_initial_young_size alignment"); 255 assert(_max_young_size % _gen_alignment == 0, "_max_young_size alignment"); 256 assert(_min_young_size <= bound_minus_alignment(_min_young_size, _min_heap_byte_size), 257 "Ergonomics made minimum young generation larger than minimum heap"); 258 assert(_initial_young_size <= bound_minus_alignment(_initial_young_size, _initial_heap_byte_size), 259 "Ergonomics made initial young generation larger than initial heap"); 260 assert(_max_young_size <= bound_minus_alignment(_max_young_size, _max_heap_byte_size), 261 "Ergonomics made maximum young generation lager than maximum heap"); 262 assert(_min_old_size <= _initial_old_size, "Ergonomics decided on incompatible minimum and initial old gen sizes"); 263 assert(_initial_old_size <= _max_old_size, "Ergonomics decided on incompatible initial and maximum old gen sizes"); 264 assert(_max_old_size % _gen_alignment == 0, "_max_old_size alignment"); 265 assert(_initial_old_size % _gen_alignment == 0, "_initial_old_size alignment"); 266 assert(_max_heap_byte_size <= (_max_young_size + _max_old_size), "Total maximum heap sizes must be sum of generation maximum sizes"); 267 assert(_min_young_size + _min_old_size <= _min_heap_byte_size, "Minimum generation sizes exceed minimum heap size"); 268 assert(_initial_young_size + _initial_old_size == _initial_heap_byte_size, "Initial generation sizes should match initial heap size"); 269 assert(_max_young_size + _max_old_size == _max_heap_byte_size, "Maximum generation sizes should match maximum heap size"); 270 } 271 #endif // ASSERT 272 273 void GenCollectorPolicy::initialize_flags() { 274 CollectorPolicy::initialize_flags(); 275 276 assert(_gen_alignment != 0, "Generation alignment not set up properly"); 277 assert(_heap_alignment >= _gen_alignment, 278 "heap_alignment: " SIZE_FORMAT " less than gen_alignment: " SIZE_FORMAT, 279 _heap_alignment, _gen_alignment); 280 assert(_gen_alignment % _space_alignment == 0, 281 "gen_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT, 282 _gen_alignment, _space_alignment); 283 assert(_heap_alignment % _gen_alignment == 0, 284 "heap_alignment: " SIZE_FORMAT " not aligned by gen_alignment: " SIZE_FORMAT, 285 _heap_alignment, _gen_alignment); 286 287 // All generational heaps have a young gen; handle those flags here 288 289 // Make sure the heap is large enough for two generations 290 size_t smallest_new_size = young_gen_size_lower_bound(); 291 size_t smallest_heap_size = align_up(smallest_new_size + old_gen_size_lower_bound(), 292 _heap_alignment); 293 if (MaxHeapSize < smallest_heap_size) { 294 FLAG_SET_ERGO(size_t, MaxHeapSize, smallest_heap_size); 295 _max_heap_byte_size = MaxHeapSize; 296 } 297 // If needed, synchronize _min_heap_byte size and _initial_heap_byte_size 298 if (_min_heap_byte_size < smallest_heap_size) { 299 _min_heap_byte_size = smallest_heap_size; 300 if (InitialHeapSize < _min_heap_byte_size) { 301 FLAG_SET_ERGO(size_t, InitialHeapSize, smallest_heap_size); 302 _initial_heap_byte_size = smallest_heap_size; 303 } 304 } 305 306 // Make sure NewSize allows an old generation to fit even if set on the command line 307 if (FLAG_IS_CMDLINE(NewSize) && NewSize >= _initial_heap_byte_size) { 308 log_warning(gc, ergo)("NewSize was set larger than initial heap size, will use initial heap size."); 309 FLAG_SET_ERGO(size_t, NewSize, bound_minus_alignment(NewSize, _initial_heap_byte_size)); 310 } 311 312 // Now take the actual NewSize into account. We will silently increase NewSize 313 // if the user specified a smaller or unaligned value. 314 size_t bounded_new_size = bound_minus_alignment(NewSize, MaxHeapSize); 315 bounded_new_size = MAX2(smallest_new_size, align_down(bounded_new_size, _gen_alignment)); 316 if (bounded_new_size != NewSize) { 317 FLAG_SET_ERGO(size_t, NewSize, bounded_new_size); 318 } 319 _min_young_size = smallest_new_size; 320 _initial_young_size = NewSize; 321 322 if (!FLAG_IS_DEFAULT(MaxNewSize)) { 323 if (MaxNewSize >= MaxHeapSize) { 324 // Make sure there is room for an old generation 325 size_t smaller_max_new_size = MaxHeapSize - _gen_alignment; 326 if (FLAG_IS_CMDLINE(MaxNewSize)) { 327 log_warning(gc, ergo)("MaxNewSize (" SIZE_FORMAT "k) is equal to or greater than the entire " 328 "heap (" SIZE_FORMAT "k). A new max generation size of " SIZE_FORMAT "k will be used.", 329 MaxNewSize/K, MaxHeapSize/K, smaller_max_new_size/K); 330 } 331 FLAG_SET_ERGO(size_t, MaxNewSize, smaller_max_new_size); 332 if (NewSize > MaxNewSize) { 333 FLAG_SET_ERGO(size_t, NewSize, MaxNewSize); 334 _initial_young_size = NewSize; 335 } 336 } else if (MaxNewSize < _initial_young_size) { 337 FLAG_SET_ERGO(size_t, MaxNewSize, _initial_young_size); 338 } else if (!is_aligned(MaxNewSize, _gen_alignment)) { 339 FLAG_SET_ERGO(size_t, MaxNewSize, align_down(MaxNewSize, _gen_alignment)); 340 } 341 _max_young_size = MaxNewSize; 342 } 343 344 if (NewSize > MaxNewSize) { 345 // At this point this should only happen if the user specifies a large NewSize and/or 346 // a small (but not too small) MaxNewSize. 347 if (FLAG_IS_CMDLINE(MaxNewSize)) { 348 log_warning(gc, ergo)("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). " 349 "A new max generation size of " SIZE_FORMAT "k will be used.", 350 NewSize/K, MaxNewSize/K, NewSize/K); 351 } 352 FLAG_SET_ERGO(size_t, MaxNewSize, NewSize); 353 _max_young_size = MaxNewSize; 354 } 355 356 if (SurvivorRatio < 1 || NewRatio < 1) { 357 vm_exit_during_initialization("Invalid young gen ratio specified"); 358 } 359 360 if (OldSize < old_gen_size_lower_bound()) { 361 FLAG_SET_ERGO(size_t, OldSize, old_gen_size_lower_bound()); 362 } 363 if (!is_aligned(OldSize, _gen_alignment)) { 364 FLAG_SET_ERGO(size_t, OldSize, align_down(OldSize, _gen_alignment)); 365 } 366 367 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(MaxHeapSize)) { 368 // NewRatio will be used later to set the young generation size so we use 369 // it to calculate how big the heap should be based on the requested OldSize 370 // and NewRatio. 371 assert(NewRatio > 0, "NewRatio should have been set up earlier"); 372 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1); 373 374 calculated_heapsize = align_up(calculated_heapsize, _heap_alignment); 375 FLAG_SET_ERGO(size_t, MaxHeapSize, calculated_heapsize); 376 _max_heap_byte_size = MaxHeapSize; 377 FLAG_SET_ERGO(size_t, InitialHeapSize, calculated_heapsize); 378 _initial_heap_byte_size = InitialHeapSize; 379 } 380 381 // Adjust NewSize and OldSize or MaxHeapSize to match each other 382 if (NewSize + OldSize > MaxHeapSize) { 383 if (FLAG_IS_CMDLINE(MaxHeapSize)) { 384 // Somebody has set a maximum heap size with the intention that we should not 385 // exceed it. Adjust New/OldSize as necessary. 386 size_t calculated_size = NewSize + OldSize; 387 double shrink_factor = (double) MaxHeapSize / calculated_size; 388 size_t smaller_new_size = align_down((size_t)(NewSize * shrink_factor), _gen_alignment); 389 FLAG_SET_ERGO(size_t, NewSize, MAX2(young_gen_size_lower_bound(), smaller_new_size)); 390 _initial_young_size = NewSize; 391 392 // OldSize is already aligned because above we aligned MaxHeapSize to 393 // _heap_alignment, and we just made sure that NewSize is aligned to 394 // _gen_alignment. In initialize_flags() we verified that _heap_alignment 395 // is a multiple of _gen_alignment. 396 FLAG_SET_ERGO(size_t, OldSize, MaxHeapSize - NewSize); 397 } else { 398 FLAG_SET_ERGO(size_t, MaxHeapSize, align_up(NewSize + OldSize, _heap_alignment)); 399 _max_heap_byte_size = MaxHeapSize; 400 } 401 } 402 403 // Update NewSize, if possible, to avoid sizing the young gen too small when only 404 // OldSize is set on the command line. 405 if (FLAG_IS_CMDLINE(OldSize) && !FLAG_IS_CMDLINE(NewSize)) { 406 if (OldSize < _initial_heap_byte_size) { 407 size_t new_size = _initial_heap_byte_size - OldSize; 408 // Need to compare against the flag value for max since _max_young_size 409 // might not have been set yet. 410 if (new_size >= _min_young_size && new_size <= MaxNewSize) { 411 FLAG_SET_ERGO(size_t, NewSize, new_size); 412 _initial_young_size = NewSize; 413 } 414 } 415 } 416 417 always_do_update_barrier = UseConcMarkSweepGC; 418 419 DEBUG_ONLY(GenCollectorPolicy::assert_flags();) 420 } 421 422 // Values set on the command line win over any ergonomically 423 // set command line parameters. 424 // Ergonomic choice of parameters are done before this 425 // method is called. Values for command line parameters such as NewSize 426 // and MaxNewSize feed those ergonomic choices into this method. 427 // This method makes the final generation sizings consistent with 428 // themselves and with overall heap sizings. 429 // In the absence of explicitly set command line flags, policies 430 // such as the use of NewRatio are used to size the generation. 431 432 // Minimum sizes of the generations may be different than 433 // the initial sizes. An inconsistency is permitted here 434 // in the total size that can be specified explicitly by 435 // command line specification of OldSize and NewSize and 436 // also a command line specification of -Xms. Issue a warning 437 // but allow the values to pass. 438 void GenCollectorPolicy::initialize_size_info() { 439 CollectorPolicy::initialize_size_info(); 440 441 _initial_young_size = NewSize; 442 _max_young_size = MaxNewSize; 443 _initial_old_size = OldSize; 444 445 // Determine maximum size of the young generation. 446 447 if (FLAG_IS_DEFAULT(MaxNewSize)) { 448 _max_young_size = scale_by_NewRatio_aligned(_max_heap_byte_size); 449 // Bound the maximum size by NewSize below (since it historically 450 // would have been NewSize and because the NewRatio calculation could 451 // yield a size that is too small) and bound it by MaxNewSize above. 452 // Ergonomics plays here by previously calculating the desired 453 // NewSize and MaxNewSize. 454 _max_young_size = MIN2(MAX2(_max_young_size, _initial_young_size), MaxNewSize); 455 } 456 457 // Given the maximum young size, determine the initial and 458 // minimum young sizes. 459 460 if (_max_heap_byte_size == _initial_heap_byte_size) { 461 // The maximum and initial heap sizes are the same so the generation's 462 // initial size must be the same as it maximum size. Use NewSize as the 463 // size if set on command line. 464 _max_young_size = FLAG_IS_CMDLINE(NewSize) ? NewSize : _max_young_size; 465 _initial_young_size = _max_young_size; 466 467 // Also update the minimum size if min == initial == max. 468 if (_max_heap_byte_size == _min_heap_byte_size) { 469 _min_young_size = _max_young_size; 470 } 471 } else { 472 if (FLAG_IS_CMDLINE(NewSize)) { 473 // If NewSize is set on the command line, we should use it as 474 // the initial size, but make sure it is within the heap bounds. 475 _initial_young_size = 476 MIN2(_max_young_size, bound_minus_alignment(NewSize, _initial_heap_byte_size)); 477 _min_young_size = bound_minus_alignment(_initial_young_size, _min_heap_byte_size); 478 } else { 479 // For the case where NewSize is not set on the command line, use 480 // NewRatio to size the initial generation size. Use the current 481 // NewSize as the floor, because if NewRatio is overly large, the resulting 482 // size can be too small. 483 _initial_young_size = 484 MIN2(_max_young_size, MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize)); 485 } 486 } 487 488 log_trace(gc, heap)("1: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT, 489 _min_young_size, _initial_young_size, _max_young_size); 490 491 // At this point the minimum, initial and maximum sizes 492 // of the overall heap and of the young generation have been determined. 493 // The maximum old size can be determined from the maximum young 494 // and maximum heap size since no explicit flags exist 495 // for setting the old generation maximum. 496 _max_old_size = MAX2(_max_heap_byte_size - _max_young_size, _gen_alignment); 497 498 // If no explicit command line flag has been set for the 499 // old generation size, use what is left. 500 if (!FLAG_IS_CMDLINE(OldSize)) { 501 // The user has not specified any value but the ergonomics 502 // may have chosen a value (which may or may not be consistent 503 // with the overall heap size). In either case make 504 // the minimum, maximum and initial sizes consistent 505 // with the young sizes and the overall heap sizes. 506 _min_old_size = _gen_alignment; 507 _initial_old_size = MIN2(_max_old_size, MAX2(_initial_heap_byte_size - _initial_young_size, _min_old_size)); 508 // _max_old_size has already been made consistent above. 509 } else { 510 // OldSize has been explicitly set on the command line. Use it 511 // for the initial size but make sure the minimum allow a young 512 // generation to fit as well. 513 // If the user has explicitly set an OldSize that is inconsistent 514 // with other command line flags, issue a warning. 515 // The generation minimums and the overall heap minimum should 516 // be within one generation alignment. 517 if (_initial_old_size > _max_old_size) { 518 log_warning(gc, ergo)("Inconsistency between maximum heap size and maximum " 519 "generation sizes: using maximum heap = " SIZE_FORMAT 520 ", -XX:OldSize flag is being ignored", 521 _max_heap_byte_size); 522 _initial_old_size = _max_old_size; 523 } 524 525 _min_old_size = MIN2(_initial_old_size, _min_heap_byte_size - _min_young_size); 526 } 527 528 // The initial generation sizes should match the initial heap size, 529 // if not issue a warning and resize the generations. This behavior 530 // differs from JDK8 where the generation sizes have higher priority 531 // than the initial heap size. 532 if ((_initial_old_size + _initial_young_size) != _initial_heap_byte_size) { 533 log_warning(gc, ergo)("Inconsistency between generation sizes and heap size, resizing " 534 "the generations to fit the heap."); 535 536 size_t desired_young_size = _initial_heap_byte_size - _initial_old_size; 537 if (_initial_heap_byte_size < _initial_old_size) { 538 // Old want all memory, use minimum for young and rest for old 539 _initial_young_size = _min_young_size; 540 _initial_old_size = _initial_heap_byte_size - _min_young_size; 541 } else if (desired_young_size > _max_young_size) { 542 // Need to increase both young and old generation 543 _initial_young_size = _max_young_size; 544 _initial_old_size = _initial_heap_byte_size - _max_young_size; 545 } else if (desired_young_size < _min_young_size) { 546 // Need to decrease both young and old generation 547 _initial_young_size = _min_young_size; 548 _initial_old_size = _initial_heap_byte_size - _min_young_size; 549 } else { 550 // The young generation boundaries allow us to only update the 551 // young generation. 552 _initial_young_size = desired_young_size; 553 } 554 555 log_trace(gc, heap)("2: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT, 556 _min_young_size, _initial_young_size, _max_young_size); 557 } 558 559 // Write back to flags if necessary. 560 if (NewSize != _initial_young_size) { 561 FLAG_SET_ERGO(size_t, NewSize, _initial_young_size); 562 } 563 564 if (MaxNewSize != _max_young_size) { 565 FLAG_SET_ERGO(size_t, MaxNewSize, _max_young_size); 566 } 567 568 if (OldSize != _initial_old_size) { 569 FLAG_SET_ERGO(size_t, OldSize, _initial_old_size); 570 } 571 572 log_trace(gc, heap)("Minimum old " SIZE_FORMAT " Initial old " SIZE_FORMAT " Maximum old " SIZE_FORMAT, 573 _min_old_size, _initial_old_size, _max_old_size); 574 575 DEBUG_ONLY(GenCollectorPolicy::assert_size_info();) 576 } 577 578 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size, 579 bool is_tlab, 580 bool* gc_overhead_limit_was_exceeded) { 581 GenCollectedHeap *gch = GenCollectedHeap::heap(); 582 583 debug_only(gch->check_for_valid_allocation_state()); 584 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed"); 585 586 // In general gc_overhead_limit_was_exceeded should be false so 587 // set it so here and reset it to true only if the gc time 588 // limit is being exceeded as checked below. 589 *gc_overhead_limit_was_exceeded = false; 590 591 HeapWord* result = NULL; 592 593 // Loop until the allocation is satisfied, or unsatisfied after GC. 594 for (uint try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) { 595 HandleMark hm; // Discard any handles allocated in each iteration. 596 597 // First allocation attempt is lock-free. 598 Generation *young = gch->young_gen(); 599 assert(young->supports_inline_contig_alloc(), 600 "Otherwise, must do alloc within heap lock"); 601 if (young->should_allocate(size, is_tlab)) { 602 result = young->par_allocate(size, is_tlab); 603 if (result != NULL) { 604 assert(gch->is_in_reserved(result), "result not in heap"); 605 return result; 606 } 607 } 608 uint gc_count_before; // Read inside the Heap_lock locked region. 609 { 610 MutexLocker ml(Heap_lock); 611 log_trace(gc, alloc)("GenCollectorPolicy::mem_allocate_work: attempting locked slow path allocation"); 612 // Note that only large objects get a shot at being 613 // allocated in later generations. 614 bool first_only = ! should_try_older_generation_allocation(size); 615 616 result = gch->attempt_allocation(size, is_tlab, first_only); 617 if (result != NULL) { 618 assert(gch->is_in_reserved(result), "result not in heap"); 619 return result; 620 } 621 622 if (GCLocker::is_active_and_needs_gc()) { 623 if (is_tlab) { 624 return NULL; // Caller will retry allocating individual object. 625 } 626 if (!gch->is_maximal_no_gc()) { 627 // Try and expand heap to satisfy request. 628 result = expand_heap_and_allocate(size, is_tlab); 629 // Result could be null if we are out of space. 630 if (result != NULL) { 631 return result; 632 } 633 } 634 635 if (gclocker_stalled_count > GCLockerRetryAllocationCount) { 636 return NULL; // We didn't get to do a GC and we didn't get any memory. 637 } 638 639 // If this thread is not in a jni critical section, we stall 640 // the requestor until the critical section has cleared and 641 // GC allowed. When the critical section clears, a GC is 642 // initiated by the last thread exiting the critical section; so 643 // we retry the allocation sequence from the beginning of the loop, 644 // rather than causing more, now probably unnecessary, GC attempts. 645 JavaThread* jthr = JavaThread::current(); 646 if (!jthr->in_critical()) { 647 MutexUnlocker mul(Heap_lock); 648 // Wait for JNI critical section to be exited 649 GCLocker::stall_until_clear(); 650 gclocker_stalled_count += 1; 651 continue; 652 } else { 653 if (CheckJNICalls) { 654 fatal("Possible deadlock due to allocating while" 655 " in jni critical section"); 656 } 657 return NULL; 658 } 659 } 660 661 // Read the gc count while the heap lock is held. 662 gc_count_before = gch->total_collections(); 663 } 664 665 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before); 666 VMThread::execute(&op); 667 if (op.prologue_succeeded()) { 668 result = op.result(); 669 if (op.gc_locked()) { 670 assert(result == NULL, "must be NULL if gc_locked() is true"); 671 continue; // Retry and/or stall as necessary. 672 } 673 674 // Allocation has failed and a collection 675 // has been done. If the gc time limit was exceeded the 676 // this time, return NULL so that an out-of-memory 677 // will be thrown. Clear gc_overhead_limit_exceeded 678 // so that the overhead exceeded does not persist. 679 680 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded(); 681 const bool softrefs_clear = all_soft_refs_clear(); 682 683 if (limit_exceeded && softrefs_clear) { 684 *gc_overhead_limit_was_exceeded = true; 685 size_policy()->set_gc_overhead_limit_exceeded(false); 686 if (op.result() != NULL) { 687 CollectedHeap::fill_with_object(op.result(), size); 688 } 689 return NULL; 690 } 691 assert(result == NULL || gch->is_in_reserved(result), 692 "result not in heap"); 693 return result; 694 } 695 696 // Give a warning if we seem to be looping forever. 697 if ((QueuedAllocationWarningCount > 0) && 698 (try_count % QueuedAllocationWarningCount == 0)) { 699 log_warning(gc, ergo)("GenCollectorPolicy::mem_allocate_work retries %d times," 700 " size=" SIZE_FORMAT " %s", try_count, size, is_tlab ? "(TLAB)" : ""); 701 } 702 } 703 } 704 705 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size, 706 bool is_tlab) { 707 GenCollectedHeap *gch = GenCollectedHeap::heap(); 708 HeapWord* result = NULL; 709 Generation *old = gch->old_gen(); 710 if (old->should_allocate(size, is_tlab)) { 711 result = old->expand_and_allocate(size, is_tlab); 712 } 713 if (result == NULL) { 714 Generation *young = gch->young_gen(); 715 if (young->should_allocate(size, is_tlab)) { 716 result = young->expand_and_allocate(size, is_tlab); 717 } 718 } 719 assert(result == NULL || gch->is_in_reserved(result), "result not in heap"); 720 return result; 721 } 722 723 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size, 724 bool is_tlab) { 725 GenCollectedHeap *gch = GenCollectedHeap::heap(); 726 GCCauseSetter x(gch, GCCause::_allocation_failure); 727 HeapWord* result = NULL; 728 729 assert(size != 0, "Precondition violated"); 730 if (GCLocker::is_active_and_needs_gc()) { 731 // GC locker is active; instead of a collection we will attempt 732 // to expand the heap, if there's room for expansion. 733 if (!gch->is_maximal_no_gc()) { 734 result = expand_heap_and_allocate(size, is_tlab); 735 } 736 return result; // Could be null if we are out of space. 737 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) { 738 // Do an incremental collection. 739 gch->do_collection(false, // full 740 false, // clear_all_soft_refs 741 size, // size 742 is_tlab, // is_tlab 743 GenCollectedHeap::OldGen); // max_generation 744 } else { 745 log_trace(gc)(" :: Trying full because partial may fail :: "); 746 // Try a full collection; see delta for bug id 6266275 747 // for the original code and why this has been simplified 748 // with from-space allocation criteria modified and 749 // such allocation moved out of the safepoint path. 750 gch->do_collection(true, // full 751 false, // clear_all_soft_refs 752 size, // size 753 is_tlab, // is_tlab 754 GenCollectedHeap::OldGen); // max_generation 755 } 756 757 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/); 758 759 if (result != NULL) { 760 assert(gch->is_in_reserved(result), "result not in heap"); 761 return result; 762 } 763 764 // OK, collection failed, try expansion. 765 result = expand_heap_and_allocate(size, is_tlab); 766 if (result != NULL) { 767 return result; 768 } 769 770 // If we reach this point, we're really out of memory. Try every trick 771 // we can to reclaim memory. Force collection of soft references. Force 772 // a complete compaction of the heap. Any additional methods for finding 773 // free memory should be here, especially if they are expensive. If this 774 // attempt fails, an OOM exception will be thrown. 775 { 776 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted 777 778 gch->do_collection(true, // full 779 true, // clear_all_soft_refs 780 size, // size 781 is_tlab, // is_tlab 782 GenCollectedHeap::OldGen); // max_generation 783 } 784 785 result = gch->attempt_allocation(size, is_tlab, false /* first_only */); 786 if (result != NULL) { 787 assert(gch->is_in_reserved(result), "result not in heap"); 788 return result; 789 } 790 791 assert(!should_clear_all_soft_refs(), 792 "Flag should have been handled and cleared prior to this point"); 793 794 // What else? We might try synchronous finalization later. If the total 795 // space available is large enough for the allocation, then a more 796 // complete compaction phase than we've tried so far might be 797 // appropriate. 798 return NULL; 799 } 800 801 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation( 802 ClassLoaderData* loader_data, 803 size_t word_size, 804 Metaspace::MetadataType mdtype) { 805 uint loop_count = 0; 806 uint gc_count = 0; 807 uint full_gc_count = 0; 808 809 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock"); 810 811 do { 812 MetaWord* result = loader_data->metaspace_non_null()->allocate(word_size, mdtype); 813 if (result != NULL) { 814 return result; 815 } 816 817 if (GCLocker::is_active_and_needs_gc()) { 818 // If the GCLocker is active, just expand and allocate. 819 // If that does not succeed, wait if this thread is not 820 // in a critical section itself. 821 result = 822 loader_data->metaspace_non_null()->expand_and_allocate(word_size, 823 mdtype); 824 if (result != NULL) { 825 return result; 826 } 827 JavaThread* jthr = JavaThread::current(); 828 if (!jthr->in_critical()) { 829 // Wait for JNI critical section to be exited 830 GCLocker::stall_until_clear(); 831 // The GC invoked by the last thread leaving the critical 832 // section will be a young collection and a full collection 833 // is (currently) needed for unloading classes so continue 834 // to the next iteration to get a full GC. 835 continue; 836 } else { 837 if (CheckJNICalls) { 838 fatal("Possible deadlock due to allocating while" 839 " in jni critical section"); 840 } 841 return NULL; 842 } 843 } 844 845 { // Need lock to get self consistent gc_count's 846 MutexLocker ml(Heap_lock); 847 gc_count = Universe::heap()->total_collections(); 848 full_gc_count = Universe::heap()->total_full_collections(); 849 } 850 851 // Generate a VM operation 852 VM_CollectForMetadataAllocation op(loader_data, 853 word_size, 854 mdtype, 855 gc_count, 856 full_gc_count, 857 GCCause::_metadata_GC_threshold); 858 VMThread::execute(&op); 859 860 // If GC was locked out, try again. Check before checking success because the 861 // prologue could have succeeded and the GC still have been locked out. 862 if (op.gc_locked()) { 863 continue; 864 } 865 866 if (op.prologue_succeeded()) { 867 return op.result(); 868 } 869 loop_count++; 870 if ((QueuedAllocationWarningCount > 0) && 871 (loop_count % QueuedAllocationWarningCount == 0)) { 872 log_warning(gc, ergo)("satisfy_failed_metadata_allocation() retries %d times," 873 " size=" SIZE_FORMAT, loop_count, word_size); 874 } 875 } while (true); // Until a GC is done 876 } 877 878 // Return true if any of the following is true: 879 // . the allocation won't fit into the current young gen heap 880 // . gc locker is occupied (jni critical section) 881 // . heap memory is tight -- the most recent previous collection 882 // was a full collection because a partial collection (would 883 // have) failed and is likely to fail again 884 bool GenCollectorPolicy::should_try_older_generation_allocation( 885 size_t word_size) const { 886 GenCollectedHeap* gch = GenCollectedHeap::heap(); 887 size_t young_capacity = gch->young_gen()->capacity_before_gc(); 888 return (word_size > heap_word_size(young_capacity)) 889 || GCLocker::is_active_and_needs_gc() 890 || gch->incremental_collection_failed(); 891 } 892 893 894 // 895 // MarkSweepPolicy methods 896 // 897 898 void MarkSweepPolicy::initialize_alignments() { 899 _space_alignment = _gen_alignment = (size_t)Generation::GenGrain; 900 _heap_alignment = compute_heap_alignment(); 901 } 902 903 void MarkSweepPolicy::initialize_generations() { 904 _young_gen_spec = new GenerationSpec(Generation::DefNew, _initial_young_size, _max_young_size, _gen_alignment); 905 _old_gen_spec = new GenerationSpec(Generation::MarkSweepCompact, _initial_old_size, _max_old_size, _gen_alignment); 906 } 907 908 void MarkSweepPolicy::initialize_gc_policy_counters() { 909 // Initialize the policy counters - 2 collectors, 3 generations. 910 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3); 911 } 912