1 /*
2 * Copyright (c) 2015, 2020, Red Hat, Inc. All rights reserved.
3 * Copyright Amazon.com Inc. or its affiliates. All Rights Reserved.
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
5 *
6 * This code is free software; you can redistribute it and/or modify it
7 * under the terms of the GNU General Public License version 2 only, as
8 * published by the Free Software Foundation.
9 *
10 * This code is distributed in the hope that it will be useful, but WITHOUT
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
13 * version 2 for more details (a copy is included in the LICENSE file that
14 * accompanied this code).
15 *
16 * You should have received a copy of the GNU General Public License version
17 * 2 along with this work; if not, write to the Free Software Foundation,
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
19 *
20 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
21 * or visit www.oracle.com if you need additional information or have any
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24 */
25
26 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
27 #define SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
28
29 #include "gc/shenandoah/shenandoahHeap.hpp"
30
31 #include "classfile/javaClasses.inline.hpp"
32 #include "gc/shared/markBitMap.inline.hpp"
33 #include "gc/shared/threadLocalAllocBuffer.inline.hpp"
34 #include "gc/shared/continuationGCSupport.inline.hpp"
35 #include "gc/shared/suspendibleThreadSet.hpp"
36 #include "gc/shared/tlab_globals.hpp"
37 #include "gc/shenandoah/shenandoahAsserts.hpp"
38 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
39 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
40 #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
41 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
42 #include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
43 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
44 #include "gc/shenandoah/shenandoahControlThread.hpp"
45 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
46 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
47 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
48 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
49 #include "gc/shenandoah/mode/shenandoahMode.hpp"
50 #include "oops/compressedOops.inline.hpp"
51 #include "oops/oop.inline.hpp"
52 #include "runtime/atomic.hpp"
53 #include "runtime/javaThread.hpp"
54 #include "runtime/prefetch.inline.hpp"
55 #include "utilities/copy.hpp"
56 #include "utilities/globalDefinitions.hpp"
57
58 inline ShenandoahHeap* ShenandoahHeap::heap() {
59 return named_heap<ShenandoahHeap>(CollectedHeap::Shenandoah);
60 }
61
62 inline ShenandoahHeapRegion* ShenandoahRegionIterator::next() {
63 size_t new_index = Atomic::add(&_index, (size_t) 1, memory_order_relaxed);
64 // get_region() provides the bounds-check and returns null on OOB.
65 return _heap->get_region(new_index - 1);
66 }
67
68 inline bool ShenandoahHeap::has_forwarded_objects() const {
69 return _gc_state.is_set(HAS_FORWARDED);
70 }
71
72 inline WorkerThreads* ShenandoahHeap::workers() const {
73 return _workers;
74 }
75
76 inline WorkerThreads* ShenandoahHeap::safepoint_workers() {
77 return _safepoint_workers;
78 }
79
80 inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
81 uintptr_t region_start = ((uintptr_t) addr);
82 uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
83 assert(index < num_regions(), "Region index is in bounds: " PTR_FORMAT, p2i(addr));
84 return index;
85 }
86
87 inline ShenandoahHeapRegion* ShenandoahHeap::heap_region_containing(const void* addr) const {
88 size_t index = heap_region_index_containing(addr);
89 ShenandoahHeapRegion* const result = get_region(index);
90 assert(addr >= result->bottom() && addr < result->end(), "Heap region contains the address: " PTR_FORMAT, p2i(addr));
91 return result;
92 }
93
94 inline void ShenandoahHeap::enter_evacuation(Thread* t) {
95 _oom_evac_handler.enter_evacuation(t);
96 }
97
98 inline void ShenandoahHeap::leave_evacuation(Thread* t) {
99 _oom_evac_handler.leave_evacuation(t);
100 }
101
102 template <class T>
103 inline void ShenandoahHeap::update_with_forwarded(T* p) {
104 T o = RawAccess<>::oop_load(p);
105 if (!CompressedOops::is_null(o)) {
106 oop obj = CompressedOops::decode_not_null(o);
107 if (in_collection_set(obj)) {
108 // Corner case: when evacuation fails, there are objects in collection
109 // set that are not really forwarded. We can still go and try and update them
110 // (uselessly) to simplify the common path.
111 shenandoah_assert_forwarded_except(p, obj, cancelled_gc());
112 oop fwd = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
113 shenandoah_assert_not_in_cset_except(p, fwd, cancelled_gc());
114
115 // Unconditionally store the update: no concurrent updates expected.
116 RawAccess<IS_NOT_NULL>::oop_store(p, fwd);
117 }
118 }
119 }
120
121 template <class T>
122 inline void ShenandoahHeap::conc_update_with_forwarded(T* p) {
123 T o = RawAccess<>::oop_load(p);
124 if (!CompressedOops::is_null(o)) {
125 oop obj = CompressedOops::decode_not_null(o);
126 if (in_collection_set(obj)) {
127 // Corner case: when evacuation fails, there are objects in collection
128 // set that are not really forwarded. We can still go and try CAS-update them
129 // (uselessly) to simplify the common path.
130 shenandoah_assert_forwarded_except(p, obj, cancelled_gc());
131 oop fwd = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
132 shenandoah_assert_not_in_cset_except(p, fwd, cancelled_gc());
133
134 // Sanity check: we should not be updating the cset regions themselves,
135 // unless we are recovering from the evacuation failure.
136 shenandoah_assert_not_in_cset_loc_except(p, !is_in(p) || cancelled_gc());
137
138 // Either we succeed in updating the reference, or something else gets in our way.
139 // We don't care if that is another concurrent GC update, or another mutator update.
140 atomic_update_oop(fwd, p, obj);
141 }
142 }
143 }
144
145 // Atomic updates of heap location. This is only expected to work with updating the same
146 // logical object with its forwardee. The reason why we need stronger-than-relaxed memory
147 // ordering has to do with coordination with GC barriers and mutator accesses.
148 //
149 // In essence, stronger CAS access is required to maintain the transitive chains that mutator
150 // accesses build by themselves. To illustrate this point, consider the following example.
151 //
152 // Suppose "o" is the object that has a field "x" and the reference to "o" is stored
153 // to field at "addr", which happens to be Java volatile field. Normally, the accesses to volatile
154 // field at "addr" would be matched with release/acquire barriers. This changes when GC moves
155 // the object under mutator feet.
156 //
157 // Thread 1 (Java)
158 // // --- previous access starts here
159 // ...
160 // T1.1: store(&o.x, 1, mo_relaxed)
161 // T1.2: store(&addr, o, mo_release) // volatile store
162 //
163 // // --- new access starts here
164 // // LRB: copy and install the new copy to fwdptr
165 // T1.3: var copy = copy(o)
166 // T1.4: cas(&fwd, t, copy, mo_release) // pointer-mediated publication
167 // <access continues>
168 //
169 // Thread 2 (GC updater)
170 // T2.1: var f = load(&fwd, mo_{consume|acquire}) // pointer-mediated acquisition
171 // T2.2: cas(&addr, o, f, mo_release) // this method
172 //
173 // Thread 3 (Java)
174 // T3.1: var o = load(&addr, mo_acquire) // volatile read
175 // T3.2: if (o != null)
176 // T3.3: var r = load(&o.x, mo_relaxed)
177 //
178 // r is guaranteed to contain "1".
179 //
180 // Without GC involvement, there is synchronizes-with edge from T1.2 to T3.1,
181 // which guarantees this. With GC involvement, when LRB copies the object and
182 // another thread updates the reference to it, we need to have the transitive edge
183 // from T1.4 to T2.1 (that one is guaranteed by forwarding accesses), plus the edge
184 // from T2.2 to T3.1 (which is brought by this CAS).
185 //
186 // Note that we do not need to "acquire" in these methods, because we do not read the
187 // failure witnesses contents on any path, and "release" is enough.
188 //
189
190 inline void ShenandoahHeap::atomic_update_oop(oop update, oop* addr, oop compare) {
191 assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
192 Atomic::cmpxchg(addr, compare, update, memory_order_release);
193 }
194
195 inline void ShenandoahHeap::atomic_update_oop(oop update, narrowOop* addr, narrowOop compare) {
196 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
197 narrowOop u = CompressedOops::encode(update);
198 Atomic::cmpxchg(addr, compare, u, memory_order_release);
199 }
200
201 inline void ShenandoahHeap::atomic_update_oop(oop update, narrowOop* addr, oop compare) {
202 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
203 narrowOop c = CompressedOops::encode(compare);
204 narrowOop u = CompressedOops::encode(update);
205 Atomic::cmpxchg(addr, c, u, memory_order_release);
206 }
207
208 inline bool ShenandoahHeap::atomic_update_oop_check(oop update, oop* addr, oop compare) {
209 assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
210 return (oop) Atomic::cmpxchg(addr, compare, update, memory_order_release) == compare;
211 }
212
213 inline bool ShenandoahHeap::atomic_update_oop_check(oop update, narrowOop* addr, narrowOop compare) {
214 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
215 narrowOop u = CompressedOops::encode(update);
216 return (narrowOop) Atomic::cmpxchg(addr, compare, u, memory_order_release) == compare;
217 }
218
219 inline bool ShenandoahHeap::atomic_update_oop_check(oop update, narrowOop* addr, oop compare) {
220 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
221 narrowOop c = CompressedOops::encode(compare);
222 narrowOop u = CompressedOops::encode(update);
223 return CompressedOops::decode(Atomic::cmpxchg(addr, c, u, memory_order_release)) == compare;
224 }
225
226 // The memory ordering discussion above does not apply for methods that store nulls:
227 // then, there is no transitive reads in mutator (as we see nulls), and we can do
228 // relaxed memory ordering there.
229
230 inline void ShenandoahHeap::atomic_clear_oop(oop* addr, oop compare) {
231 assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
232 Atomic::cmpxchg(addr, compare, oop(), memory_order_relaxed);
233 }
234
235 inline void ShenandoahHeap::atomic_clear_oop(narrowOop* addr, oop compare) {
236 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
237 narrowOop cmp = CompressedOops::encode(compare);
238 Atomic::cmpxchg(addr, cmp, narrowOop(), memory_order_relaxed);
239 }
240
241 inline void ShenandoahHeap::atomic_clear_oop(narrowOop* addr, narrowOop compare) {
242 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
243 Atomic::cmpxchg(addr, compare, narrowOop(), memory_order_relaxed);
244 }
245
246 inline bool ShenandoahHeap::cancelled_gc() const {
247 return _cancelled_gc.get() == CANCELLED;
248 }
249
250 inline bool ShenandoahHeap::check_cancelled_gc_and_yield(bool sts_active) {
251 if (sts_active && ShenandoahSuspendibleWorkers && !cancelled_gc()) {
252 if (SuspendibleThreadSet::should_yield()) {
253 SuspendibleThreadSet::yield();
254 }
255 }
256 return cancelled_gc();
257 }
258
259 inline void ShenandoahHeap::clear_cancelled_gc(bool clear_oom_handler) {
260 _cancelled_gc.set(CANCELLABLE);
261 if (_cancel_requested_time > 0) {
262 double cancel_time = os::elapsedTime() - _cancel_requested_time;
263 log_info(gc)("GC cancellation took %.3fs", cancel_time);
264 _cancel_requested_time = 0;
265 }
266
267 if (clear_oom_handler) {
268 _oom_evac_handler.clear();
269 }
270 }
271
272 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
273 assert(UseTLAB, "TLABs should be enabled");
274
275 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
276 if (gclab == nullptr) {
277 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
278 "Performance: thread should have GCLAB: %s", thread->name());
279 // No GCLABs in this thread, fallback to shared allocation
280 return nullptr;
281 }
282 HeapWord* obj = gclab->allocate(size);
283 if (obj != nullptr) {
284 return obj;
285 }
286 return allocate_from_gclab_slow(thread, size);
287 }
288
289 inline HeapWord* ShenandoahHeap::allocate_from_plab(Thread* thread, size_t size, bool is_promotion) {
290 assert(UseTLAB, "TLABs should be enabled");
291
292 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
293 HeapWord* obj;
294
295 if (plab == nullptr) {
296 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(), "Performance: thread should have PLAB: %s", thread->name());
297 // No PLABs in this thread, fallback to shared allocation
298 return nullptr;
299 } else if (is_promotion && !ShenandoahThreadLocalData::allow_plab_promotions(thread)) {
300 return nullptr;
301 }
302 // if plab->word_size() <= 0, thread's plab not yet initialized for this pass, so allow_plab_promotions() is not trustworthy
303 obj = plab->allocate(size);
304 if ((obj == nullptr) && (plab->words_remaining() < PLAB::min_size())) {
305 // allocate_from_plab_slow will establish allow_plab_promotions(thread) for future invocations
306 obj = allocate_from_plab_slow(thread, size, is_promotion);
307 }
308 // if plab->words_remaining() >= PLAB::min_size(), just return nullptr so we can use a shared allocation
309 if (obj == nullptr) {
310 return nullptr;
311 }
312
313 if (is_promotion) {
314 ShenandoahThreadLocalData::add_to_plab_promoted(thread, size * HeapWordSize);
315 } else {
316 ShenandoahThreadLocalData::add_to_plab_evacuated(thread, size * HeapWordSize);
317 }
318 return obj;
319 }
320
321 inline ShenandoahAgeCensus* ShenandoahHeap::age_census() const {
322 assert(mode()->is_generational(), "Only in generational mode");
323 assert(_age_census != nullptr, "Error: not initialized");
324 return _age_census;
325 }
326
327 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
328 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
329 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) {
330 // This thread went through the OOM during evac protocol and it is safe to return
331 // the forward pointer. It must not attempt to evacuate any more.
332 return ShenandoahBarrierSet::resolve_forwarded(p);
333 }
334
335 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
336
337 ShenandoahHeapRegion* r = heap_region_containing(p);
338 assert(!r->is_humongous(), "never evacuate humongous objects");
339
340 ShenandoahAffiliation target_gen = r->affiliation();
341 if (mode()->is_generational() && ShenandoahHeap::heap()->is_gc_generation_young() &&
342 target_gen == YOUNG_GENERATION) {
343 markWord mark = p->mark();
344 if (mark.is_marked()) {
345 // Already forwarded.
346 return ShenandoahBarrierSet::resolve_forwarded(p);
347 }
348 if (mark.has_displaced_mark_helper()) {
349 // We don't want to deal with MT here just to ensure we read the right mark word.
350 // Skip the potential promotion attempt for this one.
351 } else if (r->age() + mark.age() >= age_census()->tenuring_threshold()) {
352 oop result = try_evacuate_object(p, thread, r, OLD_GENERATION);
353 if (result != nullptr) {
354 return result;
355 }
356 // If we failed to promote this aged object, we'll fall through to code below and evacuate to young-gen.
357 }
358 }
359 return try_evacuate_object(p, thread, r, target_gen);
360 }
361
362 // try_evacuate_object registers the object and dirties the associated remembered set information when evacuating
363 // to OLD_GENERATION.
364 inline oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region,
365 ShenandoahAffiliation target_gen) {
366 bool alloc_from_lab = true;
367 bool has_plab = false;
368 HeapWord* copy = nullptr;
369 size_t size = p->size();
370 bool is_promotion = (target_gen == OLD_GENERATION) && from_region->is_young();
371
372 #ifdef ASSERT
373 if (ShenandoahOOMDuringEvacALot &&
374 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
375 copy = nullptr;
376 } else {
377 #endif
378 if (UseTLAB) {
379 switch (target_gen) {
380 case YOUNG_GENERATION: {
381 copy = allocate_from_gclab(thread, size);
382 if ((copy == nullptr) && (size < ShenandoahThreadLocalData::gclab_size(thread))) {
383 // GCLAB allocation failed because we are bumping up against the limit on young evacuation reserve. Try resetting
384 // the desired GCLAB size and retry GCLAB allocation to avoid cascading of shared memory allocations.
385 ShenandoahThreadLocalData::set_gclab_size(thread, PLAB::min_size());
386 copy = allocate_from_gclab(thread, size);
387 // If we still get nullptr, we'll try a shared allocation below.
388 }
389 break;
390 }
391 case OLD_GENERATION: {
392 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
393 if (plab != nullptr) {
394 has_plab = true;
395 }
396 copy = allocate_from_plab(thread, size, is_promotion);
397 if ((copy == nullptr) && (size < ShenandoahThreadLocalData::plab_size(thread)) &&
398 ShenandoahThreadLocalData::plab_retries_enabled(thread)) {
399 // PLAB allocation failed because we are bumping up against the limit on old evacuation reserve or because
400 // the requested object does not fit within the current plab but the plab still has an "abundance" of memory,
401 // where abundance is defined as >= PLAB::min_size(). In the former case, we try resetting the desired
402 // PLAB size and retry PLAB allocation to avoid cascading of shared memory allocations.
403
404 // In this situation, PLAB memory is precious. We'll try to preserve our existing PLAB by forcing
405 // this particular allocation to be shared.
406 if (plab->words_remaining() < PLAB::min_size()) {
407 ShenandoahThreadLocalData::set_plab_size(thread, PLAB::min_size());
408 copy = allocate_from_plab(thread, size, is_promotion);
409 // If we still get nullptr, we'll try a shared allocation below.
410 if (copy == nullptr) {
411 // If retry fails, don't continue to retry until we have success (probably in next GC pass)
412 ShenandoahThreadLocalData::disable_plab_retries(thread);
413 }
414 }
415 // else, copy still equals nullptr. this causes shared allocation below, preserving this plab for future needs.
416 }
417 break;
418 }
419 default: {
420 ShouldNotReachHere();
421 break;
422 }
423 }
424 }
425
426 if (copy == nullptr) {
427 // If we failed to allocate in LAB, we'll try a shared allocation.
428 if (!is_promotion || !has_plab || (size > PLAB::min_size())) {
429 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
430 copy = allocate_memory(req, is_promotion);
431 alloc_from_lab = false;
432 }
433 // else, we leave copy equal to nullptr, signaling a promotion failure below if appropriate.
434 // We choose not to promote objects smaller than PLAB::min_size() by way of shared allocations, as this is too
435 // costly. Instead, we'll simply "evacuate" to young-gen memory (using a GCLAB) and will promote in a future
436 // evacuation pass. This condition is denoted by: is_promotion && has_plab && (size <= PLAB::min_size())
437 }
438 #ifdef ASSERT
439 }
440 #endif
441
442 if (copy == nullptr) {
443 if (target_gen == OLD_GENERATION) {
444 assert(mode()->is_generational(), "Should only be here in generational mode.");
445 if (from_region->is_young()) {
446 // Signal that promotion failed. Will evacuate this old object somewhere in young gen.
447 report_promotion_failure(thread, size);
448 return nullptr;
449 } else {
450 // Remember that evacuation to old gen failed. We'll want to trigger a full gc to recover from this
451 // after the evacuation threads have finished.
452 handle_old_evacuation_failure();
453 }
454 }
455
456 control_thread()->handle_alloc_failure_evac(size);
457
458 _oom_evac_handler.handle_out_of_memory_during_evacuation();
459
460 return ShenandoahBarrierSet::resolve_forwarded(p);
461 }
462
463 // Copy the object:
464 _evac_tracker->begin_evacuation(thread, size * HeapWordSize);
465 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
466
467 oop copy_val = cast_to_oop(copy);
468
469 if (mode()->is_generational() && target_gen == YOUNG_GENERATION && is_aging_cycle()) {
470 ShenandoahHeap::increase_object_age(copy_val, from_region->age() + 1);
471 }
472
473 // Try to install the new forwarding pointer.
474 ContinuationGCSupport::relativize_stack_chunk(copy_val);
475
476 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
477 if (result == copy_val) {
478 // Successfully evacuated. Our copy is now the public one!
479 _evac_tracker->end_evacuation(thread, size * HeapWordSize);
480 if (mode()->is_generational()) {
481 if (target_gen == OLD_GENERATION) {
482 handle_old_evacuation(copy, size, from_region->is_young());
483 } else {
484 // When copying to the old generation above, we don't care
485 // about recording object age in the census stats.
486 assert(target_gen == YOUNG_GENERATION, "Error");
487 // We record this census only when simulating pre-adaptive tenuring behavior, or
488 // when we have been asked to record the census at evacuation rather than at mark
489 if (ShenandoahGenerationalCensusAtEvac || !ShenandoahGenerationalAdaptiveTenuring) {
490 _evac_tracker->record_age(thread, size * HeapWordSize, ShenandoahHeap::get_object_age(copy_val));
491 }
492 }
493 }
494 shenandoah_assert_correct(nullptr, copy_val);
495 return copy_val;
496 } else {
497 // Failed to evacuate. We need to deal with the object that is left behind. Since this
498 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
499 // But if it happens to contain references to evacuated regions, those references would
500 // not get updated for this stale copy during this cycle, and we will crash while scanning
501 // it the next cycle.
502 if (alloc_from_lab) {
503 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
504 // object will overwrite this stale copy, or the filler object on LAB retirement will
505 // do this.
506 switch (target_gen) {
507 case YOUNG_GENERATION: {
508 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
509 break;
510 }
511 case OLD_GENERATION: {
512 ShenandoahThreadLocalData::plab(thread)->undo_allocation(copy, size);
513 if (is_promotion) {
514 ShenandoahThreadLocalData::subtract_from_plab_promoted(thread, size * HeapWordSize);
515 } else {
516 ShenandoahThreadLocalData::subtract_from_plab_evacuated(thread, size * HeapWordSize);
517 }
518 break;
519 }
520 default: {
521 ShouldNotReachHere();
522 break;
523 }
524 }
525 } else {
526 // For non-LAB allocations, we have no way to retract the allocation, and
527 // have to explicitly overwrite the copy with the filler object. With that overwrite,
528 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
529 assert(size >= ShenandoahHeap::min_fill_size(), "previously allocated object known to be larger than min_size");
530 fill_with_object(copy, size);
531 shenandoah_assert_correct(nullptr, copy_val);
532 // For non-LAB allocations, the object has already been registered
533 }
534 shenandoah_assert_correct(nullptr, result);
535 return result;
536 }
537 }
538
539 void ShenandoahHeap::increase_object_age(oop obj, uint additional_age) {
540 markWord w = obj->has_displaced_mark() ? obj->displaced_mark() : obj->mark();
541 w = w.set_age(MIN2(markWord::max_age, w.age() + additional_age));
542 if (obj->has_displaced_mark()) {
543 obj->set_displaced_mark(w);
544 } else {
545 obj->set_mark(w);
546 }
547 }
548
549 // Return the object's age (at a safepoint or when object isn't
550 // mutable by the mutator)
551 uint ShenandoahHeap::get_object_age(oop obj) {
552 markWord w = obj->has_displaced_mark() ? obj->displaced_mark() : obj->mark();
553 assert(w.age() <= markWord::max_age, "Impossible!");
554 return w.age();
555 }
556
557 // Return the object's age, or a sentinel value when the age can't
558 // necessarily be determined because of concurrent locking by the
559 // mutator
560 uint ShenandoahHeap::get_object_age_concurrent(oop obj) {
561 // This is impossible to do unless we "freeze" ABA-type oscillations
562 // With Lilliput, we can do this more easily.
563 markWord w = obj->mark();
564 // We can do better for objects with inflated monitor
565 if (w.is_being_inflated() || w.has_displaced_mark_helper()) {
566 // Informs caller that we aren't able to determine the age
567 return markWord::max_age + 1; // sentinel
568 }
569 assert(w.age() <= markWord::max_age, "Impossible!");
570 return w.age();
571 }
572
573 inline bool ShenandoahHeap::clear_old_evacuation_failure() {
574 return _old_gen_oom_evac.try_unset();
575 }
576
577 bool ShenandoahHeap::is_in(const void* p) const {
578 HeapWord* heap_base = (HeapWord*) base();
579 HeapWord* last_region_end = heap_base + ShenandoahHeapRegion::region_size_words() * num_regions();
580 return p >= heap_base && p < last_region_end;
581 }
582
583 inline bool ShenandoahHeap::is_in_active_generation(oop obj) const {
584 if (!mode()->is_generational()) {
585 // everything is the same single generation
586 return true;
587 }
588
589 if (active_generation() == nullptr) {
590 // no collection is happening, only expect this to be called
591 // when concurrent processing is active, but that could change
592 return false;
593 }
594
595 assert(is_in(obj), "only check if is in active generation for objects (" PTR_FORMAT ") in heap", p2i(obj));
596 assert((active_generation() == (ShenandoahGeneration*) old_generation()) ||
597 (active_generation() == (ShenandoahGeneration*) young_generation()) ||
598 (active_generation() == global_generation()), "Active generation must be old, young, or global");
599
600 size_t index = heap_region_containing(obj)->index();
601 switch (_affiliations[index]) {
602 case ShenandoahAffiliation::FREE:
603 // Free regions are in Old, Young, Global
604 return true;
605 case ShenandoahAffiliation::YOUNG_GENERATION:
606 // Young regions are in young_generation and global_generation, not in old_generation
607 return (active_generation() != (ShenandoahGeneration*) old_generation());
608 case ShenandoahAffiliation::OLD_GENERATION:
609 // Old regions are in old_generation and global_generation, not in young_generation
610 return (active_generation() != (ShenandoahGeneration*) young_generation());
611 default:
612 assert(false, "Bad affiliation (%d) for region " SIZE_FORMAT, _affiliations[index], index);
613 return false;
614 }
615 }
616
617 inline bool ShenandoahHeap::is_in_young(const void* p) const {
618 return is_in(p) && (_affiliations[heap_region_index_containing(p)] == ShenandoahAffiliation::YOUNG_GENERATION);
619 }
620
621 inline bool ShenandoahHeap::is_in_old(const void* p) const {
622 return is_in(p) && (_affiliations[heap_region_index_containing(p)] == ShenandoahAffiliation::OLD_GENERATION);
623 }
624
625 inline bool ShenandoahHeap::is_old(oop obj) const {
626 return is_gc_generation_young() && is_in_old(obj);
627 }
628
629 inline ShenandoahAffiliation ShenandoahHeap::region_affiliation(const ShenandoahHeapRegion *r) {
630 return (ShenandoahAffiliation) _affiliations[r->index()];
631 }
632
633 inline void ShenandoahHeap::assert_lock_for_affiliation(ShenandoahAffiliation orig_affiliation,
634 ShenandoahAffiliation new_affiliation) {
635 // A lock is required when changing from FREE to NON-FREE. Though it may be possible to elide the lock when
636 // transitioning from in-use to FREE, the current implementation uses a lock for this transition. A lock is
637 // not required to change from YOUNG to OLD (i.e. when promoting humongous region).
638 //
639 // new_affiliation is: FREE YOUNG OLD
640 // orig_affiliation is: FREE X L L
641 // YOUNG L X
642 // OLD L X X
643 // X means state transition won't happen (so don't care)
644 // L means lock should be held
645 // Blank means no lock required because affiliation visibility will not be required until subsequent safepoint
646 //
647 // Note: during full GC, all transitions between states are possible. During Full GC, we should be in a safepoint.
648
649 if ((orig_affiliation == ShenandoahAffiliation::FREE) || (new_affiliation == ShenandoahAffiliation::FREE)) {
650 shenandoah_assert_heaplocked_or_fullgc_safepoint();
651 }
652 }
653
654 inline void ShenandoahHeap::set_affiliation(ShenandoahHeapRegion* r, ShenandoahAffiliation new_affiliation) {
655 #ifdef ASSERT
656 assert_lock_for_affiliation(region_affiliation(r), new_affiliation);
657 #endif
658 _affiliations[r->index()] = (uint8_t) new_affiliation;
659 }
660
661 inline ShenandoahAffiliation ShenandoahHeap::region_affiliation(size_t index) {
662 return (ShenandoahAffiliation) _affiliations[index];
663 }
664
665 inline void ShenandoahHeap::set_affiliation(size_t index, ShenandoahAffiliation new_affiliation) {
666 #ifdef ASSERT
667 assert_lock_for_affiliation(region_affiliation(index), new_affiliation);
668 #endif
669 _affiliations[index] = (uint8_t) new_affiliation;
670 }
671
672 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
673 oop obj = cast_to_oop(entry);
674 return !_marking_context->is_marked_strong(obj);
675 }
676
677 inline bool ShenandoahHeap::in_collection_set(oop p) const {
678 assert(collection_set() != nullptr, "Sanity");
679 return collection_set()->is_in(p);
680 }
681
682 inline bool ShenandoahHeap::in_collection_set_loc(void* p) const {
683 assert(collection_set() != nullptr, "Sanity");
684 return collection_set()->is_in_loc(p);
685 }
686
687
688 inline bool ShenandoahHeap::is_stable() const {
689 return _gc_state.is_clear();
690 }
691
692 inline bool ShenandoahHeap::has_evacuation_reserve_quantities() const {
693 return _has_evacuation_reserve_quantities;
694 }
695
696 inline bool ShenandoahHeap::is_idle() const {
697 return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS);
698 }
699
700 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
701 return _gc_state.is_set(MARKING);
702 }
703
704 inline bool ShenandoahHeap::is_concurrent_young_mark_in_progress() const {
705 return _gc_state.is_set(YOUNG_MARKING);
706 }
707
708 inline bool ShenandoahHeap::is_concurrent_old_mark_in_progress() const {
709 return _gc_state.is_set(OLD_MARKING);
710 }
711
712 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
713 return _gc_state.is_set(EVACUATION);
714 }
715
716 inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
717 return _gc_state.is_set(mask);
718 }
719
720 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
721 return _degenerated_gc_in_progress.is_set();
722 }
723
724 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
725 return _full_gc_in_progress.is_set();
726 }
727
728 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
729 return _full_gc_move_in_progress.is_set();
730 }
731
732 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
733 return _gc_state.is_set(UPDATEREFS);
734 }
735
736 inline bool ShenandoahHeap::is_stw_gc_in_progress() const {
737 return is_full_gc_in_progress() || is_degenerated_gc_in_progress();
738 }
739
740 inline bool ShenandoahHeap::is_concurrent_strong_root_in_progress() const {
741 return _concurrent_strong_root_in_progress.is_set();
742 }
743
744 inline bool ShenandoahHeap::is_concurrent_weak_root_in_progress() const {
745 return _gc_state.is_set(WEAK_ROOTS);
746 }
747
748 inline bool ShenandoahHeap::is_aging_cycle() const {
749 return _is_aging_cycle.is_set();
750 }
751
752 inline bool ShenandoahHeap::is_prepare_for_old_mark_in_progress() const {
753 return _prepare_for_old_mark;
754 }
755
756 inline size_t ShenandoahHeap::set_promoted_reserve(size_t new_val) {
757 size_t orig = _promoted_reserve;
758 _promoted_reserve = new_val;
759 return orig;
760 }
761
762 inline size_t ShenandoahHeap::get_promoted_reserve() const {
763 return _promoted_reserve;
764 }
765
766 // returns previous value
767 size_t ShenandoahHeap::capture_old_usage(size_t old_usage) {
768 size_t previous_value = _captured_old_usage;
769 _captured_old_usage = old_usage;
770 return previous_value;
771 }
772
773 void ShenandoahHeap::set_previous_promotion(size_t promoted_bytes) {
774 shenandoah_assert_heaplocked();
775 _previous_promotion = promoted_bytes;
776 }
777
778 size_t ShenandoahHeap::get_previous_promotion() const {
779 return _previous_promotion;
780 }
781
782 inline size_t ShenandoahHeap::set_old_evac_reserve(size_t new_val) {
783 size_t orig = _old_evac_reserve;
784 _old_evac_reserve = new_val;
785 return orig;
786 }
787
788 inline size_t ShenandoahHeap::get_old_evac_reserve() const {
789 return _old_evac_reserve;
790 }
791
792 inline void ShenandoahHeap::augment_old_evac_reserve(size_t increment) {
793 _old_evac_reserve += increment;
794 }
795
796 inline void ShenandoahHeap::augment_promo_reserve(size_t increment) {
797 _promoted_reserve += increment;
798 }
799
800 inline void ShenandoahHeap::reset_old_evac_expended() {
801 Atomic::store(&_old_evac_expended, (size_t) 0);
802 }
803
804 inline size_t ShenandoahHeap::expend_old_evac(size_t increment) {
805 return Atomic::add(&_old_evac_expended, increment);
806 }
807
808 inline size_t ShenandoahHeap::get_old_evac_expended() {
809 return Atomic::load(&_old_evac_expended);
810 }
811
812 inline void ShenandoahHeap::reset_promoted_expended() {
813 Atomic::store(&_promoted_expended, (size_t) 0);
814 }
815
816 inline size_t ShenandoahHeap::expend_promoted(size_t increment) {
817 return Atomic::add(&_promoted_expended, increment);
818 }
819
820 inline size_t ShenandoahHeap::unexpend_promoted(size_t decrement) {
821 return Atomic::sub(&_promoted_expended, decrement);
822 }
823
824 inline size_t ShenandoahHeap::get_promoted_expended() {
825 return Atomic::load(&_promoted_expended);
826 }
827
828 inline size_t ShenandoahHeap::set_young_evac_reserve(size_t new_val) {
829 size_t orig = _young_evac_reserve;
830 _young_evac_reserve = new_val;
831 return orig;
832 }
833
834 inline size_t ShenandoahHeap::get_young_evac_reserve() const {
835 return _young_evac_reserve;
836 }
837
838 template<class T>
839 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
840 marked_object_iterate(region, cl, region->top());
841 }
842
843 template<class T>
844 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
845 assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
846
847 ShenandoahMarkingContext* const ctx = marking_context();
848
849 HeapWord* tams = ctx->top_at_mark_start(region);
850
851 size_t skip_bitmap_delta = 1;
852 HeapWord* start = region->bottom();
853 HeapWord* end = MIN2(tams, region->end());
854
855 // Step 1. Scan below the TAMS based on bitmap data.
856 HeapWord* limit_bitmap = MIN2(limit, tams);
857
858 // Try to scan the initial candidate. If the candidate is above the TAMS, it would
859 // fail the subsequent "< limit_bitmap" checks, and fall through to Step 2.
860 HeapWord* cb = ctx->get_next_marked_addr(start, end);
861
862 intx dist = ShenandoahMarkScanPrefetch;
863 if (dist > 0) {
864 // Batched scan that prefetches the oop data, anticipating the access to
865 // either header, oop field, or forwarding pointer. Not that we cannot
866 // touch anything in oop, while it still being prefetched to get enough
867 // time for prefetch to work. This is why we try to scan the bitmap linearly,
868 // disregarding the object size. However, since we know forwarding pointer
869 // precedes the object, we can skip over it. Once we cannot trust the bitmap,
870 // there is no point for prefetching the oop contents, as oop->size() will
871 // touch it prematurely.
872
873 // No variable-length arrays in standard C++, have enough slots to fit
874 // the prefetch distance.
875 static const int SLOT_COUNT = 256;
876 guarantee(dist <= SLOT_COUNT, "adjust slot count");
877 HeapWord* slots[SLOT_COUNT];
878
879 int avail;
880 do {
881 avail = 0;
882 for (int c = 0; (c < dist) && (cb < limit_bitmap); c++) {
883 Prefetch::read(cb, oopDesc::mark_offset_in_bytes());
884 slots[avail++] = cb;
885 cb += skip_bitmap_delta;
886 if (cb < limit_bitmap) {
887 cb = ctx->get_next_marked_addr(cb, limit_bitmap);
888 }
889 }
890
891 for (int c = 0; c < avail; c++) {
892 assert (slots[c] < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams));
893 assert (slots[c] < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit));
894 oop obj = cast_to_oop(slots[c]);
895 assert(oopDesc::is_oop(obj), "sanity");
896 assert(ctx->is_marked(obj), "object expected to be marked");
897 cl->do_object(obj);
898 }
899 } while (avail > 0);
900 } else {
901 while (cb < limit_bitmap) {
902 assert (cb < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams));
903 assert (cb < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit));
904 oop obj = cast_to_oop(cb);
905 assert(oopDesc::is_oop(obj), "sanity");
906 assert(ctx->is_marked(obj), "object expected to be marked");
907 cl->do_object(obj);
908 cb += skip_bitmap_delta;
909 if (cb < limit_bitmap) {
910 cb = ctx->get_next_marked_addr(cb, limit_bitmap);
911 }
912 }
913 }
914
915 // Step 2. Accurate size-based traversal, happens past the TAMS.
916 // This restarts the scan at TAMS, which makes sure we traverse all objects,
917 // regardless of what happened at Step 1.
918 HeapWord* cs = tams;
919 while (cs < limit) {
920 assert (cs >= tams, "only objects past TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams));
921 assert (cs < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit));
922 oop obj = cast_to_oop(cs);
923 assert(oopDesc::is_oop(obj), "sanity");
924 assert(ctx->is_marked(obj), "object expected to be marked");
925 size_t size = obj->size();
926 cl->do_object(obj);
927 cs += size;
928 }
929 }
930
931 template <class T>
932 class ShenandoahObjectToOopClosure : public ObjectClosure {
933 T* _cl;
934 public:
935 ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
936
937 void do_object(oop obj) {
938 obj->oop_iterate(_cl);
939 }
940 };
941
942 template <class T>
943 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
944 T* _cl;
945 MemRegion _bounds;
946 public:
947 ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
948 _cl(cl), _bounds(bottom, top) {}
949
950 void do_object(oop obj) {
951 obj->oop_iterate(_cl, _bounds);
952 }
953 };
954
955 template<class T>
956 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
957 if (region->is_humongous()) {
958 HeapWord* bottom = region->bottom();
959 if (top > bottom) {
960 region = region->humongous_start_region();
961 ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
962 marked_object_iterate(region, &objs);
963 }
964 } else {
965 ShenandoahObjectToOopClosure<T> objs(cl);
966 marked_object_iterate(region, &objs, top);
967 }
968 }
969
970 inline ShenandoahHeapRegion* ShenandoahHeap::get_region(size_t region_idx) const {
971 if (region_idx < _num_regions) {
972 return _regions[region_idx];
973 } else {
974 return nullptr;
975 }
976 }
977
978 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
979 assert (_marking_context->is_complete()," sanity");
980 return _marking_context;
981 }
982
983 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
984 return _marking_context;
985 }
986
987 inline void ShenandoahHeap::clear_cards_for(ShenandoahHeapRegion* region) {
988 if (mode()->is_generational()) {
989 _card_scan->mark_range_as_empty(region->bottom(), pointer_delta(region->end(), region->bottom()));
990 }
991 }
992
993 inline void ShenandoahHeap::dirty_cards(HeapWord* start, HeapWord* end) {
994 assert(mode()->is_generational(), "Should only be used for generational mode");
995 size_t words = pointer_delta(end, start);
996 _card_scan->mark_range_as_dirty(start, words);
997 }
998
999 inline void ShenandoahHeap::clear_cards(HeapWord* start, HeapWord* end) {
1000 assert(mode()->is_generational(), "Should only be used for generational mode");
1001 size_t words = pointer_delta(end, start);
1002 _card_scan->mark_range_as_clean(start, words);
1003 }
1004
1005 inline void ShenandoahHeap::mark_card_as_dirty(void* location) {
1006 if (mode()->is_generational()) {
1007 _card_scan->mark_card_as_dirty((HeapWord*)location);
1008 }
1009 }
1010
1011 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP