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