1 /* 2 * Copyright (c) 2016, 2021, Red Hat, Inc. All rights reserved. 3 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved. 4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 5 * 6 * This code is free software; you can redistribute it and/or modify it 7 * under the terms of the GNU General Public License version 2 only, as 8 * published by the Free Software Foundation. 9 * 10 * This code is distributed in the hope that it will be useful, but WITHOUT 11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 13 * version 2 for more details (a copy is included in the LICENSE file that 14 * accompanied this code). 15 * 16 * You should have received a copy of the GNU General Public License version 17 * 2 along with this work; if not, write to the Free Software Foundation, 18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 19 * 20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 21 * or visit www.oracle.com if you need additional information or have any 22 * questions. 23 * 24 */ 25 26 #include "precompiled.hpp" 27 #include "gc/shared/tlab_globals.hpp" 28 #include "gc/shenandoah/shenandoahAffiliation.hpp" 29 #include "gc/shenandoah/shenandoahBarrierSet.hpp" 30 #include "gc/shenandoah/shenandoahFreeSet.hpp" 31 #include "gc/shenandoah/shenandoahHeap.inline.hpp" 32 #include "gc/shenandoah/shenandoahHeapRegionSet.hpp" 33 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp" 34 #include "gc/shenandoah/shenandoahOldGeneration.hpp" 35 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp" 36 #include "gc/shenandoah/shenandoahYoungGeneration.hpp" 37 #include "logging/logStream.hpp" 38 #include "memory/resourceArea.hpp" 39 #include "runtime/orderAccess.hpp" 40 41 ShenandoahSetsOfFree::ShenandoahSetsOfFree(size_t max_regions, ShenandoahFreeSet* free_set) : 42 _max(max_regions), 43 _free_set(free_set), 44 _region_size_bytes(ShenandoahHeapRegion::region_size_bytes()) 45 { 46 _membership = NEW_C_HEAP_ARRAY(ShenandoahFreeMemoryType, max_regions, mtGC); 47 clear_internal(); 48 } 49 50 ShenandoahSetsOfFree::~ShenandoahSetsOfFree() { 51 FREE_C_HEAP_ARRAY(ShenandoahFreeMemoryType, _membership); 52 } 53 54 55 void ShenandoahSetsOfFree::clear_internal() { 56 for (size_t idx = 0; idx < _max; idx++) { 57 _membership[idx] = NotFree; 58 } 59 60 for (size_t idx = 0; idx < NumFreeSets; idx++) { 61 _leftmosts[idx] = _max; 62 _rightmosts[idx] = 0; 63 _leftmosts_empty[idx] = _max; 64 _rightmosts_empty[idx] = 0; 65 _capacity_of[idx] = 0; 66 _used_by[idx] = 0; 67 } 68 69 _left_to_right_bias[Mutator] = true; 70 _left_to_right_bias[Collector] = false; 71 _left_to_right_bias[OldCollector] = false; 72 73 _region_counts[Mutator] = 0; 74 _region_counts[Collector] = 0; 75 _region_counts[OldCollector] = 0; 76 _region_counts[NotFree] = _max; 77 } 78 79 void ShenandoahSetsOfFree::clear_all() { 80 clear_internal(); 81 } 82 83 void ShenandoahSetsOfFree::increase_used(ShenandoahFreeMemoryType which_set, size_t bytes) { 84 assert (which_set > NotFree && which_set < NumFreeSets, "Set must correspond to a valid freeset"); 85 _used_by[which_set] += bytes; 86 assert (_used_by[which_set] <= _capacity_of[which_set], 87 "Must not use (" SIZE_FORMAT ") more than capacity (" SIZE_FORMAT ") after increase by " SIZE_FORMAT, 88 _used_by[which_set], _capacity_of[which_set], bytes); 89 } 90 91 inline void ShenandoahSetsOfFree::shrink_bounds_if_touched(ShenandoahFreeMemoryType set, size_t idx) { 92 if (idx == _leftmosts[set]) { 93 while ((_leftmosts[set] < _max) && !in_free_set(_leftmosts[set], set)) { 94 _leftmosts[set]++; 95 } 96 if (_leftmosts_empty[set] < _leftmosts[set]) { 97 // This gets us closer to where we need to be; we'll scan further when leftmosts_empty is requested. 98 _leftmosts_empty[set] = _leftmosts[set]; 99 } 100 } 101 if (idx == _rightmosts[set]) { 102 while (_rightmosts[set] > 0 && !in_free_set(_rightmosts[set], set)) { 103 _rightmosts[set]--; 104 } 105 if (_rightmosts_empty[set] > _rightmosts[set]) { 106 // This gets us closer to where we need to be; we'll scan further when rightmosts_empty is requested. 107 _rightmosts_empty[set] = _rightmosts[set]; 108 } 109 } 110 } 111 112 inline void ShenandoahSetsOfFree::expand_bounds_maybe(ShenandoahFreeMemoryType set, size_t idx, size_t region_capacity) { 113 if (region_capacity == _region_size_bytes) { 114 if (_leftmosts_empty[set] > idx) { 115 _leftmosts_empty[set] = idx; 116 } 117 if (_rightmosts_empty[set] < idx) { 118 _rightmosts_empty[set] = idx; 119 } 120 } 121 if (_leftmosts[set] > idx) { 122 _leftmosts[set] = idx; 123 } 124 if (_rightmosts[set] < idx) { 125 _rightmosts[set] = idx; 126 } 127 } 128 129 void ShenandoahSetsOfFree::remove_from_free_sets(size_t idx) { 130 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT, idx, _max); 131 ShenandoahFreeMemoryType orig_set = membership(idx); 132 assert (orig_set > NotFree && orig_set < NumFreeSets, "Cannot remove from free sets if not already free"); 133 _membership[idx] = NotFree; 134 shrink_bounds_if_touched(orig_set, idx); 135 136 _region_counts[orig_set]--; 137 _region_counts[NotFree]++; 138 } 139 140 141 void ShenandoahSetsOfFree::make_free(size_t idx, ShenandoahFreeMemoryType which_set, size_t region_capacity) { 142 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT, idx, _max); 143 assert (_membership[idx] == NotFree, "Cannot make free if already free"); 144 assert (which_set > NotFree && which_set < NumFreeSets, "selected free set must be valid"); 145 _membership[idx] = which_set; 146 _capacity_of[which_set] += region_capacity; 147 expand_bounds_maybe(which_set, idx, region_capacity); 148 149 _region_counts[NotFree]--; 150 _region_counts[which_set]++; 151 } 152 153 void ShenandoahSetsOfFree::move_to_set(size_t idx, ShenandoahFreeMemoryType new_set, size_t region_capacity) { 154 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT, idx, _max); 155 assert ((new_set > NotFree) && (new_set < NumFreeSets), "New set must be valid"); 156 ShenandoahFreeMemoryType orig_set = _membership[idx]; 157 assert ((orig_set > NotFree) && (orig_set < NumFreeSets), "Cannot move free unless already free"); 158 // Expected transitions: 159 // During rebuild: Mutator => Collector 160 // Mutator empty => Collector 161 // During flip_to_gc: 162 // Mutator empty => Collector 163 // Mutator empty => Old Collector 164 // At start of update refs: 165 // Collector => Mutator 166 // OldCollector Empty => Mutator 167 assert (((region_capacity <= _region_size_bytes) && 168 ((orig_set == Mutator) && (new_set == Collector)) || 169 ((orig_set == Collector) && (new_set == Mutator))) || 170 ((region_capacity == _region_size_bytes) && 171 ((orig_set == Mutator) && (new_set == Collector)) || 172 ((orig_set == OldCollector) && (new_set == Mutator)) || 173 (new_set == OldCollector)), "Unexpected movement between sets"); 174 175 _membership[idx] = new_set; 176 _capacity_of[orig_set] -= region_capacity; 177 shrink_bounds_if_touched(orig_set, idx); 178 179 _capacity_of[new_set] += region_capacity; 180 expand_bounds_maybe(new_set, idx, region_capacity); 181 182 _region_counts[orig_set]--; 183 _region_counts[new_set]++; 184 } 185 186 inline ShenandoahFreeMemoryType ShenandoahSetsOfFree::membership(size_t idx) const { 187 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT, idx, _max); 188 return _membership[idx]; 189 } 190 191 // Returns true iff region idx is in the test_set free_set. Before returning true, asserts that the free 192 // set is not empty. Requires that test_set != NotFree or NumFreeSets. 193 inline bool ShenandoahSetsOfFree::in_free_set(size_t idx, ShenandoahFreeMemoryType test_set) const { 194 assert (idx < _max, "index is sane: " SIZE_FORMAT " < " SIZE_FORMAT, idx, _max); 195 if (_membership[idx] == test_set) { 196 assert (test_set == NotFree || _free_set->alloc_capacity(idx) > 0, "Free regions must have alloc capacity"); 197 return true; 198 } else { 199 return false; 200 } 201 } 202 203 inline size_t ShenandoahSetsOfFree::leftmost(ShenandoahFreeMemoryType which_set) const { 204 assert (which_set > NotFree && which_set < NumFreeSets, "selected free set must be valid"); 205 size_t idx = _leftmosts[which_set]; 206 if (idx >= _max) { 207 return _max; 208 } else { 209 assert (in_free_set(idx, which_set), "left-most region must be free"); 210 return idx; 211 } 212 } 213 214 inline size_t ShenandoahSetsOfFree::rightmost(ShenandoahFreeMemoryType which_set) const { 215 assert (which_set > NotFree && which_set < NumFreeSets, "selected free set must be valid"); 216 size_t idx = _rightmosts[which_set]; 217 assert ((_leftmosts[which_set] == _max) || in_free_set(idx, which_set), "right-most region must be free"); 218 return idx; 219 } 220 221 size_t ShenandoahSetsOfFree::leftmost_empty(ShenandoahFreeMemoryType which_set) { 222 assert (which_set > NotFree && which_set < NumFreeSets, "selected free set must be valid"); 223 for (size_t idx = _leftmosts_empty[which_set]; idx < _max; idx++) { 224 if ((membership(idx) == which_set) && (_free_set->alloc_capacity(idx) == _region_size_bytes)) { 225 _leftmosts_empty[which_set] = idx; 226 return idx; 227 } 228 } 229 _leftmosts_empty[which_set] = _max; 230 _rightmosts_empty[which_set] = 0; 231 return _max; 232 } 233 234 inline size_t ShenandoahSetsOfFree::rightmost_empty(ShenandoahFreeMemoryType which_set) { 235 assert (which_set > NotFree && which_set < NumFreeSets, "selected free set must be valid"); 236 for (intptr_t idx = _rightmosts_empty[which_set]; idx >= 0; idx--) { 237 if ((membership(idx) == which_set) && (_free_set->alloc_capacity(idx) == _region_size_bytes)) { 238 _rightmosts_empty[which_set] = idx; 239 return idx; 240 } 241 } 242 _leftmosts_empty[which_set] = _max; 243 _rightmosts_empty[which_set] = 0; 244 return 0; 245 } 246 247 inline bool ShenandoahSetsOfFree::alloc_from_left_bias(ShenandoahFreeMemoryType which_set) { 248 assert (which_set > NotFree && which_set < NumFreeSets, "selected free set must be valid"); 249 return _left_to_right_bias[which_set]; 250 } 251 252 void ShenandoahSetsOfFree::establish_alloc_bias(ShenandoahFreeMemoryType which_set) { 253 ShenandoahHeap* heap = ShenandoahHeap::heap(); 254 shenandoah_assert_heaplocked(); 255 assert (which_set > NotFree && which_set < NumFreeSets, "selected free set must be valid"); 256 257 size_t middle = (_leftmosts[which_set] + _rightmosts[which_set]) / 2; 258 size_t available_in_first_half = 0; 259 size_t available_in_second_half = 0; 260 261 for (size_t index = _leftmosts[which_set]; index < middle; index++) { 262 if (in_free_set(index, which_set)) { 263 ShenandoahHeapRegion* r = heap->get_region(index); 264 available_in_first_half += r->free(); 265 } 266 } 267 for (size_t index = middle; index <= _rightmosts[which_set]; index++) { 268 if (in_free_set(index, which_set)) { 269 ShenandoahHeapRegion* r = heap->get_region(index); 270 available_in_second_half += r->free(); 271 } 272 } 273 274 // We desire to first consume the sparsely distributed regions in order that the remaining regions are densely packed. 275 // Densely packing regions reduces the effort to search for a region that has sufficient memory to satisfy a new allocation 276 // request. Regions become sparsely distributed following a Full GC, which tends to slide all regions to the front of the 277 // heap rather than allowing survivor regions to remain at the high end of the heap where we intend for them to congregate. 278 279 // TODO: In the future, we may modify Full GC so that it slides old objects to the end of the heap and young objects to the 280 // front of the heap. If this is done, we can always search survivor Collector and OldCollector regions right to left. 281 _left_to_right_bias[which_set] = (available_in_second_half > available_in_first_half); 282 } 283 284 #ifdef ASSERT 285 void ShenandoahSetsOfFree::assert_bounds() { 286 287 size_t leftmosts[NumFreeSets]; 288 size_t rightmosts[NumFreeSets]; 289 size_t empty_leftmosts[NumFreeSets]; 290 size_t empty_rightmosts[NumFreeSets]; 291 292 for (int i = 0; i < NumFreeSets; i++) { 293 leftmosts[i] = _max; 294 empty_leftmosts[i] = _max; 295 rightmosts[i] = 0; 296 empty_rightmosts[i] = 0; 297 } 298 299 for (size_t i = 0; i < _max; i++) { 300 ShenandoahFreeMemoryType set = membership(i); 301 switch (set) { 302 case NotFree: 303 break; 304 305 case Mutator: 306 case Collector: 307 case OldCollector: 308 { 309 size_t capacity = _free_set->alloc_capacity(i); 310 bool is_empty = (capacity == _region_size_bytes); 311 assert(capacity > 0, "free regions must have allocation capacity"); 312 if (i < leftmosts[set]) { 313 leftmosts[set] = i; 314 } 315 if (is_empty && (i < empty_leftmosts[set])) { 316 empty_leftmosts[set] = i; 317 } 318 if (i > rightmosts[set]) { 319 rightmosts[set] = i; 320 } 321 if (is_empty && (i > empty_rightmosts[set])) { 322 empty_rightmosts[set] = i; 323 } 324 break; 325 } 326 327 case NumFreeSets: 328 default: 329 ShouldNotReachHere(); 330 } 331 } 332 333 // Performance invariants. Failing these would not break the free set, but performance would suffer. 334 assert (leftmost(Mutator) <= _max, "leftmost in bounds: " SIZE_FORMAT " < " SIZE_FORMAT, leftmost(Mutator), _max); 335 assert (rightmost(Mutator) < _max, "rightmost in bounds: " SIZE_FORMAT " < " SIZE_FORMAT, rightmost(Mutator), _max); 336 337 assert (leftmost(Mutator) == _max || in_free_set(leftmost(Mutator), Mutator), 338 "leftmost region should be free: " SIZE_FORMAT, leftmost(Mutator)); 339 assert (leftmost(Mutator) == _max || in_free_set(rightmost(Mutator), Mutator), 340 "rightmost region should be free: " SIZE_FORMAT, rightmost(Mutator)); 341 342 // If Mutator set is empty, leftmosts will both equal max, rightmosts will both equal zero. Likewise for empty region sets. 343 size_t beg_off = leftmosts[Mutator]; 344 size_t end_off = rightmosts[Mutator]; 345 assert (beg_off >= leftmost(Mutator), 346 "free regions before the leftmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, beg_off, leftmost(Mutator)); 347 assert (end_off <= rightmost(Mutator), 348 "free regions past the rightmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, end_off, rightmost(Mutator)); 349 350 beg_off = empty_leftmosts[Mutator]; 351 end_off = empty_rightmosts[Mutator]; 352 assert (beg_off >= leftmost_empty(Mutator), 353 "free empty regions before the leftmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, beg_off, leftmost_empty(Mutator)); 354 assert (end_off <= rightmost_empty(Mutator), 355 "free empty regions past the rightmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, end_off, rightmost_empty(Mutator)); 356 357 // Performance invariants. Failing these would not break the free set, but performance would suffer. 358 assert (leftmost(Collector) <= _max, "leftmost in bounds: " SIZE_FORMAT " < " SIZE_FORMAT, leftmost(Collector), _max); 359 assert (rightmost(Collector) < _max, "rightmost in bounds: " SIZE_FORMAT " < " SIZE_FORMAT, rightmost(Collector), _max); 360 361 assert (leftmost(Collector) == _max || in_free_set(leftmost(Collector), Collector), 362 "leftmost region should be free: " SIZE_FORMAT, leftmost(Collector)); 363 assert (leftmost(Collector) == _max || in_free_set(rightmost(Collector), Collector), 364 "rightmost region should be free: " SIZE_FORMAT, rightmost(Collector)); 365 366 // If Collector set is empty, leftmosts will both equal max, rightmosts will both equal zero. Likewise for empty region sets. 367 beg_off = leftmosts[Collector]; 368 end_off = rightmosts[Collector]; 369 assert (beg_off >= leftmost(Collector), 370 "free regions before the leftmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, beg_off, leftmost(Collector)); 371 assert (end_off <= rightmost(Collector), 372 "free regions past the rightmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, end_off, rightmost(Collector)); 373 374 beg_off = empty_leftmosts[Collector]; 375 end_off = empty_rightmosts[Collector]; 376 assert (beg_off >= leftmost_empty(Collector), 377 "free empty regions before the leftmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, beg_off, leftmost_empty(Collector)); 378 assert (end_off <= rightmost_empty(Collector), 379 "free empty regions past the rightmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, end_off, rightmost_empty(Collector)); 380 381 // Performance invariants. Failing these would not break the free set, but performance would suffer. 382 assert (leftmost(OldCollector) <= _max, "leftmost in bounds: " SIZE_FORMAT " < " SIZE_FORMAT, leftmost(OldCollector), _max); 383 assert (rightmost(OldCollector) < _max, "rightmost in bounds: " SIZE_FORMAT " < " SIZE_FORMAT, rightmost(OldCollector), _max); 384 385 assert (leftmost(OldCollector) == _max || in_free_set(leftmost(OldCollector), OldCollector), 386 "leftmost region should be free: " SIZE_FORMAT, leftmost(OldCollector)); 387 assert (leftmost(OldCollector) == _max || in_free_set(rightmost(OldCollector), OldCollector), 388 "rightmost region should be free: " SIZE_FORMAT, rightmost(OldCollector)); 389 390 // If OldCollector set is empty, leftmosts will both equal max, rightmosts will both equal zero. Likewise for empty region sets. 391 beg_off = leftmosts[OldCollector]; 392 end_off = rightmosts[OldCollector]; 393 assert (beg_off >= leftmost(OldCollector), 394 "free regions before the leftmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, beg_off, leftmost(OldCollector)); 395 assert (end_off <= rightmost(OldCollector), 396 "free regions past the rightmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, end_off, rightmost(OldCollector)); 397 398 beg_off = empty_leftmosts[OldCollector]; 399 end_off = empty_rightmosts[OldCollector]; 400 assert (beg_off >= leftmost_empty(OldCollector), 401 "free empty regions before the leftmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, beg_off, leftmost_empty(OldCollector)); 402 assert (end_off <= rightmost_empty(OldCollector), 403 "free empty regions past the rightmost: " SIZE_FORMAT ", bound " SIZE_FORMAT, end_off, rightmost_empty(OldCollector)); 404 } 405 #endif 406 407 ShenandoahFreeSet::ShenandoahFreeSet(ShenandoahHeap* heap, size_t max_regions) : 408 _heap(heap), 409 _free_sets(max_regions, this) 410 { 411 clear_internal(); 412 } 413 414 // This allocates from a region within the old_collector_set. If affiliation equals OLD, the allocation must be taken 415 // from a region that is_old(). Otherwise, affiliation should be FREE, in which case this will put a previously unaffiliated 416 // region into service. 417 HeapWord* ShenandoahFreeSet::allocate_old_with_affiliation(ShenandoahAffiliation affiliation, 418 ShenandoahAllocRequest& req, bool& in_new_region) { 419 shenandoah_assert_heaplocked(); 420 421 size_t rightmost = 422 (affiliation == ShenandoahAffiliation::FREE)? _free_sets.rightmost_empty(OldCollector): _free_sets.rightmost(OldCollector); 423 size_t leftmost = 424 (affiliation == ShenandoahAffiliation::FREE)? _free_sets.leftmost_empty(OldCollector): _free_sets.leftmost(OldCollector); 425 if (_free_sets.alloc_from_left_bias(OldCollector)) { 426 // This mode picks up stragglers left by a full GC 427 for (size_t idx = leftmost; idx <= rightmost; idx++) { 428 if (_free_sets.in_free_set(idx, OldCollector)) { 429 ShenandoahHeapRegion* r = _heap->get_region(idx); 430 assert(r->is_trash() || !r->is_affiliated() || r->is_old(), "old_collector_set region has bad affiliation"); 431 if (r->affiliation() == affiliation) { 432 HeapWord* result = try_allocate_in(r, req, in_new_region); 433 if (result != nullptr) { 434 return result; 435 } 436 } 437 } 438 } 439 } else { 440 // This mode picks up stragglers left by a previous concurrent GC 441 for (size_t count = rightmost + 1; count > leftmost; count--) { 442 // size_t is unsigned, need to dodge underflow when _leftmost = 0 443 size_t idx = count - 1; 444 if (_free_sets.in_free_set(idx, OldCollector)) { 445 ShenandoahHeapRegion* r = _heap->get_region(idx); 446 assert(r->is_trash() || !r->is_affiliated() || r->is_old(), "old_collector_set region has bad affiliation"); 447 if (r->affiliation() == affiliation) { 448 HeapWord* result = try_allocate_in(r, req, in_new_region); 449 if (result != nullptr) { 450 return result; 451 } 452 } 453 } 454 } 455 } 456 return nullptr; 457 } 458 459 void ShenandoahFreeSet::add_old_collector_free_region(ShenandoahHeapRegion* region) { 460 shenandoah_assert_heaplocked(); 461 size_t idx = region->index(); 462 size_t capacity = alloc_capacity(region); 463 assert(_free_sets.membership(idx) == NotFree, "Regions promoted in place should not be in any free set"); 464 if (capacity >= PLAB::min_size() * HeapWordSize) { 465 _free_sets.make_free(idx, OldCollector, capacity); 466 _heap->augment_promo_reserve(capacity); 467 } 468 } 469 470 HeapWord* ShenandoahFreeSet::allocate_with_affiliation(ShenandoahAffiliation affiliation, 471 ShenandoahAllocRequest& req, bool& in_new_region) { 472 shenandoah_assert_heaplocked(); 473 size_t rightmost = 474 (affiliation == ShenandoahAffiliation::FREE)? _free_sets.rightmost_empty(Collector): _free_sets.rightmost(Collector); 475 size_t leftmost = 476 (affiliation == ShenandoahAffiliation::FREE)? _free_sets.leftmost_empty(Collector): _free_sets.leftmost(Collector); 477 for (size_t c = rightmost + 1; c > leftmost; c--) { 478 // size_t is unsigned, need to dodge underflow when _leftmost = 0 479 size_t idx = c - 1; 480 if (_free_sets.in_free_set(idx, Collector)) { 481 ShenandoahHeapRegion* r = _heap->get_region(idx); 482 if (r->affiliation() == affiliation) { 483 HeapWord* result = try_allocate_in(r, req, in_new_region); 484 if (result != nullptr) { 485 return result; 486 } 487 } 488 } 489 } 490 log_debug(gc, free)("Could not allocate collector region with affiliation: %s for request " PTR_FORMAT, 491 shenandoah_affiliation_name(affiliation), p2i(&req)); 492 return nullptr; 493 } 494 495 HeapWord* ShenandoahFreeSet::allocate_single(ShenandoahAllocRequest& req, bool& in_new_region) { 496 shenandoah_assert_heaplocked(); 497 498 // Scan the bitmap looking for a first fit. 499 // 500 // Leftmost and rightmost bounds provide enough caching to walk bitmap efficiently. Normally, 501 // we would find the region to allocate at right away. 502 // 503 // Allocations are biased: new application allocs go to beginning of the heap, and GC allocs 504 // go to the end. This makes application allocation faster, because we would clear lots 505 // of regions from the beginning most of the time. 506 // 507 // Free set maintains mutator and collector views, and normally they allocate in their views only, 508 // unless we special cases for stealing and mixed allocations. 509 510 // Overwrite with non-zero (non-NULL) values only if necessary for allocation bookkeeping. 511 512 bool allow_new_region = true; 513 if (_heap->mode()->is_generational()) { 514 switch (req.affiliation()) { 515 case ShenandoahAffiliation::OLD_GENERATION: 516 // Note: unsigned result from free_unaffiliated_regions() will never be less than zero, but it may equal zero. 517 if (_heap->old_generation()->free_unaffiliated_regions() <= 0) { 518 allow_new_region = false; 519 } 520 break; 521 522 case ShenandoahAffiliation::YOUNG_GENERATION: 523 // Note: unsigned result from free_unaffiliated_regions() will never be less than zero, but it may equal zero. 524 if (_heap->young_generation()->free_unaffiliated_regions() <= 0) { 525 allow_new_region = false; 526 } 527 break; 528 529 case ShenandoahAffiliation::FREE: 530 fatal("Should request affiliation"); 531 532 default: 533 ShouldNotReachHere(); 534 break; 535 } 536 } 537 switch (req.type()) { 538 case ShenandoahAllocRequest::_alloc_tlab: 539 case ShenandoahAllocRequest::_alloc_shared: { 540 // Try to allocate in the mutator view 541 for (size_t idx = _free_sets.leftmost(Mutator); idx <= _free_sets.rightmost(Mutator); idx++) { 542 ShenandoahHeapRegion* r = _heap->get_region(idx); 543 if (_free_sets.in_free_set(idx, Mutator) && (allow_new_region || r->is_affiliated())) { 544 // try_allocate_in() increases used if the allocation is successful. 545 HeapWord* result; 546 size_t min_size = (req.type() == ShenandoahAllocRequest::_alloc_tlab)? req.min_size(): req.size(); 547 if ((alloc_capacity(r) >= min_size) && ((result = try_allocate_in(r, req, in_new_region)) != nullptr)) { 548 return result; 549 } 550 } 551 } 552 // There is no recovery. Mutator does not touch collector view at all. 553 break; 554 } 555 case ShenandoahAllocRequest::_alloc_gclab: 556 // GCLABs are for evacuation so we must be in evacuation phase. If this allocation is successful, increment 557 // the relevant evac_expended rather than used value. 558 559 case ShenandoahAllocRequest::_alloc_plab: 560 // PLABs always reside in old-gen and are only allocated during evacuation phase. 561 562 case ShenandoahAllocRequest::_alloc_shared_gc: { 563 if (!_heap->mode()->is_generational()) { 564 // size_t is unsigned, need to dodge underflow when _leftmost = 0 565 // Fast-path: try to allocate in the collector view first 566 for (size_t c = _free_sets.rightmost(Collector) + 1; c > _free_sets.leftmost(Collector); c--) { 567 size_t idx = c - 1; 568 if (_free_sets.in_free_set(idx, Collector)) { 569 HeapWord* result = try_allocate_in(_heap->get_region(idx), req, in_new_region); 570 if (result != nullptr) { 571 return result; 572 } 573 } 574 } 575 } else { 576 // First try to fit into a region that is already in use in the same generation. 577 HeapWord* result; 578 if (req.is_old()) { 579 result = allocate_old_with_affiliation(req.affiliation(), req, in_new_region); 580 } else { 581 result = allocate_with_affiliation(req.affiliation(), req, in_new_region); 582 } 583 if (result != nullptr) { 584 return result; 585 } 586 if (allow_new_region) { 587 // Then try a free region that is dedicated to GC allocations. 588 if (req.is_old()) { 589 result = allocate_old_with_affiliation(FREE, req, in_new_region); 590 } else { 591 result = allocate_with_affiliation(FREE, req, in_new_region); 592 } 593 if (result != nullptr) { 594 return result; 595 } 596 } 597 } 598 // No dice. Can we borrow space from mutator view? 599 if (!ShenandoahEvacReserveOverflow) { 600 return nullptr; 601 } 602 603 if (!allow_new_region && req.is_old() && (_heap->young_generation()->free_unaffiliated_regions() > 0)) { 604 // This allows us to flip a mutator region to old_collector 605 allow_new_region = true; 606 } 607 608 // We should expand old-gen if this can prevent an old-gen evacuation failure. We don't care so much about 609 // promotion failures since they can be mitigated in a subsequent GC pass. Would be nice to know if this 610 // allocation request is for evacuation or promotion. Individual threads limit their use of PLAB memory for 611 // promotions, so we already have an assurance that any additional memory set aside for old-gen will be used 612 // only for old-gen evacuations. 613 614 // Also TODO: 615 // if (GC is idle (out of cycle) and mutator allocation fails and there is memory reserved in Collector 616 // or OldCollector sets, transfer a region of memory so that we can satisfy the allocation request, and 617 // immediately trigger the start of GC. Is better to satisfy the allocation than to trigger out-of-cycle 618 // allocation failure (even if this means we have a little less memory to handle evacuations during the 619 // subsequent GC pass). 620 621 if (allow_new_region) { 622 // Try to steal an empty region from the mutator view. 623 for (size_t c = _free_sets.rightmost_empty(Mutator) + 1; c > _free_sets.leftmost_empty(Mutator); c--) { 624 size_t idx = c - 1; 625 if (_free_sets.in_free_set(idx, Mutator)) { 626 ShenandoahHeapRegion* r = _heap->get_region(idx); 627 if (can_allocate_from(r)) { 628 if (req.is_old()) { 629 flip_to_old_gc(r); 630 } else { 631 flip_to_gc(r); 632 } 633 HeapWord *result = try_allocate_in(r, req, in_new_region); 634 if (result != nullptr) { 635 log_debug(gc, free)("Flipped region " SIZE_FORMAT " to gc for request: " PTR_FORMAT, idx, p2i(&req)); 636 return result; 637 } 638 } 639 } 640 } 641 } 642 643 // No dice. Do not try to mix mutator and GC allocations, because 644 // URWM moves due to GC allocations would expose unparsable mutator 645 // allocations. 646 break; 647 } 648 default: 649 ShouldNotReachHere(); 650 } 651 return nullptr; 652 } 653 654 // This work method takes an argument corresponding to the number of bytes 655 // free in a region, and returns the largest amount in heapwords that can be allocated 656 // such that both of the following conditions are satisfied: 657 // 658 // 1. it is a multiple of card size 659 // 2. any remaining shard may be filled with a filler object 660 // 661 // The idea is that the allocation starts and ends at card boundaries. Because 662 // a region ('s end) is card-aligned, the remainder shard that must be filled is 663 // at the start of the free space. 664 // 665 // This is merely a helper method to use for the purpose of such a calculation. 666 size_t get_usable_free_words(size_t free_bytes) { 667 // e.g. card_size is 512, card_shift is 9, min_fill_size() is 8 668 // free is 514 669 // usable_free is 512, which is decreased to 0 670 size_t usable_free = (free_bytes / CardTable::card_size()) << CardTable::card_shift(); 671 assert(usable_free <= free_bytes, "Sanity check"); 672 if ((free_bytes != usable_free) && (free_bytes - usable_free < ShenandoahHeap::min_fill_size() * HeapWordSize)) { 673 // After aligning to card multiples, the remainder would be smaller than 674 // the minimum filler object, so we'll need to take away another card's 675 // worth to construct a filler object. 676 if (usable_free >= CardTable::card_size()) { 677 usable_free -= CardTable::card_size(); 678 } else { 679 assert(usable_free == 0, "usable_free is a multiple of card_size and card_size > min_fill_size"); 680 } 681 } 682 683 return usable_free / HeapWordSize; 684 } 685 686 // Given a size argument, which is a multiple of card size, a request struct 687 // for a PLAB, and an old region, return a pointer to the allocated space for 688 // a PLAB which is card-aligned and where any remaining shard in the region 689 // has been suitably filled by a filler object. 690 // It is assumed (and assertion-checked) that such an allocation is always possible. 691 HeapWord* ShenandoahFreeSet::allocate_aligned_plab(size_t size, ShenandoahAllocRequest& req, ShenandoahHeapRegion* r) { 692 assert(_heap->mode()->is_generational(), "PLABs are only for generational mode"); 693 assert(r->is_old(), "All PLABs reside in old-gen"); 694 assert(!req.is_mutator_alloc(), "PLABs should not be allocated by mutators."); 695 assert(size % CardTable::card_size_in_words() == 0, "size must be multiple of card table size, was " SIZE_FORMAT, size); 696 697 HeapWord* result = r->allocate_aligned(size, req, CardTable::card_size()); 698 assert(result != nullptr, "Allocation cannot fail"); 699 assert(r->top() <= r->end(), "Allocation cannot span end of region"); 700 assert(req.actual_size() == size, "Should not have needed to adjust size for PLAB."); 701 assert(((uintptr_t) result) % CardTable::card_size_in_words() == 0, "PLAB start must align with card boundary"); 702 703 return result; 704 } 705 706 HeapWord* ShenandoahFreeSet::try_allocate_in(ShenandoahHeapRegion* r, ShenandoahAllocRequest& req, bool& in_new_region) { 707 assert (has_alloc_capacity(r), "Performance: should avoid full regions on this path: " SIZE_FORMAT, r->index()); 708 if (_heap->is_concurrent_weak_root_in_progress() && r->is_trash()) { 709 return nullptr; 710 } 711 712 try_recycle_trashed(r); 713 if (!r->is_affiliated()) { 714 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context(); 715 r->set_affiliation(req.affiliation()); 716 if (r->is_old()) { 717 // Any OLD region allocated during concurrent coalesce-and-fill does not need to be coalesced and filled because 718 // all objects allocated within this region are above TAMS (and thus are implicitly marked). In case this is an 719 // OLD region and concurrent preparation for mixed evacuations visits this region before the start of the next 720 // old-gen concurrent mark (i.e. this region is allocated following the start of old-gen concurrent mark but before 721 // concurrent preparations for mixed evacuations are completed), we mark this region as not requiring any 722 // coalesce-and-fill processing. 723 r->end_preemptible_coalesce_and_fill(); 724 _heap->clear_cards_for(r); 725 _heap->old_generation()->increment_affiliated_region_count(); 726 } else { 727 _heap->young_generation()->increment_affiliated_region_count(); 728 } 729 730 assert(ctx->top_at_mark_start(r) == r->bottom(), "Newly established allocation region starts with TAMS equal to bottom"); 731 assert(ctx->is_bitmap_clear_range(ctx->top_bitmap(r), r->end()), "Bitmap above top_bitmap() must be clear"); 732 } else if (r->affiliation() != req.affiliation()) { 733 assert(_heap->mode()->is_generational(), "Request for %s from %s region should only happen in generational mode.", 734 req.affiliation_name(), r->affiliation_name()); 735 return nullptr; 736 } 737 738 in_new_region = r->is_empty(); 739 HeapWord* result = nullptr; 740 741 if (in_new_region) { 742 log_debug(gc, free)("Using new region (" SIZE_FORMAT ") for %s (" PTR_FORMAT ").", 743 r->index(), ShenandoahAllocRequest::alloc_type_to_string(req.type()), p2i(&req)); 744 } 745 746 // req.size() is in words, r->free() is in bytes. 747 if (ShenandoahElasticTLAB && req.is_lab_alloc()) { 748 if (req.type() == ShenandoahAllocRequest::_alloc_plab) { 749 assert(_heap->mode()->is_generational(), "PLABs are only for generational mode"); 750 assert(_free_sets.in_free_set(r->index(), OldCollector), "PLABS must be allocated in old_collector_free regions"); 751 // Need to assure that plabs are aligned on multiple of card region. 752 // Since we have Elastic TLABs, align sizes up. They may be decreased to fit in the usable 753 // memory remaining in the region (which will also be aligned to cards). 754 size_t adjusted_size = align_up(req.size(), CardTable::card_size_in_words()); 755 size_t adjusted_min_size = align_up(req.min_size(), CardTable::card_size_in_words()); 756 size_t usable_free = get_usable_free_words(r->free()); 757 758 if (adjusted_size > usable_free) { 759 adjusted_size = usable_free; 760 } 761 762 if (adjusted_size >= adjusted_min_size) { 763 result = allocate_aligned_plab(adjusted_size, req, r); 764 } 765 // Otherwise, leave result == nullptr because the adjusted size is smaller than min size. 766 } else { 767 // This is a GCLAB or a TLAB allocation 768 size_t adjusted_size = req.size(); 769 size_t free = align_down(r->free() >> LogHeapWordSize, MinObjAlignment); 770 if (adjusted_size > free) { 771 adjusted_size = free; 772 } 773 if (adjusted_size >= req.min_size()) { 774 result = r->allocate(adjusted_size, req); 775 assert (result != nullptr, "Allocation must succeed: free " SIZE_FORMAT ", actual " SIZE_FORMAT, free, adjusted_size); 776 req.set_actual_size(adjusted_size); 777 } else { 778 log_trace(gc, free)("Failed to shrink TLAB or GCLAB request (" SIZE_FORMAT ") in region " SIZE_FORMAT " to " SIZE_FORMAT 779 " because min_size() is " SIZE_FORMAT, req.size(), r->index(), adjusted_size, req.min_size()); 780 } 781 } 782 } else if (req.is_lab_alloc() && req.type() == ShenandoahAllocRequest::_alloc_plab) { 783 784 // inelastic PLAB 785 size_t size = req.size(); 786 size_t usable_free = get_usable_free_words(r->free()); 787 if (size <= usable_free) { 788 result = allocate_aligned_plab(size, req, r); 789 } 790 } else { 791 size_t size = req.size(); 792 result = r->allocate(size, req); 793 if (result != nullptr) { 794 // Record actual allocation size 795 req.set_actual_size(size); 796 } 797 } 798 799 ShenandoahGeneration* generation = _heap->generation_for(req.affiliation()); 800 if (result != nullptr) { 801 // Allocation successful, bump stats: 802 if (req.is_mutator_alloc()) { 803 assert(req.is_young(), "Mutator allocations always come from young generation."); 804 _free_sets.increase_used(Mutator, req.actual_size() * HeapWordSize); 805 } else { 806 assert(req.is_gc_alloc(), "Should be gc_alloc since req wasn't mutator alloc"); 807 808 // For GC allocations, we advance update_watermark because the objects relocated into this memory during 809 // evacuation are not updated during evacuation. For both young and old regions r, it is essential that all 810 // PLABs be made parsable at the end of evacuation. This is enabled by retiring all plabs at end of evacuation. 811 // TODO: Making a PLAB parsable involves placing a filler object in its remnant memory but does not require 812 // that the PLAB be disabled for all future purposes. We may want to introduce a new service to make the 813 // PLABs parsable while still allowing the PLAB to serve future allocation requests that arise during the 814 // next evacuation pass. 815 r->set_update_watermark(r->top()); 816 if (r->is_old()) { 817 assert(req.type() != ShenandoahAllocRequest::_alloc_gclab, "old-gen allocations use PLAB or shared allocation"); 818 // for plabs, we'll sort the difference between evac and promotion usage when we retire the plab 819 } 820 } 821 } 822 823 if (result == nullptr || alloc_capacity(r) < PLAB::min_size() * HeapWordSize) { 824 // Region cannot afford this and is likely to not afford future allocations. Retire it. 825 // 826 // While this seems a bit harsh, especially in the case when this large allocation does not 827 // fit but the next small one would, we are risking to inflate scan times when lots of 828 // almost-full regions precede the fully-empty region where we want to allocate the entire TLAB. 829 830 // Record the remainder as allocation waste 831 size_t idx = r->index(); 832 if (req.is_mutator_alloc()) { 833 size_t waste = r->free(); 834 if (waste > 0) { 835 _free_sets.increase_used(Mutator, waste); 836 // This one request could cause several regions to be "retired", so we must accumulate the waste 837 req.set_waste((waste >> LogHeapWordSize) + req.waste()); 838 } 839 assert(_free_sets.membership(idx) == Mutator, "Must be mutator free: " SIZE_FORMAT, idx); 840 } else { 841 assert(_free_sets.membership(idx) == Collector || _free_sets.membership(idx) == OldCollector, 842 "Must be collector or old-collector free: " SIZE_FORMAT, idx); 843 } 844 // This region is no longer considered free (in any set) 845 _free_sets.remove_from_free_sets(idx); 846 _free_sets.assert_bounds(); 847 } 848 return result; 849 } 850 851 HeapWord* ShenandoahFreeSet::allocate_contiguous(ShenandoahAllocRequest& req) { 852 shenandoah_assert_heaplocked(); 853 854 size_t words_size = req.size(); 855 size_t num = ShenandoahHeapRegion::required_regions(words_size * HeapWordSize); 856 857 assert(req.is_young(), "Humongous regions always allocated in YOUNG"); 858 ShenandoahGeneration* generation = _heap->generation_for(req.affiliation()); 859 860 // Check if there are enough regions left to satisfy allocation. 861 if (_heap->mode()->is_generational()) { 862 size_t avail_young_regions = generation->free_unaffiliated_regions(); 863 if (num > _free_sets.count(Mutator) || (num > avail_young_regions)) { 864 return nullptr; 865 } 866 } else { 867 if (num > _free_sets.count(Mutator)) { 868 return nullptr; 869 } 870 } 871 872 // Find the continuous interval of $num regions, starting from $beg and ending in $end, 873 // inclusive. Contiguous allocations are biased to the beginning. 874 875 size_t beg = _free_sets.leftmost(Mutator); 876 size_t end = beg; 877 878 while (true) { 879 if (end >= _free_sets.max()) { 880 // Hit the end, goodbye 881 return nullptr; 882 } 883 884 // If regions are not adjacent, then current [beg; end] is useless, and we may fast-forward. 885 // If region is not completely free, the current [beg; end] is useless, and we may fast-forward. 886 if (!_free_sets.in_free_set(end, Mutator) || !can_allocate_from(_heap->get_region(end))) { 887 end++; 888 beg = end; 889 continue; 890 } 891 892 if ((end - beg + 1) == num) { 893 // found the match 894 break; 895 } 896 897 end++; 898 }; 899 900 size_t remainder = words_size & ShenandoahHeapRegion::region_size_words_mask(); 901 ShenandoahMarkingContext* const ctx = _heap->complete_marking_context(); 902 903 // Initialize regions: 904 for (size_t i = beg; i <= end; i++) { 905 ShenandoahHeapRegion* r = _heap->get_region(i); 906 try_recycle_trashed(r); 907 908 assert(i == beg || _heap->get_region(i - 1)->index() + 1 == r->index(), "Should be contiguous"); 909 assert(r->is_empty(), "Should be empty"); 910 911 if (i == beg) { 912 r->make_humongous_start(); 913 } else { 914 r->make_humongous_cont(); 915 } 916 917 // Trailing region may be non-full, record the remainder there 918 size_t used_words; 919 if ((i == end) && (remainder != 0)) { 920 used_words = remainder; 921 } else { 922 used_words = ShenandoahHeapRegion::region_size_words(); 923 } 924 925 r->set_affiliation(req.affiliation()); 926 r->set_update_watermark(r->bottom()); 927 r->set_top(r->bottom() + used_words); 928 929 // While individual regions report their true use, all humongous regions are marked used in the free set. 930 _free_sets.remove_from_free_sets(r->index()); 931 } 932 _heap->young_generation()->increase_affiliated_region_count(num); 933 934 size_t total_humongous_size = ShenandoahHeapRegion::region_size_bytes() * num; 935 _free_sets.increase_used(Mutator, total_humongous_size); 936 _free_sets.assert_bounds(); 937 req.set_actual_size(words_size); 938 if (remainder != 0) { 939 req.set_waste(ShenandoahHeapRegion::region_size_words() - remainder); 940 } 941 return _heap->get_region(beg)->bottom(); 942 } 943 944 // Returns true iff this region is entirely available, either because it is empty() or because it has been found to represent 945 // immediate trash and we'll be able to immediately recycle it. Note that we cannot recycle immediate trash if 946 // concurrent weak root processing is in progress. 947 bool ShenandoahFreeSet::can_allocate_from(ShenandoahHeapRegion *r) const { 948 return r->is_empty() || (r->is_trash() && !_heap->is_concurrent_weak_root_in_progress()); 949 } 950 951 bool ShenandoahFreeSet::can_allocate_from(size_t idx) const { 952 ShenandoahHeapRegion* r = _heap->get_region(idx); 953 return can_allocate_from(r); 954 } 955 956 size_t ShenandoahFreeSet::alloc_capacity(size_t idx) const { 957 ShenandoahHeapRegion* r = _heap->get_region(idx); 958 return alloc_capacity(r); 959 } 960 961 size_t ShenandoahFreeSet::alloc_capacity(ShenandoahHeapRegion *r) const { 962 if (r->is_trash()) { 963 // This would be recycled on allocation path 964 return ShenandoahHeapRegion::region_size_bytes(); 965 } else { 966 return r->free(); 967 } 968 } 969 970 bool ShenandoahFreeSet::has_alloc_capacity(ShenandoahHeapRegion *r) const { 971 return alloc_capacity(r) > 0; 972 } 973 974 bool ShenandoahFreeSet::has_alloc_capacity(size_t idx) const { 975 ShenandoahHeapRegion* r = _heap->get_region(idx); 976 return alloc_capacity(r) > 0; 977 } 978 979 bool ShenandoahFreeSet::has_no_alloc_capacity(ShenandoahHeapRegion *r) const { 980 return alloc_capacity(r) == 0; 981 } 982 983 void ShenandoahFreeSet::try_recycle_trashed(ShenandoahHeapRegion *r) { 984 if (r->is_trash()) { 985 r->recycle(); 986 } 987 } 988 989 void ShenandoahFreeSet::recycle_trash() { 990 // lock is not reentrable, check we don't have it 991 shenandoah_assert_not_heaplocked(); 992 993 for (size_t i = 0; i < _heap->num_regions(); i++) { 994 ShenandoahHeapRegion* r = _heap->get_region(i); 995 if (r->is_trash()) { 996 ShenandoahHeapLocker locker(_heap->lock()); 997 try_recycle_trashed(r); 998 } 999 SpinPause(); // allow allocators to take the lock 1000 } 1001 } 1002 1003 void ShenandoahFreeSet::flip_to_old_gc(ShenandoahHeapRegion* r) { 1004 size_t idx = r->index(); 1005 1006 assert(_free_sets.in_free_set(idx, Mutator), "Should be in mutator view"); 1007 // Note: can_allocate_from(r) means r is entirely empty 1008 assert(can_allocate_from(r), "Should not be allocated"); 1009 1010 size_t region_capacity = alloc_capacity(r); 1011 _free_sets.move_to_set(idx, OldCollector, region_capacity); 1012 _free_sets.assert_bounds(); 1013 _heap->generation_sizer()->force_transfer_to_old(1); 1014 _heap->augment_old_evac_reserve(region_capacity); 1015 // We do not ensure that the region is no longer trash, relying on try_allocate_in(), which always comes next, 1016 // to recycle trash before attempting to allocate anything in the region. 1017 } 1018 1019 void ShenandoahFreeSet::flip_to_gc(ShenandoahHeapRegion* r) { 1020 size_t idx = r->index(); 1021 1022 assert(_free_sets.in_free_set(idx, Mutator), "Should be in mutator view"); 1023 assert(can_allocate_from(r), "Should not be allocated"); 1024 1025 size_t region_capacity = alloc_capacity(r); 1026 _free_sets.move_to_set(idx, Collector, region_capacity); 1027 _free_sets.assert_bounds(); 1028 1029 // We do not ensure that the region is no longer trash, relying on try_allocate_in(), which always comes next, 1030 // to recycle trash before attempting to allocate anything in the region. 1031 } 1032 1033 void ShenandoahFreeSet::clear() { 1034 shenandoah_assert_heaplocked(); 1035 clear_internal(); 1036 } 1037 1038 void ShenandoahFreeSet::clear_internal() { 1039 _free_sets.clear_all(); 1040 } 1041 1042 // This function places all is_old() regions that have allocation capacity into the old_collector set. It places 1043 // all other regions (not is_old()) that have allocation capacity into the mutator_set. Subsequently, we will 1044 // move some of the mutator regions into the collector set or old_collector set with the intent of packing 1045 // old_collector memory into the highest (rightmost) addresses of the heap and the collector memory into the 1046 // next highest addresses of the heap, with mutator memory consuming the lowest addresses of the heap. 1047 void ShenandoahFreeSet::find_regions_with_alloc_capacity(size_t &young_cset_regions, size_t &old_cset_regions) { 1048 1049 old_cset_regions = 0; 1050 young_cset_regions = 0; 1051 for (size_t idx = 0; idx < _heap->num_regions(); idx++) { 1052 ShenandoahHeapRegion* region = _heap->get_region(idx); 1053 if (region->is_trash()) { 1054 // Trashed regions represent regions that had been in the collection set but have not yet been "cleaned up". 1055 if (region->is_old()) { 1056 old_cset_regions++; 1057 } else { 1058 assert(region->is_young(), "Trashed region should be old or young"); 1059 young_cset_regions++; 1060 } 1061 } 1062 if (region->is_alloc_allowed() || region->is_trash()) { 1063 assert(!region->is_cset(), "Shouldn't be adding cset regions to the free set"); 1064 assert(_free_sets.in_free_set(idx, NotFree), "We are about to make region free; it should not be free already"); 1065 1066 // Do not add regions that would almost surely fail allocation 1067 if (alloc_capacity(region) < PLAB::min_size() * HeapWordSize) continue; 1068 1069 if (region->is_old()) { 1070 _free_sets.make_free(idx, OldCollector, alloc_capacity(region)); 1071 log_debug(gc, free)( 1072 " Adding Region " SIZE_FORMAT " (Free: " SIZE_FORMAT "%s, Used: " SIZE_FORMAT "%s) to old collector set", 1073 idx, byte_size_in_proper_unit(region->free()), proper_unit_for_byte_size(region->free()), 1074 byte_size_in_proper_unit(region->used()), proper_unit_for_byte_size(region->used())); 1075 } else { 1076 _free_sets.make_free(idx, Mutator, alloc_capacity(region)); 1077 log_debug(gc, free)( 1078 " Adding Region " SIZE_FORMAT " (Free: " SIZE_FORMAT "%s, Used: " SIZE_FORMAT "%s) to mutator set", 1079 idx, byte_size_in_proper_unit(region->free()), proper_unit_for_byte_size(region->free()), 1080 byte_size_in_proper_unit(region->used()), proper_unit_for_byte_size(region->used())); 1081 } 1082 } 1083 } 1084 } 1085 1086 // Move no more than cset_regions from the existing Collector and OldCollector free sets to the Mutator free set. 1087 // This is called from outside the heap lock. 1088 void ShenandoahFreeSet::move_collector_sets_to_mutator(size_t max_xfer_regions) { 1089 size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes(); 1090 size_t collector_empty_xfer = 0; 1091 size_t collector_not_empty_xfer = 0; 1092 size_t old_collector_empty_xfer = 0; 1093 1094 // Process empty regions within the Collector free set 1095 if ((max_xfer_regions > 0) && (_free_sets.leftmost_empty(Collector) <= _free_sets.rightmost_empty(Collector))) { 1096 ShenandoahHeapLocker locker(_heap->lock()); 1097 for (size_t idx = _free_sets.leftmost_empty(Collector); 1098 (max_xfer_regions > 0) && (idx <= _free_sets.rightmost_empty(Collector)); idx++) { 1099 if (_free_sets.in_free_set(idx, Collector) && can_allocate_from(idx)) { 1100 _free_sets.move_to_set(idx, Mutator, region_size_bytes); 1101 max_xfer_regions--; 1102 collector_empty_xfer += region_size_bytes; 1103 } 1104 } 1105 } 1106 1107 // Process empty regions within the OldCollector free set 1108 size_t old_collector_regions = 0; 1109 if ((max_xfer_regions > 0) && (_free_sets.leftmost_empty(OldCollector) <= _free_sets.rightmost_empty(OldCollector))) { 1110 ShenandoahHeapLocker locker(_heap->lock()); 1111 for (size_t idx = _free_sets.leftmost_empty(OldCollector); 1112 (max_xfer_regions > 0) && (idx <= _free_sets.rightmost_empty(OldCollector)); idx++) { 1113 if (_free_sets.in_free_set(idx, OldCollector) && can_allocate_from(idx)) { 1114 _free_sets.move_to_set(idx, Mutator, region_size_bytes); 1115 max_xfer_regions--; 1116 old_collector_empty_xfer += region_size_bytes; 1117 old_collector_regions++; 1118 } 1119 } 1120 if (old_collector_regions > 0) { 1121 _heap->generation_sizer()->transfer_to_young(old_collector_regions); 1122 } 1123 } 1124 1125 // If there are any non-empty regions within Collector set, we can also move them to the Mutator free set 1126 if ((max_xfer_regions > 0) && (_free_sets.leftmost(Collector) <= _free_sets.rightmost(Collector))) { 1127 ShenandoahHeapLocker locker(_heap->lock()); 1128 for (size_t idx = _free_sets.leftmost(Collector); (max_xfer_regions > 0) && (idx <= _free_sets.rightmost(Collector)); idx++) { 1129 size_t alloc_capacity = this->alloc_capacity(idx); 1130 if (_free_sets.in_free_set(idx, Collector) && (alloc_capacity > 0)) { 1131 _free_sets.move_to_set(idx, Mutator, alloc_capacity); 1132 max_xfer_regions--; 1133 collector_not_empty_xfer += alloc_capacity; 1134 } 1135 } 1136 } 1137 1138 size_t collector_xfer = collector_empty_xfer + collector_not_empty_xfer; 1139 size_t total_xfer = collector_xfer + old_collector_empty_xfer; 1140 log_info(gc, free)("At start of update refs, moving " SIZE_FORMAT "%s to Mutator free set from Collector Reserve (" 1141 SIZE_FORMAT "%s) and from Old Collector Reserve (" SIZE_FORMAT "%s)", 1142 byte_size_in_proper_unit(total_xfer), proper_unit_for_byte_size(total_xfer), 1143 byte_size_in_proper_unit(collector_xfer), proper_unit_for_byte_size(collector_xfer), 1144 byte_size_in_proper_unit(old_collector_empty_xfer), proper_unit_for_byte_size(old_collector_empty_xfer)); 1145 } 1146 1147 1148 // Overwrite arguments to represent the amount of memory in each generation that is about to be recycled 1149 void ShenandoahFreeSet::prepare_to_rebuild(size_t &young_cset_regions, size_t &old_cset_regions) { 1150 shenandoah_assert_heaplocked(); 1151 // This resets all state information, removing all regions from all sets. 1152 clear(); 1153 log_debug(gc, free)("Rebuilding FreeSet"); 1154 1155 // This places regions that have alloc_capacity into the old_collector set if they identify as is_old() or the 1156 // mutator set otherwise. 1157 find_regions_with_alloc_capacity(young_cset_regions, old_cset_regions); 1158 } 1159 1160 void ShenandoahFreeSet::rebuild(size_t young_cset_regions, size_t old_cset_regions) { 1161 shenandoah_assert_heaplocked(); 1162 size_t young_reserve, old_reserve; 1163 size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes(); 1164 1165 size_t old_capacity = _heap->old_generation()->max_capacity(); 1166 size_t old_available = _heap->old_generation()->available(); 1167 size_t old_unaffiliated_regions = _heap->old_generation()->free_unaffiliated_regions(); 1168 size_t young_capacity = _heap->young_generation()->max_capacity(); 1169 size_t young_available = _heap->young_generation()->available(); 1170 size_t young_unaffiliated_regions = _heap->young_generation()->free_unaffiliated_regions(); 1171 1172 old_unaffiliated_regions += old_cset_regions; 1173 old_available += old_cset_regions * region_size_bytes; 1174 young_unaffiliated_regions += young_cset_regions; 1175 young_available += young_cset_regions * region_size_bytes; 1176 1177 // Consult old-region surplus and deficit to make adjustments to current generation capacities and availability. 1178 // The generation region transfers take place after we rebuild. 1179 size_t old_region_surplus = _heap->get_old_region_surplus(); 1180 size_t old_region_deficit = _heap->get_old_region_deficit(); 1181 1182 if (old_region_surplus > 0) { 1183 size_t xfer_bytes = old_region_surplus * region_size_bytes; 1184 assert(old_region_surplus <= old_unaffiliated_regions, "Cannot transfer regions that are affiliated"); 1185 old_capacity -= xfer_bytes; 1186 old_available -= xfer_bytes; 1187 old_unaffiliated_regions -= old_region_surplus; 1188 young_capacity += xfer_bytes; 1189 young_available += xfer_bytes; 1190 young_unaffiliated_regions += old_region_surplus; 1191 } else if (old_region_deficit > 0) { 1192 size_t xfer_bytes = old_region_deficit * region_size_bytes; 1193 assert(old_region_deficit <= young_unaffiliated_regions, "Cannot transfer regions that are affiliated"); 1194 old_capacity += xfer_bytes; 1195 old_available += xfer_bytes; 1196 old_unaffiliated_regions += old_region_deficit; 1197 young_capacity -= xfer_bytes;; 1198 young_available -= xfer_bytes; 1199 young_unaffiliated_regions -= old_region_deficit; 1200 } 1201 1202 // Evac reserve: reserve trailing space for evacuations, with regions reserved for old evacuations placed to the right 1203 // of regions reserved of young evacuations. 1204 if (!_heap->mode()->is_generational()) { 1205 young_reserve = (_heap->max_capacity() / 100) * ShenandoahEvacReserve; 1206 old_reserve = 0; 1207 } else { 1208 // All allocations taken from the old collector set are performed by GC, generally using PLABs for both 1209 // promotions and evacuations. The partition between which old memory is reserved for evacuation and 1210 // which is reserved for promotion is enforced using thread-local variables that prescribe intentons for 1211 // each PLAB's available memory. 1212 if (_heap->has_evacuation_reserve_quantities()) { 1213 // We are rebuilding at the end of final mark, having already established evacuation budgets for this GC pass. 1214 young_reserve = _heap->get_young_evac_reserve(); 1215 old_reserve = _heap->get_promoted_reserve() + _heap->get_old_evac_reserve(); 1216 assert(old_reserve <= old_available, 1217 "Cannot reserve (" SIZE_FORMAT " + " SIZE_FORMAT") more OLD than is available: " SIZE_FORMAT, 1218 _heap->get_promoted_reserve(), _heap->get_old_evac_reserve(), old_available); 1219 } else { 1220 // We are rebuilding at end of GC, so we set aside budgets specified on command line (or defaults) 1221 young_reserve = (young_capacity * ShenandoahEvacReserve) / 100; 1222 // The auto-sizer has already made old-gen large enough to hold all anticipated evacuations and promotions. 1223 // Affiliated old-gen regions are already in the OldCollector free set. Add in the relevant number of 1224 // unaffiliated regions. 1225 old_reserve = old_available; 1226 } 1227 } 1228 if (old_reserve > _free_sets.capacity_of(OldCollector)) { 1229 // Old available regions that have less than PLAB::min_size() of available memory are not placed into the OldCollector 1230 // free set. Because of this, old_available may not have enough memory to represent the intended reserve. Adjust 1231 // the reserve downward to account for this possibility. This loss is part of the reason why the original budget 1232 // was adjusted with ShenandoahOldEvacWaste and ShenandoahOldPromoWaste multipliers. 1233 if (old_reserve > _free_sets.capacity_of(OldCollector) + old_unaffiliated_regions * region_size_bytes) { 1234 old_reserve = _free_sets.capacity_of(OldCollector) + old_unaffiliated_regions * region_size_bytes; 1235 } 1236 } 1237 if (young_reserve > young_unaffiliated_regions * region_size_bytes) { 1238 young_reserve = young_unaffiliated_regions * region_size_bytes; 1239 } 1240 1241 reserve_regions(young_reserve, old_reserve); 1242 _free_sets.establish_alloc_bias(OldCollector); 1243 _free_sets.assert_bounds(); 1244 log_status(); 1245 } 1246 1247 // Having placed all regions that have allocation capacity into the mutator set if they identify as is_young() 1248 // or into the old collector set if they identify as is_old(), move some of these regions from the mutator set 1249 // into the collector set or old collector set in order to assure that the memory available for allocations within 1250 // the collector set is at least to_reserve, and the memory available for allocations within the old collector set 1251 // is at least to_reserve_old. 1252 void ShenandoahFreeSet::reserve_regions(size_t to_reserve, size_t to_reserve_old) { 1253 for (size_t i = _heap->num_regions(); i > 0; i--) { 1254 size_t idx = i - 1; 1255 ShenandoahHeapRegion* r = _heap->get_region(idx); 1256 if (_free_sets.in_free_set(idx, Mutator)) { 1257 assert (!r->is_old(), "mutator_is_free regions should not be affiliated OLD"); 1258 size_t ac = alloc_capacity(r); 1259 assert (ac > 0, "Membership in free set implies has capacity"); 1260 1261 // OLD regions that have available memory are already in the old_collector free set 1262 if ((_free_sets.capacity_of(OldCollector) < to_reserve_old) && (r->is_trash() || !r->is_affiliated())) { 1263 _free_sets.move_to_set(idx, OldCollector, alloc_capacity(r)); 1264 log_debug(gc, free)(" Shifting region " SIZE_FORMAT " from mutator_free to old_collector_free", idx); 1265 } else if (_free_sets.capacity_of(Collector) < to_reserve) { 1266 // Note: In a previous implementation, regions were only placed into the survivor space (collector_is_free) if 1267 // they were entirely empty. I'm not sure I understand the rational for that. That alternative behavior would 1268 // tend to mix survivor objects with ephemeral objects, making it more difficult to reclaim the memory for the 1269 // ephemeral objects. It also delays aging of regions, causing promotion in place to be delayed. 1270 _free_sets.move_to_set(idx, Collector, ac); 1271 log_debug(gc)(" Shifting region " SIZE_FORMAT " from mutator_free to collector_free", idx); 1272 } else { 1273 // We've satisfied both to_reserve and to_reserved_old 1274 break; 1275 } 1276 } 1277 } 1278 } 1279 1280 void ShenandoahFreeSet::log_status() { 1281 shenandoah_assert_heaplocked(); 1282 1283 #ifdef ASSERT 1284 // Dump of the FreeSet details is only enabled if assertions are enabled 1285 { 1286 #define BUFFER_SIZE 80 1287 size_t retired_old = 0; 1288 size_t retired_old_humongous = 0; 1289 size_t retired_young = 0; 1290 size_t retired_young_humongous = 0; 1291 size_t region_size_bytes = ShenandoahHeapRegion::region_size_bytes(); 1292 size_t retired_young_waste = 0; 1293 size_t retired_old_waste = 0; 1294 size_t consumed_collector = 0; 1295 size_t consumed_old_collector = 0; 1296 size_t consumed_mutator = 0; 1297 size_t available_old = 0; 1298 size_t available_young = 0; 1299 size_t available_mutator = 0; 1300 size_t available_collector = 0; 1301 size_t available_old_collector = 0; 1302 1303 char buffer[BUFFER_SIZE]; 1304 for (uint i = 0; i < BUFFER_SIZE; i++) { 1305 buffer[i] = '\0'; 1306 } 1307 log_info(gc, free)("FreeSet map legend:" 1308 " M:mutator_free C:collector_free O:old_collector_free" 1309 " H:humongous ~:retired old _:retired young"); 1310 log_info(gc, free)(" mutator free range [" SIZE_FORMAT ".." SIZE_FORMAT "], " 1311 " collector free range [" SIZE_FORMAT ".." SIZE_FORMAT "], " 1312 "old collector free range [" SIZE_FORMAT ".." SIZE_FORMAT "] allocates from %s", 1313 _free_sets.leftmost(Mutator), _free_sets.rightmost(Mutator), 1314 _free_sets.leftmost(Collector), _free_sets.rightmost(Collector), 1315 _free_sets.leftmost(OldCollector), _free_sets.rightmost(OldCollector), 1316 _free_sets.alloc_from_left_bias(OldCollector)? "left to right": "right to left"); 1317 1318 for (uint i = 0; i < _heap->num_regions(); i++) { 1319 ShenandoahHeapRegion *r = _heap->get_region(i); 1320 uint idx = i % 64; 1321 if ((i != 0) && (idx == 0)) { 1322 log_info(gc, free)(" %6u: %s", i-64, buffer); 1323 } 1324 if (_free_sets.in_free_set(i, Mutator)) { 1325 assert(!r->is_old(), "Old regions should not be in mutator_free set"); 1326 size_t capacity = alloc_capacity(r); 1327 available_mutator += capacity; 1328 consumed_mutator += region_size_bytes - capacity; 1329 buffer[idx] = (capacity == region_size_bytes)? 'M': 'm'; 1330 } else if (_free_sets.in_free_set(i, Collector)) { 1331 assert(!r->is_old(), "Old regions should not be in collector_free set"); 1332 size_t capacity = alloc_capacity(r); 1333 available_collector += capacity; 1334 consumed_collector += region_size_bytes - capacity; 1335 buffer[idx] = (capacity == region_size_bytes)? 'C': 'c'; 1336 } else if (_free_sets.in_free_set(i, OldCollector)) { 1337 size_t capacity = alloc_capacity(r); 1338 available_old_collector += capacity; 1339 consumed_old_collector += region_size_bytes - capacity; 1340 buffer[idx] = (capacity == region_size_bytes)? 'O': 'o'; 1341 } else if (r->is_humongous()) { 1342 if (r->is_old()) { 1343 buffer[idx] = 'H'; 1344 retired_old_humongous += region_size_bytes; 1345 } else { 1346 buffer[idx] = 'h'; 1347 retired_young_humongous += region_size_bytes; 1348 } 1349 } else { 1350 if (r->is_old()) { 1351 buffer[idx] = '~'; 1352 retired_old_waste += alloc_capacity(r); 1353 retired_old += region_size_bytes; 1354 } else { 1355 buffer[idx] = '_'; 1356 retired_young_waste += alloc_capacity(r); 1357 retired_young += region_size_bytes; 1358 } 1359 } 1360 } 1361 uint remnant = _heap->num_regions() % 64; 1362 if (remnant > 0) { 1363 buffer[remnant] = '\0'; 1364 } else { 1365 remnant = 64; 1366 } 1367 log_info(gc, free)(" %6u: %s", (uint) (_heap->num_regions() - remnant), buffer); 1368 size_t total_young = retired_young + retired_young_humongous; 1369 size_t total_old = retired_old + retired_old_humongous; 1370 } 1371 #endif 1372 1373 LogTarget(Info, gc, free) lt; 1374 if (lt.is_enabled()) { 1375 ResourceMark rm; 1376 LogStream ls(lt); 1377 1378 { 1379 size_t last_idx = 0; 1380 size_t max = 0; 1381 size_t max_contig = 0; 1382 size_t empty_contig = 0; 1383 1384 size_t total_used = 0; 1385 size_t total_free = 0; 1386 size_t total_free_ext = 0; 1387 1388 for (size_t idx = _free_sets.leftmost(Mutator); idx <= _free_sets.rightmost(Mutator); idx++) { 1389 if (_free_sets.in_free_set(idx, Mutator)) { 1390 ShenandoahHeapRegion *r = _heap->get_region(idx); 1391 size_t free = alloc_capacity(r); 1392 max = MAX2(max, free); 1393 if (r->is_empty()) { 1394 total_free_ext += free; 1395 if (last_idx + 1 == idx) { 1396 empty_contig++; 1397 } else { 1398 empty_contig = 1; 1399 } 1400 } else { 1401 empty_contig = 0; 1402 } 1403 total_used += r->used(); 1404 total_free += free; 1405 max_contig = MAX2(max_contig, empty_contig); 1406 last_idx = idx; 1407 } 1408 } 1409 1410 size_t max_humongous = max_contig * ShenandoahHeapRegion::region_size_bytes(); 1411 size_t free = capacity() - used(); 1412 1413 assert(free == total_free, "Sum of free within mutator regions (" SIZE_FORMAT 1414 ") should match mutator capacity (" SIZE_FORMAT ") minus mutator used (" SIZE_FORMAT ")", 1415 total_free, capacity(), used()); 1416 1417 ls.print("Free: " SIZE_FORMAT "%s, Max: " SIZE_FORMAT "%s regular, " SIZE_FORMAT "%s humongous, ", 1418 byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free), 1419 byte_size_in_proper_unit(max), proper_unit_for_byte_size(max), 1420 byte_size_in_proper_unit(max_humongous), proper_unit_for_byte_size(max_humongous) 1421 ); 1422 1423 ls.print("Frag: "); 1424 size_t frag_ext; 1425 if (total_free_ext > 0) { 1426 frag_ext = 100 - (100 * max_humongous / total_free_ext); 1427 } else { 1428 frag_ext = 0; 1429 } 1430 ls.print(SIZE_FORMAT "%% external, ", frag_ext); 1431 1432 size_t frag_int; 1433 if (_free_sets.count(Mutator) > 0) { 1434 frag_int = (100 * (total_used / _free_sets.count(Mutator)) / ShenandoahHeapRegion::region_size_bytes()); 1435 } else { 1436 frag_int = 0; 1437 } 1438 ls.print(SIZE_FORMAT "%% internal; ", frag_int); 1439 ls.print("Used: " SIZE_FORMAT "%s, Mutator Free: " SIZE_FORMAT, 1440 byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used), _free_sets.count(Mutator)); 1441 } 1442 1443 { 1444 size_t max = 0; 1445 size_t total_free = 0; 1446 size_t total_used = 0; 1447 1448 for (size_t idx = _free_sets.leftmost(Collector); idx <= _free_sets.rightmost(Collector); idx++) { 1449 if (_free_sets.in_free_set(idx, Collector)) { 1450 ShenandoahHeapRegion *r = _heap->get_region(idx); 1451 size_t free = alloc_capacity(r); 1452 max = MAX2(max, free); 1453 total_free += free; 1454 total_used += r->used(); 1455 } 1456 } 1457 ls.print(" Collector Reserve: " SIZE_FORMAT "%s, Max: " SIZE_FORMAT "%s; Used: " SIZE_FORMAT "%s", 1458 byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free), 1459 byte_size_in_proper_unit(max), proper_unit_for_byte_size(max), 1460 byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used)); 1461 } 1462 1463 if (_heap->mode()->is_generational()) { 1464 size_t max = 0; 1465 size_t total_free = 0; 1466 size_t total_used = 0; 1467 1468 for (size_t idx = _free_sets.leftmost(OldCollector); idx <= _free_sets.rightmost(OldCollector); idx++) { 1469 if (_free_sets.in_free_set(idx, OldCollector)) { 1470 ShenandoahHeapRegion *r = _heap->get_region(idx); 1471 size_t free = alloc_capacity(r); 1472 max = MAX2(max, free); 1473 total_free += free; 1474 total_used += r->used(); 1475 } 1476 } 1477 ls.print_cr(" Old Collector Reserve: " SIZE_FORMAT "%s, Max: " SIZE_FORMAT "%s; Used: " SIZE_FORMAT "%s", 1478 byte_size_in_proper_unit(total_free), proper_unit_for_byte_size(total_free), 1479 byte_size_in_proper_unit(max), proper_unit_for_byte_size(max), 1480 byte_size_in_proper_unit(total_used), proper_unit_for_byte_size(total_used)); 1481 } 1482 } 1483 } 1484 1485 HeapWord* ShenandoahFreeSet::allocate(ShenandoahAllocRequest& req, bool& in_new_region) { 1486 shenandoah_assert_heaplocked(); 1487 _free_sets.assert_bounds(); 1488 1489 // Allocation request is known to satisfy all memory budgeting constraints. 1490 if (req.size() > ShenandoahHeapRegion::humongous_threshold_words()) { 1491 switch (req.type()) { 1492 case ShenandoahAllocRequest::_alloc_shared: 1493 case ShenandoahAllocRequest::_alloc_shared_gc: 1494 in_new_region = true; 1495 return allocate_contiguous(req); 1496 case ShenandoahAllocRequest::_alloc_plab: 1497 case ShenandoahAllocRequest::_alloc_gclab: 1498 case ShenandoahAllocRequest::_alloc_tlab: 1499 in_new_region = false; 1500 assert(false, "Trying to allocate TLAB larger than the humongous threshold: " SIZE_FORMAT " > " SIZE_FORMAT, 1501 req.size(), ShenandoahHeapRegion::humongous_threshold_words()); 1502 return nullptr; 1503 default: 1504 ShouldNotReachHere(); 1505 return nullptr; 1506 } 1507 } else { 1508 return allocate_single(req, in_new_region); 1509 } 1510 } 1511 1512 size_t ShenandoahFreeSet::unsafe_peek_free() const { 1513 // Deliberately not locked, this method is unsafe when free set is modified. 1514 1515 for (size_t index = _free_sets.leftmost(Mutator); index <= _free_sets.rightmost(Mutator); index++) { 1516 if (index < _free_sets.max() && _free_sets.in_free_set(index, Mutator)) { 1517 ShenandoahHeapRegion* r = _heap->get_region(index); 1518 if (r->free() >= MinTLABSize) { 1519 return r->free(); 1520 } 1521 } 1522 } 1523 1524 // It appears that no regions left 1525 return 0; 1526 } 1527 1528 void ShenandoahFreeSet::print_on(outputStream* out) const { 1529 out->print_cr("Mutator Free Set: " SIZE_FORMAT "", _free_sets.count(Mutator)); 1530 for (size_t index = _free_sets.leftmost(Mutator); index <= _free_sets.rightmost(Mutator); index++) { 1531 if (_free_sets.in_free_set(index, Mutator)) { 1532 _heap->get_region(index)->print_on(out); 1533 } 1534 } 1535 out->print_cr("Collector Free Set: " SIZE_FORMAT "", _free_sets.count(Collector)); 1536 for (size_t index = _free_sets.leftmost(Collector); index <= _free_sets.rightmost(Collector); index++) { 1537 if (_free_sets.in_free_set(index, Collector)) { 1538 _heap->get_region(index)->print_on(out); 1539 } 1540 } 1541 if (_heap->mode()->is_generational()) { 1542 out->print_cr("Old Collector Free Set: " SIZE_FORMAT "", _free_sets.count(OldCollector)); 1543 for (size_t index = _free_sets.leftmost(OldCollector); index <= _free_sets.rightmost(OldCollector); index++) { 1544 if (_free_sets.in_free_set(index, OldCollector)) { 1545 _heap->get_region(index)->print_on(out); 1546 } 1547 } 1548 } 1549 } 1550 1551 /* 1552 * Internal fragmentation metric: describes how fragmented the heap regions are. 1553 * 1554 * It is derived as: 1555 * 1556 * sum(used[i]^2, i=0..k) 1557 * IF = 1 - ------------------------------ 1558 * C * sum(used[i], i=0..k) 1559 * 1560 * ...where k is the number of regions in computation, C is the region capacity, and 1561 * used[i] is the used space in the region. 1562 * 1563 * The non-linearity causes IF to be lower for the cases where the same total heap 1564 * used is densely packed. For example: 1565 * a) Heap is completely full => IF = 0 1566 * b) Heap is half full, first 50% regions are completely full => IF = 0 1567 * c) Heap is half full, each region is 50% full => IF = 1/2 1568 * d) Heap is quarter full, first 50% regions are completely full => IF = 0 1569 * e) Heap is quarter full, each region is 25% full => IF = 3/4 1570 * f) Heap has one small object per each region => IF =~ 1 1571 */ 1572 double ShenandoahFreeSet::internal_fragmentation() { 1573 double squared = 0; 1574 double linear = 0; 1575 int count = 0; 1576 1577 for (size_t index = _free_sets.leftmost(Mutator); index <= _free_sets.rightmost(Mutator); index++) { 1578 if (_free_sets.in_free_set(index, Mutator)) { 1579 ShenandoahHeapRegion* r = _heap->get_region(index); 1580 size_t used = r->used(); 1581 squared += used * used; 1582 linear += used; 1583 count++; 1584 } 1585 } 1586 1587 if (count > 0) { 1588 double s = squared / (ShenandoahHeapRegion::region_size_bytes() * linear); 1589 return 1 - s; 1590 } else { 1591 return 0; 1592 } 1593 } 1594 1595 /* 1596 * External fragmentation metric: describes how fragmented the heap is. 1597 * 1598 * It is derived as: 1599 * 1600 * EF = 1 - largest_contiguous_free / total_free 1601 * 1602 * For example: 1603 * a) Heap is completely empty => EF = 0 1604 * b) Heap is completely full => EF = 0 1605 * c) Heap is first-half full => EF = 1/2 1606 * d) Heap is half full, full and empty regions interleave => EF =~ 1 1607 */ 1608 double ShenandoahFreeSet::external_fragmentation() { 1609 size_t last_idx = 0; 1610 size_t max_contig = 0; 1611 size_t empty_contig = 0; 1612 1613 size_t free = 0; 1614 1615 for (size_t index = _free_sets.leftmost(Mutator); index <= _free_sets.rightmost(Mutator); index++) { 1616 if (_free_sets.in_free_set(index, Mutator)) { 1617 ShenandoahHeapRegion* r = _heap->get_region(index); 1618 if (r->is_empty()) { 1619 free += ShenandoahHeapRegion::region_size_bytes(); 1620 if (last_idx + 1 == index) { 1621 empty_contig++; 1622 } else { 1623 empty_contig = 1; 1624 } 1625 } else { 1626 empty_contig = 0; 1627 } 1628 1629 max_contig = MAX2(max_contig, empty_contig); 1630 last_idx = index; 1631 } 1632 } 1633 1634 if (free > 0) { 1635 return 1 - (1.0 * max_contig * ShenandoahHeapRegion::region_size_bytes() / free); 1636 } else { 1637 return 0; 1638 } 1639 } 1640