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