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