1 /*
  2  * Copyright (c) 2001, 2019, 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/g1Arguments.hpp"
 27 #include "gc/g1/g1CollectedHeap.inline.hpp"
 28 #include "gc/g1/g1ConcurrentRefine.hpp"
 29 #include "gc/g1/heapRegion.hpp"
 30 #include "gc/g1/heapRegionManager.inline.hpp"
 31 #include "gc/g1/heapRegionSet.inline.hpp"
 32 #include "gc/g1/heterogeneousHeapRegionManager.hpp"
 33 #include "memory/allocation.hpp"
 34 #include "utilities/bitMap.inline.hpp"
 35 
 36 class MasterFreeRegionListChecker : public HeapRegionSetChecker {
 37 public:
 38   void check_mt_safety() {
 39     // Master Free List MT safety protocol:
 40     // (a) If we're at a safepoint, operations on the master free list
 41     // should be invoked by either the VM thread (which will serialize
 42     // them) or by the GC workers while holding the
 43     // FreeList_lock.
 44     // (b) If we're not at a safepoint, operations on the master free
 45     // list should be invoked while holding the Heap_lock.
 46 
 47     if (SafepointSynchronize::is_at_safepoint()) {
 48       guarantee(Thread::current()->is_VM_thread() ||
 49                 FreeList_lock->owned_by_self(), "master free list MT safety protocol at a safepoint");
 50     } else {
 51       guarantee(Heap_lock->owned_by_self(), "master free list MT safety protocol outside a safepoint");
 52     }
 53   }
 54   bool is_correct_type(HeapRegion* hr) { return hr->is_free(); }
 55   const char* get_description() { return "Free Regions"; }
 56 };
 57 
 58 HeapRegionManager::HeapRegionManager() :
 59   _bot_mapper(NULL),
 60   _cardtable_mapper(NULL),
 61   _card_counts_mapper(NULL),
 62   _available_map(mtGC),
 63   _num_committed(0),
 64   _allocated_heapregions_length(0),
 65   _regions(), _heap_mapper(NULL),
 66   _prev_bitmap_mapper(NULL),
 67   _next_bitmap_mapper(NULL),
 68   _free_list("Free list", new MasterFreeRegionListChecker())
 69 { }
 70 
 71 HeapRegionManager* HeapRegionManager::create_manager(G1CollectedHeap* heap) {
 72   if (G1Arguments::is_heterogeneous_heap()) {
 73     return new HeterogeneousHeapRegionManager((uint)(G1Arguments::heap_max_size_bytes() / HeapRegion::GrainBytes) /*heap size as num of regions*/);
 74   }
 75   return new HeapRegionManager();
 76 }
 77 
 78 void HeapRegionManager::initialize(G1RegionToSpaceMapper* heap_storage,
 79                                G1RegionToSpaceMapper* prev_bitmap,
 80                                G1RegionToSpaceMapper* next_bitmap,
 81                                G1RegionToSpaceMapper* bot,
 82                                G1RegionToSpaceMapper* cardtable,
 83                                G1RegionToSpaceMapper* card_counts) {
 84   _allocated_heapregions_length = 0;
 85 
 86   _heap_mapper = heap_storage;
 87 
 88   _prev_bitmap_mapper = prev_bitmap;
 89   _next_bitmap_mapper = next_bitmap;
 90 
 91   _bot_mapper = bot;
 92   _cardtable_mapper = cardtable;
 93 
 94   _card_counts_mapper = card_counts;
 95 
 96   MemRegion reserved = heap_storage->reserved();
 97   _regions.initialize(reserved.start(), reserved.end(), HeapRegion::GrainBytes);
 98 
 99   _available_map.initialize(_regions.length());
100 }
101 
102 bool HeapRegionManager::is_available(uint region) const {
103   return _available_map.at(region);
104 }
105 
106 #ifdef ASSERT
107 bool HeapRegionManager::is_free(HeapRegion* hr) const {
108   return _free_list.contains(hr);
109 }
110 #endif
111 
112 HeapRegion* HeapRegionManager::new_heap_region(uint hrm_index) {
113   G1CollectedHeap* g1h = G1CollectedHeap::heap();
114   HeapWord* bottom = g1h->bottom_addr_for_region(hrm_index);
115   MemRegion mr(bottom, bottom + HeapRegion::GrainWords);
116   assert(reserved().contains(mr), "invariant");
117   return g1h->new_heap_region(hrm_index, mr);
118 }
119 
120 void HeapRegionManager::commit_regions(uint index, size_t num_regions, WorkGang* pretouch_gang) {
121   guarantee(num_regions > 0, "Must commit more than zero regions");
122   guarantee(_num_committed + num_regions <= max_length(), "Cannot commit more than the maximum amount of regions");
123 
124   _num_committed += (uint)num_regions;
125 
126   _heap_mapper->commit_regions(index, num_regions, pretouch_gang);
127 
128   // Also commit auxiliary data
129   _prev_bitmap_mapper->commit_regions(index, num_regions, pretouch_gang);
130   _next_bitmap_mapper->commit_regions(index, num_regions, pretouch_gang);
131 
132   _bot_mapper->commit_regions(index, num_regions, pretouch_gang);
133   _cardtable_mapper->commit_regions(index, num_regions, pretouch_gang);
134 
135   _card_counts_mapper->commit_regions(index, num_regions, pretouch_gang);
136 }
137 
138 void HeapRegionManager::uncommit_regions(uint start, size_t num_regions) {
139   guarantee(num_regions >= 1, "Need to specify at least one region to uncommit, tried to uncommit zero regions at %u", start);
140   guarantee(_num_committed >= num_regions, "pre-condition");
141 
142   // Print before uncommitting.
143   if (G1CollectedHeap::heap()->hr_printer()->is_active()) {
144     for (uint i = start; i < start + num_regions; i++) {
145       HeapRegion* hr = at(i);
146       G1CollectedHeap::heap()->hr_printer()->uncommit(hr);
147     }
148   }
149 
150   _num_committed -= (uint)num_regions;
151 
152   _available_map.par_clear_range(start, start + num_regions, BitMap::unknown_range);
153   _heap_mapper->uncommit_regions(start, num_regions);
154 
155   // Also uncommit auxiliary data
156   _prev_bitmap_mapper->uncommit_regions(start, num_regions);
157   _next_bitmap_mapper->uncommit_regions(start, num_regions);
158 
159   _bot_mapper->uncommit_regions(start, num_regions);
160   _cardtable_mapper->uncommit_regions(start, num_regions);
161 
162   _card_counts_mapper->uncommit_regions(start, num_regions);
163 }
164 
165 void HeapRegionManager::make_regions_available(uint start, uint num_regions, WorkGang* pretouch_gang) {
166   guarantee(num_regions > 0, "No point in calling this for zero regions");
167   commit_regions(start, num_regions, pretouch_gang);
168   for (uint i = start; i < start + num_regions; i++) {
169     if (_regions.get_by_index(i) == NULL) {
170       HeapRegion* new_hr = new_heap_region(i);
171       OrderAccess::storestore();
172       _regions.set_by_index(i, new_hr);
173       _allocated_heapregions_length = MAX2(_allocated_heapregions_length, i + 1);
174     }
175   }
176 
177   _available_map.par_set_range(start, start + num_regions, BitMap::unknown_range);
178 
179   for (uint i = start; i < start + num_regions; i++) {
180     assert(is_available(i), "Just made region %u available but is apparently not.", i);
181     HeapRegion* hr = at(i);
182     if (G1CollectedHeap::heap()->hr_printer()->is_active()) {
183       G1CollectedHeap::heap()->hr_printer()->commit(hr);
184     }
185     HeapWord* bottom = G1CollectedHeap::heap()->bottom_addr_for_region(i);
186     MemRegion mr(bottom, bottom + HeapRegion::GrainWords);
187 
188     hr->initialize(mr);
189     insert_into_free_list(at(i));
190   }
191 }
192 
193 MemoryUsage HeapRegionManager::get_auxiliary_data_memory_usage() const {
194   size_t used_sz =
195     _prev_bitmap_mapper->committed_size() +
196     _next_bitmap_mapper->committed_size() +
197     _bot_mapper->committed_size() +
198     _cardtable_mapper->committed_size() +
199     _card_counts_mapper->committed_size();
200 
201   size_t committed_sz =
202     _prev_bitmap_mapper->reserved_size() +
203     _next_bitmap_mapper->reserved_size() +
204     _bot_mapper->reserved_size() +
205     _cardtable_mapper->reserved_size() +
206     _card_counts_mapper->reserved_size();
207 
208   return MemoryUsage(0, used_sz, committed_sz, committed_sz);
209 }
210 
211 uint HeapRegionManager::expand_by(uint num_regions, WorkGang* pretouch_workers) {
212   return expand_at(0, num_regions, pretouch_workers);
213 }
214 
215 uint HeapRegionManager::expand_at(uint start, uint num_regions, WorkGang* pretouch_workers) {
216   if (num_regions == 0) {
217     return 0;
218   }
219 
220   uint cur = start;
221   uint idx_last_found = 0;
222   uint num_last_found = 0;
223 
224   uint expanded = 0;
225 
226   while (expanded < num_regions &&
227          (num_last_found = find_unavailable_from_idx(cur, &idx_last_found)) > 0) {
228     uint to_expand = MIN2(num_regions - expanded, num_last_found);
229     make_regions_available(idx_last_found, to_expand, pretouch_workers);
230     expanded += to_expand;
231     cur = idx_last_found + num_last_found + 1;
232   }
233 
234   verify_optional();
235   return expanded;
236 }
237 
238 uint HeapRegionManager::find_contiguous(size_t num, bool empty_only) {
239   uint found = 0;
240   size_t length_found = 0;
241   uint cur = 0;
242 
243   while (length_found < num && cur < max_length()) {
244     HeapRegion* hr = _regions.get_by_index(cur);
245     if ((!empty_only && !is_available(cur)) || (is_available(cur) && hr != NULL && hr->is_empty())) {
246       // This region is a potential candidate for allocation into.
247       length_found++;
248     } else {
249       // This region is not a candidate. The next region is the next possible one.
250       found = cur + 1;
251       length_found = 0;
252     }
253     cur++;
254   }
255 
256   if (length_found == num) {
257     for (uint i = found; i < (found + num); i++) {
258       HeapRegion* hr = _regions.get_by_index(i);
259       // sanity check
260       guarantee((!empty_only && !is_available(i)) || (is_available(i) && hr != NULL && hr->is_empty()),
261                 "Found region sequence starting at " UINT32_FORMAT ", length " SIZE_FORMAT
262                 " that is not empty at " UINT32_FORMAT ". Hr is " PTR_FORMAT, found, num, i, p2i(hr));
263     }
264     return found;
265   } else {
266     return G1_NO_HRM_INDEX;
267   }
268 }
269 
270 HeapRegion* HeapRegionManager::next_region_in_heap(const HeapRegion* r) const {
271   guarantee(r != NULL, "Start region must be a valid region");
272   guarantee(is_available(r->hrm_index()), "Trying to iterate starting from region %u which is not in the heap", r->hrm_index());
273   for (uint i = r->hrm_index() + 1; i < _allocated_heapregions_length; i++) {
274     HeapRegion* hr = _regions.get_by_index(i);
275     if (is_available(i)) {
276       return hr;
277     }
278   }
279   return NULL;
280 }
281 
282 void HeapRegionManager::iterate(HeapRegionClosure* blk) const {
283   uint len = max_length();
284 
285   for (uint i = 0; i < len; i++) {
286     if (!is_available(i)) {
287       continue;
288     }
289     guarantee(at(i) != NULL, "Tried to access region %u that has a NULL HeapRegion*", i);
290     bool res = blk->do_heap_region(at(i));
291     if (res) {
292       blk->set_incomplete();
293       return;
294     }
295   }
296 }
297 
298 uint HeapRegionManager::find_unavailable_from_idx(uint start_idx, uint* res_idx) const {
299   guarantee(res_idx != NULL, "checking");
300   guarantee(start_idx <= (max_length() + 1), "checking");
301 
302   uint num_regions = 0;
303 
304   uint cur = start_idx;
305   while (cur < max_length() && is_available(cur)) {
306     cur++;
307   }
308   if (cur == max_length()) {
309     return num_regions;
310   }
311   *res_idx = cur;
312   while (cur < max_length() && !is_available(cur)) {
313     cur++;
314   }
315   num_regions = cur - *res_idx;
316 #ifdef ASSERT
317   for (uint i = *res_idx; i < (*res_idx + num_regions); i++) {
318     assert(!is_available(i), "just checking");
319   }
320   assert(cur == max_length() || num_regions == 0 || is_available(cur),
321          "The region at the current position %u must be available or at the end of the heap.", cur);
322 #endif
323   return num_regions;
324 }
325 
326 uint HeapRegionManager::find_highest_free(bool* expanded) {
327   // Loop downwards from the highest region index, looking for an
328   // entry which is either free or not yet committed.  If not yet
329   // committed, expand_at that index.
330   uint curr = max_length() - 1;
331   while (true) {
332     HeapRegion *hr = _regions.get_by_index(curr);
333     if (hr == NULL || !is_available(curr)) {
334       uint res = expand_at(curr, 1, NULL);
335       if (res == 1) {
336         *expanded = true;
337         return curr;
338       }
339     } else {
340       if (hr->is_free()) {
341         *expanded = false;
342         return curr;
343       }
344     }
345     if (curr == 0) {
346       return G1_NO_HRM_INDEX;
347     }
348     curr--;
349   }
350 }
351 
352 bool HeapRegionManager::allocate_containing_regions(MemRegion range, size_t* commit_count, WorkGang* pretouch_workers) {
353   size_t commits = 0;
354   uint start_index = (uint)_regions.get_index_by_address(range.start());
355   uint last_index = (uint)_regions.get_index_by_address(range.last());
356 
357   // Ensure that each G1 region in the range is free, returning false if not.
358   // Commit those that are not yet available, and keep count.
359   for (uint curr_index = start_index; curr_index <= last_index; curr_index++) {
360     if (!is_available(curr_index)) {
361       commits++;
362       expand_at(curr_index, 1, pretouch_workers);
363     }
364     HeapRegion* curr_region  = _regions.get_by_index(curr_index);
365     if (!curr_region->is_free()) {
366       return false;
367     }
368   }
369 
370   allocate_free_regions_starting_at(start_index, (last_index - start_index) + 1);
371   *commit_count = commits;
372   return true;
373 }
374 
375 void HeapRegionManager::par_iterate(HeapRegionClosure* blk, HeapRegionClaimer* hrclaimer, const uint start_index) const {
376   // Every worker will actually look at all regions, skipping over regions that
377   // are currently not committed.
378   // This also (potentially) iterates over regions newly allocated during GC. This
379   // is no problem except for some extra work.
380   const uint n_regions = hrclaimer->n_regions();
381   for (uint count = 0; count < n_regions; count++) {
382     const uint index = (start_index + count) % n_regions;
383     assert(index < n_regions, "sanity");
384     // Skip over unavailable regions
385     if (!is_available(index)) {
386       continue;
387     }
388     HeapRegion* r = _regions.get_by_index(index);
389     // We'll ignore regions already claimed.
390     // However, if the iteration is specified as concurrent, the values for
391     // is_starts_humongous and is_continues_humongous can not be trusted,
392     // and we should just blindly iterate over regions regardless of their
393     // humongous status.
394     if (hrclaimer->is_region_claimed(index)) {
395       continue;
396     }
397     // OK, try to claim it
398     if (!hrclaimer->claim_region(index)) {
399       continue;
400     }
401     bool res = blk->do_heap_region(r);
402     if (res) {
403       return;
404     }
405   }
406 }
407 
408 uint HeapRegionManager::shrink_by(uint num_regions_to_remove) {
409   assert(length() > 0, "the region sequence should not be empty");
410   assert(length() <= _allocated_heapregions_length, "invariant");
411   assert(_allocated_heapregions_length > 0, "we should have at least one region committed");
412   assert(num_regions_to_remove < length(), "We should never remove all regions");
413 
414   if (num_regions_to_remove == 0) {
415     return 0;
416   }
417 
418   uint removed = 0;
419   uint cur = _allocated_heapregions_length - 1;
420   uint idx_last_found = 0;
421   uint num_last_found = 0;
422 
423   while ((removed < num_regions_to_remove) &&
424       (num_last_found = find_empty_from_idx_reverse(cur, &idx_last_found)) > 0) {
425     uint to_remove = MIN2(num_regions_to_remove - removed, num_last_found);
426 
427     shrink_at(idx_last_found + num_last_found - to_remove, to_remove);
428 
429     cur = idx_last_found;
430     removed += to_remove;
431   }
432 
433   verify_optional();
434 
435   return removed;
436 }
437 
438 void HeapRegionManager::shrink_at(uint index, size_t num_regions) {
439 #ifdef ASSERT
440   for (uint i = index; i < (index + num_regions); i++) {
441     assert(is_available(i), "Expected available region at index %u", i);
442     assert(at(i)->is_empty(), "Expected empty region at index %u", i);
443     assert(at(i)->is_free(), "Expected free region at index %u", i);
444   }
445 #endif
446   uncommit_regions(index, num_regions);
447 }
448 
449 uint HeapRegionManager::find_empty_from_idx_reverse(uint start_idx, uint* res_idx) const {
450   guarantee(start_idx < _allocated_heapregions_length, "checking");
451   guarantee(res_idx != NULL, "checking");
452 
453   uint num_regions_found = 0;
454 
455   jlong cur = start_idx;
456   while (cur != -1 && !(is_available(cur) && at(cur)->is_empty())) {
457     cur--;
458   }
459   if (cur == -1) {
460     return num_regions_found;
461   }
462   jlong old_cur = cur;
463   // cur indexes the first empty region
464   while (cur != -1 && is_available(cur) && at(cur)->is_empty()) {
465     cur--;
466   }
467   *res_idx = cur + 1;
468   num_regions_found = old_cur - cur;
469 
470 #ifdef ASSERT
471   for (uint i = *res_idx; i < (*res_idx + num_regions_found); i++) {
472     assert(at(i)->is_empty(), "just checking");
473   }
474 #endif
475   return num_regions_found;
476 }
477 
478 void HeapRegionManager::verify() {
479   guarantee(length() <= _allocated_heapregions_length,
480             "invariant: _length: %u _allocated_length: %u",
481             length(), _allocated_heapregions_length);
482   guarantee(_allocated_heapregions_length <= max_length(),
483             "invariant: _allocated_length: %u _max_length: %u",
484             _allocated_heapregions_length, max_length());
485 
486   bool prev_committed = true;
487   uint num_committed = 0;
488   HeapWord* prev_end = heap_bottom();
489   for (uint i = 0; i < _allocated_heapregions_length; i++) {
490     if (!is_available(i)) {
491       prev_committed = false;
492       continue;
493     }
494     num_committed++;
495     HeapRegion* hr = _regions.get_by_index(i);
496     guarantee(hr != NULL, "invariant: i: %u", i);
497     guarantee(!prev_committed || hr->bottom() == prev_end,
498               "invariant i: %u " HR_FORMAT " prev_end: " PTR_FORMAT,
499               i, HR_FORMAT_PARAMS(hr), p2i(prev_end));
500     guarantee(hr->hrm_index() == i,
501               "invariant: i: %u hrm_index(): %u", i, hr->hrm_index());
502     // Asserts will fire if i is >= _length
503     HeapWord* addr = hr->bottom();
504     guarantee(addr_to_region(addr) == hr, "sanity");
505     // We cannot check whether the region is part of a particular set: at the time
506     // this method may be called, we have only completed allocation of the regions,
507     // but not put into a region set.
508     prev_committed = true;
509     prev_end = hr->end();
510   }
511   for (uint i = _allocated_heapregions_length; i < max_length(); i++) {
512     guarantee(_regions.get_by_index(i) == NULL, "invariant i: %u", i);
513   }
514 
515   guarantee(num_committed == _num_committed, "Found %u committed regions, but should be %u", num_committed, _num_committed);
516   _free_list.verify();
517 }
518 
519 #ifndef PRODUCT
520 void HeapRegionManager::verify_optional() {
521   verify();
522 }
523 #endif // PRODUCT
524 
525 HeapRegionClaimer::HeapRegionClaimer(uint n_workers) :
526     _n_workers(n_workers), _n_regions(G1CollectedHeap::heap()->_hrm->_allocated_heapregions_length), _claims(NULL) {
527   assert(n_workers > 0, "Need at least one worker.");
528   uint* new_claims = NEW_C_HEAP_ARRAY(uint, _n_regions, mtGC);
529   memset(new_claims, Unclaimed, sizeof(*_claims) * _n_regions);
530   _claims = new_claims;
531 }
532 
533 HeapRegionClaimer::~HeapRegionClaimer() {
534   if (_claims != NULL) {
535     FREE_C_HEAP_ARRAY(uint, _claims);
536   }
537 }
538 
539 uint HeapRegionClaimer::offset_for_worker(uint worker_id) const {
540   assert(worker_id < _n_workers, "Invalid worker_id.");
541   return _n_regions * worker_id / _n_workers;
542 }
543 
544 bool HeapRegionClaimer::is_region_claimed(uint region_index) const {
545   assert(region_index < _n_regions, "Invalid index.");
546   return _claims[region_index] == Claimed;
547 }
548 
549 bool HeapRegionClaimer::claim_region(uint region_index) {
550   assert(region_index < _n_regions, "Invalid index.");
551   uint old_val = Atomic::cmpxchg(Claimed, &_claims[region_index], Unclaimed);
552   return old_val == Unclaimed;
553 }