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 {} 55 56 #ifdef ASSERT 57 void CollectorPolicy::assert_flags() { 58 assert(InitialHeapSize <= MaxHeapSize, "Ergonomics decided on incompatible initial and maximum heap sizes"); 59 assert(InitialHeapSize % _heap_alignment == 0, "InitialHeapSize alignment"); 60 assert(MaxHeapSize % _heap_alignment == 0, "MaxHeapSize alignment"); 61 } 62 63 void CollectorPolicy::assert_size_info() { 64 assert(InitialHeapSize == _initial_heap_byte_size, "Discrepancy between InitialHeapSize flag and local storage"); 65 assert(MaxHeapSize == _max_heap_byte_size, "Discrepancy between MaxHeapSize flag and local storage"); 66 assert(_max_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible minimum and maximum heap sizes"); 67 assert(_initial_heap_byte_size >= _min_heap_byte_size, "Ergonomics decided on incompatible initial and minimum heap sizes"); 68 assert(_max_heap_byte_size >= _initial_heap_byte_size, "Ergonomics decided on incompatible initial and maximum heap sizes"); 69 assert(_min_heap_byte_size % _heap_alignment == 0, "min_heap_byte_size alignment"); 70 assert(_initial_heap_byte_size % _heap_alignment == 0, "initial_heap_byte_size alignment"); 71 assert(_max_heap_byte_size % _heap_alignment == 0, "max_heap_byte_size alignment"); 72 } 73 #endif // ASSERT 74 75 void CollectorPolicy::initialize_flags() { 76 assert(_space_alignment != 0, "Space alignment not set up properly"); 77 assert(_heap_alignment != 0, "Heap alignment not set up properly"); 78 assert(_heap_alignment >= _space_alignment, 79 "heap_alignment: " SIZE_FORMAT " less than space_alignment: " SIZE_FORMAT, 80 _heap_alignment, _space_alignment); 81 assert(_heap_alignment % _space_alignment == 0, 82 "heap_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT, 83 _heap_alignment, _space_alignment); 84 85 if (FLAG_IS_CMDLINE(MaxHeapSize)) { 86 if (FLAG_IS_CMDLINE(InitialHeapSize) && InitialHeapSize > MaxHeapSize) { 87 vm_exit_during_initialization("Initial heap size set to a larger value than the maximum heap size"); 88 } 89 if (_min_heap_byte_size != 0 && MaxHeapSize < _min_heap_byte_size) { 90 vm_exit_during_initialization("Incompatible minimum and maximum heap sizes specified"); 91 } 92 } 93 94 // Check heap parameter properties 95 if (MaxHeapSize < 2 * M) { 96 vm_exit_during_initialization("Too small maximum heap"); 97 } 98 if (InitialHeapSize < M) { 99 vm_exit_during_initialization("Too small initial heap"); 100 } 101 if (_min_heap_byte_size < M) { 102 vm_exit_during_initialization("Too small minimum heap"); 103 } 104 105 // User inputs from -Xmx and -Xms must be aligned 106 _min_heap_byte_size = align_up(_min_heap_byte_size, _heap_alignment); 107 size_t aligned_initial_heap_size = align_up(InitialHeapSize, _heap_alignment); 108 size_t aligned_max_heap_size = align_up(MaxHeapSize, _heap_alignment); 109 110 // Write back to flags if the values changed 111 if (aligned_initial_heap_size != InitialHeapSize) { 112 FLAG_SET_ERGO(size_t, InitialHeapSize, aligned_initial_heap_size); 113 } 114 if (aligned_max_heap_size != MaxHeapSize) { 115 FLAG_SET_ERGO(size_t, MaxHeapSize, aligned_max_heap_size); 116 } 117 118 if (FLAG_IS_CMDLINE(InitialHeapSize) && _min_heap_byte_size != 0 && 119 InitialHeapSize < _min_heap_byte_size) { 120 vm_exit_during_initialization("Incompatible minimum and initial heap sizes specified"); 121 } 122 if (!FLAG_IS_DEFAULT(InitialHeapSize) && InitialHeapSize > MaxHeapSize) { 123 FLAG_SET_ERGO(size_t, MaxHeapSize, InitialHeapSize); 124 } else if (!FLAG_IS_DEFAULT(MaxHeapSize) && InitialHeapSize > MaxHeapSize) { 125 FLAG_SET_ERGO(size_t, InitialHeapSize, MaxHeapSize); 126 if (InitialHeapSize < _min_heap_byte_size) { 127 _min_heap_byte_size = InitialHeapSize; 128 } 129 } 130 131 _initial_heap_byte_size = InitialHeapSize; 132 _max_heap_byte_size = MaxHeapSize; 133 134 FLAG_SET_ERGO(size_t, MinHeapDeltaBytes, align_up(MinHeapDeltaBytes, _space_alignment)); 135 136 DEBUG_ONLY(CollectorPolicy::assert_flags();) 137 } 138 139 void CollectorPolicy::initialize_size_info() { 140 log_debug(gc, heap)("Minimum heap " SIZE_FORMAT " Initial heap " SIZE_FORMAT " Maximum heap " SIZE_FORMAT, 141 _min_heap_byte_size, _initial_heap_byte_size, _max_heap_byte_size); 142 143 DEBUG_ONLY(CollectorPolicy::assert_size_info();) 144 } 145 146 size_t CollectorPolicy::compute_heap_alignment() { 147 // The card marking array and the offset arrays for old generations are 148 // committed in os pages as well. Make sure they are entirely full (to 149 // avoid partial page problems), e.g. if 512 bytes heap corresponds to 1 150 // byte entry and the os page size is 4096, the maximum heap size should 151 // be 512*4096 = 2MB aligned. 152 153 size_t alignment = CardTableRS::ct_max_alignment_constraint(); 154 155 if (UseLargePages) { 156 // In presence of large pages we have to make sure that our 157 // alignment is large page aware. 158 alignment = lcm(os::large_page_size(), alignment); 159 } 160 161 return alignment; 162 } 163 164 // GenCollectorPolicy methods 165 166 GenCollectorPolicy::GenCollectorPolicy() : 167 _min_young_size(0), 168 _initial_young_size(0), 169 _max_young_size(0), 170 _min_old_size(0), 171 _initial_old_size(0), 172 _max_old_size(0), 173 _gen_alignment(0), 174 _young_gen_spec(NULL), 175 _old_gen_spec(NULL) 176 {} 177 178 size_t GenCollectorPolicy::scale_by_NewRatio_aligned(size_t base_size) { 179 return align_down_bounded(base_size / (NewRatio + 1), _gen_alignment); 180 } 181 182 size_t GenCollectorPolicy::bound_minus_alignment(size_t desired_size, 183 size_t maximum_size) { 184 size_t max_minus = maximum_size - _gen_alignment; 185 return desired_size < max_minus ? desired_size : max_minus; 186 } 187 188 size_t GenCollectorPolicy::young_gen_size_lower_bound() { 189 // The young generation must be aligned and have room for eden + two survivors 190 return align_up(3 * _space_alignment, _gen_alignment); 191 } 192 193 size_t GenCollectorPolicy::old_gen_size_lower_bound() { 194 return align_up(_space_alignment, _gen_alignment); 195 } 196 197 #ifdef ASSERT 198 void GenCollectorPolicy::assert_flags() { 199 CollectorPolicy::assert_flags(); 200 assert(NewSize >= _min_young_size, "Ergonomics decided on a too small young gen size"); 201 assert(NewSize <= MaxNewSize, "Ergonomics decided on incompatible initial and maximum young gen sizes"); 202 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young gen and heap sizes"); 203 assert(NewSize % _gen_alignment == 0, "NewSize alignment"); 204 assert(FLAG_IS_DEFAULT(MaxNewSize) || MaxNewSize % _gen_alignment == 0, "MaxNewSize alignment"); 205 assert(OldSize + NewSize <= MaxHeapSize, "Ergonomics decided on incompatible generation and heap sizes"); 206 assert(OldSize % _gen_alignment == 0, "OldSize alignment"); 207 } 208 209 void GenCollectorPolicy::assert_size_info() { 210 CollectorPolicy::assert_size_info(); 211 // GenCollectorPolicy::initialize_size_info may update the MaxNewSize 212 assert(MaxNewSize < MaxHeapSize, "Ergonomics decided on incompatible maximum young and heap sizes"); 213 assert(NewSize == _initial_young_size, "Discrepancy between NewSize flag and local storage"); 214 assert(MaxNewSize == _max_young_size, "Discrepancy between MaxNewSize flag and local storage"); 215 assert(OldSize == _initial_old_size, "Discrepancy between OldSize flag and local storage"); 216 assert(_min_young_size <= _initial_young_size, "Ergonomics decided on incompatible minimum and initial young gen sizes"); 217 assert(_initial_young_size <= _max_young_size, "Ergonomics decided on incompatible initial and maximum young gen sizes"); 218 assert(_min_young_size % _gen_alignment == 0, "_min_young_size alignment"); 219 assert(_initial_young_size % _gen_alignment == 0, "_initial_young_size alignment"); 220 assert(_max_young_size % _gen_alignment == 0, "_max_young_size alignment"); 221 assert(_min_young_size <= bound_minus_alignment(_min_young_size, _min_heap_byte_size), 222 "Ergonomics made minimum young generation larger than minimum heap"); 223 assert(_initial_young_size <= bound_minus_alignment(_initial_young_size, _initial_heap_byte_size), 224 "Ergonomics made initial young generation larger than initial heap"); 225 assert(_max_young_size <= bound_minus_alignment(_max_young_size, _max_heap_byte_size), 226 "Ergonomics made maximum young generation lager than maximum heap"); 227 assert(_min_old_size <= _initial_old_size, "Ergonomics decided on incompatible minimum and initial old gen sizes"); 228 assert(_initial_old_size <= _max_old_size, "Ergonomics decided on incompatible initial and maximum old gen sizes"); 229 assert(_max_old_size % _gen_alignment == 0, "_max_old_size alignment"); 230 assert(_initial_old_size % _gen_alignment == 0, "_initial_old_size alignment"); 231 assert(_max_heap_byte_size <= (_max_young_size + _max_old_size), "Total maximum heap sizes must be sum of generation maximum sizes"); 232 assert(_min_young_size + _min_old_size <= _min_heap_byte_size, "Minimum generation sizes exceed minimum heap size"); 233 assert(_initial_young_size + _initial_old_size == _initial_heap_byte_size, "Initial generation sizes should match initial heap size"); 234 assert(_max_young_size + _max_old_size == _max_heap_byte_size, "Maximum generation sizes should match maximum heap size"); 235 } 236 #endif // ASSERT 237 238 void GenCollectorPolicy::initialize_flags() { 239 CollectorPolicy::initialize_flags(); 240 241 assert(_gen_alignment != 0, "Generation alignment not set up properly"); 242 assert(_heap_alignment >= _gen_alignment, 243 "heap_alignment: " SIZE_FORMAT " less than gen_alignment: " SIZE_FORMAT, 244 _heap_alignment, _gen_alignment); 245 assert(_gen_alignment % _space_alignment == 0, 246 "gen_alignment: " SIZE_FORMAT " not aligned by space_alignment: " SIZE_FORMAT, 247 _gen_alignment, _space_alignment); 248 assert(_heap_alignment % _gen_alignment == 0, 249 "heap_alignment: " SIZE_FORMAT " not aligned by gen_alignment: " SIZE_FORMAT, 250 _heap_alignment, _gen_alignment); 251 252 // All generational heaps have a young gen; handle those flags here 253 254 // Make sure the heap is large enough for two generations 255 size_t smallest_new_size = young_gen_size_lower_bound(); 256 size_t smallest_heap_size = align_up(smallest_new_size + old_gen_size_lower_bound(), 257 _heap_alignment); 258 if (MaxHeapSize < smallest_heap_size) { 259 FLAG_SET_ERGO(size_t, MaxHeapSize, smallest_heap_size); 260 _max_heap_byte_size = MaxHeapSize; 261 } 262 // If needed, synchronize _min_heap_byte size and _initial_heap_byte_size 263 if (_min_heap_byte_size < smallest_heap_size) { 264 _min_heap_byte_size = smallest_heap_size; 265 if (InitialHeapSize < _min_heap_byte_size) { 266 FLAG_SET_ERGO(size_t, InitialHeapSize, smallest_heap_size); 267 _initial_heap_byte_size = smallest_heap_size; 268 } 269 } 270 271 // Make sure NewSize allows an old generation to fit even if set on the command line 272 if (FLAG_IS_CMDLINE(NewSize) && NewSize >= _initial_heap_byte_size) { 273 log_warning(gc, ergo)("NewSize was set larger than initial heap size, will use initial heap size."); 274 FLAG_SET_ERGO(size_t, NewSize, bound_minus_alignment(NewSize, _initial_heap_byte_size)); 275 } 276 277 // Now take the actual NewSize into account. We will silently increase NewSize 278 // if the user specified a smaller or unaligned value. 279 size_t bounded_new_size = bound_minus_alignment(NewSize, MaxHeapSize); 280 bounded_new_size = MAX2(smallest_new_size, align_down(bounded_new_size, _gen_alignment)); 281 if (bounded_new_size != NewSize) { 282 FLAG_SET_ERGO(size_t, NewSize, bounded_new_size); 283 } 284 _min_young_size = smallest_new_size; 285 _initial_young_size = NewSize; 286 287 if (!FLAG_IS_DEFAULT(MaxNewSize)) { 288 if (MaxNewSize >= MaxHeapSize) { 289 // Make sure there is room for an old generation 290 size_t smaller_max_new_size = MaxHeapSize - _gen_alignment; 291 if (FLAG_IS_CMDLINE(MaxNewSize)) { 292 log_warning(gc, ergo)("MaxNewSize (" SIZE_FORMAT "k) is equal to or greater than the entire " 293 "heap (" SIZE_FORMAT "k). A new max generation size of " SIZE_FORMAT "k will be used.", 294 MaxNewSize/K, MaxHeapSize/K, smaller_max_new_size/K); 295 } 296 FLAG_SET_ERGO(size_t, MaxNewSize, smaller_max_new_size); 297 if (NewSize > MaxNewSize) { 298 FLAG_SET_ERGO(size_t, NewSize, MaxNewSize); 299 _initial_young_size = NewSize; 300 } 301 } else if (MaxNewSize < _initial_young_size) { 302 FLAG_SET_ERGO(size_t, MaxNewSize, _initial_young_size); 303 } else if (!is_aligned(MaxNewSize, _gen_alignment)) { 304 FLAG_SET_ERGO(size_t, MaxNewSize, align_down(MaxNewSize, _gen_alignment)); 305 } 306 _max_young_size = MaxNewSize; 307 } 308 309 if (NewSize > MaxNewSize) { 310 // At this point this should only happen if the user specifies a large NewSize and/or 311 // a small (but not too small) MaxNewSize. 312 if (FLAG_IS_CMDLINE(MaxNewSize)) { 313 log_warning(gc, ergo)("NewSize (" SIZE_FORMAT "k) is greater than the MaxNewSize (" SIZE_FORMAT "k). " 314 "A new max generation size of " SIZE_FORMAT "k will be used.", 315 NewSize/K, MaxNewSize/K, NewSize/K); 316 } 317 FLAG_SET_ERGO(size_t, MaxNewSize, NewSize); 318 _max_young_size = MaxNewSize; 319 } 320 321 if (SurvivorRatio < 1 || NewRatio < 1) { 322 vm_exit_during_initialization("Invalid young gen ratio specified"); 323 } 324 325 if (OldSize < old_gen_size_lower_bound()) { 326 FLAG_SET_ERGO(size_t, OldSize, old_gen_size_lower_bound()); 327 } 328 if (!is_aligned(OldSize, _gen_alignment)) { 329 FLAG_SET_ERGO(size_t, OldSize, align_down(OldSize, _gen_alignment)); 330 } 331 332 if (FLAG_IS_CMDLINE(OldSize) && FLAG_IS_DEFAULT(MaxHeapSize)) { 333 // NewRatio will be used later to set the young generation size so we use 334 // it to calculate how big the heap should be based on the requested OldSize 335 // and NewRatio. 336 assert(NewRatio > 0, "NewRatio should have been set up earlier"); 337 size_t calculated_heapsize = (OldSize / NewRatio) * (NewRatio + 1); 338 339 calculated_heapsize = align_up(calculated_heapsize, _heap_alignment); 340 FLAG_SET_ERGO(size_t, MaxHeapSize, calculated_heapsize); 341 _max_heap_byte_size = MaxHeapSize; 342 FLAG_SET_ERGO(size_t, InitialHeapSize, calculated_heapsize); 343 _initial_heap_byte_size = InitialHeapSize; 344 } 345 346 // Adjust NewSize and OldSize or MaxHeapSize to match each other 347 if (NewSize + OldSize > MaxHeapSize) { 348 if (FLAG_IS_CMDLINE(MaxHeapSize)) { 349 // Somebody has set a maximum heap size with the intention that we should not 350 // exceed it. Adjust New/OldSize as necessary. 351 size_t calculated_size = NewSize + OldSize; 352 double shrink_factor = (double) MaxHeapSize / calculated_size; 353 size_t smaller_new_size = align_down((size_t)(NewSize * shrink_factor), _gen_alignment); 354 FLAG_SET_ERGO(size_t, NewSize, MAX2(young_gen_size_lower_bound(), smaller_new_size)); 355 _initial_young_size = NewSize; 356 357 // OldSize is already aligned because above we aligned MaxHeapSize to 358 // _heap_alignment, and we just made sure that NewSize is aligned to 359 // _gen_alignment. In initialize_flags() we verified that _heap_alignment 360 // is a multiple of _gen_alignment. 361 FLAG_SET_ERGO(size_t, OldSize, MaxHeapSize - NewSize); 362 } else { 363 FLAG_SET_ERGO(size_t, MaxHeapSize, align_up(NewSize + OldSize, _heap_alignment)); 364 _max_heap_byte_size = MaxHeapSize; 365 } 366 } 367 368 // Update NewSize, if possible, to avoid sizing the young gen too small when only 369 // OldSize is set on the command line. 370 if (FLAG_IS_CMDLINE(OldSize) && !FLAG_IS_CMDLINE(NewSize)) { 371 if (OldSize < _initial_heap_byte_size) { 372 size_t new_size = _initial_heap_byte_size - OldSize; 373 // Need to compare against the flag value for max since _max_young_size 374 // might not have been set yet. 375 if (new_size >= _min_young_size && new_size <= MaxNewSize) { 376 FLAG_SET_ERGO(size_t, NewSize, new_size); 377 _initial_young_size = NewSize; 378 } 379 } 380 } 381 382 always_do_update_barrier = UseConcMarkSweepGC; 383 384 DEBUG_ONLY(GenCollectorPolicy::assert_flags();) 385 } 386 387 // Values set on the command line win over any ergonomically 388 // set command line parameters. 389 // Ergonomic choice of parameters are done before this 390 // method is called. Values for command line parameters such as NewSize 391 // and MaxNewSize feed those ergonomic choices into this method. 392 // This method makes the final generation sizings consistent with 393 // themselves and with overall heap sizings. 394 // In the absence of explicitly set command line flags, policies 395 // such as the use of NewRatio are used to size the generation. 396 397 // Minimum sizes of the generations may be different than 398 // the initial sizes. An inconsistency is permitted here 399 // in the total size that can be specified explicitly by 400 // command line specification of OldSize and NewSize and 401 // also a command line specification of -Xms. Issue a warning 402 // but allow the values to pass. 403 void GenCollectorPolicy::initialize_size_info() { 404 CollectorPolicy::initialize_size_info(); 405 406 _initial_young_size = NewSize; 407 _max_young_size = MaxNewSize; 408 _initial_old_size = OldSize; 409 410 // Determine maximum size of the young generation. 411 412 if (FLAG_IS_DEFAULT(MaxNewSize)) { 413 _max_young_size = scale_by_NewRatio_aligned(_max_heap_byte_size); 414 // Bound the maximum size by NewSize below (since it historically 415 // would have been NewSize and because the NewRatio calculation could 416 // yield a size that is too small) and bound it by MaxNewSize above. 417 // Ergonomics plays here by previously calculating the desired 418 // NewSize and MaxNewSize. 419 _max_young_size = MIN2(MAX2(_max_young_size, _initial_young_size), MaxNewSize); 420 } 421 422 // Given the maximum young size, determine the initial and 423 // minimum young sizes. 424 425 if (_max_heap_byte_size == _initial_heap_byte_size) { 426 // The maximum and initial heap sizes are the same so the generation's 427 // initial size must be the same as it maximum size. Use NewSize as the 428 // size if set on command line. 429 _max_young_size = FLAG_IS_CMDLINE(NewSize) ? NewSize : _max_young_size; 430 _initial_young_size = _max_young_size; 431 432 // Also update the minimum size if min == initial == max. 433 if (_max_heap_byte_size == _min_heap_byte_size) { 434 _min_young_size = _max_young_size; 435 } 436 } else { 437 if (FLAG_IS_CMDLINE(NewSize)) { 438 // If NewSize is set on the command line, we should use it as 439 // the initial size, but make sure it is within the heap bounds. 440 _initial_young_size = 441 MIN2(_max_young_size, bound_minus_alignment(NewSize, _initial_heap_byte_size)); 442 _min_young_size = bound_minus_alignment(_initial_young_size, _min_heap_byte_size); 443 } else { 444 // For the case where NewSize is not set on the command line, use 445 // NewRatio to size the initial generation size. Use the current 446 // NewSize as the floor, because if NewRatio is overly large, the resulting 447 // size can be too small. 448 _initial_young_size = 449 MIN2(_max_young_size, MAX2(scale_by_NewRatio_aligned(_initial_heap_byte_size), NewSize)); 450 } 451 } 452 453 log_trace(gc, heap)("1: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT, 454 _min_young_size, _initial_young_size, _max_young_size); 455 456 // At this point the minimum, initial and maximum sizes 457 // of the overall heap and of the young generation have been determined. 458 // The maximum old size can be determined from the maximum young 459 // and maximum heap size since no explicit flags exist 460 // for setting the old generation maximum. 461 _max_old_size = MAX2(_max_heap_byte_size - _max_young_size, _gen_alignment); 462 463 // If no explicit command line flag has been set for the 464 // old generation size, use what is left. 465 if (!FLAG_IS_CMDLINE(OldSize)) { 466 // The user has not specified any value but the ergonomics 467 // may have chosen a value (which may or may not be consistent 468 // with the overall heap size). In either case make 469 // the minimum, maximum and initial sizes consistent 470 // with the young sizes and the overall heap sizes. 471 _min_old_size = _gen_alignment; 472 _initial_old_size = MIN2(_max_old_size, MAX2(_initial_heap_byte_size - _initial_young_size, _min_old_size)); 473 // _max_old_size has already been made consistent above. 474 } else { 475 // OldSize has been explicitly set on the command line. Use it 476 // for the initial size but make sure the minimum allow a young 477 // generation to fit as well. 478 // If the user has explicitly set an OldSize that is inconsistent 479 // with other command line flags, issue a warning. 480 // The generation minimums and the overall heap minimum should 481 // be within one generation alignment. 482 if (_initial_old_size > _max_old_size) { 483 log_warning(gc, ergo)("Inconsistency between maximum heap size and maximum " 484 "generation sizes: using maximum heap = " SIZE_FORMAT 485 ", -XX:OldSize flag is being ignored", 486 _max_heap_byte_size); 487 _initial_old_size = _max_old_size; 488 } 489 490 _min_old_size = MIN2(_initial_old_size, _min_heap_byte_size - _min_young_size); 491 } 492 493 // The initial generation sizes should match the initial heap size, 494 // if not issue a warning and resize the generations. This behavior 495 // differs from JDK8 where the generation sizes have higher priority 496 // than the initial heap size. 497 if ((_initial_old_size + _initial_young_size) != _initial_heap_byte_size) { 498 log_warning(gc, ergo)("Inconsistency between generation sizes and heap size, resizing " 499 "the generations to fit the heap."); 500 501 size_t desired_young_size = _initial_heap_byte_size - _initial_old_size; 502 if (_initial_heap_byte_size < _initial_old_size) { 503 // Old want all memory, use minimum for young and rest for old 504 _initial_young_size = _min_young_size; 505 _initial_old_size = _initial_heap_byte_size - _min_young_size; 506 } else if (desired_young_size > _max_young_size) { 507 // Need to increase both young and old generation 508 _initial_young_size = _max_young_size; 509 _initial_old_size = _initial_heap_byte_size - _max_young_size; 510 } else if (desired_young_size < _min_young_size) { 511 // Need to decrease both young and old generation 512 _initial_young_size = _min_young_size; 513 _initial_old_size = _initial_heap_byte_size - _min_young_size; 514 } else { 515 // The young generation boundaries allow us to only update the 516 // young generation. 517 _initial_young_size = desired_young_size; 518 } 519 520 log_trace(gc, heap)("2: Minimum young " SIZE_FORMAT " Initial young " SIZE_FORMAT " Maximum young " SIZE_FORMAT, 521 _min_young_size, _initial_young_size, _max_young_size); 522 } 523 524 // Write back to flags if necessary. 525 if (NewSize != _initial_young_size) { 526 FLAG_SET_ERGO(size_t, NewSize, _initial_young_size); 527 } 528 529 if (MaxNewSize != _max_young_size) { 530 FLAG_SET_ERGO(size_t, MaxNewSize, _max_young_size); 531 } 532 533 if (OldSize != _initial_old_size) { 534 FLAG_SET_ERGO(size_t, OldSize, _initial_old_size); 535 } 536 537 log_trace(gc, heap)("Minimum old " SIZE_FORMAT " Initial old " SIZE_FORMAT " Maximum old " SIZE_FORMAT, 538 _min_old_size, _initial_old_size, _max_old_size); 539 540 DEBUG_ONLY(GenCollectorPolicy::assert_size_info();) 541 } 542 543 // 544 // MarkSweepPolicy methods 545 // 546 547 void MarkSweepPolicy::initialize_alignments() { 548 _space_alignment = _gen_alignment = (size_t)Generation::GenGrain; 549 _heap_alignment = compute_heap_alignment(); 550 } 551 552 void MarkSweepPolicy::initialize_generations() { 553 _young_gen_spec = new GenerationSpec(Generation::DefNew, _initial_young_size, _max_young_size, _gen_alignment); 554 _old_gen_spec = new GenerationSpec(Generation::MarkSweepCompact, _initial_old_size, _max_old_size, _gen_alignment); 555 } 556 557 void MarkSweepPolicy::initialize_gc_policy_counters() { 558 // Initialize the policy counters - 2 collectors, 2 generations. 559 _gc_policy_counters = new GCPolicyCounters("Copy:MSC", 2, 2); 560 }