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