1 /*
2 * Copyright (c) 2015, 2018, 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_VM_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
25 #define SHARE_VM_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/shenandoahBrooksPointer.inline.hpp"
34 #include "gc/shenandoah/shenandoahCollectionSet.hpp"
35 #include "gc/shenandoah/shenandoahCollectionSet.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/oop.inline.hpp"
44 #include "runtime/atomic.hpp"
45 #include "runtime/interfaceSupport.inline.hpp"
46 #include "runtime/prefetch.hpp"
47 #include "runtime/prefetch.inline.hpp"
48 #include "runtime/thread.hpp"
49 #include "utilities/copy.hpp"
50 #include "utilities/globalDefinitions.hpp"
51
52 template <class T>
53 void ShenandoahUpdateRefsClosure::do_oop_work(T* p) {
54 T o = RawAccess<>::oop_load(p);
55 if (!CompressedOops::is_null(o)) {
56 oop obj = CompressedOops::decode_not_null(o);
57 _heap->update_with_forwarded_not_null(p, obj);
58 }
59 }
60
61 void ShenandoahUpdateRefsClosure::do_oop(oop* p) { do_oop_work(p); }
62 void ShenandoahUpdateRefsClosure::do_oop(narrowOop* p) { do_oop_work(p); }
63
64 inline ShenandoahHeapRegion* ShenandoahRegionIterator::next() {
65 size_t new_index = Atomic::add((size_t) 1, &_index);
66 // get_region() provides the bounds-check and returns NULL on OOB.
67 return _heap->get_region(new_index - 1);
68 }
69
70 inline bool ShenandoahHeap::has_forwarded_objects() const {
71 return _gc_state.is_set(HAS_FORWARDED);
72 }
73
74 inline WorkGang* ShenandoahHeap::workers() const {
75 return _workers;
76 }
77
78 inline WorkGang* ShenandoahHeap::get_safepoint_workers() {
79 return _safepoint_workers;
80 }
81
82 inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
83 uintptr_t region_start = ((uintptr_t) addr);
84 uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
85 assert(index < num_regions(), "Region index is in bounds: " PTR_FORMAT, p2i(addr));
86 return index;
87 }
88
89 inline ShenandoahHeapRegion* const ShenandoahHeap::heap_region_containing(const void* addr) const {
90 size_t index = heap_region_index_containing(addr);
91 ShenandoahHeapRegion* const result = get_region(index);
92 assert(addr >= result->bottom() && addr < result->end(), "Heap region contains the address: " PTR_FORMAT, p2i(addr));
93 return result;
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 (oopDesc::equals_raw(forwarded_oop, heap_oop)) {
130 forwarded_oop = evacuate_object(heap_oop, Thread::current());
131 }
132 oop prev = atomic_compare_exchange_oop(forwarded_oop, p, heap_oop);
133 if (oopDesc::equals_raw(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::atomic_compare_exchange_oop(oop n, oop* addr, oop c) {
146 return (oop) Atomic::cmpxchg(n, addr, c);
147 }
148
149 inline oop ShenandoahHeap::atomic_compare_exchange_oop(oop n, narrowOop* addr, oop c) {
150 narrowOop cmp = CompressedOops::encode(c);
151 narrowOop val = CompressedOops::encode(n);
152 return CompressedOops::decode((narrowOop) Atomic::cmpxchg(val, addr, cmp));
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 (oopDesc::equals_raw(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_in_cset_except(p, forwarded_oop, cancelled_gc());
169
170 // If this fails, another thread wrote to p before us, it will be logged in SATB and the
171 // reference be updated later.
172 oop result = atomic_compare_exchange_oop(forwarded_oop, p, heap_oop);
173
174 if (oopDesc::equals_raw(result, heap_oop)) { // CAS successful.
175 return forwarded_oop;
176 } else {
177 // Note: we used to assert the following here. This doesn't work because sometimes, during
178 // marking/updating-refs, it can happen that a Java thread beats us with an arraycopy,
179 // which first copies the array, which potentially contains from-space refs, and only afterwards
180 // updates all from-space refs to to-space refs, which leaves a short window where the new array
181 // elements can be from-space.
182 // assert(CompressedOops::is_null(result) ||
183 // oopDesc::equals_raw(result, ShenandoahBarrierSet::resolve_oop_static_not_null(result)),
184 // "expect not forwarded");
185 return NULL;
186 }
187 } else {
188 shenandoah_assert_not_forwarded(p, heap_oop);
189 return heap_oop;
190 }
191 }
192
193 inline bool ShenandoahHeap::cancelled_gc() const {
194 return _cancelled_gc.get() == CANCELLED;
195 }
196
197 inline bool ShenandoahHeap::check_cancelled_gc_and_yield(bool sts_active) {
198 if (! (sts_active && ShenandoahSuspendibleWorkers)) {
199 return cancelled_gc();
200 }
201
202 jbyte prev = _cancelled_gc.cmpxchg(NOT_CANCELLED, CANCELLABLE);
203 if (prev == CANCELLABLE || prev == NOT_CANCELLED) {
204 if (SuspendibleThreadSet::should_yield()) {
205 SuspendibleThreadSet::yield();
206 }
207
208 // Back to CANCELLABLE. The thread that poked NOT_CANCELLED first gets
209 // to restore to CANCELLABLE.
210 if (prev == CANCELLABLE) {
211 _cancelled_gc.set(CANCELLABLE);
212 }
213 return false;
214 } else {
215 return true;
216 }
217 }
218
219 inline bool ShenandoahHeap::try_cancel_gc() {
220 while (true) {
221 jbyte prev = _cancelled_gc.cmpxchg(CANCELLED, CANCELLABLE);
222 if (prev == CANCELLABLE) return true;
223 else if (prev == CANCELLED) return false;
224 assert(ShenandoahSuspendibleWorkers, "should not get here when not using suspendible workers");
225 assert(prev == NOT_CANCELLED, "must be NOT_CANCELLED");
226 {
227 // We need to provide a safepoint here, otherwise we might
228 // spin forever if a SP is pending.
229 ThreadBlockInVM sp(JavaThread::current());
230 SpinPause();
231 }
232 }
233 }
234
235 inline void ShenandoahHeap::clear_cancelled_gc() {
236 _cancelled_gc.set(CANCELLABLE);
237 _oom_evac_handler.clear();
238 }
239
240 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
241 assert(UseTLAB, "TLABs should be enabled");
242
243 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
244 if (gclab == NULL) {
245 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
246 "Performance: thread should have GCLAB: %s", thread->name());
247 // No GCLABs in this thread, fallback to shared allocation
248 return NULL;
249 }
250 HeapWord* obj = gclab->allocate(size);
251 if (obj != NULL) {
252 return obj;
253 }
254 // Otherwise...
255 return allocate_from_gclab_slow(thread, size);
256 }
257
258 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
259 if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
260 // This thread went through the OOM during evac protocol and it is safe to return
261 // the forward pointer. It must not attempt to evacuate any more.
262 return ShenandoahBarrierSet::resolve_forwarded(p);
263 }
264
265 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
266
267 size_t size_no_fwdptr = (size_t) p->size();
268 size_t size_with_fwdptr = size_no_fwdptr + ShenandoahBrooksPointer::word_size();
269
270 assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
271
272 bool alloc_from_gclab = true;
273 HeapWord* filler = NULL;
274
275 #ifdef ASSERT
276 if (ShenandoahOOMDuringEvacALot &&
277 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
278 filler = NULL;
279 } else {
280 #endif
281 if (UseTLAB) {
282 filler = allocate_from_gclab(thread, size_with_fwdptr);
283 }
284 if (filler == NULL) {
285 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size_with_fwdptr);
286 filler = allocate_memory(req);
287 alloc_from_gclab = false;
288 }
289 #ifdef ASSERT
290 }
291 #endif
292
293 if (filler == NULL) {
294 control_thread()->handle_alloc_failure_evac(size_with_fwdptr);
295
296 _oom_evac_handler.handle_out_of_memory_during_evacuation();
297
298 return ShenandoahBarrierSet::resolve_forwarded(p);
299 }
300
301 // Copy the object and initialize its forwarding ptr:
302 HeapWord* copy = filler + ShenandoahBrooksPointer::word_size();
303 oop copy_val = oop(copy);
304
305 Copy::aligned_disjoint_words((HeapWord*) p, copy, size_no_fwdptr);
306 ShenandoahBrooksPointer::initialize(oop(copy));
307
308 // Try to install the new forwarding pointer.
309 oop result = ShenandoahBrooksPointer::try_update_forwardee(p, copy_val);
310
311 if (oopDesc::equals_raw(result, p)) {
312 // Successfully evacuated. Our copy is now the public one!
313 shenandoah_assert_correct(NULL, copy_val);
314 return copy_val;
315 } else {
316 // Failed to evacuate. We need to deal with the object that is left behind. Since this
317 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
318 // But if it happens to contain references to evacuated regions, those references would
319 // not get updated for this stale copy during this cycle, and we will crash while scanning
320 // it the next cycle.
321 //
322 // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
323 // object will overwrite this stale copy, or the filler object on LAB retirement will
324 // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
325 // have to explicitly overwrite the copy with the filler object. With that overwrite,
326 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
327 if (alloc_from_gclab) {
328 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(filler, size_with_fwdptr);
329 } else {
330 fill_with_object(copy, size_no_fwdptr);
331 }
332 shenandoah_assert_correct(NULL, copy_val);
333 shenandoah_assert_correct(NULL, result);
334 return result;
335 }
336 }
337
338 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
339 return !_marking_context->is_marked(oop(entry));
340 }
341
342 template <class T>
343 inline bool ShenandoahHeap::in_collection_set(T p) const {
344 HeapWord* obj = (HeapWord*) p;
345 assert(collection_set() != NULL, "Sanity");
346 assert(is_in(obj), "should be in heap");
347
348 return collection_set()->is_in(obj);
349 }
350
351 inline bool ShenandoahHeap::is_stable() const {
352 return _gc_state.is_clear();
353 }
354
355 inline bool ShenandoahHeap::is_idle() const {
356 return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS | TRAVERSAL);
357 }
358
359 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
360 return _gc_state.is_set(MARKING);
361 }
362
363 inline bool ShenandoahHeap::is_concurrent_traversal_in_progress() const {
364 return _gc_state.is_set(TRAVERSAL);
365 }
366
367 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
368 return _gc_state.is_set(EVACUATION);
369 }
370
371 inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
372 return _gc_state.is_set(mask);
373 }
374
375 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
376 return _degenerated_gc_in_progress.is_set();
377 }
378
379 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
380 return _full_gc_in_progress.is_set();
381 }
382
383 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
384 return _full_gc_move_in_progress.is_set();
385 }
386
387 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
388 return _gc_state.is_set(UPDATEREFS);
389 }
390
391 template<class T>
392 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
393 marked_object_iterate(region, cl, region->top());
394 }
395
396 template<class T>
397 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
398 assert(ShenandoahBrooksPointer::word_offset() < 0, "skip_delta calculation below assumes the forwarding ptr is before obj");
399 assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
400
401 ShenandoahMarkingContext* const ctx = complete_marking_context();
402 assert(ctx->is_complete(), "sanity");
403
404 MarkBitMap* mark_bit_map = ctx->mark_bit_map();
405 HeapWord* tams = ctx->top_at_mark_start(region);
406
407 size_t skip_bitmap_delta = ShenandoahBrooksPointer::word_size() + 1;
408 size_t skip_objsize_delta = ShenandoahBrooksPointer::word_size() /* + actual obj.size() below */;
409 HeapWord* start = region->bottom() + ShenandoahBrooksPointer::word_size();
410 HeapWord* end = MIN2(tams + ShenandoahBrooksPointer::word_size(), region->end());
411
412 // Step 1. Scan below the TAMS based on bitmap data.
413 HeapWord* limit_bitmap = MIN2(limit, tams);
414
415 // Try to scan the initial candidate. If the candidate is above the TAMS, it would
416 // fail the subsequent "< limit_bitmap" checks, and fall through to Step 2.
417 HeapWord* cb = mark_bit_map->get_next_marked_addr(start, end);
418
419 intx dist = ShenandoahMarkScanPrefetch;
420 if (dist > 0) {
421 // Batched scan that prefetches the oop data, anticipating the access to
422 // either header, oop field, or forwarding pointer. Not that we cannot
423 // touch anything in oop, while it still being prefetched to get enough
424 // time for prefetch to work. This is why we try to scan the bitmap linearly,
425 // disregarding the object size. However, since we know forwarding pointer
426 // preceeds the object, we can skip over it. Once we cannot trust the bitmap,
427 // there is no point for prefetching the oop contents, as oop->size() will
428 // touch it prematurely.
429
430 // No variable-length arrays in standard C++, have enough slots to fit
431 // the prefetch distance.
432 static const int SLOT_COUNT = 256;
433 guarantee(dist <= SLOT_COUNT, "adjust slot count");
434 HeapWord* slots[SLOT_COUNT];
435
436 int avail;
437 do {
438 avail = 0;
439 for (int c = 0; (c < dist) && (cb < limit_bitmap); c++) {
440 Prefetch::read(cb, ShenandoahBrooksPointer::byte_offset());
441 slots[avail++] = cb;
442 cb += skip_bitmap_delta;
443 if (cb < limit_bitmap) {
444 cb = mark_bit_map->get_next_marked_addr(cb, limit_bitmap);
445 }
446 }
447
448 for (int c = 0; c < avail; c++) {
449 assert (slots[c] < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams));
450 assert (slots[c] < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit));
451 oop obj = oop(slots[c]);
452 assert(oopDesc::is_oop(obj), "sanity");
453 assert(ctx->is_marked(obj), "object expected to be marked");
454 cl->do_object(obj);
455 }
456 } while (avail > 0);
457 } else {
458 while (cb < limit_bitmap) {
459 assert (cb < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams));
460 assert (cb < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit));
461 oop obj = oop(cb);
462 assert(oopDesc::is_oop(obj), "sanity");
463 assert(ctx->is_marked(obj), "object expected to be marked");
464 cl->do_object(obj);
465 cb += skip_bitmap_delta;
466 if (cb < limit_bitmap) {
467 cb = mark_bit_map->get_next_marked_addr(cb, limit_bitmap);
468 }
469 }
470 }
471
472 // Step 2. Accurate size-based traversal, happens past the TAMS.
473 // This restarts the scan at TAMS, which makes sure we traverse all objects,
474 // regardless of what happened at Step 1.
475 HeapWord* cs = tams + ShenandoahBrooksPointer::word_size();
476 while (cs < limit) {
477 assert (cs > tams, "only objects past TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams));
478 assert (cs < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit));
479 oop obj = oop(cs);
480 assert(oopDesc::is_oop(obj), "sanity");
481 assert(ctx->is_marked(obj), "object expected to be marked");
482 int size = obj->size();
483 cl->do_object(obj);
484 cs += size + skip_objsize_delta;
485 }
486 }
487
488 template <class T>
489 class ShenandoahObjectToOopClosure : public ObjectClosure {
490 T* _cl;
491 public:
492 ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
493
494 void do_object(oop obj) {
495 obj->oop_iterate(_cl);
496 }
497 };
498
499 template <class T>
500 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
501 T* _cl;
502 MemRegion _bounds;
503 public:
504 ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
505 _cl(cl), _bounds(bottom, top) {}
506
507 void do_object(oop obj) {
508 obj->oop_iterate(_cl, _bounds);
509 }
510 };
511
512 template<class T>
513 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
514 if (region->is_humongous()) {
515 HeapWord* bottom = region->bottom();
516 if (top > bottom) {
517 region = region->humongous_start_region();
518 ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
519 marked_object_iterate(region, &objs);
520 }
521 } else {
522 ShenandoahObjectToOopClosure<T> objs(cl);
523 marked_object_iterate(region, &objs, top);
524 }
525 }
526
527 inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
528 if (region_idx < _num_regions) {
529 return _regions[region_idx];
530 } else {
531 return NULL;
532 }
533 }
534
535 inline void ShenandoahHeap::mark_complete_marking_context() {
536 _marking_context->mark_complete();
537 }
538
539 inline void ShenandoahHeap::mark_incomplete_marking_context() {
540 _marking_context->mark_incomplete();
541 }
542
543 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
544 assert (_marking_context->is_complete()," sanity");
545 return _marking_context;
546 }
547
548 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
549 return _marking_context;
550 }
551
552 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP