1 /*
   2  * Copyright (c) 2001, 2018, 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/g1/g1CollectedHeap.inline.hpp"
  27 #include "gc/g1/g1ConcurrentRefine.hpp"
  28 #include "gc/g1/heapRegion.hpp"
  29 #include "gc/g1/heapRegionManager.inline.hpp"
  30 #include "gc/g1/heapRegionSet.inline.hpp"
  31 #include "memory/allocation.hpp"
  32 
  33 class MasterFreeRegionListChecker : public HeapRegionSetChecker {
  34 public:
  35   void check_mt_safety() {
  36     // Master Free List MT safety protocol:
  37     // (a) If we're at a safepoint, operations on the master free list
  38     // should be invoked by either the VM thread (which will serialize
  39     // them) or by the GC workers while holding the
  40     // FreeList_lock.
  41     // (b) If we're not at a safepoint, operations on the master free
  42     // list should be invoked while holding the Heap_lock.
  43 
  44     if (SafepointSynchronize::is_at_safepoint()) {
  45       guarantee(Thread::current()->is_VM_thread() ||
  46                 FreeList_lock->owned_by_self(), "master free list MT safety protocol at a safepoint");
  47     } else {
  48       guarantee(Heap_lock->owned_by_self(), "master free list MT safety protocol outside a safepoint");
  49     }
  50   }
  51   bool is_correct_type(HeapRegion* hr) { return hr->is_free(); }
  52   const char* get_description() { return "Free Regions"; }
  53 };
  54 
  55 HeapRegionManager::HeapRegionManager() :
  56   _regions(), _heap_mapper(NULL),
  57   _prev_bitmap_mapper(NULL),
  58   _next_bitmap_mapper(NULL),
  59   _bot_mapper(NULL),
  60   _cardtable_mapper(NULL),
  61   _card_counts_mapper(NULL),
  62   _free_list("Free list", new MasterFreeRegionListChecker()),
  63   _available_map(mtGC),
  64   _num_committed(0),
  65   _allocated_heapregions_length(0)
  66 { }
  67 
  68 void HeapRegionManager::initialize(G1RegionToSpaceMapper* heap_storage,
  69                                G1RegionToSpaceMapper* prev_bitmap,
  70                                G1RegionToSpaceMapper* next_bitmap,
  71                                G1RegionToSpaceMapper* bot,
  72                                G1RegionToSpaceMapper* cardtable,
  73                                G1RegionToSpaceMapper* card_counts) {
  74   _allocated_heapregions_length = 0;
  75 
  76   _heap_mapper = heap_storage;
  77 
  78   _prev_bitmap_mapper = prev_bitmap;
  79   _next_bitmap_mapper = next_bitmap;
  80 
  81   _bot_mapper = bot;
  82   _cardtable_mapper = cardtable;
  83 
  84   _card_counts_mapper = card_counts;
  85 
  86   MemRegion reserved = heap_storage->reserved();
  87   _regions.initialize(reserved.start(), reserved.end(), HeapRegion::GrainBytes);
  88 
  89   _available_map.initialize(_regions.length());
  90 }
  91 
  92 bool HeapRegionManager::is_available(uint region) const {
  93   return _available_map.at(region);
  94 }
  95 
  96 #ifdef ASSERT
  97 bool HeapRegionManager::is_free(HeapRegion* hr) const {
  98   return _free_list.contains(hr);
  99 }
 100 #endif
 101 
 102 HeapRegion* HeapRegionManager::new_heap_region(uint hrm_index) {
 103   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 104   HeapWord* bottom = g1h->bottom_addr_for_region(hrm_index);
 105   MemRegion mr(bottom, bottom + HeapRegion::GrainWords);
 106   assert(reserved().contains(mr), "invariant");
 107   return g1h->new_heap_region(hrm_index, mr);
 108 }
 109 
 110 void HeapRegionManager::commit_regions(uint index, size_t num_regions, WorkGang* pretouch_gang) {
 111   guarantee(num_regions > 0, "Must commit more than zero regions");
 112   guarantee(_num_committed + num_regions <= max_length(), "Cannot commit more than the maximum amount of regions");
 113 
 114   _num_committed += (uint)num_regions;
 115 
 116   _heap_mapper->commit_regions(index, num_regions, pretouch_gang);
 117 
 118   // Also commit auxiliary data
 119   _prev_bitmap_mapper->commit_regions(index, num_regions, pretouch_gang);
 120   _next_bitmap_mapper->commit_regions(index, num_regions, pretouch_gang);
 121 
 122   _bot_mapper->commit_regions(index, num_regions, pretouch_gang);
 123   _cardtable_mapper->commit_regions(index, num_regions, pretouch_gang);
 124 
 125   _card_counts_mapper->commit_regions(index, num_regions, pretouch_gang);
 126 }
 127 
 128 void HeapRegionManager::uncommit_regions(uint start, size_t num_regions) {
 129   guarantee(num_regions >= 1, "Need to specify at least one region to uncommit, tried to uncommit zero regions at %u", start);
 130   guarantee(_num_committed >= num_regions, "pre-condition");
 131 
 132   // Print before uncommitting.
 133   if (G1CollectedHeap::heap()->hr_printer()->is_active()) {
 134     for (uint i = start; i < start + num_regions; i++) {
 135       HeapRegion* hr = at(i);
 136       G1CollectedHeap::heap()->hr_printer()->uncommit(hr);
 137     }
 138   }
 139 
 140   _num_committed -= (uint)num_regions;
 141 
 142   _available_map.par_clear_range(start, start + num_regions, BitMap::unknown_range);
 143   _heap_mapper->uncommit_regions(start, num_regions);
 144 
 145   // Also uncommit auxiliary data
 146   _prev_bitmap_mapper->uncommit_regions(start, num_regions);
 147   _next_bitmap_mapper->uncommit_regions(start, num_regions);
 148 
 149   _bot_mapper->uncommit_regions(start, num_regions);
 150   _cardtable_mapper->uncommit_regions(start, num_regions);
 151 
 152   _card_counts_mapper->uncommit_regions(start, num_regions);
 153 }
 154 
 155 void HeapRegionManager::make_regions_available(uint start, uint num_regions, WorkGang* pretouch_gang) {
 156   guarantee(num_regions > 0, "No point in calling this for zero regions");
 157   commit_regions(start, num_regions, pretouch_gang);
 158   for (uint i = start; i < start + num_regions; i++) {
 159     if (_regions.get_by_index(i) == NULL) {
 160       HeapRegion* new_hr = new_heap_region(i);
 161       OrderAccess::storestore();
 162       _regions.set_by_index(i, new_hr);
 163       _allocated_heapregions_length = MAX2(_allocated_heapregions_length, i + 1);
 164     }
 165   }
 166 
 167   _available_map.par_set_range(start, start + num_regions, BitMap::unknown_range);
 168 
 169   for (uint i = start; i < start + num_regions; i++) {
 170     assert(is_available(i), "Just made region %u available but is apparently not.", i);
 171     HeapRegion* hr = at(i);
 172     if (G1CollectedHeap::heap()->hr_printer()->is_active()) {
 173       G1CollectedHeap::heap()->hr_printer()->commit(hr);
 174     }
 175     HeapWord* bottom = G1CollectedHeap::heap()->bottom_addr_for_region(i);
 176     MemRegion mr(bottom, bottom + HeapRegion::GrainWords);
 177 
 178     hr->initialize(mr);
 179     insert_into_free_list(at(i));
 180   }
 181 }
 182 
 183 MemoryUsage HeapRegionManager::get_auxiliary_data_memory_usage() const {
 184   size_t used_sz =
 185     _prev_bitmap_mapper->committed_size() +
 186     _next_bitmap_mapper->committed_size() +
 187     _bot_mapper->committed_size() +
 188     _cardtable_mapper->committed_size() +
 189     _card_counts_mapper->committed_size();
 190 
 191   size_t committed_sz =
 192     _prev_bitmap_mapper->reserved_size() +
 193     _next_bitmap_mapper->reserved_size() +
 194     _bot_mapper->reserved_size() +
 195     _cardtable_mapper->reserved_size() +
 196     _card_counts_mapper->reserved_size();
 197 
 198   return MemoryUsage(0, used_sz, committed_sz, committed_sz);
 199 }
 200 
 201 uint HeapRegionManager::expand_by(uint num_regions, WorkGang* pretouch_workers) {
 202   return expand_at(0, num_regions, pretouch_workers);
 203 }
 204 
 205 uint HeapRegionManager::expand_at(uint start, uint num_regions, WorkGang* pretouch_workers) {
 206   if (num_regions == 0) {
 207     return 0;
 208   }
 209 
 210   uint cur = start;
 211   uint idx_last_found = 0;
 212   uint num_last_found = 0;
 213 
 214   uint expanded = 0;
 215 
 216   while (expanded < num_regions &&
 217          (num_last_found = find_unavailable_from_idx(cur, &idx_last_found)) > 0) {
 218     uint to_expand = MIN2(num_regions - expanded, num_last_found);
 219     make_regions_available(idx_last_found, to_expand, pretouch_workers);
 220     expanded += to_expand;
 221     cur = idx_last_found + num_last_found + 1;
 222   }
 223 
 224   verify_optional();
 225   return expanded;
 226 }
 227 
 228 uint HeapRegionManager::find_contiguous(size_t num, bool empty_only) {
 229   uint found = 0;
 230   size_t length_found = 0;
 231   uint cur = 0;
 232 
 233   while (length_found < num && cur < max_length()) {
 234     HeapRegion* hr = _regions.get_by_index(cur);
 235     if ((!empty_only && !is_available(cur)) || (is_available(cur) && hr != NULL && hr->is_empty())) {
 236       // This region is a potential candidate for allocation into.
 237       length_found++;
 238     } else {
 239       // This region is not a candidate. The next region is the next possible one.
 240       found = cur + 1;
 241       length_found = 0;
 242     }
 243     cur++;
 244   }
 245 
 246   if (length_found == num) {
 247     for (uint i = found; i < (found + num); i++) {
 248       HeapRegion* hr = _regions.get_by_index(i);
 249       // sanity check
 250       guarantee((!empty_only && !is_available(i)) || (is_available(i) && hr != NULL && hr->is_empty()),
 251                 "Found region sequence starting at " UINT32_FORMAT ", length " SIZE_FORMAT
 252                 " that is not empty at " UINT32_FORMAT ". Hr is " PTR_FORMAT, found, num, i, p2i(hr));
 253     }
 254     return found;
 255   } else {
 256     return G1_NO_HRM_INDEX;
 257   }
 258 }
 259 
 260 HeapRegion* HeapRegionManager::next_region_in_heap(const HeapRegion* r) const {
 261   guarantee(r != NULL, "Start region must be a valid region");
 262   guarantee(is_available(r->hrm_index()), "Trying to iterate starting from region %u which is not in the heap", r->hrm_index());
 263   for (uint i = r->hrm_index() + 1; i < _allocated_heapregions_length; i++) {
 264     HeapRegion* hr = _regions.get_by_index(i);
 265     if (is_available(i)) {
 266       return hr;
 267     }
 268   }
 269   return NULL;
 270 }
 271 
 272 void HeapRegionManager::iterate(HeapRegionClosure* blk) const {
 273   uint len = max_length();
 274 
 275   for (uint i = 0; i < len; i++) {
 276     if (!is_available(i)) {
 277       continue;
 278     }
 279     guarantee(at(i) != NULL, "Tried to access region %u that has a NULL HeapRegion*", i);
 280     bool res = blk->do_heap_region(at(i));
 281     if (res) {
 282       blk->set_incomplete();
 283       return;
 284     }
 285   }
 286 }
 287 
 288 uint HeapRegionManager::find_unavailable_from_idx(uint start_idx, uint* res_idx) const {
 289   guarantee(res_idx != NULL, "checking");
 290   guarantee(start_idx <= (max_length() + 1), "checking");
 291 
 292   uint num_regions = 0;
 293 
 294   uint cur = start_idx;
 295   while (cur < max_length() && is_available(cur)) {
 296     cur++;
 297   }
 298   if (cur == max_length()) {
 299     return num_regions;
 300   }
 301   *res_idx = cur;
 302   while (cur < max_length() && !is_available(cur)) {
 303     cur++;
 304   }
 305   num_regions = cur - *res_idx;
 306 #ifdef ASSERT
 307   for (uint i = *res_idx; i < (*res_idx + num_regions); i++) {
 308     assert(!is_available(i), "just checking");
 309   }
 310   assert(cur == max_length() || num_regions == 0 || is_available(cur),
 311          "The region at the current position %u must be available or at the end of the heap.", cur);
 312 #endif
 313   return num_regions;
 314 }
 315 
 316 uint HeapRegionManager::find_highest_free(bool* expanded) {
 317   // Loop downwards from the highest region index, looking for an
 318   // entry which is either free or not yet committed.  If not yet
 319   // committed, expand_at that index.
 320   uint curr = max_length() - 1;
 321   while (true) {
 322     HeapRegion *hr = _regions.get_by_index(curr);
 323     if (hr == NULL || !is_available(curr)) {
 324       uint res = expand_at(curr, 1, NULL);
 325       if (res == 1) {
 326         *expanded = true;
 327         return curr;
 328       }
 329     } else {
 330       if (hr->is_free()) {
 331         *expanded = false;
 332         return curr;
 333       }
 334     }
 335     if (curr == 0) {
 336       return G1_NO_HRM_INDEX;
 337     }
 338     curr--;
 339   }
 340 }
 341 
 342 bool HeapRegionManager::allocate_containing_regions(MemRegion range, size_t* commit_count, WorkGang* pretouch_workers) {
 343   size_t commits = 0;
 344   uint start_index = (uint)_regions.get_index_by_address(range.start());
 345   uint last_index = (uint)_regions.get_index_by_address(range.last());
 346 
 347   // Ensure that each G1 region in the range is free, returning false if not.
 348   // Commit those that are not yet available, and keep count.
 349   for (uint curr_index = start_index; curr_index <= last_index; curr_index++) {
 350     if (!is_available(curr_index)) {
 351       commits++;
 352       expand_at(curr_index, 1, pretouch_workers);
 353     }
 354     HeapRegion* curr_region  = _regions.get_by_index(curr_index);
 355     if (!curr_region->is_free()) {
 356       return false;
 357     }
 358   }
 359 
 360   allocate_free_regions_starting_at(start_index, (last_index - start_index) + 1);
 361   *commit_count = commits;
 362   return true;
 363 }
 364 
 365 void HeapRegionManager::par_iterate(HeapRegionClosure* blk, HeapRegionClaimer* hrclaimer, const uint start_index) const {
 366   // Every worker will actually look at all regions, skipping over regions that
 367   // are currently not committed.
 368   // This also (potentially) iterates over regions newly allocated during GC. This
 369   // is no problem except for some extra work.
 370   const uint n_regions = hrclaimer->n_regions();
 371   for (uint count = 0; count < n_regions; count++) {
 372     const uint index = (start_index + count) % n_regions;
 373     assert(index < n_regions, "sanity");
 374     // Skip over unavailable regions
 375     if (!is_available(index)) {
 376       continue;
 377     }
 378     HeapRegion* r = _regions.get_by_index(index);
 379     // We'll ignore regions already claimed.
 380     // However, if the iteration is specified as concurrent, the values for
 381     // is_starts_humongous and is_continues_humongous can not be trusted,
 382     // and we should just blindly iterate over regions regardless of their
 383     // humongous status.
 384     if (hrclaimer->is_region_claimed(index)) {
 385       continue;
 386     }
 387     // OK, try to claim it
 388     if (!hrclaimer->claim_region(index)) {
 389       continue;
 390     }
 391     bool res = blk->do_heap_region(r);
 392     if (res) {
 393       return;
 394     }
 395   }
 396 }
 397 
 398 uint HeapRegionManager::shrink_by(uint num_regions_to_remove) {
 399   assert(length() > 0, "the region sequence should not be empty");
 400   assert(length() <= _allocated_heapregions_length, "invariant");
 401   assert(_allocated_heapregions_length > 0, "we should have at least one region committed");
 402   assert(num_regions_to_remove < length(), "We should never remove all regions");
 403 
 404   if (num_regions_to_remove == 0) {
 405     return 0;
 406   }
 407 
 408   uint removed = 0;
 409   uint cur = _allocated_heapregions_length - 1;
 410   uint idx_last_found = 0;
 411   uint num_last_found = 0;
 412 
 413   while ((removed < num_regions_to_remove) &&
 414       (num_last_found = find_empty_from_idx_reverse(cur, &idx_last_found)) > 0) {
 415     uint to_remove = MIN2(num_regions_to_remove - removed, num_last_found);
 416 
 417     shrink_at(idx_last_found + num_last_found - to_remove, to_remove);
 418 
 419     cur = idx_last_found;
 420     removed += to_remove;
 421   }
 422 
 423   verify_optional();
 424 
 425   return removed;
 426 }
 427 
 428 void HeapRegionManager::shrink_at(uint index, size_t num_regions) {
 429 #ifdef ASSERT
 430   for (uint i = index; i < (index + num_regions); i++) {
 431     assert(is_available(i), "Expected available region at index %u", i);
 432     assert(at(i)->is_empty(), "Expected empty region at index %u", i);
 433     assert(at(i)->is_free(), "Expected free region at index %u", i);
 434   }
 435 #endif
 436   uncommit_regions(index, num_regions);
 437 }
 438 
 439 uint HeapRegionManager::find_empty_from_idx_reverse(uint start_idx, uint* res_idx) const {
 440   guarantee(start_idx < _allocated_heapregions_length, "checking");
 441   guarantee(res_idx != NULL, "checking");
 442 
 443   uint num_regions_found = 0;
 444 
 445   jlong cur = start_idx;
 446   while (cur != -1 && !(is_available(cur) && at(cur)->is_empty())) {
 447     cur--;
 448   }
 449   if (cur == -1) {
 450     return num_regions_found;
 451   }
 452   jlong old_cur = cur;
 453   // cur indexes the first empty region
 454   while (cur != -1 && is_available(cur) && at(cur)->is_empty()) {
 455     cur--;
 456   }
 457   *res_idx = cur + 1;
 458   num_regions_found = old_cur - cur;
 459 
 460 #ifdef ASSERT
 461   for (uint i = *res_idx; i < (*res_idx + num_regions_found); i++) {
 462     assert(at(i)->is_empty(), "just checking");
 463   }
 464 #endif
 465   return num_regions_found;
 466 }
 467 
 468 void HeapRegionManager::verify() {
 469   guarantee(length() <= _allocated_heapregions_length,
 470             "invariant: _length: %u _allocated_length: %u",
 471             length(), _allocated_heapregions_length);
 472   guarantee(_allocated_heapregions_length <= max_length(),
 473             "invariant: _allocated_length: %u _max_length: %u",
 474             _allocated_heapregions_length, max_length());
 475 
 476   bool prev_committed = true;
 477   uint num_committed = 0;
 478   HeapWord* prev_end = heap_bottom();
 479   for (uint i = 0; i < _allocated_heapregions_length; i++) {
 480     if (!is_available(i)) {
 481       prev_committed = false;
 482       continue;
 483     }
 484     num_committed++;
 485     HeapRegion* hr = _regions.get_by_index(i);
 486     guarantee(hr != NULL, "invariant: i: %u", i);
 487     guarantee(!prev_committed || hr->bottom() == prev_end,
 488               "invariant i: %u " HR_FORMAT " prev_end: " PTR_FORMAT,
 489               i, HR_FORMAT_PARAMS(hr), p2i(prev_end));
 490     guarantee(hr->hrm_index() == i,
 491               "invariant: i: %u hrm_index(): %u", i, hr->hrm_index());
 492     // Asserts will fire if i is >= _length
 493     HeapWord* addr = hr->bottom();
 494     guarantee(addr_to_region(addr) == hr, "sanity");
 495     // We cannot check whether the region is part of a particular set: at the time
 496     // this method may be called, we have only completed allocation of the regions,
 497     // but not put into a region set.
 498     prev_committed = true;
 499     prev_end = hr->end();
 500   }
 501   for (uint i = _allocated_heapregions_length; i < max_length(); i++) {
 502     guarantee(_regions.get_by_index(i) == NULL, "invariant i: %u", i);
 503   }
 504 
 505   guarantee(num_committed == _num_committed, "Found %u committed regions, but should be %u", num_committed, _num_committed);
 506   _free_list.verify();
 507 }
 508 
 509 #ifndef PRODUCT
 510 void HeapRegionManager::verify_optional() {
 511   verify();
 512 }
 513 #endif // PRODUCT
 514 
 515 HeapRegionClaimer::HeapRegionClaimer(uint n_workers) :
 516     _n_workers(n_workers), _n_regions(G1CollectedHeap::heap()->_hrm._allocated_heapregions_length), _claims(NULL) {
 517   assert(n_workers > 0, "Need at least one worker.");
 518   uint* new_claims = NEW_C_HEAP_ARRAY(uint, _n_regions, mtGC);
 519   memset(new_claims, Unclaimed, sizeof(*_claims) * _n_regions);
 520   _claims = new_claims;
 521 }
 522 
 523 HeapRegionClaimer::~HeapRegionClaimer() {
 524   if (_claims != NULL) {
 525     FREE_C_HEAP_ARRAY(uint, _claims);
 526   }
 527 }
 528 
 529 uint HeapRegionClaimer::offset_for_worker(uint worker_id) const {
 530   assert(worker_id < _n_workers, "Invalid worker_id.");
 531   return _n_regions * worker_id / _n_workers;
 532 }
 533 
 534 bool HeapRegionClaimer::is_region_claimed(uint region_index) const {
 535   assert(region_index < _n_regions, "Invalid index.");
 536   return _claims[region_index] == Claimed;
 537 }
 538 
 539 bool HeapRegionClaimer::claim_region(uint region_index) {
 540   assert(region_index < _n_regions, "Invalid index.");
 541   uint old_val = Atomic::cmpxchg(Claimed, &_claims[region_index], Unclaimed);
 542   return old_val == Unclaimed;
 543 }