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 obj = CompressedOops::decode_not_null(o);
119 if (in_collection_set(obj)) {
120 oop fwd = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
121 if (fwd == obj) {
122 fwd = evacuate_object(obj, Thread::current());
123 }
124 if (fwd != obj) { // evac failure otherwise
125 oop prev = cas_oop(fwd, p, obj);
126 if (prev == obj) {
127 return fwd;
128 }
129 }
130 }
131 }
132 return NULL;
133 }
134
135 inline oop ShenandoahHeap::cas_oop(oop n, oop* addr, oop c) {
136 assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
137 return (oop) Atomic::cmpxchg(addr, c, n);
138 }
139
140 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, narrowOop c) {
141 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
142 narrowOop val = CompressedOops::encode(n);
143 return CompressedOops::decode((narrowOop) Atomic::cmpxchg(addr, c, val));
144 }
145
146 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, oop c) {
147 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
148 narrowOop cmp = CompressedOops::encode(c);
149 narrowOop val = CompressedOops::encode(n);
150 return CompressedOops::decode((narrowOop) Atomic::cmpxchg(addr, cmp, val));
151 }
152
153 template <class T>
154 inline oop ShenandoahHeap::maybe_update_with_forwarded_not_null(T* p, oop heap_oop) {
155 shenandoah_assert_not_in_cset_loc_except(p, !is_in(p) || is_full_gc_in_progress() || is_degenerated_gc_in_progress());
156 shenandoah_assert_correct(p, heap_oop);
157
158 if (in_collection_set(heap_oop)) {
159 oop forwarded_oop = ShenandoahBarrierSet::resolve_forwarded_not_null(heap_oop);
160 if (forwarded_oop == heap_oop) {
161 // E.g. during evacuation.
162 return forwarded_oop;
163 }
164
165 shenandoah_assert_forwarded_except(p, heap_oop, is_full_gc_in_progress() || is_degenerated_gc_in_progress());
166 shenandoah_assert_not_forwarded(p, forwarded_oop);
167 shenandoah_assert_not_in_cset_except(p, forwarded_oop, cancelled_gc());
168
169 // If this fails, another thread wrote to p before us, it will be logged in SATB and the
170 // reference be updated later.
171 oop witness = cas_oop(forwarded_oop, p, heap_oop);
172
173 if (witness != heap_oop) {
174 // CAS failed, someone had beat us to it. Normally, we would return the failure witness,
175 // because that would be the proper write of to-space object, enforced by strong barriers.
176 // However, there is a corner case with arraycopy. It can happen that a Java thread
177 // beats us with an arraycopy, which first copies the array, which potentially contains
178 // from-space refs, and only afterwards updates all from-space refs to to-space refs,
179 // which leaves a short window where the new array elements can be from-space.
180 // In this case, we can just resolve the result again. As we resolve, we need to consider
181 // the contended write might have been NULL.
182 oop result = ShenandoahBarrierSet::resolve_forwarded(witness);
183 shenandoah_assert_not_forwarded_except(p, result, (result == NULL));
184 shenandoah_assert_not_in_cset_except(p, result, (result == NULL) || cancelled_gc());
185 return result;
186 } else {
187 // Success! We have updated with known to-space copy. We have already asserted it is sane.
188 return forwarded_oop;
189 }
190 } else {
191 shenandoah_assert_not_forwarded(p, heap_oop);
192 return heap_oop;
193 }
194 }
195
196 inline bool ShenandoahHeap::cancelled_gc() const {
197 return _cancelled_gc.get() == CANCELLED;
198 }
199
200 inline bool ShenandoahHeap::check_cancelled_gc_and_yield(bool sts_active) {
201 if (! (sts_active && ShenandoahSuspendibleWorkers)) {
202 return cancelled_gc();
203 }
204
205 jbyte prev = _cancelled_gc.cmpxchg(NOT_CANCELLED, CANCELLABLE);
206 if (prev == CANCELLABLE || prev == NOT_CANCELLED) {
207 if (SuspendibleThreadSet::should_yield()) {
208 SuspendibleThreadSet::yield();
209 }
210
211 // Back to CANCELLABLE. The thread that poked NOT_CANCELLED first gets
212 // to restore to CANCELLABLE.
213 if (prev == CANCELLABLE) {
214 _cancelled_gc.set(CANCELLABLE);
215 }
216 return false;
217 } else {
218 return true;
219 }
220 }
221
222 inline void ShenandoahHeap::clear_cancelled_gc() {
223 _cancelled_gc.set(CANCELLABLE);
224 _oom_evac_handler.clear();
225 }
226
227 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
228 assert(UseTLAB, "TLABs should be enabled");
229
230 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
231 if (gclab == NULL) {
232 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
233 "Performance: thread should have GCLAB: %s", thread->name());
234 // No GCLABs in this thread, fallback to shared allocation
235 return NULL;
236 }
237 HeapWord* obj = gclab->allocate(size);
238 if (obj != NULL) {
239 return obj;
240 }
241 // Otherwise...
242 return allocate_from_gclab_slow(thread, size);
243 }
244
245 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
246 if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
247 // This thread went through the OOM during evac protocol and it is safe to return
248 // the forward pointer. It must not attempt to evacuate any more.
249 return ShenandoahBarrierSet::resolve_forwarded(p);
250 }
251
252 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
253
254 size_t size = p->size();
255
256 assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
257
258 bool alloc_from_gclab = true;
259 HeapWord* copy = NULL;
260
261 #ifdef ASSERT
262 if (ShenandoahOOMDuringEvacALot &&
263 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
264 copy = NULL;
265 } else {
266 #endif
267 if (UseTLAB) {
268 copy = allocate_from_gclab(thread, size);
269 }
270 if (copy == NULL) {
271 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
272 copy = allocate_memory(req);
273 alloc_from_gclab = false;
274 }
275 #ifdef ASSERT
276 }
277 #endif
278
279 if (copy == NULL) {
280 control_thread()->handle_alloc_failure_evac(size);
281
282 _oom_evac_handler.handle_out_of_memory_during_evacuation();
283
284 return ShenandoahBarrierSet::resolve_forwarded(p);
285 }
286
287 // Copy the object:
288 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
289
290 // Try to install the new forwarding pointer.
291 oop copy_val = oop(copy);
292 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
293 if (result == copy_val) {
294 // Successfully evacuated. Our copy is now the public one!
295 shenandoah_assert_correct(NULL, copy_val);
296 return copy_val;
297 } else {
298 // Failed to evacuate. We need to deal with the object that is left behind. Since this
299 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
300 // But if it happens to contain references to evacuated regions, those references would
301 // not get updated for this stale copy during this cycle, and we will crash while scanning
302 // it the next cycle.
303 //
304 // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
305 // object will overwrite this stale copy, or the filler object on LAB retirement will
306 // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
307 // have to explicitly overwrite the copy with the filler object. With that overwrite,
308 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
309 if (alloc_from_gclab) {
310 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
311 } else {
312 fill_with_object(copy, size);
313 shenandoah_assert_correct(NULL, copy_val);
314 }
315 shenandoah_assert_correct(NULL, result);
316 return result;
317 }
318 }
319
320 template<bool RESOLVE>
321 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
322 oop obj = oop(entry);
323 if (RESOLVE) {
324 obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
325 }
326 return !_marking_context->is_marked(obj);
327 }
328
329 inline bool ShenandoahHeap::in_collection_set(oop p) const {
330 assert(collection_set() != NULL, "Sanity");
331 return collection_set()->is_in(p);
332 }
333
334 inline bool ShenandoahHeap::in_collection_set_loc(void* p) const {
335 assert(collection_set() != NULL, "Sanity");
336 return collection_set()->is_in_loc(p);
337 }
338
339 inline bool ShenandoahHeap::is_stable() const {
340 return _gc_state.is_clear();
341 }
342
343 inline bool ShenandoahHeap::is_idle() const {
344 return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS);
345 }
346
347 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
348 return _gc_state.is_set(MARKING);
349 }
350
351 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
352 return _gc_state.is_set(EVACUATION);
353 }
354
355 inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
356 return _gc_state.is_set(mask);
357 }
358
359 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
360 return _degenerated_gc_in_progress.is_set();
361 }
362
363 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
364 return _full_gc_in_progress.is_set();
365 }
366
367 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
368 return _full_gc_move_in_progress.is_set();
369 }
370
371 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
372 return _gc_state.is_set(UPDATEREFS);
373 }
374
375 inline bool ShenandoahHeap::is_stw_gc_in_progress() const {
376 return is_full_gc_in_progress() || is_degenerated_gc_in_progress();
377 }
378
379 inline bool ShenandoahHeap::is_concurrent_strong_root_in_progress() const {
380 return _concurrent_strong_root_in_progress.is_set();
381 }
382
383 inline bool ShenandoahHeap::is_concurrent_weak_root_in_progress() const {
384 return _concurrent_weak_root_in_progress.is_set();
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->get_next_marked_addr(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->get_next_marked_addr(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->get_next_marked_addr(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 inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
483 if (region_idx < _num_regions) {
484 return _regions[region_idx];
485 } else {
486 return NULL;
487 }
488 }
489
490 inline void ShenandoahHeap::mark_complete_marking_context() {
491 _marking_context->mark_complete();
492 }
493
494 inline void ShenandoahHeap::mark_incomplete_marking_context() {
495 _marking_context->mark_incomplete();
496 }
497
498 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
499 assert (_marking_context->is_complete()," sanity");
500 return _marking_context;
501 }
502
503 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
504 return _marking_context;
505 }
506
507 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP