1 /*
2 * Copyright Amazon.com Inc. 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
26 #include "precompiled.hpp"
27
28 #include "gc/shared/fullGCForwarding.inline.hpp"
29 #include "gc/shared/preservedMarks.inline.hpp"
30 #include "gc/shenandoah/shenandoahGenerationalFullGC.hpp"
31 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
32 #include "gc/shenandoah/shenandoahGeneration.hpp"
33 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
34 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
35 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
36 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
37 #include "gc/shenandoah/shenandoahUtils.hpp"
38
39 #ifdef ASSERT
40 void assert_regions_used_not_more_than_capacity(ShenandoahGeneration* generation) {
41 assert(generation->used_regions_size() <= generation->max_capacity(),
42 "%s generation affiliated regions must be less than capacity", generation->name());
43 }
44
45 void assert_usage_not_more_than_regions_used(ShenandoahGeneration* generation) {
46 assert(generation->used_including_humongous_waste() <= generation->used_regions_size(),
47 "%s consumed can be no larger than span of affiliated regions", generation->name());
48 }
49 #else
50 void assert_regions_used_not_more_than_capacity(ShenandoahGeneration* generation) {}
51 void assert_usage_not_more_than_regions_used(ShenandoahGeneration* generation) {}
52 #endif
53
54
55 void ShenandoahGenerationalFullGC::prepare() {
56 auto heap = ShenandoahGenerationalHeap::heap();
57 // Since we may arrive here from degenerated GC failure of either young or old, establish generation as GLOBAL.
58 heap->set_gc_generation(heap->global_generation());
59 heap->set_active_generation();
60
61 // No need for old_gen->increase_used() as this was done when plabs were allocated.
62 heap->reset_generation_reserves();
63
64 // Full GC supersedes any marking or coalescing in old generation.
65 heap->old_generation()->cancel_gc();
66 }
67
68 void ShenandoahGenerationalFullGC::handle_completion(ShenandoahHeap* heap) {
69 // Full GC should reset time since last gc for young and old heuristics
70 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::cast(heap);
71 ShenandoahYoungGeneration* young = gen_heap->young_generation();
72 ShenandoahOldGeneration* old = gen_heap->old_generation();
73 young->heuristics()->record_cycle_end();
74 old->heuristics()->record_cycle_end();
75
76 gen_heap->mmu_tracker()->record_full(GCId::current());
77 gen_heap->log_heap_status("At end of Full GC");
78
79 assert(old->is_idle(), "After full GC, old generation should be idle.");
80
81 // Since we allow temporary violation of these constraints during Full GC, we want to enforce that the assertions are
82 // made valid by the time Full GC completes.
83 assert_regions_used_not_more_than_capacity(old);
84 assert_regions_used_not_more_than_capacity(young);
85 assert_usage_not_more_than_regions_used(old);
86 assert_usage_not_more_than_regions_used(young);
87
88 // Establish baseline for next old-has-grown trigger.
89 old->set_live_bytes_after_last_mark(old->used_including_humongous_waste());
90 }
91
92 void ShenandoahGenerationalFullGC::rebuild_remembered_set(ShenandoahHeap* heap) {
93 ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_reconstruct_remembered_set);
94 ShenandoahRegionIterator regions;
95 ShenandoahReconstructRememberedSetTask task(®ions);
96 heap->workers()->run_task(&task);
97
98 // Rebuilding the remembered set recomputes all the card offsets for objects.
99 // The adjust pointers phase coalesces and fills all necessary regions. In case
100 // we came to the full GC from an incomplete global cycle, we need to indicate
101 // that the old regions are parsable.
102 heap->old_generation()->set_parsable(true);
103 }
104
105 void ShenandoahGenerationalFullGC::balance_generations_after_gc(ShenandoahHeap* heap) {
106 ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::cast(heap);
107 ShenandoahOldGeneration* const old_gen = gen_heap->old_generation();
108
109 size_t old_usage = old_gen->used_regions_size();
110 size_t old_capacity = old_gen->max_capacity();
111
112 assert(old_usage % ShenandoahHeapRegion::region_size_bytes() == 0, "Old usage must align with region size");
113 assert(old_capacity % ShenandoahHeapRegion::region_size_bytes() == 0, "Old capacity must align with region size");
114
115 if (old_capacity > old_usage) {
116 size_t excess_old_regions = (old_capacity - old_usage) / ShenandoahHeapRegion::region_size_bytes();
117 gen_heap->generation_sizer()->transfer_to_young(excess_old_regions);
118 } else if (old_capacity < old_usage) {
119 size_t old_regions_deficit = (old_usage - old_capacity) / ShenandoahHeapRegion::region_size_bytes();
120 gen_heap->generation_sizer()->force_transfer_to_old(old_regions_deficit);
121 }
122
123 log_info(gc, ergo)("FullGC done: young usage: " PROPERFMT ", old usage: " PROPERFMT,
124 PROPERFMTARGS(gen_heap->young_generation()->used()),
125 PROPERFMTARGS(old_gen->used()));
126 }
127
128 void ShenandoahGenerationalFullGC::balance_generations_after_rebuilding_free_set() {
129 auto result = ShenandoahGenerationalHeap::heap()->balance_generations();
130 LogTarget(Info, gc, ergo) lt;
131 if (lt.is_enabled()) {
132 LogStream ls(lt);
133 result.print_on("Full GC", &ls);
134 }
135 }
136
137 void ShenandoahGenerationalFullGC::log_live_in_old(ShenandoahHeap* heap) {
138 LogTarget(Debug, gc) lt;
139 if (lt.is_enabled()) {
140 size_t live_bytes_in_old = 0;
141 for (size_t i = 0; i < heap->num_regions(); i++) {
142 ShenandoahHeapRegion* r = heap->get_region(i);
143 if (r->is_old()) {
144 live_bytes_in_old += r->get_live_data_bytes();
145 }
146 }
147 log_debug(gc)("Live bytes in old after STW mark: " PROPERFMT, PROPERFMTARGS(live_bytes_in_old));
148 }
149 }
150
151 void ShenandoahGenerationalFullGC::restore_top_before_promote(ShenandoahHeap* heap) {
152 for (size_t i = 0; i < heap->num_regions(); i++) {
153 ShenandoahHeapRegion* r = heap->get_region(i);
154 if (r->get_top_before_promote() != nullptr) {
155 r->restore_top_before_promote();
156 }
157 }
158 }
159
160 void ShenandoahGenerationalFullGC::account_for_region(ShenandoahHeapRegion* r, size_t ®ion_count, size_t ®ion_usage, size_t &humongous_waste) {
161 region_count++;
162 region_usage += r->used();
163 if (r->is_humongous_start()) {
164 // For each humongous object, we take this path once regardless of how many regions it spans.
165 HeapWord* obj_addr = r->bottom();
166 oop obj = cast_to_oop(obj_addr);
167 size_t word_size = obj->size();
168 size_t region_size_words = ShenandoahHeapRegion::region_size_words();
169 size_t overreach = word_size % region_size_words;
170 if (overreach != 0) {
171 humongous_waste += (region_size_words - overreach) * HeapWordSize;
172 }
173 // else, this humongous object aligns exactly on region size, so no waste.
174 }
175 }
176
177 void ShenandoahGenerationalFullGC::maybe_coalesce_and_fill_region(ShenandoahHeapRegion* r) {
178 if (r->is_pinned() && r->is_old() && r->is_active() && !r->is_humongous()) {
179 r->begin_preemptible_coalesce_and_fill();
180 r->oop_coalesce_and_fill(false);
181 }
182 }
183
184 void ShenandoahGenerationalFullGC::compute_balances() {
185 auto heap = ShenandoahGenerationalHeap::heap();
186
187 // In case this Full GC resulted from degeneration, clear the tally on anticipated promotion.
188 heap->old_generation()->set_promotion_potential(0);
189 // Invoke this in case we are able to transfer memory from OLD to YOUNG.
190 heap->compute_old_generation_balance(0, 0);
191 }
192
193 ShenandoahPrepareForGenerationalCompactionObjectClosure::ShenandoahPrepareForGenerationalCompactionObjectClosure(PreservedMarks* preserved_marks,
194 GrowableArray<ShenandoahHeapRegion*>& empty_regions,
195 ShenandoahHeapRegion* from_region, uint worker_id) :
196 _preserved_marks(preserved_marks),
197 _heap(ShenandoahGenerationalHeap::heap()),
198 _tenuring_threshold(0),
199 _empty_regions(empty_regions),
200 _empty_regions_pos(0),
201 _old_to_region(nullptr),
202 _young_to_region(nullptr),
203 _from_region(nullptr),
204 _from_affiliation(ShenandoahAffiliation::FREE),
205 _old_compact_point(nullptr),
206 _young_compact_point(nullptr),
207 _worker_id(worker_id) {
208 assert(from_region != nullptr, "Worker needs from_region");
209 // assert from_region has live?
210 if (from_region->is_old()) {
211 _old_to_region = from_region;
212 _old_compact_point = from_region->bottom();
213 } else if (from_region->is_young()) {
214 _young_to_region = from_region;
215 _young_compact_point = from_region->bottom();
216 }
217
218 _tenuring_threshold = _heap->age_census()->tenuring_threshold();
219 }
220
221 void ShenandoahPrepareForGenerationalCompactionObjectClosure::set_from_region(ShenandoahHeapRegion* from_region) {
222 log_debug(gc)("Worker %u compacting %s Region " SIZE_FORMAT " which had used " SIZE_FORMAT " and %s live",
223 _worker_id, from_region->affiliation_name(),
224 from_region->index(), from_region->used(), from_region->has_live()? "has": "does not have");
225
226 _from_region = from_region;
227 _from_affiliation = from_region->affiliation();
228 if (_from_region->has_live()) {
229 if (_from_affiliation == ShenandoahAffiliation::OLD_GENERATION) {
230 if (_old_to_region == nullptr) {
231 _old_to_region = from_region;
232 _old_compact_point = from_region->bottom();
233 }
234 } else {
235 assert(_from_affiliation == ShenandoahAffiliation::YOUNG_GENERATION, "from_region must be OLD or YOUNG");
236 if (_young_to_region == nullptr) {
237 _young_to_region = from_region;
238 _young_compact_point = from_region->bottom();
239 }
240 }
241 } // else, we won't iterate over this _from_region so we don't need to set up to region to hold copies
242 }
243
244 void ShenandoahPrepareForGenerationalCompactionObjectClosure::finish() {
245 finish_old_region();
246 finish_young_region();
247 }
248
249 void ShenandoahPrepareForGenerationalCompactionObjectClosure::finish_old_region() {
250 if (_old_to_region != nullptr) {
251 log_debug(gc)("Planned compaction into Old Region " SIZE_FORMAT ", used: " SIZE_FORMAT " tabulated by worker %u",
252 _old_to_region->index(), _old_compact_point - _old_to_region->bottom(), _worker_id);
253 _old_to_region->set_new_top(_old_compact_point);
254 _old_to_region = nullptr;
255 }
256 }
257
258 void ShenandoahPrepareForGenerationalCompactionObjectClosure::finish_young_region() {
259 if (_young_to_region != nullptr) {
260 log_debug(gc)("Worker %u planned compaction into Young Region " SIZE_FORMAT ", used: " SIZE_FORMAT,
261 _worker_id, _young_to_region->index(), _young_compact_point - _young_to_region->bottom());
262 _young_to_region->set_new_top(_young_compact_point);
263 _young_to_region = nullptr;
264 }
265 }
266
267 bool ShenandoahPrepareForGenerationalCompactionObjectClosure::is_compact_same_region() {
268 return (_from_region == _old_to_region) || (_from_region == _young_to_region);
269 }
270
271 void ShenandoahPrepareForGenerationalCompactionObjectClosure::do_object(oop p) {
272 assert(_from_region != nullptr, "must set before work");
273 assert((_from_region->bottom() <= cast_from_oop<HeapWord*>(p)) && (cast_from_oop<HeapWord*>(p) < _from_region->top()),
274 "Object must reside in _from_region");
275 assert(_heap->complete_marking_context()->is_marked(p), "must be marked");
276 assert(!_heap->complete_marking_context()->allocated_after_mark_start(p), "must be truly marked");
277
278 size_t obj_size = p->size();
279 uint from_region_age = _from_region->age();
280 uint object_age = p->age();
281
282 bool promote_object = false;
283 if ((_from_affiliation == ShenandoahAffiliation::YOUNG_GENERATION) &&
284 (from_region_age + object_age >= _tenuring_threshold)) {
285 if ((_old_to_region != nullptr) && (_old_compact_point + obj_size > _old_to_region->end())) {
286 finish_old_region();
287 _old_to_region = nullptr;
288 }
289 if (_old_to_region == nullptr) {
290 if (_empty_regions_pos < _empty_regions.length()) {
291 ShenandoahHeapRegion* new_to_region = _empty_regions.at(_empty_regions_pos);
292 _empty_regions_pos++;
293 new_to_region->set_affiliation(OLD_GENERATION);
294 _old_to_region = new_to_region;
295 _old_compact_point = _old_to_region->bottom();
296 promote_object = true;
297 }
298 // Else this worker thread does not yet have any empty regions into which this aged object can be promoted so
299 // we leave promote_object as false, deferring the promotion.
300 } else {
301 promote_object = true;
302 }
303 }
304
305 if (promote_object || (_from_affiliation == ShenandoahAffiliation::OLD_GENERATION)) {
306 assert(_old_to_region != nullptr, "_old_to_region should not be nullptr when evacuating to OLD region");
307 if (_old_compact_point + obj_size > _old_to_region->end()) {
308 ShenandoahHeapRegion* new_to_region;
309
310 log_debug(gc)("Worker %u finishing old region " SIZE_FORMAT ", compact_point: " PTR_FORMAT ", obj_size: " SIZE_FORMAT
311 ", &compact_point[obj_size]: " PTR_FORMAT ", region end: " PTR_FORMAT, _worker_id, _old_to_region->index(),
312 p2i(_old_compact_point), obj_size, p2i(_old_compact_point + obj_size), p2i(_old_to_region->end()));
313
314 // Object does not fit. Get a new _old_to_region.
315 finish_old_region();
316 if (_empty_regions_pos < _empty_regions.length()) {
317 new_to_region = _empty_regions.at(_empty_regions_pos);
318 _empty_regions_pos++;
319 new_to_region->set_affiliation(OLD_GENERATION);
320 } else {
321 // If we've exhausted the previously selected _old_to_region, we know that the _old_to_region is distinct
322 // from _from_region. That's because there is always room for _from_region to be compacted into itself.
323 // Since we're out of empty regions, let's use _from_region to hold the results of its own compaction.
324 new_to_region = _from_region;
325 }
326
327 assert(new_to_region != _old_to_region, "must not reuse same OLD to-region");
328 assert(new_to_region != nullptr, "must not be nullptr");
329 _old_to_region = new_to_region;
330 _old_compact_point = _old_to_region->bottom();
331 }
332
333 // Object fits into current region, record new location, if object does not move:
334 assert(_old_compact_point + obj_size <= _old_to_region->end(), "must fit");
335 shenandoah_assert_not_forwarded(nullptr, p);
336 if (_old_compact_point != cast_from_oop<HeapWord*>(p)) {
337 _preserved_marks->push_if_necessary(p, p->mark());
338 FullGCForwarding::forward_to(p, cast_to_oop(_old_compact_point));
339 }
340 _old_compact_point += obj_size;
341 } else {
342 assert(_from_affiliation == ShenandoahAffiliation::YOUNG_GENERATION,
343 "_from_region must be OLD_GENERATION or YOUNG_GENERATION");
344 assert(_young_to_region != nullptr, "_young_to_region should not be nullptr when compacting YOUNG _from_region");
345
346 // After full gc compaction, all regions have age 0. Embed the region's age into the object's age in order to preserve
347 // tenuring progress.
348 if (_heap->is_aging_cycle()) {
349 ShenandoahHeap::increase_object_age(p, from_region_age + 1);
350 } else {
351 ShenandoahHeap::increase_object_age(p, from_region_age);
352 }
353
354 if (_young_compact_point + obj_size > _young_to_region->end()) {
355 ShenandoahHeapRegion* new_to_region;
356
357 log_debug(gc)("Worker %u finishing young region " SIZE_FORMAT ", compact_point: " PTR_FORMAT ", obj_size: " SIZE_FORMAT
358 ", &compact_point[obj_size]: " PTR_FORMAT ", region end: " PTR_FORMAT, _worker_id, _young_to_region->index(),
359 p2i(_young_compact_point), obj_size, p2i(_young_compact_point + obj_size), p2i(_young_to_region->end()));
360
361 // Object does not fit. Get a new _young_to_region.
362 finish_young_region();
363 if (_empty_regions_pos < _empty_regions.length()) {
364 new_to_region = _empty_regions.at(_empty_regions_pos);
365 _empty_regions_pos++;
366 new_to_region->set_affiliation(YOUNG_GENERATION);
367 } else {
368 // If we've exhausted the previously selected _young_to_region, we know that the _young_to_region is distinct
369 // from _from_region. That's because there is always room for _from_region to be compacted into itself.
370 // Since we're out of empty regions, let's use _from_region to hold the results of its own compaction.
371 new_to_region = _from_region;
372 }
373
374 assert(new_to_region != _young_to_region, "must not reuse same OLD to-region");
375 assert(new_to_region != nullptr, "must not be nullptr");
376 _young_to_region = new_to_region;
377 _young_compact_point = _young_to_region->bottom();
378 }
379
380 // Object fits into current region, record new location, if object does not move:
381 assert(_young_compact_point + obj_size <= _young_to_region->end(), "must fit");
382 shenandoah_assert_not_forwarded(nullptr, p);
383
384 if (_young_compact_point != cast_from_oop<HeapWord*>(p)) {
385 _preserved_marks->push_if_necessary(p, p->mark());
386 FullGCForwarding::forward_to(p, cast_to_oop(_young_compact_point));
387 }
388 _young_compact_point += obj_size;
389 }
390 }