1 /*
2 * Copyright (c) 2015, 2019, Red Hat, Inc. All rights reserved.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
25 #define SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
26
27 #include "classfile/javaClasses.inline.hpp"
28 #include "gc/shared/markBitMap.inline.hpp"
29 #include "gc/shared/threadLocalAllocBuffer.inline.hpp"
30 #include "gc/shared/suspendibleThreadSet.hpp"
31 #include "gc/shenandoah/shenandoahAsserts.hpp"
32 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
33 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
34 #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
35 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
36 #include "gc/shenandoah/shenandoahHeap.hpp"
37 #include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
38 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
39 #include "gc/shenandoah/shenandoahControlThread.hpp"
40 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
41 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
42 #include "oops/compressedOops.inline.hpp"
43 #include "oops/oop.inline.hpp"
44 #include "runtime/atomic.hpp"
45 #include "runtime/prefetch.inline.hpp"
46 #include "runtime/thread.hpp"
47 #include "utilities/copy.hpp"
48 #include "utilities/globalDefinitions.hpp"
49
50
51 inline ShenandoahHeapRegion* ShenandoahRegionIterator::next() {
52 size_t new_index = Atomic::add((size_t) 1, &_index);
53 // get_region() provides the bounds-check and returns NULL on OOB.
54 return _heap->get_region(new_index - 1);
55 }
56
57 inline bool ShenandoahHeap::has_forwarded_objects() const {
58 return _gc_state.is_set(HAS_FORWARDED);
59 }
60
61 inline WorkGang* ShenandoahHeap::workers() const {
62 return _workers;
63 }
64
65 inline WorkGang* ShenandoahHeap::get_safepoint_workers() {
66 return _safepoint_workers;
67 }
68
69 inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
70 uintptr_t region_start = ((uintptr_t) addr);
71 uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
72 assert(index < num_regions(), "Region index is in bounds: " PTR_FORMAT, p2i(addr));
73 return index;
74 }
75
76 inline ShenandoahHeapRegion* const ShenandoahHeap::heap_region_containing(const void* addr) const {
77 size_t index = heap_region_index_containing(addr);
78 ShenandoahHeapRegion* const result = get_region(index);
79 assert(addr >= result->bottom() && addr < result->end(), "Heap region contains the address: " PTR_FORMAT, p2i(addr));
80 return result;
81 }
82
83 template <class T>
84 inline oop ShenandoahHeap::update_with_forwarded_not_null(T* p, oop obj) {
85 if (in_collection_set(obj)) {
86 shenandoah_assert_forwarded_except(p, obj, is_full_gc_in_progress() || cancelled_gc() || is_degenerated_gc_in_progress());
87 obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
88 RawAccess<IS_NOT_NULL>::oop_store(p, obj);
89 }
90 #ifdef ASSERT
91 else {
92 shenandoah_assert_not_forwarded(p, obj);
93 }
94 #endif
95 return obj;
96 }
97
98 template <class T>
99 inline oop ShenandoahHeap::maybe_update_with_forwarded(T* p) {
100 T o = RawAccess<>::oop_load(p);
101 if (!CompressedOops::is_null(o)) {
102 oop obj = CompressedOops::decode_not_null(o);
103 return maybe_update_with_forwarded_not_null(p, obj);
104 } else {
105 return NULL;
106 }
107 }
108
109 template <class T>
110 inline oop ShenandoahHeap::evac_update_with_forwarded(T* p) {
111 T o = RawAccess<>::oop_load(p);
112 if (!CompressedOops::is_null(o)) {
113 oop heap_oop = CompressedOops::decode_not_null(o);
114 if (in_collection_set(heap_oop)) {
115 oop forwarded_oop = ShenandoahBarrierSet::resolve_forwarded_not_null(heap_oop);
116 if (oopDesc::equals_raw(forwarded_oop, heap_oop)) {
117 forwarded_oop = evacuate_object(heap_oop, Thread::current());
118 }
119 oop prev = cas_oop(forwarded_oop, p, heap_oop);
120 if (oopDesc::equals_raw(prev, heap_oop)) {
121 return forwarded_oop;
122 } else {
123 return NULL;
124 }
125 }
126 return heap_oop;
127 } else {
128 return NULL;
129 }
130 }
131
132 inline oop ShenandoahHeap::cas_oop(oop n, oop* addr, oop c) {
133 return (oop) Atomic::cmpxchg(n, addr, c);
134 }
135
136 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, oop c) {
137 narrowOop cmp = CompressedOops::encode(c);
138 narrowOop val = CompressedOops::encode(n);
139 return CompressedOops::decode((narrowOop) Atomic::cmpxchg(val, addr, cmp));
140 }
141
142 template <class T>
143 inline oop ShenandoahHeap::maybe_update_with_forwarded_not_null(T* p, oop heap_oop) {
144 shenandoah_assert_not_in_cset_loc_except(p, !is_in(p) || is_full_gc_in_progress() || is_degenerated_gc_in_progress());
145 shenandoah_assert_correct(p, heap_oop);
146
147 if (in_collection_set(heap_oop)) {
148 oop forwarded_oop = ShenandoahBarrierSet::resolve_forwarded_not_null(heap_oop);
149 if (oopDesc::equals_raw(forwarded_oop, heap_oop)) {
150 // E.g. during evacuation.
151 return forwarded_oop;
152 }
153
154 shenandoah_assert_forwarded_except(p, heap_oop, is_full_gc_in_progress() || is_degenerated_gc_in_progress());
155 shenandoah_assert_not_forwarded(p, forwarded_oop);
156 shenandoah_assert_not_in_cset_except(p, forwarded_oop, cancelled_gc());
157
158 // If this fails, another thread wrote to p before us, it will be logged in SATB and the
159 // reference be updated later.
160 oop witness = cas_oop(forwarded_oop, p, heap_oop);
161
162 if (!oopDesc::equals_raw(witness, heap_oop)) {
163 // CAS failed, someone had beat us to it. Normally, we would return the failure witness,
164 // because that would be the proper write of to-space object, enforced by strong barriers.
165 // However, there is a corner case with arraycopy. It can happen that a Java thread
166 // beats us with an arraycopy, which first copies the array, which potentially contains
167 // from-space refs, and only afterwards updates all from-space refs to to-space refs,
168 // which leaves a short window where the new array elements can be from-space.
169 // In this case, we can just resolve the result again. As we resolve, we need to consider
170 // the contended write might have been NULL.
171 oop result = ShenandoahBarrierSet::resolve_forwarded(witness);
172 shenandoah_assert_not_forwarded_except(p, result, (result == NULL));
173 shenandoah_assert_not_in_cset_except(p, result, (result == NULL) || cancelled_gc());
174 return result;
175 } else {
176 // Success! We have updated with known to-space copy. We have already asserted it is sane.
177 return forwarded_oop;
178 }
179 } else {
180 shenandoah_assert_not_forwarded(p, heap_oop);
181 return heap_oop;
182 }
183 }
184
185 inline bool ShenandoahHeap::cancelled_gc() const {
186 return _cancelled_gc.get() == CANCELLED;
187 }
188
189 inline bool ShenandoahHeap::check_cancelled_gc_and_yield(bool sts_active) {
190 if (!sts_active) {
191 return cancelled_gc();
192 }
193
194 jbyte prev = _cancelled_gc.cmpxchg(NOT_CANCELLED, CANCELLABLE);
195 if (prev == CANCELLABLE || prev == NOT_CANCELLED) {
196 if (SuspendibleThreadSet::should_yield()) {
197 SuspendibleThreadSet::yield();
198 }
199
200 // Back to CANCELLABLE. The thread that poked NOT_CANCELLED first gets
201 // to restore to CANCELLABLE.
202 if (prev == CANCELLABLE) {
203 _cancelled_gc.set(CANCELLABLE);
204 }
205 return false;
206 } else {
207 return true;
208 }
209 }
210
211 inline void ShenandoahHeap::clear_cancelled_gc() {
212 _cancelled_gc.set(CANCELLABLE);
213 _oom_evac_handler.clear();
214 }
215
216 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
217 assert(UseTLAB, "TLABs should be enabled");
218
219 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
220 if (gclab == NULL) {
221 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
222 "Performance: thread should have GCLAB: %s", thread->name());
223 // No GCLABs in this thread, fallback to shared allocation
224 return NULL;
225 }
226 HeapWord* obj = gclab->allocate(size);
227 if (obj != NULL) {
228 return obj;
229 }
230 // Otherwise...
231 return allocate_from_gclab_slow(thread, size);
232 }
233
234 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
235 if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
236 // This thread went through the OOM during evac protocol and it is safe to return
237 // the forward pointer. It must not attempt to evacuate any more.
238 return ShenandoahBarrierSet::resolve_forwarded(p);
239 }
240
241 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
242
243 size_t size = p->size();
244
245 assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
246
247 bool alloc_from_gclab = true;
248 HeapWord* copy = NULL;
249
250 #ifdef ASSERT
251 if (ShenandoahOOMDuringEvacALot &&
252 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
253 copy = NULL;
254 } else {
255 #endif
256 if (UseTLAB) {
257 copy = allocate_from_gclab(thread, size);
258 }
259 if (copy == NULL) {
260 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
261 copy = allocate_memory(req);
262 alloc_from_gclab = false;
263 }
264 #ifdef ASSERT
265 }
266 #endif
267
268 if (copy == NULL) {
269 control_thread()->handle_alloc_failure_evac(size);
270
271 _oom_evac_handler.handle_out_of_memory_during_evacuation();
272
273 return ShenandoahBarrierSet::resolve_forwarded(p);
274 }
275
276 // Copy the object:
277 Copy::aligned_disjoint_words((HeapWord*) p, copy, size);
278
279 // Try to install the new forwarding pointer.
280 oop copy_val = oop(copy);
281 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
282 if (oopDesc::equals_raw(result, copy_val)) {
283 // Successfully evacuated. Our copy is now the public one!
284 shenandoah_assert_correct(NULL, copy_val);
285 return copy_val;
286 } else {
287 // Failed to evacuate. We need to deal with the object that is left behind. Since this
288 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
289 // But if it happens to contain references to evacuated regions, those references would
290 // not get updated for this stale copy during this cycle, and we will crash while scanning
291 // it the next cycle.
292 //
293 // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
294 // object will overwrite this stale copy, or the filler object on LAB retirement will
295 // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
296 // have to explicitly overwrite the copy with the filler object. With that overwrite,
297 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
298 if (alloc_from_gclab) {
299 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
300 } else {
301 fill_with_object(copy, size);
302 shenandoah_assert_correct(NULL, copy_val);
303 }
304 shenandoah_assert_correct(NULL, result);
305 return result;
306 }
307 }
308
309 template<bool RESOLVE>
310 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
311 oop obj = oop(entry);
312 if (RESOLVE) {
313 obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
314 }
315 return !_marking_context->is_marked(obj);
316 }
317
318 template <class T>
319 inline bool ShenandoahHeap::in_collection_set(T p) const {
320 HeapWord* obj = (HeapWord*) p;
321 assert(collection_set() != NULL, "Sanity");
322 assert(is_in(obj), "should be in heap");
323
324 return collection_set()->is_in(obj);
325 }
326
327 inline bool ShenandoahHeap::is_stable() const {
328 return _gc_state.is_clear();
329 }
330
331 inline bool ShenandoahHeap::is_idle() const {
332 return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS | TRAVERSAL);
333 }
334
335 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
336 return _gc_state.is_set(MARKING);
337 }
338
339 inline bool ShenandoahHeap::is_concurrent_traversal_in_progress() const {
340 return _gc_state.is_set(TRAVERSAL);
341 }
342
343 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
344 return _gc_state.is_set(EVACUATION);
345 }
346
347 inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
348 return _gc_state.is_set(mask);
349 }
350
351 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
352 return _degenerated_gc_in_progress.is_set();
353 }
354
355 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
356 return _full_gc_in_progress.is_set();
357 }
358
359 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
360 return _full_gc_move_in_progress.is_set();
361 }
362
363 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
364 return _gc_state.is_set(UPDATEREFS);
365 }
366
367 template<class T>
368 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
369 marked_object_iterate(region, cl, region->top());
370 }
371
372 template<class T>
373 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
374 assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
375
376 ShenandoahMarkingContext* const ctx = complete_marking_context();
377 assert(ctx->is_complete(), "sanity");
378
379 MarkBitMap* mark_bit_map = ctx->mark_bit_map();
380 HeapWord* tams = ctx->top_at_mark_start(region);
381
382 size_t skip_bitmap_delta = 1;
383 HeapWord* start = region->bottom();
384 HeapWord* end = MIN2(tams, region->end());
385
386 // Step 1. Scan below the TAMS based on bitmap data.
387 HeapWord* limit_bitmap = MIN2(limit, tams);
388
389 // Try to scan the initial candidate. If the candidate is above the TAMS, it would
390 // fail the subsequent "< limit_bitmap" checks, and fall through to Step 2.
391 HeapWord* cb = mark_bit_map->get_next_marked_addr(start, end);
392
393 intx dist = ShenandoahMarkScanPrefetch;
394 if (dist > 0) {
395 // Batched scan that prefetches the oop data, anticipating the access to
396 // either header, oop field, or forwarding pointer. Not that we cannot
397 // touch anything in oop, while it still being prefetched to get enough
398 // time for prefetch to work. This is why we try to scan the bitmap linearly,
399 // disregarding the object size. However, since we know forwarding pointer
400 // preceeds the object, we can skip over it. Once we cannot trust the bitmap,
401 // there is no point for prefetching the oop contents, as oop->size() will
402 // touch it prematurely.
403
404 // No variable-length arrays in standard C++, have enough slots to fit
405 // the prefetch distance.
406 static const int SLOT_COUNT = 256;
407 guarantee(dist <= SLOT_COUNT, "adjust slot count");
408 HeapWord* slots[SLOT_COUNT];
409
410 int avail;
411 do {
412 avail = 0;
413 for (int c = 0; (c < dist) && (cb < limit_bitmap); c++) {
414 Prefetch::read(cb, oopDesc::mark_offset_in_bytes());
415 slots[avail++] = cb;
416 cb += skip_bitmap_delta;
417 if (cb < limit_bitmap) {
418 cb = mark_bit_map->get_next_marked_addr(cb, limit_bitmap);
419 }
420 }
421
422 for (int c = 0; c < avail; c++) {
423 assert (slots[c] < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams));
424 assert (slots[c] < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit));
425 oop obj = oop(slots[c]);
426 assert(oopDesc::is_oop(obj), "sanity");
427 assert(ctx->is_marked(obj), "object expected to be marked");
428 cl->do_object(obj);
429 }
430 } while (avail > 0);
431 } else {
432 while (cb < limit_bitmap) {
433 assert (cb < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams));
434 assert (cb < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit));
435 oop obj = oop(cb);
436 assert(oopDesc::is_oop(obj), "sanity");
437 assert(ctx->is_marked(obj), "object expected to be marked");
438 cl->do_object(obj);
439 cb += skip_bitmap_delta;
440 if (cb < limit_bitmap) {
441 cb = mark_bit_map->get_next_marked_addr(cb, limit_bitmap);
442 }
443 }
444 }
445
446 // Step 2. Accurate size-based traversal, happens past the TAMS.
447 // This restarts the scan at TAMS, which makes sure we traverse all objects,
448 // regardless of what happened at Step 1.
449 HeapWord* cs = tams;
450 while (cs < limit) {
451 assert (cs >= tams, "only objects past TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams));
452 assert (cs < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit));
453 oop obj = oop(cs);
454 assert(oopDesc::is_oop(obj), "sanity");
455 assert(ctx->is_marked(obj), "object expected to be marked");
456 int size = obj->size();
457 cl->do_object(obj);
458 cs += size;
459 }
460 }
461
462 template <class T>
463 class ShenandoahObjectToOopClosure : public ObjectClosure {
464 T* _cl;
465 public:
466 ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
467
468 void do_object(oop obj) {
469 obj->oop_iterate(_cl);
470 }
471 };
472
473 template <class T>
474 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
475 T* _cl;
476 MemRegion _bounds;
477 public:
478 ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
479 _cl(cl), _bounds(bottom, top) {}
480
481 void do_object(oop obj) {
482 obj->oop_iterate(_cl, _bounds);
483 }
484 };
485
486 template<class T>
487 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
488 if (region->is_humongous()) {
489 HeapWord* bottom = region->bottom();
490 if (top > bottom) {
491 region = region->humongous_start_region();
492 ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
493 marked_object_iterate(region, &objs);
494 }
495 } else {
496 ShenandoahObjectToOopClosure<T> objs(cl);
497 marked_object_iterate(region, &objs, top);
498 }
499 }
500
501 inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
502 if (region_idx < _num_regions) {
503 return _regions[region_idx];
504 } else {
505 return NULL;
506 }
507 }
508
509 inline void ShenandoahHeap::mark_complete_marking_context() {
510 _marking_context->mark_complete();
511 }
512
513 inline void ShenandoahHeap::mark_incomplete_marking_context() {
514 _marking_context->mark_incomplete();
515 }
516
517 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
518 assert (_marking_context->is_complete()," sanity");
519 return _marking_context;
520 }
521
522 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
523 return _marking_context;
524 }
525
526 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP