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