1 /*
2 * Copyright (c) 2015, 2020, Red Hat, Inc. 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 *
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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).
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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24
25 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
26 #define SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
27
28 #include "gc/shenandoah/shenandoahHeap.hpp"
29
30 #include "classfile/javaClasses.inline.hpp"
31 #include "gc/shared/markBitMap.inline.hpp"
32 #include "gc/shared/threadLocalAllocBuffer.inline.hpp"
33 #include "gc/shared/suspendibleThreadSet.hpp"
34 #include "gc/shared/tlab_globals.hpp"
35 #include "gc/shenandoah/shenandoahAsserts.hpp"
36 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
37 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
38 #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
39 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
40 #include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
41 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
42 #include "gc/shenandoah/shenandoahControlThread.hpp"
43 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
44 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
45 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
46 #include "gc/shenandoah/shenandoahScanRemembered.inline.hpp"
47 #include "gc/shenandoah/mode/shenandoahMode.hpp"
48 #include "oops/compressedOops.inline.hpp"
49 #include "oops/oop.inline.hpp"
50 #include "runtime/atomic.hpp"
51 #include "runtime/prefetch.inline.hpp"
52 #include "runtime/thread.hpp"
53 #include "utilities/copy.hpp"
54 #include "utilities/globalDefinitions.hpp"
55
56 inline ShenandoahHeap* ShenandoahHeap::heap() {
57 return named_heap<ShenandoahHeap>(CollectedHeap::Shenandoah);
58 }
59
60 inline ShenandoahHeapRegion* ShenandoahRegionIterator::next() {
61 size_t new_index = Atomic::add(&_index, (size_t) 1, memory_order_relaxed);
62 // get_region() provides the bounds-check and returns NULL on OOB.
63 return _heap->get_region(new_index - 1);
64 }
65
66 inline bool ShenandoahHeap::has_forwarded_objects() const {
67 return _gc_state.is_set(HAS_FORWARDED);
68 }
69
70 inline WorkGang* ShenandoahHeap::workers() const {
71 return _workers;
72 }
73
74 inline WorkGang* ShenandoahHeap::safepoint_workers() {
75 return _safepoint_workers;
76 }
77
78 inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
79 uintptr_t region_start = ((uintptr_t) addr);
80 uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
81 assert(index < num_regions(), "Region index is in bounds: " PTR_FORMAT, p2i(addr));
82 return index;
83 }
84
85 inline ShenandoahHeapRegion* const ShenandoahHeap::heap_region_containing(const void* addr) const {
86 size_t index = heap_region_index_containing(addr);
87 ShenandoahHeapRegion* const result = get_region(index);
88 assert(addr >= result->bottom() && addr < result->end(), "Heap region contains the address: " PTR_FORMAT, p2i(addr));
89 return result;
90 }
91
92 inline void ShenandoahHeap::enter_evacuation(Thread* t) {
93 _oom_evac_handler.enter_evacuation(t);
94 }
95
96 inline void ShenandoahHeap::leave_evacuation(Thread* t) {
97 _oom_evac_handler.leave_evacuation(t);
98 }
99
100 template <class T>
101 inline void ShenandoahHeap::update_with_forwarded(T* p) {
102 T o = RawAccess<>::oop_load(p);
103 if (!CompressedOops::is_null(o)) {
104 oop obj = CompressedOops::decode_not_null(o);
105 if (in_collection_set(obj)) {
106 // Corner case: when evacuation fails, there are objects in collection
107 // set that are not really forwarded. We can still go and try and update them
108 // (uselessly) to simplify the common path.
109 shenandoah_assert_forwarded_except(p, obj, cancelled_gc());
110 oop fwd = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
111 shenandoah_assert_not_in_cset_except(p, fwd, cancelled_gc());
112
113 // Unconditionally store the update: no concurrent updates expected.
114 RawAccess<IS_NOT_NULL>::oop_store(p, fwd);
115 }
116 }
117 }
118
119 template <class T>
120 inline void ShenandoahHeap::conc_update_with_forwarded(T* p) {
121 T o = RawAccess<>::oop_load(p);
122 if (!CompressedOops::is_null(o)) {
123 oop obj = CompressedOops::decode_not_null(o);
124 if (in_collection_set(obj)) {
125 // Corner case: when evacuation fails, there are objects in collection
126 // set that are not really forwarded. We can still go and try CAS-update them
127 // (uselessly) to simplify the common path.
128 shenandoah_assert_forwarded_except(p, obj, cancelled_gc());
129 oop fwd = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
130 shenandoah_assert_not_in_cset_except(p, fwd, cancelled_gc());
131
132 // Sanity check: we should not be updating the cset regions themselves,
133 // unless we are recovering from the evacuation failure.
134 shenandoah_assert_not_in_cset_loc_except(p, !is_in(p) || cancelled_gc());
135
136 // Either we succeed in updating the reference, or something else gets in our way.
137 // We don't care if that is another concurrent GC update, or another mutator update.
138 atomic_update_oop(fwd, p, obj);
139 }
140 }
141 }
142
143 // Atomic updates of heap location. This is only expected to work with updating the same
144 // logical object with its forwardee. The reason why we need stronger-than-relaxed memory
145 // ordering has to do with coordination with GC barriers and mutator accesses.
146 //
147 // In essence, stronger CAS access is required to maintain the transitive chains that mutator
148 // accesses build by themselves. To illustrate this point, consider the following example.
149 //
150 // Suppose "o" is the object that has a field "x" and the reference to "o" is stored
151 // to field at "addr", which happens to be Java volatile field. Normally, the accesses to volatile
152 // field at "addr" would be matched with release/acquire barriers. This changes when GC moves
153 // the object under mutator feet.
154 //
155 // Thread 1 (Java)
156 // // --- previous access starts here
157 // ...
158 // T1.1: store(&o.x, 1, mo_relaxed)
159 // T1.2: store(&addr, o, mo_release) // volatile store
160 //
161 // // --- new access starts here
162 // // LRB: copy and install the new copy to fwdptr
163 // T1.3: var copy = copy(o)
164 // T1.4: cas(&fwd, t, copy, mo_release) // pointer-mediated publication
165 // <access continues>
166 //
167 // Thread 2 (GC updater)
168 // T2.1: var f = load(&fwd, mo_{consume|acquire}) // pointer-mediated acquisition
169 // T2.2: cas(&addr, o, f, mo_release) // this method
170 //
171 // Thread 3 (Java)
172 // T3.1: var o = load(&addr, mo_acquire) // volatile read
173 // T3.2: if (o != null)
174 // T3.3: var r = load(&o.x, mo_relaxed)
175 //
176 // r is guaranteed to contain "1".
177 //
178 // Without GC involvement, there is synchronizes-with edge from T1.2 to T3.1,
179 // which guarantees this. With GC involvement, when LRB copies the object and
180 // another thread updates the reference to it, we need to have the transitive edge
181 // from T1.4 to T2.1 (that one is guaranteed by forwarding accesses), plus the edge
182 // from T2.2 to T3.1 (which is brought by this CAS).
183 //
184 // Note that we do not need to "acquire" in these methods, because we do not read the
185 // failure witnesses contents on any path, and "release" is enough.
186 //
187
188 inline void ShenandoahHeap::atomic_update_oop(oop update, oop* addr, oop compare) {
189 assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
190 Atomic::cmpxchg(addr, compare, update, memory_order_release);
191 }
192
193 inline void ShenandoahHeap::atomic_update_oop(oop update, narrowOop* addr, narrowOop compare) {
194 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
195 narrowOop u = CompressedOops::encode(update);
196 Atomic::cmpxchg(addr, compare, u, memory_order_release);
197 }
198
199 inline void ShenandoahHeap::atomic_update_oop(oop update, narrowOop* addr, oop compare) {
200 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
201 narrowOop c = CompressedOops::encode(compare);
202 narrowOop u = CompressedOops::encode(update);
203 Atomic::cmpxchg(addr, c, u, memory_order_release);
204 }
205
206 inline bool ShenandoahHeap::atomic_update_oop_check(oop update, oop* addr, oop compare) {
207 assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
208 return (oop) Atomic::cmpxchg(addr, compare, update, memory_order_release) == compare;
209 }
210
211 inline bool ShenandoahHeap::atomic_update_oop_check(oop update, narrowOop* addr, narrowOop compare) {
212 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
213 narrowOop u = CompressedOops::encode(update);
214 return (narrowOop) Atomic::cmpxchg(addr, compare, u, memory_order_release) == compare;
215 }
216
217 inline bool ShenandoahHeap::atomic_update_oop_check(oop update, narrowOop* addr, oop compare) {
218 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
219 narrowOop c = CompressedOops::encode(compare);
220 narrowOop u = CompressedOops::encode(update);
221 return CompressedOops::decode(Atomic::cmpxchg(addr, c, u, memory_order_release)) == compare;
222 }
223
224 // The memory ordering discussion above does not apply for methods that store NULLs:
225 // then, there is no transitive reads in mutator (as we see NULLs), and we can do
226 // relaxed memory ordering there.
227
228 inline void ShenandoahHeap::atomic_clear_oop(oop* addr, oop compare) {
229 assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
230 Atomic::cmpxchg(addr, compare, oop(), memory_order_relaxed);
231 }
232
233 inline void ShenandoahHeap::atomic_clear_oop(narrowOop* addr, oop compare) {
234 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
235 narrowOop cmp = CompressedOops::encode(compare);
236 Atomic::cmpxchg(addr, cmp, narrowOop(), memory_order_relaxed);
237 }
238
239 inline void ShenandoahHeap::atomic_clear_oop(narrowOop* addr, narrowOop compare) {
240 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
241 Atomic::cmpxchg(addr, compare, narrowOop(), memory_order_relaxed);
242 }
243
244 inline bool ShenandoahHeap::cancelled_gc() const {
245 return _cancelled_gc.get() == CANCELLED;
246 }
247
248 inline bool ShenandoahHeap::check_cancelled_gc_and_yield(bool sts_active) {
249 if (! (sts_active && ShenandoahSuspendibleWorkers)) {
250 return cancelled_gc();
251 }
252
253 jbyte prev = _cancelled_gc.cmpxchg(NOT_CANCELLED, CANCELLABLE);
254 if (prev == CANCELLABLE || prev == NOT_CANCELLED) {
255 if (SuspendibleThreadSet::should_yield()) {
256 SuspendibleThreadSet::yield();
257 }
258
259 // Back to CANCELLABLE. The thread that poked NOT_CANCELLED first gets
260 // to restore to CANCELLABLE.
261 if (prev == CANCELLABLE) {
262 _cancelled_gc.set(CANCELLABLE);
263 }
264 return false;
265 } else {
266 return true;
267 }
268 }
269
270 inline void ShenandoahHeap::clear_cancelled_gc(bool clear_oom_handler) {
271 _cancelled_gc.set(CANCELLABLE);
272 if (_cancel_requested_time > 0) {
273 double cancel_time = os::elapsedTime() - _cancel_requested_time;
274 log_info(gc)("GC cancellation took %.3fs", cancel_time);
275 _cancel_requested_time = 0;
276 }
277
278 if (clear_oom_handler) {
279 _oom_evac_handler.clear();
280 }
281 }
282
283 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
284 assert(UseTLAB, "TLABs should be enabled");
285
286 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
287 if (gclab == NULL) {
288 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
289 "Performance: thread should have GCLAB: %s", thread->name());
290 // No GCLABs in this thread, fallback to shared allocation
291 return NULL;
292 }
293 HeapWord* obj = gclab->allocate(size);
294 if (obj != NULL) {
295 return obj;
296 }
297 return allocate_from_gclab_slow(thread, size);
298 }
299
300 inline HeapWord* ShenandoahHeap::allocate_from_plab(Thread* thread, size_t size) {
301 assert(UseTLAB, "TLABs should be enabled");
302
303 PLAB* plab = ShenandoahThreadLocalData::plab(thread);
304 if (plab == NULL) {
305 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
306 "Performance: thread should have PLAB: %s", thread->name());
307 // No PLABs in this thread, fallback to shared allocation
308 return NULL;
309 }
310 HeapWord* obj = plab->allocate(size);
311 if (obj == NULL) {
312 obj = allocate_from_plab_slow(thread, size);
313 }
314 return obj;
315 }
316
317 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
318 assert(thread == Thread::current(), "Expected thread parameter to be current thread.");
319 if (ShenandoahThreadLocalData::is_oom_during_evac(thread)) {
320 // This thread went through the OOM during evac protocol and it is safe to return
321 // the forward pointer. It must not attempt to evacuate any more.
322 return ShenandoahBarrierSet::resolve_forwarded(p);
323 }
324
325 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
326
327 ShenandoahHeapRegion* r = heap_region_containing(p);
328 assert(!r->is_humongous(), "never evacuate humongous objects");
329
330 ShenandoahRegionAffiliation target_gen = r->affiliation();
331 if (mode()->is_generational() && ShenandoahHeap::heap()->is_gc_generation_young() &&
332 target_gen == YOUNG_GENERATION && ShenandoahPromoteTenuredObjects) {
333 markWord mark = p->mark();
334 if (mark.is_marked()) {
335 // Already forwarded.
336 return ShenandoahBarrierSet::resolve_forwarded(p);
337 }
338 if (mark.has_displaced_mark_helper()) {
339 // We don't want to deal with MT here just to ensure we read the right mark word.
340 // Skip the potential promotion attempt for this one.
341 } else if (mark.age() >= InitialTenuringThreshold) {
342 oop result = try_evacuate_object(p, thread, r, OLD_GENERATION);
343 if (result != NULL) {
344 return result;
345 }
346 }
347 }
348 return try_evacuate_object(p, thread, r, target_gen);
349 }
350
351 // try_evacuate_object registers the object and dirties the associated remembered set information when evacuating
352 // to OLD_GENERATION.
353 inline oop ShenandoahHeap::try_evacuate_object(oop p, Thread* thread, ShenandoahHeapRegion* from_region, ShenandoahRegionAffiliation target_gen) {
354 bool alloc_from_lab = true;
355 HeapWord* copy = NULL;
356 size_t size = p->size();
357
358 #ifdef ASSERT
359 if (ShenandoahOOMDuringEvacALot &&
360 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
361 copy = NULL;
362 } else {
363 #endif
364 if (UseTLAB) {
365 switch (target_gen) {
366 case YOUNG_GENERATION: {
367 copy = allocate_from_gclab(thread, size);
368 break;
369 }
370 case OLD_GENERATION: {
371 if (ShenandoahUsePLAB) {
372 copy = allocate_from_plab(thread, size);
373 }
374 break;
375 }
376 default: {
377 ShouldNotReachHere();
378 break;
379 }
380 }
381 }
382 if (copy == NULL) {
383 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size, target_gen);
384 copy = allocate_memory(req);
385 alloc_from_lab = false;
386 }
387 #ifdef ASSERT
388 }
389 #endif
390
391 if (copy == NULL) {
392 if (target_gen == OLD_GENERATION) {
393 assert(mode()->is_generational(), "Should only be here in generational mode.");
394 if (from_region->is_young()) {
395 // Signal that promotion failed. Will evacuate this old object somewhere in young gen.
396 handle_promotion_failure();
397 return NULL;
398 } else {
399 // Remember that evacuation to old gen failed. We'll want to trigger a full gc to recover from this
400 // after the evacuation threads have finished.
401 handle_old_evacuation_failure();
402 }
403 }
404
405 control_thread()->handle_alloc_failure_evac(size);
406
407 _oom_evac_handler.handle_out_of_memory_during_evacuation();
408
409 return ShenandoahBarrierSet::resolve_forwarded(p);
410 }
411
412 // Copy the object:
413 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
414
415 oop copy_val = cast_to_oop(copy);
416
417 // Try to install the new forwarding pointer.
418 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
419 if (result == copy_val) {
420 // Successfully evacuated. Our copy is now the public one!
421 if (mode()->is_generational()) {
422 if (target_gen == OLD_GENERATION) {
423 handle_old_evacuation(copy, size, from_region->is_young());
424 } else if (target_gen == YOUNG_GENERATION) {
425 if (is_aging_cycle()) {
426 ShenandoahHeap::increase_object_age(copy_val, from_region->age() + 1);
427 }
428 } else {
429 ShouldNotReachHere();
430 }
431 }
432 shenandoah_assert_correct(NULL, copy_val);
433 return copy_val;
434 } else {
435 // Failed to evacuate. We need to deal with the object that is left behind. Since this
436 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
437 // But if it happens to contain references to evacuated regions, those references would
438 // not get updated for this stale copy during this cycle, and we will crash while scanning
439 // it the next cycle.
440 if (alloc_from_lab) {
441 // For LAB allocations, it is enough to rollback the allocation ptr. Either the next
442 // object will overwrite this stale copy, or the filler object on LAB retirement will
443 // do this.
444 switch (target_gen) {
445 case YOUNG_GENERATION: {
446 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
447 break;
448 }
449 case OLD_GENERATION: {
450 ShenandoahThreadLocalData::plab(thread)->undo_allocation(copy, size);
451 break;
452 }
453 default: {
454 ShouldNotReachHere();
455 break;
456 }
457 }
458 } else {
459 // For non-LAB allocations, we have no way to retract the allocation, and
460 // have to explicitly overwrite the copy with the filler object. With that overwrite,
461 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
462 fill_with_object(copy, size);
463 shenandoah_assert_correct(NULL, copy_val);
464 // For non-LAB allocations, the object has already been registered
465 }
466 shenandoah_assert_correct(NULL, result);
467 return result;
468 }
469 }
470
471 void ShenandoahHeap::increase_object_age(oop obj, uint additional_age) {
472 markWord w = obj->has_displaced_mark() ? obj->displaced_mark() : obj->mark();
473 w = w.set_age(MIN2(markWord::max_age, w.age() + additional_age));
474 if (obj->has_displaced_mark()) {
475 obj->set_displaced_mark(w);
476 } else {
477 obj->set_mark(w);
478 }
479 }
480
481 inline bool ShenandoahHeap::clear_old_evacuation_failure() {
482 return _old_gen_oom_evac.try_unset();
483 }
484
485 inline bool ShenandoahHeap::is_old(oop obj) const {
486 return is_gc_generation_young() && is_in_old(obj);
487 }
488
489 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
490 oop obj = cast_to_oop(entry);
491 return !_marking_context->is_marked_strong(obj);
492 }
493
494 inline bool ShenandoahHeap::in_collection_set(oop p) const {
495 assert(collection_set() != NULL, "Sanity");
496 return collection_set()->is_in(p);
497 }
498
499 inline bool ShenandoahHeap::in_collection_set_loc(void* p) const {
500 assert(collection_set() != NULL, "Sanity");
501 return collection_set()->is_in_loc(p);
502 }
503
504 inline bool ShenandoahHeap::is_stable() const {
505 return _gc_state.is_clear();
506 }
507
508 inline bool ShenandoahHeap::is_idle() const {
509 return _gc_state.is_unset(YOUNG_MARKING | OLD_MARKING | EVACUATION | UPDATEREFS);
510 }
511
512 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
513 return _gc_state.is_set(YOUNG_MARKING | OLD_MARKING);
514 }
515
516 inline bool ShenandoahHeap::is_concurrent_young_mark_in_progress() const {
517 return _gc_state.is_set(YOUNG_MARKING);
518 }
519
520 inline bool ShenandoahHeap::is_concurrent_old_mark_in_progress() const {
521 return _gc_state.is_set(OLD_MARKING);
522 }
523
524 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
525 return _gc_state.is_set(EVACUATION);
526 }
527
528 inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
529 return _gc_state.is_set(mask);
530 }
531
532 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
533 return _degenerated_gc_in_progress.is_set();
534 }
535
536 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
537 return _full_gc_in_progress.is_set();
538 }
539
540 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
541 return _full_gc_move_in_progress.is_set();
542 }
543
544 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
545 return _gc_state.is_set(UPDATEREFS);
546 }
547
548 inline bool ShenandoahHeap::is_stw_gc_in_progress() const {
549 return is_full_gc_in_progress() || is_degenerated_gc_in_progress();
550 }
551
552 inline bool ShenandoahHeap::is_concurrent_strong_root_in_progress() const {
553 return _concurrent_strong_root_in_progress.is_set();
554 }
555
556 inline bool ShenandoahHeap::is_concurrent_weak_root_in_progress() const {
557 return _gc_state.is_set(WEAK_ROOTS);
558 }
559
560 inline bool ShenandoahHeap::is_aging_cycle() const {
561 return _is_aging_cycle.is_set();
562 }
563
564 template<class T>
565 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
566 marked_object_iterate(region, cl, region->top());
567 }
568
569 template<class T>
570 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
571 assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
572
573 ShenandoahMarkingContext* const ctx = marking_context();
574
575 HeapWord* tams = ctx->top_at_mark_start(region);
576
577 size_t skip_bitmap_delta = 1;
578 HeapWord* start = region->bottom();
579 HeapWord* end = MIN2(tams, region->end());
580
581 // Step 1. Scan below the TAMS based on bitmap data.
582 HeapWord* limit_bitmap = MIN2(limit, tams);
583
584 // Try to scan the initial candidate. If the candidate is above the TAMS, it would
585 // fail the subsequent "< limit_bitmap" checks, and fall through to Step 2.
586 HeapWord* cb = ctx->get_next_marked_addr(start, end);
587
588 intx dist = ShenandoahMarkScanPrefetch;
589 if (dist > 0) {
590 // Batched scan that prefetches the oop data, anticipating the access to
591 // either header, oop field, or forwarding pointer. Not that we cannot
592 // touch anything in oop, while it still being prefetched to get enough
593 // time for prefetch to work. This is why we try to scan the bitmap linearly,
594 // disregarding the object size. However, since we know forwarding pointer
595 // preceeds the object, we can skip over it. Once we cannot trust the bitmap,
596 // there is no point for prefetching the oop contents, as oop->size() will
597 // touch it prematurely.
598
599 // No variable-length arrays in standard C++, have enough slots to fit
600 // the prefetch distance.
601 static const int SLOT_COUNT = 256;
602 guarantee(dist <= SLOT_COUNT, "adjust slot count");
603 HeapWord* slots[SLOT_COUNT];
604
605 int avail;
606 do {
607 avail = 0;
608 for (int c = 0; (c < dist) && (cb < limit_bitmap); c++) {
609 Prefetch::read(cb, oopDesc::mark_offset_in_bytes());
610 slots[avail++] = cb;
611 cb += skip_bitmap_delta;
612 if (cb < limit_bitmap) {
613 cb = ctx->get_next_marked_addr(cb, limit_bitmap);
614 }
615 }
616
617 for (int c = 0; c < avail; c++) {
618 assert (slots[c] < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams));
619 assert (slots[c] < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit));
620 oop obj = cast_to_oop(slots[c]);
621 assert(oopDesc::is_oop(obj), "sanity");
622 assert(ctx->is_marked(obj), "object expected to be marked");
623 cl->do_object(obj);
624 }
625 } while (avail > 0);
626 } else {
627 while (cb < limit_bitmap) {
628 assert (cb < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams));
629 assert (cb < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit));
630 oop obj = cast_to_oop(cb);
631 assert(oopDesc::is_oop(obj), "sanity");
632 assert(ctx->is_marked(obj), "object expected to be marked");
633 cl->do_object(obj);
634 cb += skip_bitmap_delta;
635 if (cb < limit_bitmap) {
636 cb = ctx->get_next_marked_addr(cb, limit_bitmap);
637 }
638 }
639 }
640
641 // Step 2. Accurate size-based traversal, happens past the TAMS.
642 // This restarts the scan at TAMS, which makes sure we traverse all objects,
643 // regardless of what happened at Step 1.
644 HeapWord* cs = tams;
645 while (cs < limit) {
646 assert (cs >= tams, "only objects past TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams));
647 assert (cs < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit));
648 oop obj = cast_to_oop(cs);
649 assert(oopDesc::is_oop(obj), "sanity");
650 assert(ctx->is_marked(obj), "object expected to be marked");
651 int size = obj->size();
652 cl->do_object(obj);
653 cs += size;
654 }
655 }
656
657 template <class T>
658 class ShenandoahObjectToOopClosure : public ObjectClosure {
659 T* _cl;
660 public:
661 ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
662
663 void do_object(oop obj) {
664 obj->oop_iterate(_cl);
665 }
666 };
667
668 template <class T>
669 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
670 T* _cl;
671 MemRegion _bounds;
672 public:
673 ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
674 _cl(cl), _bounds(bottom, top) {}
675
676 void do_object(oop obj) {
677 obj->oop_iterate(_cl, _bounds);
678 }
679 };
680
681 template<class T>
682 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
683 if (region->is_humongous()) {
684 HeapWord* bottom = region->bottom();
685 if (top > bottom) {
686 region = region->humongous_start_region();
687 ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
688 marked_object_iterate(region, &objs);
689 }
690 } else {
691 ShenandoahObjectToOopClosure<T> objs(cl);
692 marked_object_iterate(region, &objs, top);
693 }
694 }
695
696 inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
697 if (region_idx < _num_regions) {
698 return _regions[region_idx];
699 } else {
700 return NULL;
701 }
702 }
703
704 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
705 assert (_marking_context->is_complete()," sanity");
706 return _marking_context;
707 }
708
709 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
710 return _marking_context;
711 }
712
713 inline void ShenandoahHeap::clear_cards_for(ShenandoahHeapRegion* region) {
714 if (mode()->is_generational()) {
715 _card_scan->mark_range_as_empty(region->bottom(), pointer_delta(region->end(), region->bottom()));
716 }
717 }
718
719 inline void ShenandoahHeap::dirty_cards(HeapWord* start, HeapWord* end) {
720 assert(mode()->is_generational(), "Should only be used for generational mode");
721 size_t words = pointer_delta(end, start);
722 _card_scan->mark_range_as_dirty(start, words);
723 }
724
725 inline void ShenandoahHeap::clear_cards(HeapWord* start, HeapWord* end) {
726 assert(mode()->is_generational(), "Should only be used for generational mode");
727 size_t words = pointer_delta(end, start);
728 _card_scan->mark_range_as_clean(start, words);
729 }
730
731 inline void ShenandoahHeap::mark_card_as_dirty(void* location) {
732 if (mode()->is_generational()) {
733 _card_scan->mark_card_as_dirty((HeapWord*)location);
734 }
735 }
736
737 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP