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 *
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.
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23 */
24
25 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
26 #define SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
27
28 #include "classfile/javaClasses.inline.hpp"
29 #include "gc/shared/markBitMap.inline.hpp"
30 #include "gc/shared/threadLocalAllocBuffer.inline.hpp"
31 #include "gc/shared/suspendibleThreadSet.hpp"
32 #include "gc/shenandoah/shenandoahAsserts.hpp"
33 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
34 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
35 #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
36 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
37 #include "gc/shenandoah/shenandoahHeap.hpp"
38 #include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
39 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
40 #include "gc/shenandoah/shenandoahControlThread.hpp"
41 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
42 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
43 #include "oops/compressedOops.inline.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "runtime/atomic.hpp"
46 #include "runtime/prefetch.inline.hpp"
47 #include "runtime/thread.hpp"
48 #include "utilities/copy.hpp"
49 #include "utilities/globalDefinitions.hpp"
50
51 inline ShenandoahHeap* ShenandoahHeap::heap() {
52 assert(_heap != NULL, "Heap is not initialized yet");
53 return _heap;
54 }
55
56 inline ShenandoahHeapRegion* ShenandoahRegionIterator::next() {
57 size_t new_index = Atomic::add(&_index, (size_t) 1);
58 // get_region() provides the bounds-check and returns NULL on OOB.
59 return _heap->get_region(new_index - 1);
60 }
61
62 inline bool ShenandoahHeap::has_forwarded_objects() const {
63 return _gc_state.is_set(HAS_FORWARDED);
64 }
65
66 inline WorkGang* ShenandoahHeap::workers() const {
67 return _workers;
68 }
69
70 inline WorkGang* ShenandoahHeap::get_safepoint_workers() {
71 return _safepoint_workers;
72 }
73
74 inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
75 uintptr_t region_start = ((uintptr_t) addr);
76 uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
77 assert(index < num_regions(), "Region index is in bounds: " PTR_FORMAT, p2i(addr));
78 return index;
79 }
80
81 inline ShenandoahHeapRegion* const ShenandoahHeap::heap_region_containing(const void* addr) const {
82 size_t index = heap_region_index_containing(addr);
83 ShenandoahHeapRegion* const result = get_region(index);
84 assert(addr >= result->bottom() && addr < result->end(), "Heap region contains the address: " PTR_FORMAT, p2i(addr));
85 return result;
86 }
87
88 inline void ShenandoahHeap::enter_evacuation(Thread* t) {
89 _oom_evac_handler.enter_evacuation(t);
90 }
91
92 inline void ShenandoahHeap::leave_evacuation(Thread* t) {
93 _oom_evac_handler.leave_evacuation(t);
94 }
95
96 template <class T>
97 inline oop ShenandoahHeap::update_with_forwarded_not_null(T* p, oop obj) {
98 if (in_collection_set(obj)) {
99 shenandoah_assert_forwarded_except(p, obj, is_full_gc_in_progress() || cancelled_gc() || is_degenerated_gc_in_progress());
100 obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
101 RawAccess<IS_NOT_NULL>::oop_store(p, obj);
102 }
103 #ifdef ASSERT
104 else {
105 shenandoah_assert_not_forwarded(p, obj);
106 }
107 #endif
108 return obj;
109 }
110
111 template <class T>
112 inline oop ShenandoahHeap::maybe_update_with_forwarded(T* p) {
113 T o = RawAccess<>::oop_load(p);
114 if (!CompressedOops::is_null(o)) {
115 oop obj = CompressedOops::decode_not_null(o);
116 return maybe_update_with_forwarded_not_null(p, obj);
117 } else {
118 return NULL;
119 }
120 }
121
122 template <class T>
123 inline oop ShenandoahHeap::evac_update_with_forwarded(T* p) {
124 T o = RawAccess<>::oop_load(p);
125 if (!CompressedOops::is_null(o)) {
126 oop heap_oop = CompressedOops::decode_not_null(o);
127 if (in_collection_set(heap_oop)) {
128 oop forwarded_oop = ShenandoahBarrierSet::resolve_forwarded_not_null(heap_oop);
129 if (forwarded_oop == heap_oop) {
130 forwarded_oop = evacuate_object(heap_oop, Thread::current());
131 }
132 oop prev = cas_oop(forwarded_oop, p, heap_oop);
133 if (prev == heap_oop) {
134 return forwarded_oop;
135 } else {
136 return NULL;
137 }
138 }
139 return heap_oop;
140 } else {
141 return NULL;
142 }
143 }
144
145 inline oop ShenandoahHeap::cas_oop(oop n, oop* addr, oop c) {
146 assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
147 return (oop) Atomic::cmpxchg(addr, c, n);
148 }
149
150 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, narrowOop c) {
151 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
152 narrowOop val = CompressedOops::encode(n);
153 return CompressedOops::decode((narrowOop) Atomic::cmpxchg(addr, c, val));
154 }
155
156 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, oop c) {
157 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
158 narrowOop cmp = CompressedOops::encode(c);
159 narrowOop val = CompressedOops::encode(n);
160 return CompressedOops::decode((narrowOop) Atomic::cmpxchg(addr, cmp, val));
161 }
162
163 template <class T>
164 inline oop ShenandoahHeap::maybe_update_with_forwarded_not_null(T* p, oop heap_oop) {
165 shenandoah_assert_not_in_cset_loc_except(p, !is_in(p) || is_full_gc_in_progress() || is_degenerated_gc_in_progress());
166 shenandoah_assert_correct(p, heap_oop);
167
168 if (in_collection_set(heap_oop)) {
169 oop forwarded_oop = ShenandoahBarrierSet::resolve_forwarded_not_null(heap_oop);
170 if (forwarded_oop == heap_oop) {
171 // E.g. during evacuation.
172 return forwarded_oop;
173 }
174
175 shenandoah_assert_forwarded_except(p, heap_oop, is_full_gc_in_progress() || is_degenerated_gc_in_progress());
176 shenandoah_assert_not_forwarded(p, forwarded_oop);
177 shenandoah_assert_not_in_cset_except(p, forwarded_oop, cancelled_gc());
178
179 // If this fails, another thread wrote to p before us, it will be logged in SATB and the
180 // reference be updated later.
181 oop witness = cas_oop(forwarded_oop, p, heap_oop);
182
183 if (witness != heap_oop) {
184 // CAS failed, someone had beat us to it. Normally, we would return the failure witness,
185 // because that would be the proper write of to-space object, enforced by strong barriers.
186 // However, there is a corner case with arraycopy. It can happen that a Java thread
187 // beats us with an arraycopy, which first copies the array, which potentially contains
188 // from-space refs, and only afterwards updates all from-space refs to to-space refs,
189 // which leaves a short window where the new array elements can be from-space.
190 // In this case, we can just resolve the result again. As we resolve, we need to consider
191 // the contended write might have been NULL.
192 oop result = ShenandoahBarrierSet::resolve_forwarded(witness);
193 shenandoah_assert_not_forwarded_except(p, result, (result == NULL));
194 shenandoah_assert_not_in_cset_except(p, result, (result == NULL) || cancelled_gc());
195 return result;
196 } else {
197 // Success! We have updated with known to-space copy. We have already asserted it is sane.
198 return forwarded_oop;
199 }
200 } else {
201 shenandoah_assert_not_forwarded(p, heap_oop);
202 return heap_oop;
203 }
204 }
205
206 inline bool ShenandoahHeap::cancelled_gc() const {
207 return _cancelled_gc.get() == CANCELLED;
208 }
209
210 inline bool ShenandoahHeap::check_cancelled_gc_and_yield(bool sts_active) {
211 if (! (sts_active && ShenandoahSuspendibleWorkers)) {
212 return cancelled_gc();
213 }
214
215 jbyte prev = _cancelled_gc.cmpxchg(NOT_CANCELLED, CANCELLABLE);
216 if (prev == CANCELLABLE || prev == NOT_CANCELLED) {
217 if (SuspendibleThreadSet::should_yield()) {
218 SuspendibleThreadSet::yield();
219 }
220
221 // Back to CANCELLABLE. The thread that poked NOT_CANCELLED first gets
222 // to restore to CANCELLABLE.
223 if (prev == CANCELLABLE) {
224 _cancelled_gc.set(CANCELLABLE);
225 }
226 return false;
227 } else {
228 return true;
229 }
230 }
231
232 inline void ShenandoahHeap::clear_cancelled_gc() {
233 _cancelled_gc.set(CANCELLABLE);
234 _oom_evac_handler.clear();
235 }
236
237 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
238 assert(UseTLAB, "TLABs should be enabled");
239
240 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
241 if (gclab == NULL) {
242 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
243 "Performance: thread should have GCLAB: %s", thread->name());
244 // No GCLABs in this thread, fallback to shared allocation
245 return NULL;
246 }
247 HeapWord* obj = gclab->allocate(size);
248 if (obj != NULL) {
249 return obj;
250 }
251 // Otherwise...
252 return allocate_from_gclab_slow(thread, size);
253 }
254
255 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
256 if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
257 // This thread went through the OOM during evac protocol and it is safe to return
258 // the forward pointer. It must not attempt to evacuate any more.
259 return ShenandoahBarrierSet::resolve_forwarded(p);
260 }
261
262 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
263
264 size_t size = p->size();
265
266 assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
267
268 bool alloc_from_gclab = true;
269 HeapWord* copy = NULL;
270
271 #ifdef ASSERT
272 if (ShenandoahOOMDuringEvacALot &&
273 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
274 copy = NULL;
275 } else {
276 #endif
277 if (UseTLAB) {
278 copy = allocate_from_gclab(thread, size);
279 }
280 if (copy == NULL) {
281 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
282 copy = allocate_memory(req);
283 alloc_from_gclab = false;
284 }
285 #ifdef ASSERT
286 }
287 #endif
288
289 if (copy == NULL) {
290 control_thread()->handle_alloc_failure_evac(size);
291
292 _oom_evac_handler.handle_out_of_memory_during_evacuation();
293
294 return ShenandoahBarrierSet::resolve_forwarded(p);
295 }
296
297 // Copy the object:
298 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
299
300 // Try to install the new forwarding pointer.
301 oop copy_val = oop(copy);
302 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
303 if (result == copy_val) {
304 // Successfully evacuated. Our copy is now the public one!
305 shenandoah_assert_correct(NULL, copy_val);
306 return copy_val;
307 } else {
308 // Failed to evacuate. We need to deal with the object that is left behind. Since this
309 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
310 // But if it happens to contain references to evacuated regions, those references would
311 // not get updated for this stale copy during this cycle, and we will crash while scanning
312 // it the next cycle.
313 //
314 // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
315 // object will overwrite this stale copy, or the filler object on LAB retirement will
316 // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
317 // have to explicitly overwrite the copy with the filler object. With that overwrite,
318 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
319 if (alloc_from_gclab) {
320 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
321 } else {
322 fill_with_object(copy, size);
323 shenandoah_assert_correct(NULL, copy_val);
324 }
325 shenandoah_assert_correct(NULL, result);
326 return result;
327 }
328 }
329
330 template<bool RESOLVE>
331 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
332 oop obj = oop(entry);
333 if (RESOLVE) {
334 obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
335 }
336 return !_marking_context->is_marked(obj);
337 }
338
339 inline bool ShenandoahHeap::in_collection_set(oop p) const {
340 assert(collection_set() != NULL, "Sanity");
341 return collection_set()->is_in(p);
342 }
343
344 inline bool ShenandoahHeap::in_collection_set_loc(void* p) const {
345 assert(collection_set() != NULL, "Sanity");
346 return collection_set()->is_in_loc(p);
347 }
348
349 inline bool ShenandoahHeap::is_stable() const {
350 return _gc_state.is_clear();
351 }
352
353 inline bool ShenandoahHeap::is_idle() const {
354 return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS);
355 }
356
357 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
358 return _gc_state.is_set(MARKING);
359 }
360
361 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
362 return _gc_state.is_set(EVACUATION);
363 }
364
365 inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
366 return _gc_state.is_set(mask);
367 }
368
369 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
370 return _degenerated_gc_in_progress.is_set();
371 }
372
373 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
374 return _full_gc_in_progress.is_set();
375 }
376
377 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
378 return _full_gc_move_in_progress.is_set();
379 }
380
381 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
382 return _gc_state.is_set(UPDATEREFS);
383 }
384
385 inline bool ShenandoahHeap::is_stw_gc_in_progress() const {
386 return is_full_gc_in_progress() || is_degenerated_gc_in_progress();
387 }
388
389 inline bool ShenandoahHeap::is_concurrent_strong_root_in_progress() const {
390 return _concurrent_strong_root_in_progress.is_set();
391 }
392
393 inline bool ShenandoahHeap::is_concurrent_weak_root_in_progress() const {
394 return _concurrent_weak_root_in_progress.is_set();
395 }
396
397 template<class T>
398 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
399 marked_object_iterate(region, cl, region->top());
400 }
401
402 template<class T>
403 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
404 assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
405
406 ShenandoahMarkingContext* const ctx = complete_marking_context();
407 assert(ctx->is_complete(), "sanity");
408
409 MarkBitMap* mark_bit_map = ctx->mark_bit_map();
410 HeapWord* tams = ctx->top_at_mark_start(region);
411
412 size_t skip_bitmap_delta = 1;
413 HeapWord* start = region->bottom();
414 HeapWord* end = MIN2(tams, region->end());
415
416 // Step 1. Scan below the TAMS based on bitmap data.
417 HeapWord* limit_bitmap = MIN2(limit, tams);
418
419 // Try to scan the initial candidate. If the candidate is above the TAMS, it would
420 // fail the subsequent "< limit_bitmap" checks, and fall through to Step 2.
421 HeapWord* cb = mark_bit_map->get_next_marked_addr(start, end);
422
423 intx dist = ShenandoahMarkScanPrefetch;
424 if (dist > 0) {
425 // Batched scan that prefetches the oop data, anticipating the access to
426 // either header, oop field, or forwarding pointer. Not that we cannot
427 // touch anything in oop, while it still being prefetched to get enough
428 // time for prefetch to work. This is why we try to scan the bitmap linearly,
429 // disregarding the object size. However, since we know forwarding pointer
430 // preceeds the object, we can skip over it. Once we cannot trust the bitmap,
431 // there is no point for prefetching the oop contents, as oop->size() will
432 // touch it prematurely.
433
434 // No variable-length arrays in standard C++, have enough slots to fit
435 // the prefetch distance.
436 static const int SLOT_COUNT = 256;
437 guarantee(dist <= SLOT_COUNT, "adjust slot count");
438 HeapWord* slots[SLOT_COUNT];
439
440 int avail;
441 do {
442 avail = 0;
443 for (int c = 0; (c < dist) && (cb < limit_bitmap); c++) {
444 Prefetch::read(cb, oopDesc::mark_offset_in_bytes());
445 slots[avail++] = cb;
446 cb += skip_bitmap_delta;
447 if (cb < limit_bitmap) {
448 cb = mark_bit_map->get_next_marked_addr(cb, limit_bitmap);
449 }
450 }
451
452 for (int c = 0; c < avail; c++) {
453 assert (slots[c] < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams));
454 assert (slots[c] < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit));
455 oop obj = oop(slots[c]);
456 assert(oopDesc::is_oop(obj), "sanity");
457 assert(ctx->is_marked(obj), "object expected to be marked");
458 cl->do_object(obj);
459 }
460 } while (avail > 0);
461 } else {
462 while (cb < limit_bitmap) {
463 assert (cb < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams));
464 assert (cb < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit));
465 oop obj = oop(cb);
466 assert(oopDesc::is_oop(obj), "sanity");
467 assert(ctx->is_marked(obj), "object expected to be marked");
468 cl->do_object(obj);
469 cb += skip_bitmap_delta;
470 if (cb < limit_bitmap) {
471 cb = mark_bit_map->get_next_marked_addr(cb, limit_bitmap);
472 }
473 }
474 }
475
476 // Step 2. Accurate size-based traversal, happens past the TAMS.
477 // This restarts the scan at TAMS, which makes sure we traverse all objects,
478 // regardless of what happened at Step 1.
479 HeapWord* cs = tams;
480 while (cs < limit) {
481 assert (cs >= tams, "only objects past TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams));
482 assert (cs < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit));
483 oop obj = oop(cs);
484 assert(oopDesc::is_oop(obj), "sanity");
485 assert(ctx->is_marked(obj), "object expected to be marked");
486 int size = obj->size();
487 cl->do_object(obj);
488 cs += size;
489 }
490 }
491
492 template <class T>
493 class ShenandoahObjectToOopClosure : public ObjectClosure {
494 T* _cl;
495 public:
496 ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
497
498 void do_object(oop obj) {
499 obj->oop_iterate(_cl);
500 }
501 };
502
503 template <class T>
504 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
505 T* _cl;
506 MemRegion _bounds;
507 public:
508 ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
509 _cl(cl), _bounds(bottom, top) {}
510
511 void do_object(oop obj) {
512 obj->oop_iterate(_cl, _bounds);
513 }
514 };
515
516 template<class T>
517 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
518 if (region->is_humongous()) {
519 HeapWord* bottom = region->bottom();
520 if (top > bottom) {
521 region = region->humongous_start_region();
522 ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
523 marked_object_iterate(region, &objs);
524 }
525 } else {
526 ShenandoahObjectToOopClosure<T> objs(cl);
527 marked_object_iterate(region, &objs, top);
528 }
529 }
530
531 inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
532 if (region_idx < _num_regions) {
533 return _regions[region_idx];
534 } else {
535 return NULL;
536 }
537 }
538
539 inline void ShenandoahHeap::mark_complete_marking_context() {
540 _marking_context->mark_complete();
541 }
542
543 inline void ShenandoahHeap::mark_incomplete_marking_context() {
544 _marking_context->mark_incomplete();
545 }
546
547 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
548 assert (_marking_context->is_complete()," sanity");
549 return _marking_context;
550 }
551
552 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
553 return _marking_context;
554 }
555
556 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP