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/macros.hpp" 44 45 // CollectorPolicy methods 46 47 CollectorPolicy::CollectorPolicy() : 48 _space_alignment(0), 49 _heap_alignment(0), 50 _initial_heap_byte_size(InitialHeapSize), 51 _max_heap_byte_size(MaxHeapSize), 52 _min_heap_byte_size(Arguments::min_heap_size()), 53 _size_policy(NULL), 54 _should_clear_all_soft_refs(false), 55 _all_soft_refs_clear(false) 56 {} 57 58 #ifdef ASSERT 59 void CollectorPolicy::assert_flags() { 60 assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes"); 61 assert(InitialHeapSize % _heap_alignment == 0, "InitialHeapSize alignment"); 62 assert(MaxHeapSize % _heap_alignment == 0, "MaxHeapSize alignment"); 63 } 64 65 void CollectorPolicy::assert_size_info() { 66 assert(InitialHeapSize == _initial_heap_byte_size, "Discrepancy between InitialHeapSize flag and local storage"); 67 assert(MaxHeapSize == _max_heap_byte_size, "Discrepancy between MaxHeapSize flag and local storage"); 68 assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes"); 69 assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes"); 70 assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes"); 71 assert(_min_heap_byte_size % _heap_alignment == 0, "min_heap_byte_size alignment"); 72 assert(_initial_heap_byte_size % _heap_alignment == 0, "initial_heap_byte_size alignment"); 73 assert(_max_heap_byte_size % _heap_alignment == 0, "max_heap_byte_size alignment"); 74 } 75 #endif // ASSERT 76 77 void CollectorPolicy::initialize_flags() { 78 assert(_space_alignment != 0, "Space alignment not set up properly"); 79 assert(_heap_alignment != 0, "Heap alignment not set up properly"); 80 assert(_heap_alignment >= _space_alignment, 81 "heap_alignment: " SIZE_FORMAT " less than space_alignment: " SIZE_FORMAT, 82 _heap_alignment, _space_alignment); 83 assert(_heap_alignment % _space_alignment == 0, 84 "heap_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT, 85 _heap_alignment, _space_alignment); 86 87 if (FLAG_IS_CMDLINE(MaxHeapSize)) { 88 if (FLAG_IS_CMDLINE(InitialHeapSize) && InitialHeapSize > MaxHeapSize) { 89 vm_exit_during_initialization("Initial heap size set to a larger value than the maximum heap size"); 90 } 91 if (_min_heap_byte_size != 0 && MaxHeapSize < _min_heap_byte_size) { 92 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified"); 93 } 94 } 95 96 // Check heap parameter properties 97 if (MaxHeapSize < 2 * M) { 98 vm_exit_during_initialization("Too small maximum heap"); 99 } 100 if (InitialHeapSize < M) { 101 vm_exit_during_initialization("Too small initial heap"); 102 } 103 if (_min_heap_byte_size < M) { 104 vm_exit_during_initialization("Too small minimum heap"); 105 } 106 107 // User inputs from -Xmx and -Xms must be aligned 108 _min_heap_byte_size = align_size_up(_min_heap_byte_size, _heap_alignment); 109 size_t aligned_initial_heap_size = align_size_up(InitialHeapSize, _heap_alignment); 110 size_t aligned_max_heap_size = align_size_up(MaxHeapSize, _heap_alignment); 111 112 // Write back to flags if the values changed 113 if (aligned_initial_heap_size != InitialHeapSize) { 114 FLAG_SET_ERGO(size_t, InitialHeapSize, aligned_initial_heap_size); 115 } 116 if (aligned_max_heap_size != MaxHeapSize) { 117 FLAG_SET_ERGO(size_t, MaxHeapSize, aligned_max_heap_size); 118 } 119 120 if (FLAG_IS_CMDLINE(InitialHeapSize) && _min_heap_byte_size != 0 && 121 InitialHeapSize < _min_heap_byte_size) { 122 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified"); 123 } 124 if (!FLAG_IS_DEFAULT(InitialHeapSize) && InitialHeapSize > MaxHeapSize) { 125 FLAG_SET_ERGO(size_t, MaxHeapSize, InitialHeapSize); 126 } else if (!FLAG_IS_DEFAULT(MaxHeapSize) && InitialHeapSize > MaxHeapSize) { 127 FLAG_SET_ERGO(size_t, InitialHeapSize, MaxHeapSize); 128 if (InitialHeapSize < _min_heap_byte_size) { 129 _min_heap_byte_size = InitialHeapSize; 130 } 131 } 132 133 _initial_heap_byte_size = InitialHeapSize; 134 _max_heap_byte_size = MaxHeapSize; 135 136 FLAG_SET_ERGO(size_t, MinHeapDeltaBytes, align_size_up(MinHeapDeltaBytes, _space_alignment)); 137 138 DEBUG_ONLY(CollectorPolicy::assert_flags();) 139 } 140 141 void CollectorPolicy::initialize_size_info() { 142 log_debug(gc, heap)("Minimum heap " SIZE_FORMAT " Initial heap " SIZE_FORMAT " Maximum heap " SIZE_FORMAT, 143 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size); 144 145 DEBUG_ONLY(CollectorPolicy::assert_size_info();) 146 } 147 148 bool CollectorPolicy::use_should_clear_all_soft_refs(bool v) { 149 bool result = _should_clear_all_soft_refs; 150 set_should_clear_all_soft_refs(false); 151 return result; 152 } 153 154 CardTableRS* CollectorPolicy::create_rem_set(MemRegion whole_heap) { 155 return new CardTableRS(whole_heap); 156 } 157 158 void CollectorPolicy::cleared_all_soft_refs() { 159 // If near gc overhear limit, continue to clear SoftRefs. SoftRefs may 160 // have been cleared in the last collection but if the gc overhear 161 // limit continues to be near, SoftRefs should still be cleared. 162 if (size_policy() != NULL) { 163 _should_clear_all_soft_refs = size_policy()->gc_overhead_limit_near(); 164 } 165 _all_soft_refs_clear = true; 166 } 167 168 size_t CollectorPolicy::compute_heap_alignment() { 169 // The card marking array and the offset arrays for old generations are 170 // committed in os pages as well. Make sure they are entirely full (to 171 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1 172 // byte entry and the os page size is 4096, the maximum heap size should 173 // be 512*4096 = 2MB aligned. 174 175 size_t alignment = CardTableRS::ct_max_alignment_constraint(); 176 177 if (UseLargePages) { 178 // In presence of large pages we have to make sure that our 179 // alignment is large page aware. 180 alignment = lcm(os::large_page_size(), alignment); 181 } 182 183 return alignment; 184 } 185 186 // GenCollectorPolicy methods 187 188 GenCollectorPolicy::GenCollectorPolicy() : 189 _min_young_size(0), 190 _initial_young_size(0), 191 _max_young_size(0), 192 _min_old_size(0), 193 _initial_old_size(0), 194 _max_old_size(0), 195 _gen_alignment(0), 196 _young_gen_spec(NULL), 197 _old_gen_spec(NULL) 198 {} 199 200 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) { 201 return align_size_down_bounded(base_size / (NewRatio + 1), _gen_alignment); 202 } 203 204 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size, 205 size_t maximum_size) { 206 size_t max_minus = maximum_size - _gen_alignment; 207 return desired_size < max_minus ? desired_size : max_minus; 208 } 209 210 211 void GenCollectorPolicy::initialize_size_policy(size_t init_eden_size, 212 size_t init_promo_size, 213 size_t init_survivor_size) { 214 const double max_gc_pause_sec = ((double) MaxGCPauseMillis) / 1000.0; 215 _size_policy = new AdaptiveSizePolicy(init_eden_size, 216 init_promo_size, 217 init_survivor_size, 218 max_gc_pause_sec, 219 GCTimeRatio); 220 } 221 222 size_t GenCollectorPolicy::young_gen_size_lower_bound() { 223 // The young generation must be aligned and have room for eden + two survivors 224 return align_size_up(3 * _space_alignment, _gen_alignment); 225 } 226 227 size_t GenCollectorPolicy::old_gen_size_lower_bound() { 228 return align_size_up(_space_alignment, _gen_alignment); 229 } 230 231 #ifdef ASSERT 232 void GenCollectorPolicy::assert_flags() { 233 CollectorPolicy::assert_flags(); 234 assert(NewSize >= _min_young_size, "Ergonomics decided on a too small young gen size"); 235 assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes"); 236 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes"); 237 assert(NewSize % _gen_alignment == 0, "NewSize alignment"); 238 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _gen_alignment == 0, "MaxNewSize alignment"); 239 assert(OldSize + NewSize <= MaxHeapSize, "Ergonomics decided on incompatible generation and heap sizes"); 240 assert(OldSize % _gen_alignment == 0, "OldSize alignment"); 241 } 242 243 void GenCollectorPolicy::assert_size_info() { 244 CollectorPolicy::assert_size_info(); 245 // GenCollectorPolicy::initialize_size_info may update the MaxNewSize 246 assert(MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young and heap sizes"); 247 assert(NewSize == _initial_young_size, "Discrepancy between NewSize flag and local storage"); 248 assert(MaxNewSize == _max_young_size, "Discrepancy between MaxNewSize flag and local storage"); 249 assert(OldSize == _initial_old_size, "Discrepancy between OldSize flag and local storage"); 250 assert(_min_young_size <= _initial_young_size, "Ergonomics decided on incompatible minimum and initial young gen sizes"); 251 assert(_initial_young_size <= _max_young_size, "Ergonomics decided on incompatible initial and maximum young gen sizes"); 252 assert(_min_young_size % _gen_alignment == 0, "_min_young_size alignment"); 253 assert(_initial_young_size % _gen_alignment == 0, "_initial_young_size alignment"); 254 assert(_max_young_size % _gen_alignment == 0, "_max_young_size alignment"); 255 assert(_min_young_size <= bound_minus_alignment(_min_young_size, _min_heap_byte_size), 256 "Ergonomics made minimum young generation larger than minimum heap"); 257 assert(_initial_young_size <= bound_minus_alignment(_initial_young_size, _initial_heap_byte_size), 258 "Ergonomics made initial young generation larger than initial heap"); 259 assert(_max_young_size <= bound_minus_alignment(_max_young_size, _max_heap_byte_size), 260 "Ergonomics made maximum young generation lager than maximum heap"); 261 assert(_min_old_size <= _initial_old_size, "Ergonomics decided on incompatible minimum and initial old gen sizes"); 262 assert(_initial_old_size <= _max_old_size, "Ergonomics decided on incompatible initial and maximum old gen sizes"); 263 assert(_max_old_size % _gen_alignment == 0, "_max_old_size alignment"); 264 assert(_initial_old_size % _gen_alignment == 0, "_initial_old_size alignment"); 265 assert(_max_heap_byte_size <= (_max_young_size + _max_old_size), "Total maximum heap sizes must be sum of generation maximum sizes"); 266 assert(_min_young_size + _min_old_size <= _min_heap_byte_size, "Minimum generation sizes exceed minimum heap size"); 267 assert(_initial_young_size + _initial_old_size == _initial_heap_byte_size, "Initial generation sizes should match initial heap size"); 268 assert(_max_young_size + _max_old_size == _max_heap_byte_size, "Maximum generation sizes should match maximum heap size"); 269 } 270 #endif // ASSERT 271 272 void GenCollectorPolicy::initialize_flags() { 273 CollectorPolicy::initialize_flags(); 274 275 assert(_gen_alignment != 0, "Generation alignment not set up properly"); 276 assert(_heap_alignment >= _gen_alignment, 277 "heap_alignment: " SIZE_FORMAT " less than gen_alignment: " SIZE_FORMAT, 278 _heap_alignment, _gen_alignment); 279 assert(_gen_alignment % _space_alignment == 0, 280 "gen_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT, 281 _gen_alignment, _space_alignment); 282 assert(_heap_alignment % _gen_alignment == 0, 283 "heap_alignment: " SIZE_FORMAT " not aligned by gen_alignment: " SIZE_FORMAT, 284 _heap_alignment, _gen_alignment); 285 286 // All generational heaps have a young gen; handle those flags here 287 288 // Make sure the heap is large enough for two generations 289 size_t smallest_new_size = young_gen_size_lower_bound(); 290 size_t smallest_heap_size = align_size_up(smallest_new_size + old_gen_size_lower_bound(), 291 _heap_alignment); 292 if (MaxHeapSize < smallest_heap_size) { 293 FLAG_SET_ERGO(size_t, MaxHeapSize, smallest_heap_size); 294 _max_heap_byte_size = MaxHeapSize; 295 } 296 // If needed, synchronize _min_heap_byte size and _initial_heap_byte_size 297 if (_min_heap_byte_size < smallest_heap_size) { 298 _min_heap_byte_size = smallest_heap_size; 299 if (InitialHeapSize < _min_heap_byte_size) { 300 FLAG_SET_ERGO(size_t, InitialHeapSize, smallest_heap_size); 301 _initial_heap_byte_size = smallest_heap_size; 302 } 303 } 304 305 // Make sure NewSize allows an old generation to fit even if set on the command line 306 if (FLAG_IS_CMDLINE(NewSize) && NewSize >= _initial_heap_byte_size) { 307 log_warning(gc, ergo)("NewSize was set larger than initial heap size, will use initial heap size."); 308 FLAG_SET_ERGO(size_t, NewSize, bound_minus_alignment(NewSize, _initial_heap_byte_size)); 309 } 310 311 // Now take the actual NewSize into account. We will silently increase NewSize 312 // if the user specified a smaller or unaligned value. 313 size_t bounded_new_size = bound_minus_alignment(NewSize, MaxHeapSize); 314 bounded_new_size = MAX2(smallest_new_size, (size_t)align_size_down(bounded_new_size, _gen_alignment)); 315 if (bounded_new_size != NewSize) { 316 FLAG_SET_ERGO(size_t, NewSize, bounded_new_size); 317 } 318 _min_young_size = smallest_new_size; 319 _initial_young_size = NewSize; 320 321 if (!FLAG_IS_DEFAULT(MaxNewSize)) { 322 if (MaxNewSize >= MaxHeapSize) { 323 // Make sure there is room for an old generation 324 size_t smaller_max_new_size = MaxHeapSize - _gen_alignment; 325 if (FLAG_IS_CMDLINE(MaxNewSize)) { 326 log_warning(gc, ergo)("MaxNewSize (" SIZE_FORMAT "k) is equal to or greater than the entire " 327 "heap (" SIZE_FORMAT "k). A new max generation size of " SIZE_FORMAT "k will be used.", 328 MaxNewSize/K, MaxHeapSize/K, smaller_max_new_size/K); 329 } 330 FLAG_SET_ERGO(size_t, MaxNewSize, smaller_max_new_size); 331 if (NewSize > MaxNewSize) { 332 FLAG_SET_ERGO(size_t, NewSize, MaxNewSize); 333 _initial_young_size = NewSize; 334 } 335 } else if (MaxNewSize < _initial_young_size) { 336 FLAG_SET_ERGO(size_t, MaxNewSize, _initial_young_size); 337 } else if (!is_size_aligned(MaxNewSize, _gen_alignment)) { 338 FLAG_SET_ERGO(size_t, MaxNewSize, align_size_down(MaxNewSize, _gen_alignment)); 339 } 340 _max_young_size = MaxNewSize; 341 } 342 343 if (NewSize > MaxNewSize) { 344 // At this point this should only happen if the user specifies a large NewSize and/or 345 // a small (but not too small) MaxNewSize. 346 if (FLAG_IS_CMDLINE(MaxNewSize)) { 347 log_warning(gc, ergo)("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). " 348 "A new max generation size of " SIZE_FORMAT "k will be used.", 349 NewSize/K, MaxNewSize/K, NewSize/K); 350 } 351 FLAG_SET_ERGO(size_t, MaxNewSize, NewSize); 352 _max_young_size = MaxNewSize; 353 } 354 355 if (SurvivorRatio < 1 || NewRatio < 1) { 356 vm_exit_during_initialization("Invalid young gen ratio specified"); 357 } 358 359 if (OldSize < old_gen_size_lower_bound()) { 360 FLAG_SET_ERGO(size_t, OldSize, old_gen_size_lower_bound()); 361 } 362 if (!is_size_aligned(OldSize, _gen_alignment)) { 363 FLAG_SET_ERGO(size_t, OldSize, align_size_down(OldSize, _gen_alignment)); 364 } 365 366 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(MaxHeapSize)) { 367 // NewRatio will be used later to set the young generation size so we use 368 // it to calculate how big the heap should be based on the requested OldSize 369 // and NewRatio. 370 assert(NewRatio > 0, "NewRatio should have been set up earlier"); 371 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1); 372 373 calculated_heapsize = align_size_up(calculated_heapsize, _heap_alignment); 374 FLAG_SET_ERGO(size_t, MaxHeapSize, calculated_heapsize); 375 _max_heap_byte_size = MaxHeapSize; 376 FLAG_SET_ERGO(size_t, InitialHeapSize, calculated_heapsize); 377 _initial_heap_byte_size = InitialHeapSize; 378 } 379 380 // Adjust NewSize and OldSize or MaxHeapSize to match each other 381 if (NewSize + OldSize > MaxHeapSize) { 382 if (FLAG_IS_CMDLINE(MaxHeapSize)) { 383 // Somebody has set a maximum heap size with the intention that we should not 384 // exceed it. Adjust New/OldSize as necessary. 385 size_t calculated_size = NewSize + OldSize; 386 double shrink_factor = (double) MaxHeapSize / calculated_size; 387 size_t smaller_new_size = align_size_down((size_t)(NewSize * shrink_factor), _gen_alignment); 388 FLAG_SET_ERGO(size_t, NewSize, MAX2(young_gen_size_lower_bound(), smaller_new_size)); 389 _initial_young_size = NewSize; 390 391 // OldSize is already aligned because above we aligned MaxHeapSize to 392 // _heap_alignment, and we just made sure that NewSize is aligned to 393 // _gen_alignment. In initialize_flags() we verified that _heap_alignment 394 // is a multiple of _gen_alignment. 395 FLAG_SET_ERGO(size_t, OldSize, MaxHeapSize - NewSize); 396 } else { 397 FLAG_SET_ERGO(size_t, MaxHeapSize, align_size_up(NewSize + OldSize, _heap_alignment)); 398 _max_heap_byte_size = MaxHeapSize; 399 } 400 } 401 402 // Update NewSize, if possible, to avoid sizing the young gen too small when only 403 // OldSize is set on the command line. 404 if (FLAG_IS_CMDLINE(OldSize) && !FLAG_IS_CMDLINE(NewSize)) { 405 if (OldSize < _initial_heap_byte_size) { 406 size_t new_size = _initial_heap_byte_size - OldSize; 407 // Need to compare against the flag value for max since _max_young_size 408 // might not have been set yet. 409 if (new_size >= _min_young_size && new_size <= MaxNewSize) { 410 FLAG_SET_ERGO(size_t, NewSize, new_size); 411 _initial_young_size = NewSize; 412 } 413 } 414 } 415 416 always_do_update_barrier = UseConcMarkSweepGC; 417 418 DEBUG_ONLY(GenCollectorPolicy::assert_flags();) 419 } 420 421 // Values set on the command line win over any ergonomically 422 // set command line parameters. 423 // Ergonomic choice of parameters are done before this 424 // method is called. Values for command line parameters such as NewSize 425 // and MaxNewSize feed those ergonomic choices into this method. 426 // This method makes the final generation sizings consistent with 427 // themselves and with overall heap sizings. 428 // In the absence of explicitly set command line flags, policies 429 // such as the use of NewRatio are used to size the generation. 430 431 // Minimum sizes of the generations may be different than 432 // the initial sizes. An inconsistency is permitted here 433 // in the total size that can be specified explicitly by 434 // command line specification of OldSize and NewSize and 435 // also a command line specification of -Xms. Issue a warning 436 // but allow the values to pass. 437 void GenCollectorPolicy::initialize_size_info() { 438 CollectorPolicy::initialize_size_info(); 439 440 _initial_young_size = NewSize; 441 _max_young_size = MaxNewSize; 442 _initial_old_size = OldSize; 443 444 // Determine maximum size of the young generation. 445 446 if (FLAG_IS_DEFAULT(MaxNewSize)) { 447 _max_young_size = scale_by_NewRatio_aligned(_max_heap_byte_size); 448 // Bound the maximum size by NewSize below (since it historically 449 // would have been NewSize and because the NewRatio calculation could 450 // yield a size that is too small) and bound it by MaxNewSize above. 451 // Ergonomics plays here by previously calculating the desired 452 // NewSize and MaxNewSize. 453 _max_young_size = MIN2(MAX2(_max_young_size, _initial_young_size), MaxNewSize); 454 } 455 456 // Given the maximum young size, determine the initial and 457 // minimum young sizes. 458 459 if (_max_heap_byte_size == _initial_heap_byte_size) { 460 // The maximum and initial heap sizes are the same so the generation's 461 // initial size must be the same as it maximum size. Use NewSize as the 462 // size if set on command line. 463 _max_young_size = FLAG_IS_CMDLINE(NewSize) ? NewSize : _max_young_size; 464 _initial_young_size = _max_young_size; 465 466 // Also update the minimum size if min == initial == max. 467 if (_max_heap_byte_size == _min_heap_byte_size) { 468 _min_young_size = _max_young_size; 469 } 470 } else { 471 if (FLAG_IS_CMDLINE(NewSize)) { 472 // If NewSize is set on the command line, we should use it as 473 // the initial size, but make sure it is within the heap bounds. 474 _initial_young_size = 475 MIN2(_max_young_size, bound_minus_alignment(NewSize, _initial_heap_byte_size)); 476 _min_young_size = bound_minus_alignment(_initial_young_size, _min_heap_byte_size); 477 } else { 478 // For the case where NewSize is not set on the command line, use 479 // NewRatio to size the initial generation size. Use the current 480 // NewSize as the floor, because if NewRatio is overly large, the resulting 481 // size can be too small. 482 _initial_young_size = 483 MIN2(_max_young_size, MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize)); 484 } 485 } 486 487 log_trace(gc, heap)("1: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT, 488 _min_young_size, _initial_young_size, _max_young_size); 489 490 // At this point the minimum, initial and maximum sizes 491 // of the overall heap and of the young generation have been determined. 492 // The maximum old size can be determined from the maximum young 493 // and maximum heap size since no explicit flags exist 494 // for setting the old generation maximum. 495 _max_old_size = MAX2(_max_heap_byte_size - _max_young_size, _gen_alignment); 496 497 // If no explicit command line flag has been set for the 498 // old generation size, use what is left. 499 if (!FLAG_IS_CMDLINE(OldSize)) { 500 // The user has not specified any value but the ergonomics 501 // may have chosen a value (which may or may not be consistent 502 // with the overall heap size). In either case make 503 // the minimum, maximum and initial sizes consistent 504 // with the young sizes and the overall heap sizes. 505 _min_old_size = _gen_alignment; 506 _initial_old_size = MIN2(_max_old_size, MAX2(_initial_heap_byte_size - _initial_young_size, _min_old_size)); 507 // _max_old_size has already been made consistent above. 508 } else { 509 // OldSize has been explicitly set on the command line. Use it 510 // for the initial size but make sure the minimum allow a young 511 // generation to fit as well. 512 // If the user has explicitly set an OldSize that is inconsistent 513 // with other command line flags, issue a warning. 514 // The generation minimums and the overall heap minimum should 515 // be within one generation alignment. 516 if (_initial_old_size > _max_old_size) { 517 log_warning(gc, ergo)("Inconsistency between maximum heap size and maximum " 518 "generation sizes: using maximum heap = " SIZE_FORMAT 519 ", -XX:OldSize flag is being ignored", 520 _max_heap_byte_size); 521 _initial_old_size = _max_old_size; 522 } 523 524 _min_old_size = MIN2(_initial_old_size, _min_heap_byte_size - _min_young_size); 525 } 526 527 // The initial generation sizes should match the initial heap size, 528 // if not issue a warning and resize the generations. This behavior 529 // differs from JDK8 where the generation sizes have higher priority 530 // than the initial heap size. 531 if ((_initial_old_size + _initial_young_size) != _initial_heap_byte_size) { 532 log_warning(gc, ergo)("Inconsistency between generation sizes and heap size, resizing " 533 "the generations to fit the heap."); 534 535 size_t desired_young_size = _initial_heap_byte_size - _initial_old_size; 536 if (_initial_heap_byte_size < _initial_old_size) { 537 // Old want all memory, use minimum for young and rest for old 538 _initial_young_size = _min_young_size; 539 _initial_old_size = _initial_heap_byte_size - _min_young_size; 540 } else if (desired_young_size > _max_young_size) { 541 // Need to increase both young and old generation 542 _initial_young_size = _max_young_size; 543 _initial_old_size = _initial_heap_byte_size - _max_young_size; 544 } else if (desired_young_size < _min_young_size) { 545 // Need to decrease both young and old generation 546 _initial_young_size = _min_young_size; 547 _initial_old_size = _initial_heap_byte_size - _min_young_size; 548 } else { 549 // The young generation boundaries allow us to only update the 550 // young generation. 551 _initial_young_size = desired_young_size; 552 } 553 554 log_trace(gc, heap)("2: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT, 555 _min_young_size, _initial_young_size, _max_young_size); 556 } 557 558 // Write back to flags if necessary. 559 if (NewSize != _initial_young_size) { 560 FLAG_SET_ERGO(size_t, NewSize, _initial_young_size); 561 } 562 563 if (MaxNewSize != _max_young_size) { 564 FLAG_SET_ERGO(size_t, MaxNewSize, _max_young_size); 565 } 566 567 if (OldSize != _initial_old_size) { 568 FLAG_SET_ERGO(size_t, OldSize, _initial_old_size); 569 } 570 571 log_trace(gc, heap)("Minimum old " SIZE_FORMAT " Initial old " SIZE_FORMAT " Maximum old " SIZE_FORMAT, 572 _min_old_size, _initial_old_size, _max_old_size); 573 574 DEBUG_ONLY(GenCollectorPolicy::assert_size_info();) 575 } 576 577 HeapWord* GenCollectorPolicy::mem_allocate_work(size_t size, 578 bool is_tlab, 579 bool* gc_overhead_limit_was_exceeded) { 580 GenCollectedHeap *gch = GenCollectedHeap::heap(); 581 582 debug_only(gch->check_for_valid_allocation_state()); 583 assert(gch->no_gc_in_progress(), "Allocation during gc not allowed"); 584 585 // In general gc_overhead_limit_was_exceeded should be false so 586 // set it so here and reset it to true only if the gc time 587 // limit is being exceeded as checked below. 588 *gc_overhead_limit_was_exceeded = false; 589 590 HeapWord* result = NULL; 591 592 // Loop until the allocation is satisfied, or unsatisfied after GC. 593 for (uint try_count = 1, gclocker_stalled_count = 0; /* return or throw */; try_count += 1) { 594 HandleMark hm; // Discard any handles allocated in each iteration. 595 596 // First allocation attempt is lock-free. 597 Generation *young = gch->young_gen(); 598 assert(young->supports_inline_contig_alloc(), 599 "Otherwise, must do alloc within heap lock"); 600 if (young->should_allocate(size, is_tlab)) { 601 result = young->par_allocate(size, is_tlab); 602 if (result != NULL) { 603 assert(gch->is_in_reserved(result), "result not in heap"); 604 return result; 605 } 606 } 607 uint gc_count_before; // Read inside the Heap_lock locked region. 608 { 609 MutexLocker ml(Heap_lock); 610 log_trace(gc, alloc)("GenCollectorPolicy::mem_allocate_work: attempting locked slow path allocation"); 611 // Note that only large objects get a shot at being 612 // allocated in later generations. 613 bool first_only = ! should_try_older_generation_allocation(size); 614 615 result = gch->attempt_allocation(size, is_tlab, first_only); 616 if (result != NULL) { 617 assert(gch->is_in_reserved(result), "result not in heap"); 618 return result; 619 } 620 621 if (GCLocker::is_active_and_needs_gc()) { 622 if (is_tlab) { 623 return NULL; // Caller will retry allocating individual object. 624 } 625 if (!gch->is_maximal_no_gc()) { 626 // Try and expand heap to satisfy request. 627 result = expand_heap_and_allocate(size, is_tlab); 628 // Result could be null if we are out of space. 629 if (result != NULL) { 630 return result; 631 } 632 } 633 634 if (gclocker_stalled_count > GCLockerRetryAllocationCount) { 635 return NULL; // We didn't get to do a GC and we didn't get any memory. 636 } 637 638 // If this thread is not in a jni critical section, we stall 639 // the requestor until the critical section has cleared and 640 // GC allowed. When the critical section clears, a GC is 641 // initiated by the last thread exiting the critical section; so 642 // we retry the allocation sequence from the beginning of the loop, 643 // rather than causing more, now probably unnecessary, GC attempts. 644 JavaThread* jthr = JavaThread::current(); 645 if (!jthr->in_critical()) { 646 MutexUnlocker mul(Heap_lock); 647 // Wait for JNI critical section to be exited 648 GCLocker::stall_until_clear(); 649 gclocker_stalled_count += 1; 650 continue; 651 } else { 652 if (CheckJNICalls) { 653 fatal("Possible deadlock due to allocating while" 654 " in jni critical section"); 655 } 656 return NULL; 657 } 658 } 659 660 // Read the gc count while the heap lock is held. 661 gc_count_before = gch->total_collections(); 662 } 663 664 VM_GenCollectForAllocation op(size, is_tlab, gc_count_before); 665 VMThread::execute(&op); 666 if (op.prologue_succeeded()) { 667 result = op.result(); 668 if (op.gc_locked()) { 669 assert(result == NULL, "must be NULL if gc_locked() is true"); 670 continue; // Retry and/or stall as necessary. 671 } 672 673 // Allocation has failed and a collection 674 // has been done. If the gc time limit was exceeded the 675 // this time, return NULL so that an out-of-memory 676 // will be thrown. Clear gc_overhead_limit_exceeded 677 // so that the overhead exceeded does not persist. 678 679 const bool limit_exceeded = size_policy()->gc_overhead_limit_exceeded(); 680 const bool softrefs_clear = all_soft_refs_clear(); 681 682 if (limit_exceeded && softrefs_clear) { 683 *gc_overhead_limit_was_exceeded = true; 684 size_policy()->set_gc_overhead_limit_exceeded(false); 685 if (op.result() != NULL) { 686 CollectedHeap::fill_with_object(op.result(), size); 687 } 688 return NULL; 689 } 690 assert(result == NULL || gch->is_in_reserved(result), 691 "result not in heap"); 692 return result; 693 } 694 695 // Give a warning if we seem to be looping forever. 696 if ((QueuedAllocationWarningCount > 0) && 697 (try_count % QueuedAllocationWarningCount == 0)) { 698 log_warning(gc, ergo)("GenCollectorPolicy::mem_allocate_work retries %d times," 699 " size=" SIZE_FORMAT " %s", try_count, size, is_tlab ? "(TLAB)" : ""); 700 } 701 } 702 } 703 704 HeapWord* GenCollectorPolicy::expand_heap_and_allocate(size_t size, 705 bool is_tlab) { 706 GenCollectedHeap *gch = GenCollectedHeap::heap(); 707 HeapWord* result = NULL; 708 Generation *old = gch->old_gen(); 709 if (old->should_allocate(size, is_tlab)) { 710 result = old->expand_and_allocate(size, is_tlab); 711 } 712 if (result == NULL) { 713 Generation *young = gch->young_gen(); 714 if (young->should_allocate(size, is_tlab)) { 715 result = young->expand_and_allocate(size, is_tlab); 716 } 717 } 718 assert(result == NULL || gch->is_in_reserved(result), "result not in heap"); 719 return result; 720 } 721 722 HeapWord* GenCollectorPolicy::satisfy_failed_allocation(size_t size, 723 bool is_tlab) { 724 GenCollectedHeap *gch = GenCollectedHeap::heap(); 725 GCCauseSetter x(gch, GCCause::_allocation_failure); 726 HeapWord* result = NULL; 727 728 assert(size != 0, "Precondition violated"); 729 if (GCLocker::is_active_and_needs_gc()) { 730 // GC locker is active; instead of a collection we will attempt 731 // to expand the heap, if there's room for expansion. 732 if (!gch->is_maximal_no_gc()) { 733 result = expand_heap_and_allocate(size, is_tlab); 734 } 735 return result; // Could be null if we are out of space. 736 } else if (!gch->incremental_collection_will_fail(false /* don't consult_young */)) { 737 // Do an incremental collection. 738 gch->do_collection(false, // full 739 false, // clear_all_soft_refs 740 size, // size 741 is_tlab, // is_tlab 742 GenCollectedHeap::OldGen); // max_generation 743 } else { 744 log_trace(gc)(" :: Trying full because partial may fail :: "); 745 // Try a full collection; see delta for bug id 6266275 746 // for the original code and why this has been simplified 747 // with from-space allocation criteria modified and 748 // such allocation moved out of the safepoint path. 749 gch->do_collection(true, // full 750 false, // clear_all_soft_refs 751 size, // size 752 is_tlab, // is_tlab 753 GenCollectedHeap::OldGen); // max_generation 754 } 755 756 result = gch->attempt_allocation(size, is_tlab, false /*first_only*/); 757 758 if (result != NULL) { 759 assert(gch->is_in_reserved(result), "result not in heap"); 760 return result; 761 } 762 763 // OK, collection failed, try expansion. 764 result = expand_heap_and_allocate(size, is_tlab); 765 if (result != NULL) { 766 return result; 767 } 768 769 // If we reach this point, we're really out of memory. Try every trick 770 // we can to reclaim memory. Force collection of soft references. Force 771 // a complete compaction of the heap. Any additional methods for finding 772 // free memory should be here, especially if they are expensive. If this 773 // attempt fails, an OOM exception will be thrown. 774 { 775 UIntFlagSetting flag_change(MarkSweepAlwaysCompactCount, 1); // Make sure the heap is fully compacted 776 777 gch->do_collection(true, // full 778 true, // clear_all_soft_refs 779 size, // size 780 is_tlab, // is_tlab 781 GenCollectedHeap::OldGen); // max_generation 782 } 783 784 result = gch->attempt_allocation(size, is_tlab, false /* first_only */); 785 if (result != NULL) { 786 assert(gch->is_in_reserved(result), "result not in heap"); 787 return result; 788 } 789 790 assert(!should_clear_all_soft_refs(), 791 "Flag should have been handled and cleared prior to this point"); 792 793 // What else? We might try synchronous finalization later. If the total 794 // space available is large enough for the allocation, then a more 795 // complete compaction phase than we've tried so far might be 796 // appropriate. 797 return NULL; 798 } 799 800 MetaWord* CollectorPolicy::satisfy_failed_metadata_allocation( 801 ClassLoaderData* loader_data, 802 size_t word_size, 803 Metaspace::MetadataType mdtype) { 804 uint loop_count = 0; 805 uint gc_count = 0; 806 uint full_gc_count = 0; 807 808 assert(!Heap_lock->owned_by_self(), "Should not be holding the Heap_lock"); 809 810 do { 811 MetaWord* result = loader_data->metaspace_non_null()->allocate(word_size, mdtype); 812 if (result != NULL) { 813 return result; 814 } 815 816 if (GCLocker::is_active_and_needs_gc()) { 817 // If the GCLocker is active, just expand and allocate. 818 // If that does not succeed, wait if this thread is not 819 // in a critical section itself. 820 result = 821 loader_data->metaspace_non_null()->expand_and_allocate(word_size, 822 mdtype); 823 if (result != NULL) { 824 return result; 825 } 826 JavaThread* jthr = JavaThread::current(); 827 if (!jthr->in_critical()) { 828 // Wait for JNI critical section to be exited 829 GCLocker::stall_until_clear(); 830 // The GC invoked by the last thread leaving the critical 831 // section will be a young collection and a full collection 832 // is (currently) needed for unloading classes so continue 833 // to the next iteration to get a full GC. 834 continue; 835 } else { 836 if (CheckJNICalls) { 837 fatal("Possible deadlock due to allocating while" 838 " in jni critical section"); 839 } 840 return NULL; 841 } 842 } 843 844 { // Need lock to get self consistent gc_count's 845 MutexLocker ml(Heap_lock); 846 gc_count = Universe::heap()->total_collections(); 847 full_gc_count = Universe::heap()->total_full_collections(); 848 } 849 850 // Generate a VM operation 851 VM_CollectForMetadataAllocation op(loader_data, 852 word_size, 853 mdtype, 854 gc_count, 855 full_gc_count, 856 GCCause::_metadata_GC_threshold); 857 VMThread::execute(&op); 858 859 // If GC was locked out, try again. Check before checking success because the 860 // prologue could have succeeded and the GC still have been locked out. 861 if (op.gc_locked()) { 862 continue; 863 } 864 865 if (op.prologue_succeeded()) { 866 return op.result(); 867 } 868 loop_count++; 869 if ((QueuedAllocationWarningCount > 0) && 870 (loop_count % QueuedAllocationWarningCount == 0)) { 871 log_warning(gc, ergo)("satisfy_failed_metadata_allocation() retries %d times," 872 " size=" SIZE_FORMAT, loop_count, word_size); 873 } 874 } while (true); // Until a GC is done 875 } 876 877 // Return true if any of the following is true: 878 // . the allocation won't fit into the current young gen heap 879 // . gc locker is occupied (jni critical section) 880 // . heap memory is tight -- the most recent previous collection 881 // was a full collection because a partial collection (would 882 // have) failed and is likely to fail again 883 bool GenCollectorPolicy::should_try_older_generation_allocation( 884 size_t word_size) const { 885 GenCollectedHeap* gch = GenCollectedHeap::heap(); 886 size_t young_capacity = gch->young_gen()->capacity_before_gc(); 887 return (word_size > heap_word_size(young_capacity)) 888 || GCLocker::is_active_and_needs_gc() 889 || gch->incremental_collection_failed(); 890 } 891 892 893 // 894 // MarkSweepPolicy methods 895 // 896 897 void MarkSweepPolicy::initialize_alignments() { 898 _space_alignment = _gen_alignment = (size_t)Generation::GenGrain; 899 _heap_alignment = compute_heap_alignment(); 900 } 901 902 void MarkSweepPolicy::initialize_generations() { 903 _young_gen_spec = new GenerationSpec(Generation::DefNew, _initial_young_size, _max_young_size, _gen_alignment); 904 _old_gen_spec = new GenerationSpec(Generation::MarkSweepCompact, _initial_old_size, _max_old_size, _gen_alignment); 905 } 906 907 void MarkSweepPolicy::initialize_gc_policy_counters() { 908 // Initialize the policy counters - 2 collectors, 3 generations. 909 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 3); 910 } 911