1 /*
2 * Copyright (c) 2021, 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/strongRootsScope.hpp"
29 #include "gc/shenandoah/shenandoahCollectorPolicy.hpp"
30 #include "gc/shenandoah/heuristics/shenandoahAdaptiveHeuristics.hpp"
31 #include "gc/shenandoah/heuristics/shenandoahAggressiveHeuristics.hpp"
32 #include "gc/shenandoah/heuristics/shenandoahCompactHeuristics.hpp"
33 #include "gc/shenandoah/heuristics/shenandoahOldHeuristics.hpp"
34 #include "gc/shenandoah/heuristics/shenandoahStaticHeuristics.hpp"
35 #include "gc/shenandoah/shenandoahAsserts.hpp"
36 #include "gc/shenandoah/shenandoahFreeSet.hpp"
37 #include "gc/shenandoah/shenandoahHeap.hpp"
38 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
39 #include "gc/shenandoah/shenandoahHeapRegion.hpp"
40 #include "gc/shenandoah/shenandoahMarkClosures.hpp"
41 #include "gc/shenandoah/shenandoahMark.inline.hpp"
42 #include "gc/shenandoah/shenandoahMonitoringSupport.hpp"
43 #include "gc/shenandoah/shenandoahOldGeneration.hpp"
44 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
45 #include "gc/shenandoah/shenandoahReferenceProcessor.hpp"
46 #include "gc/shenandoah/shenandoahStringDedup.hpp"
47 #include "gc/shenandoah/shenandoahUtils.hpp"
48 #include "gc/shenandoah/shenandoahWorkerPolicy.hpp"
49 #include "gc/shenandoah/shenandoahYoungGeneration.hpp"
50 #include "prims/jvmtiTagMap.hpp"
51 #include "runtime/threads.hpp"
52 #include "utilities/events.hpp"
53
54 class ShenandoahFlushAllSATB : public ThreadClosure {
55 private:
56 SATBMarkQueueSet& _satb_qset;
57
58 public:
59 explicit ShenandoahFlushAllSATB(SATBMarkQueueSet& satb_qset) :
60 _satb_qset(satb_qset) {}
61
62 void do_thread(Thread* thread) {
63 // Transfer any partial buffer to the qset for completed buffer processing.
64 _satb_qset.flush_queue(ShenandoahThreadLocalData::satb_mark_queue(thread));
65 }
66 };
67
68 class ShenandoahProcessOldSATB : public SATBBufferClosure {
69 private:
70 ShenandoahObjToScanQueue* _queue;
71 ShenandoahHeap* _heap;
72 ShenandoahMarkingContext* const _mark_context;
73
74 public:
75 size_t _trashed_oops;
76
77 explicit ShenandoahProcessOldSATB(ShenandoahObjToScanQueue* q) :
78 _queue(q),
79 _heap(ShenandoahHeap::heap()),
80 _mark_context(_heap->marking_context()),
81 _trashed_oops(0) {}
82
83 void do_buffer(void **buffer, size_t size) {
84 assert(size == 0 || !_heap->has_forwarded_objects() || _heap->is_concurrent_old_mark_in_progress(), "Forwarded objects are not expected here");
85 for (size_t i = 0; i < size; ++i) {
86 oop *p = (oop *) &buffer[i];
87 ShenandoahHeapRegion* region = _heap->heap_region_containing(*p);
88 if (region->is_old() && region->is_active()) {
89 ShenandoahMark::mark_through_ref<oop, OLD>(p, _queue, nullptr, _mark_context, false);
90 } else {
91 ++_trashed_oops;
92 }
93 }
94 }
95 };
96
97 class ShenandoahPurgeSATBTask : public WorkerTask {
98 private:
99 ShenandoahObjToScanQueueSet* _mark_queues;
100
101 public:
102 volatile size_t _trashed_oops;
103
104 explicit ShenandoahPurgeSATBTask(ShenandoahObjToScanQueueSet* queues) :
105 WorkerTask("Purge SATB"),
106 _mark_queues(queues),
107 _trashed_oops(0) {
108 Threads::change_thread_claim_token();
109 }
110
111 ~ShenandoahPurgeSATBTask() {
112 if (_trashed_oops > 0) {
113 log_info(gc)("Purged " SIZE_FORMAT " oops from old generation SATB buffers.", _trashed_oops);
114 }
115 }
116
117 void work(uint worker_id) {
118 ShenandoahParallelWorkerSession worker_session(worker_id);
119 ShenandoahSATBMarkQueueSet &satb_queues = ShenandoahBarrierSet::satb_mark_queue_set();
120 ShenandoahFlushAllSATB flusher(satb_queues);
121 Threads::possibly_parallel_threads_do(true /* is_par */, &flusher);
122
123 ShenandoahObjToScanQueue* mark_queue = _mark_queues->queue(worker_id);
124 ShenandoahProcessOldSATB processor(mark_queue);
125 while (satb_queues.apply_closure_to_completed_buffer(&processor)) {}
126
127 Atomic::add(&_trashed_oops, processor._trashed_oops);
128 }
129 };
130
131 class ShenandoahConcurrentCoalesceAndFillTask : public WorkerTask {
132 private:
133 uint _nworkers;
134 ShenandoahHeapRegion** _coalesce_and_fill_region_array;
135 uint _coalesce_and_fill_region_count;
136 volatile bool _is_preempted;
137
138 public:
139 ShenandoahConcurrentCoalesceAndFillTask(uint nworkers, ShenandoahHeapRegion** coalesce_and_fill_region_array,
140 uint region_count) :
141 WorkerTask("Shenandoah Concurrent Coalesce and Fill"),
142 _nworkers(nworkers),
143 _coalesce_and_fill_region_array(coalesce_and_fill_region_array),
144 _coalesce_and_fill_region_count(region_count),
145 _is_preempted(false) {
146 }
147
148 void work(uint worker_id) {
149 for (uint region_idx = worker_id; region_idx < _coalesce_and_fill_region_count; region_idx += _nworkers) {
150 ShenandoahHeapRegion* r = _coalesce_and_fill_region_array[region_idx];
151 if (r->is_humongous()) {
152 // there's only one object in this region and it's not garbage, so no need to coalesce or fill
153 continue;
154 }
155
156 if (!r->oop_fill_and_coalesce()) {
157 // Coalesce and fill has been preempted
158 Atomic::store(&_is_preempted, true);
159 return;
160 }
161 }
162 }
163
164 // Value returned from is_completed() is only valid after all worker thread have terminated.
165 bool is_completed() {
166 return !Atomic::load(&_is_preempted);
167 }
168 };
169
170 ShenandoahOldGeneration::ShenandoahOldGeneration(uint max_queues, size_t max_capacity, size_t soft_max_capacity)
171 : ShenandoahGeneration(OLD, max_queues, max_capacity, soft_max_capacity),
172 _coalesce_and_fill_region_array(NEW_C_HEAP_ARRAY(ShenandoahHeapRegion*, ShenandoahHeap::heap()->num_regions(), mtGC)),
173 _state(IDLE)
174 {
175 // Always clear references for old generation
176 ref_processor()->set_soft_reference_policy(true);
177 }
178
179 const char* ShenandoahOldGeneration::name() const {
180 return "OLD";
181 }
182
183 bool ShenandoahOldGeneration::contains(ShenandoahHeapRegion* region) const {
184 return region->affiliation() != YOUNG_GENERATION;
185 }
186
187 void ShenandoahOldGeneration::parallel_heap_region_iterate(ShenandoahHeapRegionClosure* cl) {
188 ShenandoahGenerationRegionClosure<OLD> old_regions(cl);
189 ShenandoahHeap::heap()->parallel_heap_region_iterate(&old_regions);
190 }
191
192 void ShenandoahOldGeneration::heap_region_iterate(ShenandoahHeapRegionClosure* cl) {
193 ShenandoahGenerationRegionClosure<OLD> old_regions(cl);
194 ShenandoahHeap::heap()->heap_region_iterate(&old_regions);
195 }
196
197 void ShenandoahOldGeneration::set_concurrent_mark_in_progress(bool in_progress) {
198 ShenandoahHeap::heap()->set_concurrent_old_mark_in_progress(in_progress);
199 }
200
201 bool ShenandoahOldGeneration::is_concurrent_mark_in_progress() {
202 return ShenandoahHeap::heap()->is_concurrent_old_mark_in_progress();
203 }
204
205 void ShenandoahOldGeneration::cancel_marking() {
206 if (is_concurrent_mark_in_progress()) {
207 log_info(gc)("Abandon satb buffers.");
208 ShenandoahBarrierSet::satb_mark_queue_set().abandon_partial_marking();
209 }
210
211 ShenandoahGeneration::cancel_marking();
212 }
213
214 void ShenandoahOldGeneration::prepare_gc() {
215
216 // Make the old generation regions parseable, so they can be safely
217 // scanned when looking for objects in memory indicated by dirty cards.
218 if (entry_coalesce_and_fill()) {
219 // Now that we have made the old generation parseable, it is safe to reset the mark bitmap.
220 static const char* msg = "Concurrent reset (OLD)";
221 ShenandoahConcurrentPhase gc_phase(msg, ShenandoahPhaseTimings::conc_reset_old);
222 ShenandoahWorkerScope scope(ShenandoahHeap::heap()->workers(),
223 ShenandoahWorkerPolicy::calc_workers_for_conc_reset(),
224 msg);
225 ShenandoahGeneration::prepare_gc();
226 }
227 // Else, coalesce-and-fill has been preempted and we'll finish that effort in the future. Do not invoke
228 // ShenandoahGeneration::prepare_gc() until coalesce-and-fill is done because it resets the mark bitmap
229 // and invokes set_mark_incomplete(). Coalesce-and-fill depends on the mark bitmap.
230 }
231
232 bool ShenandoahOldGeneration::entry_coalesce_and_fill() {
233 char msg[1024];
234 ShenandoahHeap* const heap = ShenandoahHeap::heap();
235
236 ShenandoahConcurrentPhase gc_phase("Coalescing and filling (OLD)", ShenandoahPhaseTimings::coalesce_and_fill);
237
238 // TODO: I don't think we're using these concurrent collection counters correctly.
239 TraceCollectorStats tcs(heap->monitoring_support()->concurrent_collection_counters());
240 EventMark em("%s", msg);
241 ShenandoahWorkerScope scope(heap->workers(),
242 ShenandoahWorkerPolicy::calc_workers_for_conc_marking(),
243 "concurrent coalesce and fill");
244
245 return coalesce_and_fill();
246 }
247
248 bool ShenandoahOldGeneration::coalesce_and_fill() {
249 ShenandoahHeap* const heap = ShenandoahHeap::heap();
250 heap->set_prepare_for_old_mark_in_progress(true);
251 transition_to(FILLING);
252
253 ShenandoahOldHeuristics* old_heuristics = heap->old_heuristics();
254 WorkerThreads* workers = heap->workers();
255 uint nworkers = workers->active_workers();
256
257 log_debug(gc)("Starting (or resuming) coalesce-and-fill of old heap regions");
258 uint coalesce_and_fill_regions_count = old_heuristics->get_coalesce_and_fill_candidates(_coalesce_and_fill_region_array);
259 assert(coalesce_and_fill_regions_count <= heap->num_regions(), "Sanity");
260 ShenandoahConcurrentCoalesceAndFillTask task(nworkers, _coalesce_and_fill_region_array, coalesce_and_fill_regions_count);
261
262 workers->run_task(&task);
263 if (task.is_completed()) {
264 // Remember that we're done with coalesce-and-fill.
265 heap->set_prepare_for_old_mark_in_progress(false);
266 transition_to(BOOTSTRAPPING);
267 return true;
268 } else {
269 log_debug(gc)("Suspending coalesce-and-fill of old heap regions");
270 // Otherwise, we got preempted before the work was done.
271 return false;
272 }
273 }
274
275 void ShenandoahOldGeneration::transfer_pointers_from_satb() {
276 ShenandoahHeap* heap = ShenandoahHeap::heap();
277 shenandoah_assert_safepoint();
278 assert(heap->is_concurrent_old_mark_in_progress(), "Only necessary during old marking.");
279 log_info(gc)("Transfer satb buffers.");
280 uint nworkers = heap->workers()->active_workers();
281 StrongRootsScope scope(nworkers);
282
283 ShenandoahPurgeSATBTask purge_satb_task(task_queues());
284 heap->workers()->run_task(&purge_satb_task);
285 }
286
287 bool ShenandoahOldGeneration::contains(oop obj) const {
288 return ShenandoahHeap::heap()->is_in_old(obj);
289 }
290
291 void ShenandoahOldGeneration::prepare_regions_and_collection_set(bool concurrent) {
292 ShenandoahHeap* heap = ShenandoahHeap::heap();
293 assert(!heap->is_full_gc_in_progress(), "Only for concurrent and degenerated GC");
294
295 {
296 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_update_region_states : ShenandoahPhaseTimings::degen_gc_final_update_region_states);
297 ShenandoahFinalMarkUpdateRegionStateClosure cl(complete_marking_context());
298
299 parallel_heap_region_iterate(&cl);
300 heap->assert_pinned_region_status();
301 }
302
303 {
304 // This doesn't actually choose a collection set, but prepares a list of
305 // regions as 'candidates' for inclusion in a mixed collection.
306 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::choose_cset : ShenandoahPhaseTimings::degen_gc_choose_cset);
307 ShenandoahHeapLocker locker(heap->lock());
308 heuristics()->choose_collection_set(nullptr, nullptr);
309 }
310
311 {
312 // Though we did not choose a collection set above, we still may have
313 // freed up immediate garbage regions so proceed with rebuilding the free set.
314 ShenandoahGCPhase phase(concurrent ? ShenandoahPhaseTimings::final_rebuild_freeset : ShenandoahPhaseTimings::degen_gc_final_rebuild_freeset);
315 ShenandoahHeapLocker locker(heap->lock());
316 heap->free_set()->rebuild();
317 }
318 }
319
320 const char* ShenandoahOldGeneration::state_name(State state) {
321 switch (state) {
322 case IDLE: return "Idle";
323 case FILLING: return "Coalescing";
324 case BOOTSTRAPPING: return "Bootstrapping";
325 case MARKING: return "Marking";
326 case WAITING: return "Waiting";
327 default:
328 ShouldNotReachHere();
329 return "Unknown";
330 }
331 }
332
333 void ShenandoahOldGeneration::transition_to(State new_state) {
334 if (_state != new_state) {
335 log_info(gc)("Old generation transition from %s to %s", state_name(_state), state_name(new_state));
336 assert(validate_transition(new_state), "Invalid state transition.");
337 _state = new_state;
338 }
339 }
340
341 #ifdef ASSERT
342 // This diagram depicts the expected state transitions for marking the old generation
343 // and preparing for old collections. When a young generation cycle executes, the
344 // remembered set scan must visit objects in old regions. Visiting an object which
345 // has become dead on previous old cycles will result in crashes. To avoid visiting
346 // such objects, the remembered set scan will use the old generation mark bitmap when
347 // possible. It is _not_ possible to use the old generation bitmap when old marking
348 // is active (bitmap is not complete). For this reason, the old regions are made
349 // parseable _before_ the old generation bitmap is reset. The diagram does not depict
350 // global and full collections, both of which cancel any old generation activity.
351 //
352 // +-----------------+
353 // +------------> | IDLE |
354 // | +--------> | |
355 // | | +-----------------+
356 // | | |
357 // | | | Begin Old Mark
358 // | | v
359 // | | +-----------------+ +--------------------+
360 // | | | FILLING | <-> | YOUNG GC |
361 // | | | | | (RSet Uses Bitmap) |
362 // | | +-----------------+ +--------------------+
363 // | | |
364 // | | | Reset Bitmap
365 // | | v
366 // | | +-----------------+
367 // | | | BOOTSTRAP |
368 // | | | |
369 // | | +-----------------+
370 // | | |
371 // | | | Continue Marking
372 // | | v
373 // | | +-----------------+ +----------------------+
374 // | | | MARKING | <-> | YOUNG GC |
375 // | +----------| | | (RSet Parses Region) |
376 // | +-----------------+ +----------------------+
377 // | |
378 // | | Has Candidates
379 // | v
380 // | +-----------------+
381 // | | WAITING |
382 // +------------- | |
383 // +-----------------+
384 //
385 bool ShenandoahOldGeneration::validate_transition(State new_state) {
386 ShenandoahHeap* heap = ShenandoahHeap::heap();
387 switch (new_state) {
388 case IDLE:
389 assert(!heap->is_concurrent_old_mark_in_progress(), "Cannot become idle during old mark.");
390 assert(_old_heuristics->unprocessed_old_collection_candidates() == 0, "Cannot become idle with collection candidates");
391 assert(!heap->is_prepare_for_old_mark_in_progress(), "Cannot become idle while making old generation parseable.");
392 assert(heap->young_generation()->old_gen_task_queues() == nullptr, "Cannot become idle when setup for bootstrapping.");
393 return true;
394 case FILLING:
395 assert(_state == IDLE, "Cannot begin filling without first being idle.");
396 assert(heap->is_prepare_for_old_mark_in_progress(), "Should be preparing for old mark now.");
397 return true;
398 case BOOTSTRAPPING:
399 assert(_state == FILLING, "Cannot reset bitmap without making old regions parseable.");
400 // assert(heap->young_generation()->old_gen_task_queues() != nullptr, "Cannot bootstrap without old mark queues.");
401 assert(!heap->is_prepare_for_old_mark_in_progress(), "Cannot still be making old regions parseable.");
402 return true;
403 case MARKING:
404 assert(_state == BOOTSTRAPPING, "Must have finished bootstrapping before marking.");
405 assert(heap->young_generation()->old_gen_task_queues() != nullptr, "Young generation needs old mark queues.");
406 assert(heap->is_concurrent_old_mark_in_progress(), "Should be marking old now.");
407 return true;
408 case WAITING:
409 assert(_state == MARKING, "Cannot have old collection candidates without first marking.");
410 assert(_old_heuristics->unprocessed_old_collection_candidates() > 0, "Must have collection candidates here.");
411 return true;
412 default:
413 ShouldNotReachHere();
414 return false;
415 }
416 }
417 #endif
418
419 ShenandoahHeuristics* ShenandoahOldGeneration::initialize_heuristics(ShenandoahMode* gc_mode) {
420 assert(ShenandoahOldGCHeuristics != nullptr, "ShenandoahOldGCHeuristics should not be unset");
421 ShenandoahHeuristics* trigger;
422 if (strcmp(ShenandoahOldGCHeuristics, "static") == 0) {
423 trigger = new ShenandoahStaticHeuristics(this);
424 } else if (strcmp(ShenandoahOldGCHeuristics, "adaptive") == 0) {
425 trigger = new ShenandoahAdaptiveHeuristics(this);
426 } else if (strcmp(ShenandoahOldGCHeuristics, "compact") == 0) {
427 trigger = new ShenandoahCompactHeuristics(this);
428 } else {
429 vm_exit_during_initialization("Unknown -XX:ShenandoahOldGCHeuristics option (must be one of: static, adaptive, compact)");
430 ShouldNotReachHere();
431 return nullptr;
432 }
433 trigger->set_guaranteed_gc_interval(ShenandoahGuaranteedOldGCInterval);
434 _old_heuristics = new ShenandoahOldHeuristics(this, trigger);
435 _heuristics = _old_heuristics;
436 return _heuristics;
437 }
438
439 void ShenandoahOldGeneration::record_success_concurrent(bool abbreviated) {
440 heuristics()->record_success_concurrent(abbreviated);
441 ShenandoahHeap::heap()->shenandoah_policy()->record_success_old();
442 }