1 /*
2 * Copyright (c) 2015, 2020, 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 "gc_implementation/shared/markBitMap.inline.hpp"
28 #include "memory/threadLocalAllocBuffer.inline.hpp"
29 #include "gc_implementation/shenandoah/shenandoahAsserts.hpp"
30 #include "gc_implementation/shenandoah/shenandoahBarrierSet.inline.hpp"
31 #include "gc_implementation/shenandoah/shenandoahCollectionSet.hpp"
32 #include "gc_implementation/shenandoah/shenandoahCollectionSet.inline.hpp"
33 #include "gc_implementation/shenandoah/shenandoahForwarding.inline.hpp"
34 #include "gc_implementation/shenandoah/shenandoahControlThread.hpp"
35 #include "gc_implementation/shenandoah/shenandoahMarkingContext.inline.hpp"
36 #include "gc_implementation/shenandoah/shenandoahHeap.hpp"
37 #include "gc_implementation/shenandoah/shenandoahHeapRegionSet.hpp"
38 #include "gc_implementation/shenandoah/shenandoahHeapRegion.inline.hpp"
39 #include "oops/oop.inline.hpp"
40 #include "runtime/atomic.hpp"
41 #include "runtime/prefetch.hpp"
42 #include "runtime/prefetch.inline.hpp"
43 #include "utilities/copy.hpp"
44 #include "utilities/globalDefinitions.hpp"
45
46 inline ShenandoahHeap* ShenandoahHeap::heap() {
47 assert(_heap != NULL, "Heap is not initialized yet");
48 return _heap;
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 ShenandoahWorkGang* ShenandoahHeap::workers() const {
62 return (ShenandoahWorkGang*)_workers;
63 }
64
65 inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
66 uintptr_t region_start = ((uintptr_t) addr);
67 uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
68 assert(index < num_regions(), err_msg("Region index is in bounds: " PTR_FORMAT, p2i(addr)));
69 return index;
70 }
71
72 inline ShenandoahHeapRegion* const ShenandoahHeap::heap_region_containing(const void* addr) const {
73 size_t index = heap_region_index_containing(addr);
74 ShenandoahHeapRegion* const result = get_region(index);
75 assert(addr >= result->bottom() && addr < result->end(), err_msg("Heap region contains the address: " PTR_FORMAT, p2i(addr)));
76 return result;
77 }
78
79 template <class T>
80 inline oop ShenandoahHeap::update_with_forwarded_not_null(T* p, oop obj) {
81 if (in_collection_set(obj)) {
82 shenandoah_assert_forwarded_except(p, obj, is_full_gc_in_progress() || cancelled_gc() || is_degenerated_gc_in_progress());
83 obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
84 oopDesc::encode_store_heap_oop(p, obj);
85 }
86 #ifdef ASSERT
87 else {
88 shenandoah_assert_not_forwarded(p, obj);
89 }
90 #endif
91 return obj;
92 }
93
94 template <class T>
95 inline oop ShenandoahHeap::maybe_update_with_forwarded(T* p) {
96 T o = oopDesc::load_heap_oop(p);
97 if (! oopDesc::is_null(o)) {
98 oop obj = oopDesc::decode_heap_oop_not_null(o);
99 return maybe_update_with_forwarded_not_null(p, obj);
100 } else {
101 return NULL;
102 }
103 }
104
105 template <class T>
106 inline oop ShenandoahHeap::evac_update_with_forwarded(T* p) {
107 T o = oopDesc::load_heap_oop(p);
108 if (!oopDesc::is_null(o)) {
109 oop heap_oop = oopDesc::decode_heap_oop_not_null(o);
110 if (in_collection_set(heap_oop)) {
111 oop forwarded_oop = ShenandoahBarrierSet::resolve_forwarded_not_null(heap_oop);
112 if (forwarded_oop == heap_oop) {
113 forwarded_oop = evacuate_object(heap_oop, Thread::current());
114 }
115 oop prev = cas_oop(forwarded_oop, p, heap_oop);
116 if (prev == heap_oop) {
117 return forwarded_oop;
118 } else {
119 return NULL;
120 }
121 }
122 return heap_oop;
123 } else {
124 return NULL;
125 }
126 }
127
128 inline oop ShenandoahHeap::cas_oop(oop n, oop* addr, oop c) {
129 assert(is_ptr_aligned(addr, sizeof(narrowOop)), err_msg("Address should be aligned: " PTR_FORMAT, p2i(addr)));
130 return (oop) Atomic::cmpxchg_ptr(n, addr, c);
131 }
132
133 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, narrowOop c) {
134 narrowOop val = oopDesc::encode_heap_oop(n);
135 return oopDesc::decode_heap_oop((narrowOop) Atomic::cmpxchg(val, addr, c));
136 }
137
138 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, oop c) {
139 assert(is_ptr_aligned(addr, sizeof(narrowOop)), err_msg("Address should be aligned: " PTR_FORMAT, p2i(addr)));
140 narrowOop cmp = oopDesc::encode_heap_oop(c);
141 narrowOop val = oopDesc::encode_heap_oop(n);
142 return oopDesc::decode_heap_oop((narrowOop) Atomic::cmpxchg(val, addr, cmp));
143 }
144
145 template <class T>
146 inline oop ShenandoahHeap::maybe_update_with_forwarded_not_null(T* p, oop heap_oop) {
147 shenandoah_assert_not_in_cset_loc_except(p, !is_in(p) || is_full_gc_in_progress() || is_degenerated_gc_in_progress());
148 shenandoah_assert_correct(p, heap_oop);
149
150 if (in_collection_set(heap_oop)) {
151 oop forwarded_oop = ShenandoahBarrierSet::resolve_forwarded_not_null(heap_oop);
152
153 shenandoah_assert_forwarded_except(p, heap_oop, is_full_gc_in_progress() || is_degenerated_gc_in_progress());
154 shenandoah_assert_not_forwarded(p, forwarded_oop);
155 shenandoah_assert_not_in_cset_except(p, forwarded_oop, cancelled_gc());
156
157 // If this fails, another thread wrote to p before us, it will be logged in SATB and the
158 // reference be updated later.
159 oop witness = cas_oop(forwarded_oop, p, heap_oop);
160
161 if (witness != heap_oop) {
162 // CAS failed, someone had beat us to it. Normally, we would return the failure witness,
163 // because that would be the proper write of to-space object, enforced by strong barriers.
164 // However, there is a corner case with arraycopy. It can happen that a Java thread
165 // beats us with an arraycopy, which first copies the array, which potentially contains
166 // from-space refs, and only afterwards updates all from-space refs to to-space refs,
167 // which leaves a short window where the new array elements can be from-space.
168 // In this case, we can just resolve the result again. As we resolve, we need to consider
169 // the contended write might have been NULL.
170 oop result = ShenandoahBarrierSet::resolve_forwarded(witness);
171 shenandoah_assert_not_forwarded_except(p, result, (result == NULL));
172 shenandoah_assert_not_in_cset_except(p, result, (result == NULL) || cancelled_gc());
173 return result;
174 } else {
175 // Success! We have updated with known to-space copy. We have already asserted it is sane.
176 return forwarded_oop;
177 }
178 } else {
179 shenandoah_assert_not_forwarded(p, heap_oop);
180 return heap_oop;
181 }
182 }
183
184 inline bool ShenandoahHeap::cancelled_gc() const {
185 return _cancelled_gc.is_set();
186 }
187
188 inline bool ShenandoahHeap::try_cancel_gc() {
189 return _cancelled_gc.try_set();
190 }
191
192 inline void ShenandoahHeap::clear_cancelled_gc() {
193 _cancelled_gc.unset();
194 _oom_evac_handler.clear();
195 }
196
197 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
198 assert(UseTLAB, "TLABs should be enabled");
199
200 if (!thread->gclab().is_initialized()) {
201 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
202 err_msg("Performance: thread should have GCLAB: %s", thread->name()));
203 // No GCLABs in this thread, fallback to shared allocation
204 return NULL;
205 }
206 HeapWord *obj = thread->gclab().allocate(size);
207 if (obj != NULL) {
208 return obj;
209 }
210 // Otherwise...
211 return allocate_from_gclab_slow(thread, size);
212 }
213
214 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
215 if (Thread::current()->is_oom_during_evac()) {
216 // This thread went through the OOM during evac protocol and it is safe to return
217 // the forward pointer. It must not attempt to evacuate any more.
218 return ShenandoahBarrierSet::resolve_forwarded(p);
219 }
220
221 assert(thread->is_evac_allowed(), "must be enclosed in in oom-evac scope");
222
223 size_t size = p->size();
224
225 assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
226
227 bool alloc_from_gclab = true;
228 HeapWord* copy = NULL;
229
230 #ifdef ASSERT
231 if (ShenandoahOOMDuringEvacALot &&
232 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
233 copy = NULL;
234 } else {
235 #endif
236 if (UseTLAB) {
237 copy = allocate_from_gclab(thread, size);
238 }
239 if (copy == NULL) {
240 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
241 copy = allocate_memory(req);
242 alloc_from_gclab = false;
243 }
244 #ifdef ASSERT
245 }
246 #endif
247
248 if (copy == NULL) {
249 control_thread()->handle_alloc_failure_evac(size);
250
251 _oom_evac_handler.handle_out_of_memory_during_evacuation();
252
253 return ShenandoahBarrierSet::resolve_forwarded(p);
254 }
255
256 // Copy the object:
257 Copy::aligned_disjoint_words((HeapWord*) p, copy, size);
258
259 // Try to install the new forwarding pointer.
260 oop copy_val = oop(copy);
261 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
262 if (result == copy_val) {
263 // Successfully evacuated. Our copy is now the public one!
264 shenandoah_assert_correct(NULL, copy_val);
265 return copy_val;
266 } else {
267 // Failed to evacuate. We need to deal with the object that is left behind. Since this
268 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
269 // But if it happens to contain references to evacuated regions, those references would
270 // not get updated for this stale copy during this cycle, and we will crash while scanning
271 // it the next cycle.
272 //
273 // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
274 // object will overwrite this stale copy, or the filler object on LAB retirement will
275 // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
276 // have to explicitly overwrite the copy with the filler object. With that overwrite,
277 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
278 if (alloc_from_gclab) {
279 thread->gclab().rollback(size);
280 } else {
281 fill_with_object(copy, size);
282 shenandoah_assert_correct(NULL, copy_val);
283 }
284 shenandoah_assert_correct(NULL, result);
285 return result;
286 }
287 }
288
289 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
290 return !_marking_context->is_marked(oop(entry));
291 }
292
293 inline bool ShenandoahHeap::in_collection_set(oop p) const {
294 assert(collection_set() != NULL, "Sanity");
295 return collection_set()->is_in(p);
296 }
297
298 inline bool ShenandoahHeap::in_collection_set_loc(void* p) const {
299 assert(collection_set() != NULL, "Sanity");
300 return collection_set()->is_in_loc(p);
301 }
302
303 inline bool ShenandoahHeap::is_stable() const {
304 return _gc_state.is_clear();
305 }
306
307 inline bool ShenandoahHeap::is_idle() const {
308 return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS);
309 }
310
311 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
312 return _gc_state.is_set(MARKING);
313 }
314
315 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
316 return _gc_state.is_set(EVACUATION);
317 }
318
319 inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
320 return _gc_state.is_set(mask);
321 }
322
323 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
324 return _degenerated_gc_in_progress.is_set();
325 }
326
327 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
328 return _full_gc_in_progress.is_set();
329 }
330
331 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
332 return _full_gc_move_in_progress.is_set();
333 }
334
335 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
336 return _gc_state.is_set(UPDATEREFS);
337 }
338
339 template<class T>
340 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
341 marked_object_iterate(region, cl, region->top());
342 }
343
344 template<class T>
345 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
346 assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
347
348 ShenandoahMarkingContext* const ctx = complete_marking_context();
349 assert(ctx->is_complete(), "sanity");
350
351 MarkBitMap* mark_bit_map = ctx->mark_bit_map();
352 HeapWord* tams = ctx->top_at_mark_start(region);
353
354 size_t skip_bitmap_delta = 1;
355 HeapWord* start = region->bottom();
356 HeapWord* end = MIN2(tams, region->end());
357
358 // Step 1. Scan below the TAMS based on bitmap data.
359 HeapWord* limit_bitmap = MIN2(limit, tams);
360
361 // Try to scan the initial candidate. If the candidate is above the TAMS, it would
362 // fail the subsequent "< limit_bitmap" checks, and fall through to Step 2.
363 HeapWord* cb = mark_bit_map->getNextMarkedWordAddress(start, end);
364
365 intx dist = ShenandoahMarkScanPrefetch;
366 if (dist > 0) {
367 // Batched scan that prefetches the oop data, anticipating the access to
368 // either header, oop field, or forwarding pointer. Not that we cannot
369 // touch anything in oop, while it still being prefetched to get enough
370 // time for prefetch to work. This is why we try to scan the bitmap linearly,
371 // disregarding the object size. However, since we know forwarding pointer
372 // preceeds the object, we can skip over it. Once we cannot trust the bitmap,
373 // there is no point for prefetching the oop contents, as oop->size() will
374 // touch it prematurely.
375
376 // No variable-length arrays in standard C++, have enough slots to fit
377 // the prefetch distance.
378 static const int SLOT_COUNT = 256;
379 guarantee(dist <= SLOT_COUNT, "adjust slot count");
380 HeapWord* slots[SLOT_COUNT];
381
382 int avail;
383 do {
384 avail = 0;
385 for (int c = 0; (c < dist) && (cb < limit_bitmap); c++) {
386 Prefetch::read(cb, oopDesc::mark_offset_in_bytes());
387 slots[avail++] = cb;
388 cb += skip_bitmap_delta;
389 if (cb < limit_bitmap) {
390 cb = mark_bit_map->getNextMarkedWordAddress(cb, limit_bitmap);
391 }
392 }
393
394 for (int c = 0; c < avail; c++) {
395 assert (slots[c] < tams, err_msg("only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams)));
396 assert (slots[c] < limit, err_msg("only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit)));
397 oop obj = oop(slots[c]);
398 assert(!oopDesc::is_null(obj), "sanity");
399 assert(obj->is_oop(), "sanity");
400 assert(_marking_context->is_marked(obj), "object expected to be marked");
401 cl->do_object(obj);
402 }
403 } while (avail > 0);
404 } else {
405 while (cb < limit_bitmap) {
406 assert (cb < tams, err_msg("only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams)));
407 assert (cb < limit, err_msg("only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit)));
408 oop obj = oop(cb);
409 assert(!oopDesc::is_null(obj), "sanity");
410 assert(obj->is_oop(), "sanity");
411 assert(_marking_context->is_marked(obj), "object expected to be marked");
412 cl->do_object(obj);
413 cb += skip_bitmap_delta;
414 if (cb < limit_bitmap) {
415 cb = mark_bit_map->getNextMarkedWordAddress(cb, limit_bitmap);
416 }
417 }
418 }
419
420 // Step 2. Accurate size-based traversal, happens past the TAMS.
421 // This restarts the scan at TAMS, which makes sure we traverse all objects,
422 // regardless of what happened at Step 1.
423 HeapWord* cs = tams;
424 while (cs < limit) {
425 assert (cs >= tams, err_msg("only objects past TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams)));
426 assert (cs < limit, err_msg("only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit)));
427 oop obj = oop(cs);
428 int size = obj->size();
429 assert(!oopDesc::is_null(obj), "sanity");
430 assert(obj->is_oop(), "sanity");
431 assert(_marking_context->is_marked(obj), "object expected to be marked");
432 cl->do_object(obj);
433 cs += size;
434 }
435 }
436
437 template <class T>
438 class ShenandoahObjectToOopClosure : public ObjectClosure {
439 T* _cl;
440 public:
441 ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
442
443 void do_object(oop obj) {
444 obj->oop_iterate(_cl);
445 }
446 };
447
448 template <class T>
449 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
450 T* _cl;
451 MemRegion _bounds;
452 public:
453 ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
454 _cl(cl), _bounds(bottom, top) {}
455
456 void do_object(oop obj) {
457 obj->oop_iterate(_cl, _bounds);
458 }
459 };
460
461 template<class T>
462 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
463 if (region->is_humongous()) {
464 HeapWord* bottom = region->bottom();
465 if (top > bottom) {
466 region = region->humongous_start_region();
467 ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
468 marked_object_iterate(region, &objs);
469 }
470 } else {
471 ShenandoahObjectToOopClosure<T> objs(cl);
472 marked_object_iterate(region, &objs, top);
473 }
474 }
475
476 inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
477 if (region_idx < _num_regions) {
478 return _regions[region_idx];
479 } else {
480 return NULL;
481 }
482 }
483
484 inline void ShenandoahHeap::mark_complete_marking_context() {
485 _marking_context->mark_complete();
486 }
487
488 inline void ShenandoahHeap::mark_incomplete_marking_context() {
489 _marking_context->mark_incomplete();
490 }
491
492 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
493 assert (_marking_context->is_complete()," sanity");
494 return _marking_context;
495 }
496
497 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
498 return _marking_context;
499 }
500
501 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP