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