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 #include "precompiled.hpp"
 26 
 27 #include "gc/shared/preservedMarks.inline.hpp"
 28 #include "gc/shenandoah/shenandoahGenerationalFullGC.hpp"
 29 #include "gc/shenandoah/shenandoahGenerationalHeap.hpp"
 30 #include "gc/shenandoah/shenandoahGeneration.hpp"
 31 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
 32 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
 33 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
 34 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
 35 #include "gc/shenandoah/shenandoahUtils.hpp"
 36 
 37 #ifdef ASSERT
 38 void assert_regions_used_not_more_than_capacity(ShenandoahGeneration* generation) {
 39   assert(generation->used_regions_size() <= generation->max_capacity(),
 40          "%s generation affiliated regions must be less than capacity", generation->name());
 41 }
 42 
 43 void assert_usage_not_more_than_regions_used(ShenandoahGeneration* generation) {
 44   assert(generation->used_including_humongous_waste() <= generation->used_regions_size(),
 45          "%s consumed can be no larger than span of affiliated regions", generation->name());
 46 }
 47 #else
 48 void assert_regions_used_not_more_than_capacity(ShenandoahGeneration* generation) {}
 49 void assert_usage_not_more_than_regions_used(ShenandoahGeneration* generation) {}
 50 #endif
 51 
 52 
 53 void ShenandoahGenerationalFullGC::prepare() {
 54   auto heap = ShenandoahGenerationalHeap::heap();
 55   // Since we may arrive here from degenerated GC failure of either young or old, establish generation as GLOBAL.
 56   heap->set_gc_generation(heap->global_generation());
 57   heap->set_active_generation();
 58 
 59   // No need for old_gen->increase_used() as this was done when plabs were allocated.
 60   heap->reset_generation_reserves();
 61 
 62   // Full GC supersedes any marking or coalescing in old generation.
 63   heap->old_generation()->cancel_gc();
 64 }
 65 
 66 void ShenandoahGenerationalFullGC::handle_completion(ShenandoahHeap* heap) {
 67   // Full GC should reset time since last gc for young and old heuristics
 68   ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::cast(heap);
 69   ShenandoahYoungGeneration* young = gen_heap->young_generation();
 70   ShenandoahOldGeneration* old = gen_heap->old_generation();
 71   young->heuristics()->record_cycle_end();
 72   old->heuristics()->record_cycle_end();
 73 
 74   gen_heap->mmu_tracker()->record_full(GCId::current());
 75   gen_heap->log_heap_status("At end of Full GC");
 76 
 77   assert(old->is_idle(), "After full GC, old generation should be idle.");
 78 
 79   // Since we allow temporary violation of these constraints during Full GC, we want to enforce that the assertions are
 80   // made valid by the time Full GC completes.
 81   assert_regions_used_not_more_than_capacity(old);
 82   assert_regions_used_not_more_than_capacity(young);
 83   assert_usage_not_more_than_regions_used(old);
 84   assert_usage_not_more_than_regions_used(young);
 85 
 86   // Establish baseline for next old-has-grown trigger.
 87   old->set_live_bytes_after_last_mark(old->used_including_humongous_waste());
 88 }
 89 
 90 void ShenandoahGenerationalFullGC::rebuild_remembered_set(ShenandoahHeap* heap) {
 91   ShenandoahGCPhase phase(ShenandoahPhaseTimings::full_gc_reconstruct_remembered_set);
 92 
 93   ShenandoahScanRemembered* scanner = heap->old_generation()->card_scan();
 94   scanner->mark_read_table_as_clean();
 95   scanner->swap_card_tables();
 96 
 97   ShenandoahRegionIterator regions;
 98   ShenandoahReconstructRememberedSetTask task(&regions);
 99   heap->workers()->run_task(&task);
100 
101   // Rebuilding the remembered set recomputes all the card offsets for objects.
102   // The adjust pointers phase coalesces and fills all necessary regions. In case
103   // we came to the full GC from an incomplete global cycle, we need to indicate
104   // that the old regions are parsable.
105   heap->old_generation()->set_parsable(true);
106 }
107 
108 void ShenandoahGenerationalFullGC::balance_generations_after_gc(ShenandoahHeap* heap) {
109   ShenandoahGenerationalHeap* gen_heap = ShenandoahGenerationalHeap::cast(heap);
110   ShenandoahOldGeneration* const old_gen = gen_heap->old_generation();
111 
112   size_t old_usage = old_gen->used_regions_size();
113   size_t old_capacity = old_gen->max_capacity();
114 
115   assert(old_usage % ShenandoahHeapRegion::region_size_bytes() == 0, "Old usage must align with region size");
116   assert(old_capacity % ShenandoahHeapRegion::region_size_bytes() == 0, "Old capacity must align with region size");
117 
118   if (old_capacity > old_usage) {
119     size_t excess_old_regions = (old_capacity - old_usage) / ShenandoahHeapRegion::region_size_bytes();
120     gen_heap->generation_sizer()->transfer_to_young(excess_old_regions);
121   } else if (old_capacity < old_usage) {
122     size_t old_regions_deficit = (old_usage - old_capacity) / ShenandoahHeapRegion::region_size_bytes();
123     gen_heap->generation_sizer()->force_transfer_to_old(old_regions_deficit);
124   }
125 
126   log_info(gc, ergo)("FullGC done: young usage: " PROPERFMT ", old usage: " PROPERFMT,
127                PROPERFMTARGS(gen_heap->young_generation()->used()),
128                PROPERFMTARGS(old_gen->used()));
129 }
130 
131 void ShenandoahGenerationalFullGC::balance_generations_after_rebuilding_free_set() {
132   auto result = ShenandoahGenerationalHeap::heap()->balance_generations();
133   LogTarget(Info, gc, ergo) lt;
134   if (lt.is_enabled()) {
135     LogStream ls(lt);
136     result.print_on("Full GC", &ls);
137   }
138 }
139 
140 void ShenandoahGenerationalFullGC::log_live_in_old(ShenandoahHeap* heap) {
141   LogTarget(Debug, gc) lt;
142   if (lt.is_enabled()) {
143     size_t live_bytes_in_old = 0;
144     for (size_t i = 0; i < heap->num_regions(); i++) {
145       ShenandoahHeapRegion* r = heap->get_region(i);
146       if (r->is_old()) {
147         live_bytes_in_old += r->get_live_data_bytes();
148       }
149     }
150     log_debug(gc)("Live bytes in old after STW mark: " PROPERFMT, PROPERFMTARGS(live_bytes_in_old));
151   }
152 }
153 
154 void ShenandoahGenerationalFullGC::restore_top_before_promote(ShenandoahHeap* heap) {
155   for (size_t i = 0; i < heap->num_regions(); i++) {
156     ShenandoahHeapRegion* r = heap->get_region(i);
157     if (r->get_top_before_promote() != nullptr) {
158       r->restore_top_before_promote();
159     }
160   }
161 }
162 
163 void ShenandoahGenerationalFullGC::account_for_region(ShenandoahHeapRegion* r, size_t &region_count, size_t &region_usage, size_t &humongous_waste) {
164   region_count++;
165   region_usage += r->used();
166   if (r->is_humongous_start()) {
167     // For each humongous object, we take this path once regardless of how many regions it spans.
168     HeapWord* obj_addr = r->bottom();
169     oop obj = cast_to_oop(obj_addr);
170     size_t word_size = obj->size();
171     size_t region_size_words = ShenandoahHeapRegion::region_size_words();
172     size_t overreach = word_size % region_size_words;
173     if (overreach != 0) {
174       humongous_waste += (region_size_words - overreach) * HeapWordSize;
175     }
176     // else, this humongous object aligns exactly on region size, so no waste.
177   }
178 }
179 
180 void ShenandoahGenerationalFullGC::maybe_coalesce_and_fill_region(ShenandoahHeapRegion* r) {
181   if (r->is_pinned() && r->is_old() && r->is_active() && !r->is_humongous()) {
182     r->begin_preemptible_coalesce_and_fill();
183     r->oop_coalesce_and_fill(false);
184   }
185 }
186 
187 void ShenandoahGenerationalFullGC::compute_balances() {
188   auto heap = ShenandoahGenerationalHeap::heap();
189 
190   // In case this Full GC resulted from degeneration, clear the tally on anticipated promotion.
191   heap->old_generation()->set_promotion_potential(0);
192   // Invoke this in case we are able to transfer memory from OLD to YOUNG.
193   heap->compute_old_generation_balance(0, 0);
194 }
195 
196 ShenandoahPrepareForGenerationalCompactionObjectClosure::ShenandoahPrepareForGenerationalCompactionObjectClosure(PreservedMarks* preserved_marks,
197                                                           GrowableArray<ShenandoahHeapRegion*>& empty_regions,
198                                                           ShenandoahHeapRegion* from_region, uint worker_id) :
199         _preserved_marks(preserved_marks),
200         _heap(ShenandoahGenerationalHeap::heap()),
201         _empty_regions(empty_regions),
202         _empty_regions_pos(0),
203         _old_to_region(nullptr),
204         _young_to_region(nullptr),
205         _from_region(nullptr),
206         _from_affiliation(ShenandoahAffiliation::FREE),
207         _old_compact_point(nullptr),
208         _young_compact_point(nullptr),
209         _worker_id(worker_id) {
210   assert(from_region != nullptr, "Worker needs from_region");
211   // assert from_region has live?
212   if (from_region->is_old()) {
213     _old_to_region = from_region;
214     _old_compact_point = from_region->bottom();
215   } else if (from_region->is_young()) {
216     _young_to_region = from_region;
217     _young_compact_point = from_region->bottom();
218   }
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->global_generation()->complete_marking_context()->is_marked(p), "must be marked");
276   assert(!_heap->global_generation()->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       _heap->age_census()->is_tenurable(from_region_age + object_age)) {
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       p->forward_to(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       p->forward_to(cast_to_oop(_young_compact_point));
387     }
388     _young_compact_point += obj_size;
389   }
390 }