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.
22 *
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 template <class T>
89 inline oop ShenandoahHeap::update_with_forwarded_not_null(T* p, oop obj) {
90 if (in_collection_set(obj)) {
91 shenandoah_assert_forwarded_except(p, obj, is_full_gc_in_progress() || cancelled_gc() || is_degenerated_gc_in_progress());
92 obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
93 RawAccess<IS_NOT_NULL>::oop_store(p, obj);
94 }
95 #ifdef ASSERT
96 else {
97 shenandoah_assert_not_forwarded(p, obj);
98 }
99 #endif
100 return obj;
101 }
102
103 template <class T>
104 inline oop ShenandoahHeap::maybe_update_with_forwarded(T* p) {
105 T o = RawAccess<>::oop_load(p);
106 if (!CompressedOops::is_null(o)) {
107 oop obj = CompressedOops::decode_not_null(o);
108 return maybe_update_with_forwarded_not_null(p, obj);
109 } else {
110 return NULL;
111 }
112 }
113
114 template <class T>
115 inline oop ShenandoahHeap::evac_update_with_forwarded(T* p) {
116 T o = RawAccess<>::oop_load(p);
117 if (!CompressedOops::is_null(o)) {
118 oop heap_oop = CompressedOops::decode_not_null(o);
119 if (in_collection_set(heap_oop)) {
120 oop forwarded_oop = ShenandoahBarrierSet::resolve_forwarded_not_null(heap_oop);
121 if (forwarded_oop == heap_oop) {
122 forwarded_oop = evacuate_object(heap_oop, Thread::current());
123 }
124 oop prev = cas_oop(forwarded_oop, p, heap_oop);
125 if (prev == heap_oop) {
126 return forwarded_oop;
127 } else {
128 return NULL;
129 }
130 }
131 return heap_oop;
132 } else {
133 return NULL;
134 }
135 }
136
137 inline oop ShenandoahHeap::cas_oop(oop n, oop* addr, oop c) {
138 assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
139 return (oop) Atomic::cmpxchg(addr, c, n);
140 }
141
142 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, narrowOop c) {
143 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
144 narrowOop val = CompressedOops::encode(n);
145 return CompressedOops::decode((narrowOop) Atomic::cmpxchg(addr, c, val));
146 }
147
148 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, oop c) {
149 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
150 narrowOop cmp = CompressedOops::encode(c);
151 narrowOop val = CompressedOops::encode(n);
152 return CompressedOops::decode((narrowOop) Atomic::cmpxchg(addr, cmp, val));
153 }
154
155 template <class T>
156 inline oop ShenandoahHeap::maybe_update_with_forwarded_not_null(T* p, oop heap_oop) {
157 shenandoah_assert_not_in_cset_loc_except(p, !is_in(p) || is_full_gc_in_progress() || is_degenerated_gc_in_progress());
158 shenandoah_assert_correct(p, heap_oop);
159
160 if (in_collection_set(heap_oop)) {
161 oop forwarded_oop = ShenandoahBarrierSet::resolve_forwarded_not_null(heap_oop);
162 if (forwarded_oop == heap_oop) {
163 // E.g. during evacuation.
164 return forwarded_oop;
165 }
166
167 shenandoah_assert_forwarded_except(p, heap_oop, is_full_gc_in_progress() || is_degenerated_gc_in_progress());
168 shenandoah_assert_not_forwarded(p, forwarded_oop);
169 shenandoah_assert_not_in_cset_except(p, forwarded_oop, cancelled_gc());
170
171 // If this fails, another thread wrote to p before us, it will be logged in SATB and the
172 // reference be updated later.
173 oop witness = cas_oop(forwarded_oop, p, heap_oop);
174
175 if (witness != heap_oop) {
176 // CAS failed, someone had beat us to it. Normally, we would return the failure witness,
177 // because that would be the proper write of to-space object, enforced by strong barriers.
178 // However, there is a corner case with arraycopy. It can happen that a Java thread
179 // beats us with an arraycopy, which first copies the array, which potentially contains
180 // from-space refs, and only afterwards updates all from-space refs to to-space refs,
181 // which leaves a short window where the new array elements can be from-space.
182 // In this case, we can just resolve the result again. As we resolve, we need to consider
183 // the contended write might have been NULL.
184 oop result = ShenandoahBarrierSet::resolve_forwarded(witness);
185 shenandoah_assert_not_forwarded_except(p, result, (result == NULL));
186 shenandoah_assert_not_in_cset_except(p, result, (result == NULL) || cancelled_gc());
187 return result;
188 } else {
189 // Success! We have updated with known to-space copy. We have already asserted it is sane.
190 return forwarded_oop;
191 }
192 } else {
193 shenandoah_assert_not_forwarded(p, heap_oop);
194 return heap_oop;
195 }
196 }
197
198 inline bool ShenandoahHeap::cancelled_gc() const {
199 return _cancelled_gc.get() == CANCELLED;
200 }
201
202 inline bool ShenandoahHeap::check_cancelled_gc_and_yield(bool sts_active) {
203 if (! (sts_active && ShenandoahSuspendibleWorkers)) {
204 return cancelled_gc();
205 }
206
207 jbyte prev = _cancelled_gc.cmpxchg(NOT_CANCELLED, CANCELLABLE);
208 if (prev == CANCELLABLE || prev == NOT_CANCELLED) {
209 if (SuspendibleThreadSet::should_yield()) {
210 SuspendibleThreadSet::yield();
211 }
212
213 // Back to CANCELLABLE. The thread that poked NOT_CANCELLED first gets
214 // to restore to CANCELLABLE.
215 if (prev == CANCELLABLE) {
216 _cancelled_gc.set(CANCELLABLE);
217 }
218 return false;
219 } else {
220 return true;
221 }
222 }
223
224 inline void ShenandoahHeap::clear_cancelled_gc() {
225 _cancelled_gc.set(CANCELLABLE);
226 _oom_evac_handler.clear();
227 }
228
229 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
230 assert(UseTLAB, "TLABs should be enabled");
231
232 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
233 if (gclab == NULL) {
234 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
235 "Performance: thread should have GCLAB: %s", thread->name());
236 // No GCLABs in this thread, fallback to shared allocation
237 return NULL;
238 }
239 HeapWord* obj = gclab->allocate(size);
240 if (obj != NULL) {
241 return obj;
242 }
243 // Otherwise...
244 return allocate_from_gclab_slow(thread, size);
245 }
246
247 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
248 if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
249 // This thread went through the OOM during evac protocol and it is safe to return
250 // the forward pointer. It must not attempt to evacuate any more.
251 return ShenandoahBarrierSet::resolve_forwarded(p);
252 }
253
254 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
255
256 size_t size = p->size();
257
258 assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
259
260 bool alloc_from_gclab = true;
261 HeapWord* copy = NULL;
262
263 #ifdef ASSERT
264 if (ShenandoahOOMDuringEvacALot &&
265 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
266 copy = NULL;
267 } else {
268 #endif
269 if (UseTLAB) {
270 copy = allocate_from_gclab(thread, size);
271 }
272 if (copy == NULL) {
273 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
274 copy = allocate_memory(req);
275 alloc_from_gclab = false;
276 }
277 #ifdef ASSERT
278 }
279 #endif
280
281 if (copy == NULL) {
282 control_thread()->handle_alloc_failure_evac(size);
283
284 _oom_evac_handler.handle_out_of_memory_during_evacuation();
285
286 return ShenandoahBarrierSet::resolve_forwarded(p);
287 }
288
289 // Copy the object:
290 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
291
292 // Try to install the new forwarding pointer.
293 oop copy_val = oop(copy);
294 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
295 if (result == copy_val) {
296 // Successfully evacuated. Our copy is now the public one!
297 shenandoah_assert_correct(NULL, copy_val);
298 return copy_val;
299 } else {
300 // Failed to evacuate. We need to deal with the object that is left behind. Since this
301 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
302 // But if it happens to contain references to evacuated regions, those references would
303 // not get updated for this stale copy during this cycle, and we will crash while scanning
304 // it the next cycle.
305 //
306 // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
307 // object will overwrite this stale copy, or the filler object on LAB retirement will
308 // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
309 // have to explicitly overwrite the copy with the filler object. With that overwrite,
310 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
311 if (alloc_from_gclab) {
312 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
313 } else {
314 fill_with_object(copy, size);
315 shenandoah_assert_correct(NULL, copy_val);
316 }
317 shenandoah_assert_correct(NULL, result);
318 return result;
319 }
320 }
321
322 template<bool RESOLVE>
323 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
324 oop obj = oop(entry);
325 if (RESOLVE) {
326 obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
327 }
328 return !_marking_context->is_marked(obj);
329 }
330
331 inline bool ShenandoahHeap::in_collection_set(oop p) const {
332 assert(collection_set() != NULL, "Sanity");
333 return collection_set()->is_in(p);
334 }
335
336 inline bool ShenandoahHeap::in_collection_set_loc(void* p) const {
337 assert(collection_set() != NULL, "Sanity");
338 return collection_set()->is_in_loc(p);
339 }
340
341 inline bool ShenandoahHeap::is_stable() const {
342 return _gc_state.is_clear();
343 }
344
345 inline bool ShenandoahHeap::is_idle() const {
346 return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS);
347 }
348
349 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
350 return _gc_state.is_set(MARKING);
351 }
352
353 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
354 return _gc_state.is_set(EVACUATION);
355 }
356
357 inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
358 return _gc_state.is_set(mask);
359 }
360
361 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
362 return _degenerated_gc_in_progress.is_set();
363 }
364
365 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
366 return _full_gc_in_progress.is_set();
367 }
368
369 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
370 return _full_gc_move_in_progress.is_set();
371 }
372
373 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
374 return _gc_state.is_set(UPDATEREFS);
375 }
376
377 inline bool ShenandoahHeap::is_stw_gc_in_progress() const {
378 return is_full_gc_in_progress() || is_degenerated_gc_in_progress();
379 }
380
381 inline bool ShenandoahHeap::is_concurrent_strong_root_in_progress() const {
382 return _concurrent_strong_root_in_progress.is_set();
383 }
384
385 inline bool ShenandoahHeap::is_concurrent_weak_root_in_progress() const {
386 return _concurrent_weak_root_in_progress.is_set();
387 }
388
389 template<class T>
390 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
391 marked_object_iterate(region, cl, region->top());
392 }
393
394 template<class T>
395 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
396 assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
397
398 ShenandoahMarkingContext* const ctx = complete_marking_context();
399 assert(ctx->is_complete(), "sanity");
400
401 MarkBitMap* mark_bit_map = ctx->mark_bit_map();
402 HeapWord* tams = ctx->top_at_mark_start(region);
403
404 size_t skip_bitmap_delta = 1;
405 HeapWord* start = region->bottom();
406 HeapWord* end = MIN2(tams, region->end());
407
408 // Step 1. Scan below the TAMS based on bitmap data.
409 HeapWord* limit_bitmap = MIN2(limit, tams);
410
411 // Try to scan the initial candidate. If the candidate is above the TAMS, it would
412 // fail the subsequent "< limit_bitmap" checks, and fall through to Step 2.
413 HeapWord* cb = mark_bit_map->get_next_marked_addr(start, end);
414
415 intx dist = ShenandoahMarkScanPrefetch;
416 if (dist > 0) {
417 // Batched scan that prefetches the oop data, anticipating the access to
418 // either header, oop field, or forwarding pointer. Not that we cannot
419 // touch anything in oop, while it still being prefetched to get enough
420 // time for prefetch to work. This is why we try to scan the bitmap linearly,
421 // disregarding the object size. However, since we know forwarding pointer
422 // preceeds the object, we can skip over it. Once we cannot trust the bitmap,
423 // there is no point for prefetching the oop contents, as oop->size() will
424 // touch it prematurely.
425
426 // No variable-length arrays in standard C++, have enough slots to fit
427 // the prefetch distance.
428 static const int SLOT_COUNT = 256;
429 guarantee(dist <= SLOT_COUNT, "adjust slot count");
430 HeapWord* slots[SLOT_COUNT];
431
432 int avail;
433 do {
434 avail = 0;
435 for (int c = 0; (c < dist) && (cb < limit_bitmap); c++) {
436 Prefetch::read(cb, oopDesc::mark_offset_in_bytes());
437 slots[avail++] = cb;
438 cb += skip_bitmap_delta;
439 if (cb < limit_bitmap) {
440 cb = mark_bit_map->get_next_marked_addr(cb, limit_bitmap);
441 }
442 }
443
444 for (int c = 0; c < avail; c++) {
445 assert (slots[c] < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams));
446 assert (slots[c] < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit));
447 oop obj = oop(slots[c]);
448 assert(oopDesc::is_oop(obj), "sanity");
449 assert(ctx->is_marked(obj), "object expected to be marked");
450 cl->do_object(obj);
451 }
452 } while (avail > 0);
453 } else {
454 while (cb < limit_bitmap) {
455 assert (cb < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams));
456 assert (cb < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit));
457 oop obj = oop(cb);
458 assert(oopDesc::is_oop(obj), "sanity");
459 assert(ctx->is_marked(obj), "object expected to be marked");
460 cl->do_object(obj);
461 cb += skip_bitmap_delta;
462 if (cb < limit_bitmap) {
463 cb = mark_bit_map->get_next_marked_addr(cb, limit_bitmap);
464 }
465 }
466 }
467
468 // Step 2. Accurate size-based traversal, happens past the TAMS.
469 // This restarts the scan at TAMS, which makes sure we traverse all objects,
470 // regardless of what happened at Step 1.
471 HeapWord* cs = tams;
472 while (cs < limit) {
473 assert (cs >= tams, "only objects past TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams));
474 assert (cs < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit));
475 oop obj = oop(cs);
476 assert(oopDesc::is_oop(obj), "sanity");
477 assert(ctx->is_marked(obj), "object expected to be marked");
478 int size = obj->size();
479 cl->do_object(obj);
480 cs += size;
481 }
482 }
483
484 template <class T>
485 class ShenandoahObjectToOopClosure : public ObjectClosure {
486 T* _cl;
487 public:
488 ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
489
490 void do_object(oop obj) {
491 obj->oop_iterate(_cl);
492 }
493 };
494
495 template <class T>
496 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
497 T* _cl;
498 MemRegion _bounds;
499 public:
500 ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
501 _cl(cl), _bounds(bottom, top) {}
502
503 void do_object(oop obj) {
504 obj->oop_iterate(_cl, _bounds);
505 }
506 };
507
508 template<class T>
509 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
510 if (region->is_humongous()) {
511 HeapWord* bottom = region->bottom();
512 if (top > bottom) {
513 region = region->humongous_start_region();
514 ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
515 marked_object_iterate(region, &objs);
516 }
517 } else {
518 ShenandoahObjectToOopClosure<T> objs(cl);
519 marked_object_iterate(region, &objs, top);
520 }
521 }
522
523 inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
524 if (region_idx < _num_regions) {
525 return _regions[region_idx];
526 } else {
527 return NULL;
528 }
529 }
530
531 inline void ShenandoahHeap::mark_complete_marking_context() {
532 _marking_context->mark_complete();
533 }
534
535 inline void ShenandoahHeap::mark_incomplete_marking_context() {
536 _marking_context->mark_incomplete();
537 }
538
539 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
540 assert (_marking_context->is_complete()," sanity");
541 return _marking_context;
542 }
543
544 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
545 return _marking_context;
546 }
547
548 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP