1 /*
2 * Copyright (c) 2018, 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/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 "gc/g1/heterogeneousHeapRegionManager.hpp"
32 #include "memory/allocation.hpp"
33
34
35 HeterogeneousHeapRegionManager* HeterogeneousHeapRegionManager::manager() {
36 G1CollectedHeap* g1h = G1CollectedHeap::heap();
37 assert(g1h != NULL, "Uninitialized access to HeterogeneousHeapRegionManager::manager()");
38
39 HeapRegionManager* hrm = g1h->hrm();
40 assert(hrm != NULL, "Uninitialized access to HeterogeneousHeapRegionManager::manager()");
41 return (HeterogeneousHeapRegionManager*)hrm;
42 }
43
44 void HeterogeneousHeapRegionManager::initialize(G1RegionToSpaceMapper* heap_storage,
45 G1RegionToSpaceMapper* prev_bitmap,
46 G1RegionToSpaceMapper* next_bitmap,
47 G1RegionToSpaceMapper* bot,
48 G1RegionToSpaceMapper* cardtable,
49 G1RegionToSpaceMapper* card_counts) {
50 HeapRegionManager::initialize(heap_storage, prev_bitmap, next_bitmap, bot, cardtable, card_counts);
51
52 // We commit bitmap for all regions during initialization and mark the bitmap space as special.
53 // This allows regions to be un-committed while concurrent-marking threads are accessing the bitmap concurrently.
54 _prev_bitmap_mapper->commit_and_set_special();
55 _next_bitmap_mapper->commit_and_set_special();
56 }
57
58 // expand_by() is called to grow the heap. We grow into nvdimm now.
59 // Dram regions are committed later as needed during mutator region allocation or
60 // when young list target length is determined after gc cycle.
61 uint HeterogeneousHeapRegionManager::expand_by(uint num_regions, WorkGang* pretouch_workers) {
62 uint num_regions_possible = total_regions_committed() >= max_expandable_length() ? 0 : max_expandable_length() - total_regions_committed();
63 uint num_expanded = expand_nvdimm(MIN2(num_regions, num_regions_possible), pretouch_workers);
64 return num_expanded;
65 }
66
67 // Expands heap starting from 'start' index. The question is should we expand from one memory (e.g. nvdimm) to another (e.g. dram).
68 // Looking at the code, expand_at() is called for humongous allocation where 'start' is in nv-dimm.
69 // So we only allocate regions in the same kind of memory as 'start'.
70 uint HeterogeneousHeapRegionManager::expand_at(uint start, uint num_regions, WorkGang* pretouch_workers) {
71 if (num_regions == 0) {
72 return 0;
73 }
74 uint target_num_regions = MIN2(num_regions, max_expandable_length() - total_regions_committed());
75 uint end = is_in_nvdimm(start) ? end_index_of_nvdimm() : end_index_of_dram();
76
77 uint num_expanded = expand_in_range(start, end, target_num_regions, pretouch_workers);
78 assert(total_regions_committed() <= max_expandable_length(), "must be");
79 return num_expanded;
80 }
81
82 // This function ensures that there are 'expected_num_regions' committed regions in dram.
83 // If new regions are committed, it un-commits that many regions from nv-dimm.
84 // If there are already more regions committed in dram, extra regions are un-committed.
85 void HeterogeneousHeapRegionManager::adjust_dram_regions(uint expected_num_regions, WorkGang* pretouch_workers) {
86
87 // Release back the extra regions allocated in evacuation failure scenario.
88 if(_no_borrowed_regions > 0) {
89 _no_borrowed_regions -= shrink_dram(_no_borrowed_regions);
90 _no_borrowed_regions -= shrink_nvdimm(_no_borrowed_regions);
91 }
92
93 if(expected_num_regions > free_list_dram_length()) {
94 // If we are going to expand DRAM, we expand a little more so that we can absorb small variations in Young gen sizing.
95 uint targeted_dram_regions = expected_num_regions * (1 + (double)G1YoungExpansionBufferPercent / 100);
96 uint to_be_made_available = targeted_dram_regions - free_list_dram_length();
97
98 #ifdef ASSERT
99 uint total_committed_before = total_regions_committed();
100 #endif
101 uint can_be_made_available = shrink_nvdimm(to_be_made_available);
102 uint ret = expand_dram(can_be_made_available, pretouch_workers);
103 #ifdef ASSERT
104 assert(ret == can_be_made_available, "should be equal");
105 assert(total_committed_before == total_regions_committed(), "invariant not met");
106 #endif
107 } else {
108 uint to_be_released = free_list_dram_length() - expected_num_regions;
109 // if number of extra DRAM regions is small, do not shrink.
110 if (to_be_released < expected_num_regions * G1YoungExpansionBufferPercent / 100) {
111 return;
112 }
113
114 #ifdef ASSERT
115 uint total_committed_before = total_regions_committed();
116 #endif
117 uint ret = shrink_dram(to_be_released);
118 assert(ret == to_be_released, "Should be able to shrink by given amount");
119 ret = expand_nvdimm(to_be_released, pretouch_workers);
120 #ifdef ASSERT
121 assert(ret == to_be_released, "Should be able to expand by given amount");
122 assert(total_committed_before == total_regions_committed(), "invariant not met");
123 #endif
124 }
125 }
126
127 uint HeterogeneousHeapRegionManager::total_regions_committed() const {
128 return num_committed_dram() + num_committed_nvdimm();
129 }
130
131 uint HeterogeneousHeapRegionManager::num_committed_dram() const {
132 // This class does not keep count of committed regions in dram and nv-dimm.
133 // G1RegionToHeteroSpaceMapper keeps this information.
134 return static_cast<G1RegionToHeteroSpaceMapper*>(_heap_mapper)->num_committed_dram();
135 }
136
137 uint HeterogeneousHeapRegionManager::num_committed_nvdimm() const {
138 // See comment for num_committed_dram()
139 return static_cast<G1RegionToHeteroSpaceMapper*>(_heap_mapper)->num_committed_nvdimm();
140 }
141
142 // Return maximum number of regions that heap can expand to.
143 uint HeterogeneousHeapRegionManager::max_expandable_length() const {
144 return _max_regions;
145 }
146
147 uint HeterogeneousHeapRegionManager::find_unavailable_in_range(uint start_idx, uint end_idx, uint* res_idx) const {
148 guarantee(res_idx != NULL, "checking");
149 guarantee(start_idx <= (max_length() + 1), "checking");
150
151 uint num_regions = 0;
152
153 uint cur = start_idx;
154 while (cur <= end_idx && is_available(cur)) {
155 cur++;
156 }
157 if (cur == end_idx + 1) {
158 return num_regions;
159 }
160 *res_idx = cur;
161 while (cur <= end_idx && is_unavailable_for_allocation(cur)) {
162 cur++;
163 }
164 num_regions = cur - *res_idx;
165
166 #ifdef ASSERT
167 for (uint i = *res_idx; i < (*res_idx + num_regions); i++) {
168 assert(is_unavailable_for_allocation(i), "just checking");
169 }
170 assert(cur == end_idx + 1 || num_regions == 0 || is_available(cur),
171 "The region at the current position %u must be available or at the end", cur);
172 #endif
173 return num_regions;
174 }
175
176 uint HeterogeneousHeapRegionManager::expand_dram(uint num_regions, WorkGang* pretouch_workers) {
177 return expand_in_range(start_index_of_dram(), end_index_of_dram(), num_regions, pretouch_workers);
178 }
179
180 uint HeterogeneousHeapRegionManager::expand_nvdimm(uint num_regions, WorkGang* pretouch_workers) {
181 return expand_in_range(start_index_of_nvdimm(), end_index_of_nvdimm(), num_regions, pretouch_workers);
182 }
183
184 // Follows same logic as expand_at() form HeapRegionManager.
185 uint HeterogeneousHeapRegionManager::expand_in_range(uint start, uint end, uint num_regions, WorkGang* pretouch_gang) {
186
187 uint so_far = 0;
188 uint chunk_start = 0;
189 uint num_last_found = 0;
190 while (so_far < num_regions &&
191 (num_last_found = find_unavailable_in_range(start, end, &chunk_start)) > 0) {
192 uint to_commit = MIN2(num_regions - so_far, num_last_found);
193 make_regions_available(chunk_start, to_commit, pretouch_gang);
194 so_far += to_commit;
195 start = chunk_start + to_commit + 1;
196 }
197
198 return so_far;
199 }
200
201 // Shrink in the range of indexes which are reserved for dram.
202 uint HeterogeneousHeapRegionManager::shrink_dram(uint num_regions, bool update_free_list) {
203 return shrink_in_range(start_index_of_dram(), end_index_of_dram(), num_regions, update_free_list);
204 }
205
206 // Shrink in the range of indexes which are reserved for nv-dimm.
207 uint HeterogeneousHeapRegionManager::shrink_nvdimm(uint num_regions, bool update_free_list) {
208 return shrink_in_range(start_index_of_nvdimm(), end_index_of_nvdimm(), num_regions, update_free_list);
209 }
210
211 // Find empty regions in given range, un-commit them and return the count.
212 uint HeterogeneousHeapRegionManager::shrink_in_range(uint start, uint end, uint num_regions, bool update_free_list) {
213
214 if (num_regions == 0) {
215 return 0;
216 }
217 uint so_far = 0;
218 uint idx_last_found = 0;
219 uint num_last_found;
220 while (so_far < num_regions &&
221 (num_last_found = find_empty_in_range_reverse(start, end, &idx_last_found)) > 0) {
222 uint to_uncommit = MIN2(num_regions - so_far, num_last_found);
223 if(update_free_list) {
224 _free_list.remove_starting_at(at(idx_last_found + num_last_found - to_uncommit), to_uncommit);
225 }
226 uncommit_regions(idx_last_found + num_last_found - to_uncommit, to_uncommit);
227 so_far += to_uncommit;
228 end = idx_last_found;
229 }
230 return so_far;
231 }
232
233 uint HeterogeneousHeapRegionManager::find_empty_in_range_reverse(uint start_idx, uint end_idx, uint* res_idx) {
234 guarantee(res_idx != NULL, "checking");
235 guarantee(start_idx < max_length(), "checking");
236 guarantee(end_idx < max_length(), "checking");
237 if(start_idx > end_idx) {
238 return 0;
239 }
240
241 uint num_regions_found = 0;
242
243 jlong cur = end_idx;
244 while (cur >= start_idx && !(is_available(cur) && at(cur)->is_empty())) {
245 cur--;
246 }
247 if (cur == start_idx - 1) {
248 return num_regions_found;
249 }
250 jlong old_cur = cur;
251 // cur indexes the first empty region
252 while (cur >= start_idx && is_available(cur) && at(cur)->is_empty()) {
253 cur--;
254 }
255 *res_idx = cur + 1;
256 num_regions_found = old_cur - cur;
257
258 #ifdef ASSERT
259 for (uint i = *res_idx; i < (*res_idx + num_regions_found); i++) {
260 assert(at(i)->is_empty(), "just checking");
261 }
262 #endif
263 return num_regions_found;
264 }
265
266 HeapRegion* HeterogeneousHeapRegionManager::allocate_free_region(HeapRegionType type, uint node_index) {
267
268 // We want to prevent mutators from proceeding when we have borrowed regions from the last collection. This
269 // will force a full collection to remedy the situation.
270 // Free region requests from GC threads can proceed.
271 if(type.is_eden() || type.is_humongous()) {
272 if(has_borrowed_regions()) {
273 return NULL;
274 }
275 }
276
277 // old and humongous regions are allocated from nv-dimm; eden and survivor regions are allocated from dram
278 // assumption: dram regions take higher indexes
279 bool from_nvdimm = (type.is_old() || type.is_humongous()) ? true : false;
280 bool from_head = from_nvdimm;
281 HeapRegion* hr = _free_list.remove_region(from_head);
282
283 if (hr != NULL && ( (from_nvdimm && !is_in_nvdimm(hr->hrm_index())) || (!from_nvdimm && !is_in_dram(hr->hrm_index())) ) ) {
284 _free_list.add_ordered(hr);
285 hr = NULL;
286 }
287
288 #ifdef ASSERT
289 uint total_committed_before = total_regions_committed();
290 #endif
291
292 if (hr == NULL) {
293 if (!from_nvdimm) {
294 uint ret = shrink_nvdimm(1);
295 if (ret == 1) {
296 ret = expand_dram(1, NULL);
297 assert(ret == 1, "We should be able to commit one region");
298 hr = _free_list.remove_region(from_head);
299 }
300 }
301 else { /*is_old*/
302 uint ret = shrink_dram(1);
303 if (ret == 1) {
304 ret = expand_nvdimm(1, NULL);
305 assert(ret == 1, "We should be able to commit one region");
306 hr = _free_list.remove_region(from_head);
307 }
308 }
309 }
310 #ifdef ASSERT
311 assert(total_committed_before == total_regions_committed(), "invariant not met");
312 #endif
313
314 // When an old region is requested (which happens during collection pause) and we can't find any empty region
315 // in the set of available regions (which is an evacuation failure scenario), we borrow (or pre-allocate) an unavailable region
316 // from nv-dimm. This region is used to evacuate surviving objects from eden, survivor or old.
317 if(hr == NULL && type.is_old()) {
318 hr = borrow_old_region_for_gc();
319 }
320
321 if (hr != NULL) {
322 assert(hr->next() == NULL, "Single region should not have next");
323 assert(is_available(hr->hrm_index()), "Must be committed");
324 }
325 return hr;
326 }
327
328 uint HeterogeneousHeapRegionManager::find_contiguous_only_empty(size_t num) {
329 if (has_borrowed_regions()) {
330 return G1_NO_HRM_INDEX;
331 }
332 return find_contiguous(start_index_of_nvdimm(), end_index_of_nvdimm(), num, true);
333 }
334
335 uint HeterogeneousHeapRegionManager::find_contiguous_empty_or_unavailable(size_t num) {
336 if (has_borrowed_regions()) {
337 return G1_NO_HRM_INDEX;
338 }
339 return find_contiguous(start_index_of_nvdimm(), end_index_of_nvdimm(), num, false);
340 }
341
342 uint HeterogeneousHeapRegionManager::find_contiguous(size_t start, size_t end, size_t num, bool empty_only) {
343 uint found = 0;
344 size_t length_found = 0;
345 uint cur = (uint)start;
346 uint length_unavailable = 0;
347
348 while (length_found < num && cur <= end) {
349 HeapRegion* hr = _regions.get_by_index(cur);
350 if ((!empty_only && is_unavailable_for_allocation(cur)) || (is_available(cur) && hr != NULL && hr->is_empty())) {
351 // This region is a potential candidate for allocation into.
352 if (is_unavailable_for_allocation(cur)) {
353 if(shrink_dram(1) == 1) {
354 uint ret = expand_in_range(cur, cur, 1, NULL);
355 assert(ret == 1, "We should be able to expand at this index");
356 } else {
357 length_unavailable++;
358 }
359 }
360 length_found++;
361 }
362 else {
363 // This region is not a candidate. The next region is the next possible one.
364 found = cur + 1;
365 length_found = 0;
366 }
367 cur++;
368 }
369
370 if (length_found == num) {
371 for (uint i = found; i < (found + num); i++) {
372 HeapRegion* hr = _regions.get_by_index(i);
373 // sanity check
374 guarantee((!empty_only && is_unavailable_for_allocation(i)) || (is_available(i) && hr != NULL && hr->is_empty()),
375 "Found region sequence starting at " UINT32_FORMAT ", length " SIZE_FORMAT
376 " that is not empty at " UINT32_FORMAT ". Hr is " PTR_FORMAT, found, num, i, p2i(hr));
377 }
378 if (!empty_only && length_unavailable > (max_expandable_length() - total_regions_committed())) {
379 // if 'length_unavailable' number of regions will be made available, we will exceed max regions.
380 return G1_NO_HRM_INDEX;
381 }
382 return found;
383 }
384 else {
385 return G1_NO_HRM_INDEX;
386 }
387 }
388
389 uint HeterogeneousHeapRegionManager::find_highest_free(bool* expanded) {
390 // Loop downwards from the highest dram region index, looking for an
391 // entry which is either free or not yet committed. If not yet
392 // committed, expand_at that index.
393 uint curr = end_index_of_dram();
394 while (true) {
395 HeapRegion *hr = _regions.get_by_index(curr);
396 if (hr == NULL && !(total_regions_committed() < _max_regions)) {
397 uint res = shrink_nvdimm(1);
398 if (res == 1) {
399 res = expand_in_range(curr, curr, 1, NULL);
400 assert(res == 1, "We should be able to expand since shrink was successful");
401 *expanded = true;
402 return curr;
403 }
404 }
405 else {
406 if (hr->is_free()) {
407 *expanded = false;
408 return curr;
409 }
410 }
411 if (curr == start_index_of_dram()) {
412 return G1_NO_HRM_INDEX;
413 }
414 curr--;
415 }
416 }
417
418 // We need to override this since region 0 which serves are dummy region in base class may not be available here.
419 // This is a corner condition when either number of regions is small. When adaptive sizing is used, initial heap size
420 // could be just one region. This region is commited in dram to be used for young generation, leaving region 0 (which is in nvdimm)
421 // unavailable.
422 HeapRegion* HeterogeneousHeapRegionManager::get_dummy_region() {
423 uint curr = 0;
424
425 while (curr < _regions.length()) {
426 if (is_available(curr)) {
427 return new_heap_region(curr);
428 }
429 curr++;
430 }
431 assert(false, "We should always find a region available for dummy region");
432 return NULL;
433 }
434
435 // First shrink in dram, then in nv-dimm.
436 uint HeterogeneousHeapRegionManager::shrink_by(uint num_regions) {
437 // This call is made at end of full collection. Before making this call the region sets are tore down (tear_down_region_sets()).
438 // So shrink() calls below do not need to remove uncomitted regions from free list.
439 uint ret = shrink_dram(num_regions, false /* update_free_list */);
440 ret += shrink_nvdimm(num_regions - ret, false /* update_free_list */);
441 return ret;
442 }
443
444 void HeterogeneousHeapRegionManager::verify() {
445 HeapRegionManager::verify();
446 }
447
448 uint HeterogeneousHeapRegionManager::free_list_dram_length() const {
449 return _free_list.num_of_regions_in_range(start_index_of_dram(), end_index_of_dram());
450 }
451
452 uint HeterogeneousHeapRegionManager::free_list_nvdimm_length() const {
453 return _free_list.num_of_regions_in_range(start_index_of_nvdimm(), end_index_of_nvdimm());
454 }
455
456 bool HeterogeneousHeapRegionManager::is_in_nvdimm(uint index) const {
457 return index >= start_index_of_nvdimm() && index <= end_index_of_nvdimm();
458 }
459
460 bool HeterogeneousHeapRegionManager::is_in_dram(uint index) const {
461 return index >= start_index_of_dram() && index <= end_index_of_dram();
462 }
463
464 // We have to make sure full collection copies all surviving objects to NV-DIMM.
465 // We might not have enough regions in nvdimm_set, so we need to make more regions on NV-DIMM available for full collection.
466 // Note: by doing this we are breaking the in-variant that total number of committed regions is equal to current heap size.
467 // After full collection ends, we will re-establish this in-variant by freeing DRAM regions.
468 void HeterogeneousHeapRegionManager::prepare_for_full_collection_start() {
469 _total_commited_before_full_gc = total_regions_committed() - _no_borrowed_regions;
470 _no_borrowed_regions = 0;
471 expand_nvdimm(num_committed_dram(), NULL);
472 remove_all_free_regions();
473 }
474
475 // We need to bring back the total committed regions to before full collection start.
476 // Unless we are close to OOM, all regular (not pinned) regions in DRAM should be free.
477 // We shrink all free regions in DRAM and if needed from NV-DIMM (when there are pinned DRAM regions)
478 // If we can't bring back committed regions count to _total_commited_before_full_gc, we keep the extra count in _no_borrowed_regions.
479 // When this GC finishes, new regions won't be allocated since has_borrowed_regions() is true. VM will be forced to re-try GC
480 // with clear soft references followed by OOM error in worst case.
481 void HeterogeneousHeapRegionManager::prepare_for_full_collection_end() {
482 uint shrink_size = total_regions_committed() - _total_commited_before_full_gc;
483 uint so_far = 0;
484 uint idx_last_found = 0;
485 uint num_last_found;
486 uint end = (uint)_regions.length() - 1;
487 while (so_far < shrink_size &&
488 (num_last_found = find_empty_in_range_reverse(0, end, &idx_last_found)) > 0) {
489 uint to_uncommit = MIN2(shrink_size - so_far, num_last_found);
490 uncommit_regions(idx_last_found + num_last_found - to_uncommit, to_uncommit);
491 so_far += to_uncommit;
492 end = idx_last_found;
493 }
494 // See comment above the function.
495 _no_borrowed_regions = shrink_size - so_far;
496 }
497
498 uint HeterogeneousHeapRegionManager::start_index_of_dram() const { return _max_regions;}
499
500 uint HeterogeneousHeapRegionManager::end_index_of_dram() const { return 2*_max_regions - 1; }
501
502 uint HeterogeneousHeapRegionManager::start_index_of_nvdimm() const { return 0; }
503
504 uint HeterogeneousHeapRegionManager::end_index_of_nvdimm() const { return _max_regions - 1; }
505
506 // This function is called when there are no free nv-dimm regions.
507 // It borrows a region from the set of unavailable regions in nv-dimm for GC purpose.
508 HeapRegion* HeterogeneousHeapRegionManager::borrow_old_region_for_gc() {
509 assert(free_list_nvdimm_length() == 0, "this function should be called only when there are no nv-dimm regions in free list");
510
511 uint ret = expand_nvdimm(1, NULL);
512 if(ret != 1) {
513 return NULL;
514 }
515 HeapRegion* hr = _free_list.remove_region(true /*from_head*/);
516 assert(is_in_nvdimm(hr->hrm_index()), "allocated region should be in nv-dimm");
517 _no_borrowed_regions++;
518 return hr;
519 }
520
521 bool HeterogeneousHeapRegionManager::has_borrowed_regions() const {
522 return _no_borrowed_regions > 0;
523 }