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 "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
47 inline ShenandoahHeapRegion* ShenandoahRegionIterator::next() {
48 size_t new_index = Atomic::add((size_t) 1, &_index);
49 // get_region() provides the bounds-check and returns NULL on OOB.
50 return _heap->get_region(new_index - 1);
51 }
52
53 inline bool ShenandoahHeap::has_forwarded_objects() const {
54 return _gc_state.is_set(HAS_FORWARDED);
55 }
56
57 inline ShenandoahWorkGang* ShenandoahHeap::workers() const {
58 return (ShenandoahWorkGang*)_workers;
59 }
60
61 inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
62 uintptr_t region_start = ((uintptr_t) addr);
63 uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
64 assert(index < num_regions(), err_msg("Region index is in bounds: " PTR_FORMAT, p2i(addr)));
65 return index;
66 }
67
68 inline ShenandoahHeapRegion* const ShenandoahHeap::heap_region_containing(const void* addr) const {
69 size_t index = heap_region_index_containing(addr);
70 ShenandoahHeapRegion* const result = get_region(index);
71 assert(addr >= result->bottom() && addr < result->end(), err_msg("Heap region contains the address: " PTR_FORMAT, p2i(addr)));
72 return result;
73 }
74
75 template <class T>
76 inline oop ShenandoahHeap::update_with_forwarded_not_null(T* p, oop obj) {
77 if (in_collection_set(obj)) {
78 shenandoah_assert_forwarded_except(p, obj, is_full_gc_in_progress() || cancelled_gc() || is_degenerated_gc_in_progress());
79 obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
80 oopDesc::encode_store_heap_oop(p, obj);
81 }
82 #ifdef ASSERT
83 else {
84 shenandoah_assert_not_forwarded(p, obj);
85 }
86 #endif
87 return obj;
88 }
89
90 template <class T>
91 inline oop ShenandoahHeap::maybe_update_with_forwarded(T* p) {
92 T o = oopDesc::load_heap_oop(p);
93 if (! oopDesc::is_null(o)) {
94 oop obj = oopDesc::decode_heap_oop_not_null(o);
95 return maybe_update_with_forwarded_not_null(p, obj);
96 } else {
97 return NULL;
98 }
99 }
100
101 template <class T>
102 inline oop ShenandoahHeap::evac_update_with_forwarded(T* p) {
103 T o = oopDesc::load_heap_oop(p);
104 if (!oopDesc::is_null(o)) {
105 oop heap_oop = oopDesc::decode_heap_oop_not_null(o);
106 if (in_collection_set(heap_oop)) {
107 oop forwarded_oop = ShenandoahBarrierSet::resolve_forwarded_not_null(heap_oop);
108 if (forwarded_oop == heap_oop) {
109 forwarded_oop = evacuate_object(heap_oop, Thread::current());
110 }
111 oop prev = cas_oop(forwarded_oop, p, heap_oop);
112 if (prev == heap_oop) {
113 return forwarded_oop;
114 } else {
115 return NULL;
116 }
117 }
118 return heap_oop;
119 } else {
120 return NULL;
121 }
122 }
123
124 inline oop ShenandoahHeap::cas_oop(oop n, oop* addr, oop c) {
125 assert(is_ptr_aligned(addr, sizeof(narrowOop)), err_msg("Address should be aligned: " PTR_FORMAT, p2i(addr)));
126 return (oop) Atomic::cmpxchg_ptr(n, addr, c);
127 }
128
129 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, oop c) {
130 assert(is_ptr_aligned(addr, sizeof(narrowOop)), err_msg("Address should be aligned: " PTR_FORMAT, p2i(addr)));
131 narrowOop cmp = oopDesc::encode_heap_oop(c);
132 narrowOop val = oopDesc::encode_heap_oop(n);
133 return oopDesc::decode_heap_oop((narrowOop) Atomic::cmpxchg(val, addr, cmp));
134 }
135
136 template <class T>
137 inline oop ShenandoahHeap::maybe_update_with_forwarded_not_null(T* p, oop heap_oop) {
138 shenandoah_assert_not_in_cset_loc_except(p, !is_in(p) || is_full_gc_in_progress() || is_degenerated_gc_in_progress());
139 shenandoah_assert_correct(p, heap_oop);
140
141 if (in_collection_set(heap_oop)) {
142 oop forwarded_oop = ShenandoahBarrierSet::resolve_forwarded_not_null(heap_oop);
143
144 shenandoah_assert_forwarded_except(p, heap_oop, is_full_gc_in_progress() || is_degenerated_gc_in_progress());
145 shenandoah_assert_not_forwarded(p, forwarded_oop);
146 shenandoah_assert_not_in_cset_except(p, forwarded_oop, cancelled_gc());
147
148 // If this fails, another thread wrote to p before us, it will be logged in SATB and the
149 // reference be updated later.
150 oop witness = cas_oop(forwarded_oop, p, heap_oop);
151
152 if (witness != heap_oop) {
153 // CAS failed, someone had beat us to it. Normally, we would return the failure witness,
154 // because that would be the proper write of to-space object, enforced by strong barriers.
155 // However, there is a corner case with arraycopy. It can happen that a Java thread
156 // beats us with an arraycopy, which first copies the array, which potentially contains
157 // from-space refs, and only afterwards updates all from-space refs to to-space refs,
158 // which leaves a short window where the new array elements can be from-space.
159 // In this case, we can just resolve the result again. As we resolve, we need to consider
160 // the contended write might have been NULL.
161 oop result = ShenandoahBarrierSet::resolve_forwarded(witness);
162 shenandoah_assert_not_forwarded_except(p, result, (result == NULL));
163 shenandoah_assert_not_in_cset_except(p, result, (result == NULL) || cancelled_gc());
164 return result;
165 } else {
166 // Success! We have updated with known to-space copy. We have already asserted it is sane.
167 return forwarded_oop;
168 }
169 } else {
170 shenandoah_assert_not_forwarded(p, heap_oop);
171 return heap_oop;
172 }
173 }
174
175 inline bool ShenandoahHeap::cancelled_gc() const {
176 return _cancelled_gc.is_set();
177 }
178
179 inline bool ShenandoahHeap::try_cancel_gc() {
180 return _cancelled_gc.try_set();
181 }
182
183 inline void ShenandoahHeap::clear_cancelled_gc() {
184 _cancelled_gc.unset();
185 _oom_evac_handler.clear();
186 }
187
188 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
189 assert(UseTLAB, "TLABs should be enabled");
190
191 if (!thread->gclab().is_initialized()) {
192 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
193 err_msg("Performance: thread should have GCLAB: %s", thread->name()));
194 // No GCLABs in this thread, fallback to shared allocation
195 return NULL;
196 }
197 HeapWord *obj = thread->gclab().allocate(size);
198 if (obj != NULL) {
199 return obj;
200 }
201 // Otherwise...
202 return allocate_from_gclab_slow(thread, size);
203 }
204
205 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
206 if (Thread::current()->is_oom_during_evac()) {
207 // This thread went through the OOM during evac protocol and it is safe to return
208 // the forward pointer. It must not attempt to evacuate any more.
209 return ShenandoahBarrierSet::resolve_forwarded(p);
210 }
211
212 assert(thread->is_evac_allowed(), "must be enclosed in in oom-evac scope");
213
214 size_t size = p->size();
215
216 assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
217
218 bool alloc_from_gclab = true;
219 HeapWord* copy = NULL;
220
221 #ifdef ASSERT
222 if (ShenandoahOOMDuringEvacALot &&
223 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
224 copy = NULL;
225 } else {
226 #endif
227 if (UseTLAB) {
228 copy = allocate_from_gclab(thread, size);
229 }
230 if (copy == NULL) {
231 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
232 copy = allocate_memory(req);
233 alloc_from_gclab = false;
234 }
235 #ifdef ASSERT
236 }
237 #endif
238
239 if (copy == NULL) {
240 control_thread()->handle_alloc_failure_evac(size);
241
242 _oom_evac_handler.handle_out_of_memory_during_evacuation();
243
244 return ShenandoahBarrierSet::resolve_forwarded(p);
245 }
246
247 // Copy the object:
248 Copy::aligned_disjoint_words((HeapWord*) p, copy, size);
249
250 // Try to install the new forwarding pointer.
251 oop copy_val = oop(copy);
252 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
253 if (result == copy_val) {
254 // Successfully evacuated. Our copy is now the public one!
255 shenandoah_assert_correct(NULL, copy_val);
256 return copy_val;
257 } else {
258 // Failed to evacuate. We need to deal with the object that is left behind. Since this
259 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
260 // But if it happens to contain references to evacuated regions, those references would
261 // not get updated for this stale copy during this cycle, and we will crash while scanning
262 // it the next cycle.
263 //
264 // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
265 // object will overwrite this stale copy, or the filler object on LAB retirement will
266 // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
267 // have to explicitly overwrite the copy with the filler object. With that overwrite,
268 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
269 if (alloc_from_gclab) {
270 thread->gclab().rollback(size);
271 } else {
272 fill_with_object(copy, size);
273 shenandoah_assert_correct(NULL, copy_val);
274 }
275 shenandoah_assert_correct(NULL, result);
276 return result;
277 }
278 }
279
280 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
281 return !_marking_context->is_marked(oop(entry));
282 }
283
284 template <class T>
285 inline bool ShenandoahHeap::in_collection_set(T p) const {
286 HeapWord* obj = (HeapWord*) p;
287 assert(collection_set() != NULL, "Sanity");
288 assert(is_in(obj), "should be in heap");
289
290 return collection_set()->is_in(obj);
291 }
292
293 inline bool ShenandoahHeap::is_stable() const {
294 return _gc_state.is_clear();
295 }
296
297 inline bool ShenandoahHeap::is_idle() const {
298 return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS | TRAVERSAL);
299 }
300
301 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
302 return _gc_state.is_set(MARKING);
303 }
304
305 inline bool ShenandoahHeap::is_concurrent_traversal_in_progress() const {
306 return _gc_state.is_set(TRAVERSAL);
307 }
308
309 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
310 return _gc_state.is_set(EVACUATION);
311 }
312
313 inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
314 return _gc_state.is_set(mask);
315 }
316
317 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
318 return _degenerated_gc_in_progress.is_set();
319 }
320
321 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
322 return _full_gc_in_progress.is_set();
323 }
324
325 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
326 return _full_gc_move_in_progress.is_set();
327 }
328
329 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
330 return _gc_state.is_set(UPDATEREFS);
331 }
332
333 template<class T>
334 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
335 marked_object_iterate(region, cl, region->top());
336 }
337
338 template<class T>
339 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
340 assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
341
342 ShenandoahMarkingContext* const ctx = complete_marking_context();
343 assert(ctx->is_complete(), "sanity");
344
345 MarkBitMap* mark_bit_map = ctx->mark_bit_map();
346 HeapWord* tams = ctx->top_at_mark_start(region);
347
348 size_t skip_bitmap_delta = 1;
349 HeapWord* start = region->bottom();
350 HeapWord* end = MIN2(tams, region->end());
351
352 // Step 1. Scan below the TAMS based on bitmap data.
353 HeapWord* limit_bitmap = MIN2(limit, tams);
354
355 // Try to scan the initial candidate. If the candidate is above the TAMS, it would
356 // fail the subsequent "< limit_bitmap" checks, and fall through to Step 2.
357 HeapWord* cb = mark_bit_map->getNextMarkedWordAddress(start, end);
358
359 intx dist = ShenandoahMarkScanPrefetch;
360 if (dist > 0) {
361 // Batched scan that prefetches the oop data, anticipating the access to
362 // either header, oop field, or forwarding pointer. Not that we cannot
363 // touch anything in oop, while it still being prefetched to get enough
364 // time for prefetch to work. This is why we try to scan the bitmap linearly,
365 // disregarding the object size. However, since we know forwarding pointer
366 // preceeds the object, we can skip over it. Once we cannot trust the bitmap,
367 // there is no point for prefetching the oop contents, as oop->size() will
368 // touch it prematurely.
369
370 // No variable-length arrays in standard C++, have enough slots to fit
371 // the prefetch distance.
372 static const int SLOT_COUNT = 256;
373 guarantee(dist <= SLOT_COUNT, "adjust slot count");
374 HeapWord* slots[SLOT_COUNT];
375
376 int avail;
377 do {
378 avail = 0;
379 for (int c = 0; (c < dist) && (cb < limit_bitmap); c++) {
380 Prefetch::read(cb, oopDesc::mark_offset_in_bytes());
381 slots[avail++] = cb;
382 cb += skip_bitmap_delta;
383 if (cb < limit_bitmap) {
384 cb = mark_bit_map->getNextMarkedWordAddress(cb, limit_bitmap);
385 }
386 }
387
388 for (int c = 0; c < avail; c++) {
389 assert (slots[c] < tams, err_msg("only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams)));
390 assert (slots[c] < limit, err_msg("only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit)));
391 oop obj = oop(slots[c]);
392 assert(!oopDesc::is_null(obj), "sanity");
393 assert(obj->is_oop(), "sanity");
394 assert(_marking_context->is_marked(obj), "object expected to be marked");
395 cl->do_object(obj);
396 }
397 } while (avail > 0);
398 } else {
399 while (cb < limit_bitmap) {
400 assert (cb < tams, err_msg("only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams)));
401 assert (cb < limit, err_msg("only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit)));
402 oop obj = oop(cb);
403 assert(!oopDesc::is_null(obj), "sanity");
404 assert(obj->is_oop(), "sanity");
405 assert(_marking_context->is_marked(obj), "object expected to be marked");
406 cl->do_object(obj);
407 cb += skip_bitmap_delta;
408 if (cb < limit_bitmap) {
409 cb = mark_bit_map->getNextMarkedWordAddress(cb, limit_bitmap);
410 }
411 }
412 }
413
414 // Step 2. Accurate size-based traversal, happens past the TAMS.
415 // This restarts the scan at TAMS, which makes sure we traverse all objects,
416 // regardless of what happened at Step 1.
417 HeapWord* cs = tams;
418 while (cs < limit) {
419 assert (cs >= tams, err_msg("only objects past TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams)));
420 assert (cs < limit, err_msg("only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit)));
421 oop obj = oop(cs);
422 int size = obj->size();
423 assert(!oopDesc::is_null(obj), "sanity");
424 assert(obj->is_oop(), "sanity");
425 assert(_marking_context->is_marked(obj), "object expected to be marked");
426 cl->do_object(obj);
427 cs += size;
428 }
429 }
430
431 template <class T>
432 class ShenandoahObjectToOopClosure : public ObjectClosure {
433 T* _cl;
434 public:
435 ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
436
437 void do_object(oop obj) {
438 obj->oop_iterate(_cl);
439 }
440 };
441
442 template <class T>
443 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
444 T* _cl;
445 MemRegion _bounds;
446 public:
447 ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
448 _cl(cl), _bounds(bottom, top) {}
449
450 void do_object(oop obj) {
451 obj->oop_iterate(_cl, _bounds);
452 }
453 };
454
455 template<class T>
456 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
457 if (region->is_humongous()) {
458 HeapWord* bottom = region->bottom();
459 if (top > bottom) {
460 region = region->humongous_start_region();
461 ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
462 marked_object_iterate(region, &objs);
463 }
464 } else {
465 ShenandoahObjectToOopClosure<T> objs(cl);
466 marked_object_iterate(region, &objs, top);
467 }
468 }
469
470 inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
471 if (region_idx < _num_regions) {
472 return _regions[region_idx];
473 } else {
474 return NULL;
475 }
476 }
477
478 inline void ShenandoahHeap::mark_complete_marking_context() {
479 _marking_context->mark_complete();
480 }
481
482 inline void ShenandoahHeap::mark_incomplete_marking_context() {
483 _marking_context->mark_incomplete();
484 }
485
486 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
487 assert (_marking_context->is_complete()," sanity");
488 return _marking_context;
489 }
490
491 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
492 return _marking_context;
493 }
494
495 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP