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
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23 */
24
25 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
26 #define SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP
27
28 #include "gc/shenandoah/shenandoahHeap.hpp"
29
30 #include "classfile/javaClasses.inline.hpp"
31 #include "gc/shared/markBitMap.inline.hpp"
32 #include "gc/shared/threadLocalAllocBuffer.inline.hpp"
33 #include "gc/shared/suspendibleThreadSet.hpp"
34 #include "gc/shared/tlab_globals.hpp"
35 #include "gc/shenandoah/shenandoahAsserts.hpp"
36 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
37 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
38 #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
39 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
40 #include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
41 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
42 #include "gc/shenandoah/shenandoahControlThread.hpp"
43 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
44 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
45 #include "oops/compressedOops.inline.hpp"
46 #include "oops/oop.inline.hpp"
47 #include "runtime/atomic.hpp"
48 #include "runtime/prefetch.inline.hpp"
49 #include "runtime/thread.hpp"
50 #include "utilities/copy.hpp"
51 #include "utilities/globalDefinitions.hpp"
52
53 inline ShenandoahHeap* ShenandoahHeap::heap() {
54 return named_heap<ShenandoahHeap>(CollectedHeap::Shenandoah);
55 }
56
57 inline ShenandoahHeapRegion* ShenandoahRegionIterator::next() {
58 size_t new_index = Atomic::add(&_index, (size_t) 1, memory_order_relaxed);
59 // get_region() provides the bounds-check and returns NULL on OOB.
60 return _heap->get_region(new_index - 1);
61 }
62
63 inline bool ShenandoahHeap::has_forwarded_objects() const {
64 return _gc_state.is_set(HAS_FORWARDED);
65 }
66
67 inline WorkGang* ShenandoahHeap::workers() const {
68 return _workers;
69 }
70
71 inline WorkGang* ShenandoahHeap::safepoint_workers() {
72 return _safepoint_workers;
73 }
74
75 inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
76 uintptr_t region_start = ((uintptr_t) addr);
77 uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
78 assert(index < num_regions(), "Region index is in bounds: " PTR_FORMAT, p2i(addr));
79 return index;
80 }
81
82 inline ShenandoahHeapRegion* const ShenandoahHeap::heap_region_containing(const void* addr) const {
83 size_t index = heap_region_index_containing(addr);
84 ShenandoahHeapRegion* const result = get_region(index);
85 assert(addr >= result->bottom() && addr < result->end(), "Heap region contains the address: " PTR_FORMAT, p2i(addr));
86 return result;
87 }
88
89 inline void ShenandoahHeap::enter_evacuation(Thread* t) {
90 _oom_evac_handler.enter_evacuation(t);
91 }
92
93 inline void ShenandoahHeap::leave_evacuation(Thread* t) {
94 _oom_evac_handler.leave_evacuation(t);
95 }
96
97 template <class T>
98 inline void ShenandoahHeap::update_with_forwarded(T* p) {
99 T o = RawAccess<>::oop_load(p);
100 if (!CompressedOops::is_null(o)) {
101 oop obj = CompressedOops::decode_not_null(o);
102 if (in_collection_set(obj)) {
103 // Corner case: when evacuation fails, there are objects in collection
104 // set that are not really forwarded. We can still go and try and update them
105 // (uselessly) to simplify the common path.
106 shenandoah_assert_forwarded_except(p, obj, cancelled_gc());
107 oop fwd = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
108 shenandoah_assert_not_in_cset_except(p, fwd, cancelled_gc());
109
110 // Unconditionally store the update: no concurrent updates expected.
111 RawAccess<IS_NOT_NULL>::oop_store(p, fwd);
112 }
113 }
114 }
115
116 template <class T>
117 inline void ShenandoahHeap::conc_update_with_forwarded(T* p) {
118 T o = RawAccess<>::oop_load(p);
119 if (!CompressedOops::is_null(o)) {
120 oop obj = CompressedOops::decode_not_null(o);
121 if (in_collection_set(obj)) {
122 // Corner case: when evacuation fails, there are objects in collection
123 // set that are not really forwarded. We can still go and try CAS-update them
124 // (uselessly) to simplify the common path.
125 shenandoah_assert_forwarded_except(p, obj, cancelled_gc());
126 oop fwd = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
127 shenandoah_assert_not_in_cset_except(p, fwd, cancelled_gc());
128
129 // Sanity check: we should not be updating the cset regions themselves,
130 // unless we are recovering from the evacuation failure.
131 shenandoah_assert_not_in_cset_loc_except(p, !is_in(p) || cancelled_gc());
132
133 // Either we succeed in updating the reference, or something else gets in our way.
134 // We don't care if that is another concurrent GC update, or another mutator update.
135 // We only check that non-NULL store still updated with non-forwarded reference.
136 oop witness = cas_oop(fwd, p, obj);
137 shenandoah_assert_not_forwarded_except(p, witness, (witness == NULL) || (witness == obj));
138 }
139 }
140 }
141
142 inline oop ShenandoahHeap::cas_oop(oop n, oop* addr, oop c) {
143 assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
144 return (oop) Atomic::cmpxchg(addr, c, n);
145 }
146
147 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, narrowOop c) {
148 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
149 narrowOop val = CompressedOops::encode(n);
150 return CompressedOops::decode(Atomic::cmpxchg(addr, c, val));
151 }
152
153 inline oop ShenandoahHeap::cas_oop(oop n, narrowOop* addr, oop c) {
154 assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
155 narrowOop cmp = CompressedOops::encode(c);
156 narrowOop val = CompressedOops::encode(n);
157 return CompressedOops::decode(Atomic::cmpxchg(addr, cmp, val));
158 }
159
160 inline bool ShenandoahHeap::cancelled_gc() const {
161 return _cancelled_gc.get() == CANCELLED;
162 }
163
164 inline bool ShenandoahHeap::check_cancelled_gc_and_yield(bool sts_active) {
165 if (! (sts_active && ShenandoahSuspendibleWorkers)) {
166 return cancelled_gc();
167 }
168
169 jbyte prev = _cancelled_gc.cmpxchg(NOT_CANCELLED, CANCELLABLE);
170 if (prev == CANCELLABLE || prev == NOT_CANCELLED) {
171 if (SuspendibleThreadSet::should_yield()) {
172 SuspendibleThreadSet::yield();
173 }
174
175 // Back to CANCELLABLE. The thread that poked NOT_CANCELLED first gets
176 // to restore to CANCELLABLE.
177 if (prev == CANCELLABLE) {
178 _cancelled_gc.set(CANCELLABLE);
179 }
180 return false;
181 } else {
182 return true;
183 }
184 }
185
186 inline void ShenandoahHeap::clear_cancelled_gc() {
187 _cancelled_gc.set(CANCELLABLE);
188 _oom_evac_handler.clear();
189 }
190
191 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
192 assert(UseTLAB, "TLABs should be enabled");
193
194 PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
195 if (gclab == NULL) {
196 assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
197 "Performance: thread should have GCLAB: %s", thread->name());
198 // No GCLABs in this thread, fallback to shared allocation
199 return NULL;
200 }
201 HeapWord* obj = gclab->allocate(size);
202 if (obj != NULL) {
203 return obj;
204 }
205 // Otherwise...
206 return allocate_from_gclab_slow(thread, size);
207 }
208
209 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
210 if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
211 // This thread went through the OOM during evac protocol and it is safe to return
212 // the forward pointer. It must not attempt to evacuate any more.
213 return ShenandoahBarrierSet::resolve_forwarded(p);
214 }
215
216 assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
217
218 size_t size = p->size();
219
220 assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
221
222 bool alloc_from_gclab = true;
223 HeapWord* copy = NULL;
224
225 #ifdef ASSERT
226 if (ShenandoahOOMDuringEvacALot &&
227 (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
228 copy = NULL;
229 } else {
230 #endif
231 if (UseTLAB) {
232 copy = allocate_from_gclab(thread, size);
233 }
234 if (copy == NULL) {
235 ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
236 copy = allocate_memory(req);
237 alloc_from_gclab = false;
238 }
239 #ifdef ASSERT
240 }
241 #endif
242
243 if (copy == NULL) {
244 control_thread()->handle_alloc_failure_evac(size);
245
246 _oom_evac_handler.handle_out_of_memory_during_evacuation();
247
248 return ShenandoahBarrierSet::resolve_forwarded(p);
249 }
250
251 // Copy the object:
252 Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
253
254 // Try to install the new forwarding pointer.
255 oop copy_val = cast_to_oop(copy);
256 oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
257 if (result == copy_val) {
258 // Successfully evacuated. Our copy is now the public one!
259 shenandoah_assert_correct(NULL, copy_val);
260 return copy_val;
261 } else {
262 // Failed to evacuate. We need to deal with the object that is left behind. Since this
263 // new allocation is certainly after TAMS, it will be considered live in the next cycle.
264 // But if it happens to contain references to evacuated regions, those references would
265 // not get updated for this stale copy during this cycle, and we will crash while scanning
266 // it the next cycle.
267 //
268 // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
269 // object will overwrite this stale copy, or the filler object on LAB retirement will
270 // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
271 // have to explicitly overwrite the copy with the filler object. With that overwrite,
272 // we have to keep the fwdptr initialized and pointing to our (stale) copy.
273 if (alloc_from_gclab) {
274 ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
275 } else {
276 fill_with_object(copy, size);
277 shenandoah_assert_correct(NULL, copy_val);
278 }
279 shenandoah_assert_correct(NULL, result);
280 return result;
281 }
282 }
283
284 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
285 oop obj = cast_to_oop(entry);
286 return !_marking_context->is_marked_strong(obj);
287 }
288
289 inline bool ShenandoahHeap::in_collection_set(oop p) const {
290 assert(collection_set() != NULL, "Sanity");
291 return collection_set()->is_in(p);
292 }
293
294 inline bool ShenandoahHeap::in_collection_set_loc(void* p) const {
295 assert(collection_set() != NULL, "Sanity");
296 return collection_set()->is_in_loc(p);
297 }
298
299 inline bool ShenandoahHeap::is_stable() const {
300 return _gc_state.is_clear();
301 }
302
303 inline bool ShenandoahHeap::is_idle() const {
304 return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS);
305 }
306
307 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
308 return _gc_state.is_set(MARKING);
309 }
310
311 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
312 return _gc_state.is_set(EVACUATION);
313 }
314
315 inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
316 return _gc_state.is_set(mask);
317 }
318
319 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
320 return _degenerated_gc_in_progress.is_set();
321 }
322
323 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
324 return _full_gc_in_progress.is_set();
325 }
326
327 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
328 return _full_gc_move_in_progress.is_set();
329 }
330
331 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
332 return _gc_state.is_set(UPDATEREFS);
333 }
334
335 inline bool ShenandoahHeap::is_stw_gc_in_progress() const {
336 return is_full_gc_in_progress() || is_degenerated_gc_in_progress();
337 }
338
339 inline bool ShenandoahHeap::is_concurrent_strong_root_in_progress() const {
340 return _concurrent_strong_root_in_progress.is_set();
341 }
342
343 inline bool ShenandoahHeap::is_concurrent_weak_root_in_progress() const {
344 return _gc_state.is_set(WEAK_ROOTS);
345 }
346
347 template<class T>
348 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
349 marked_object_iterate(region, cl, region->top());
350 }
351
352 template<class T>
353 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
354 assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
355
356 ShenandoahMarkingContext* const ctx = complete_marking_context();
357 assert(ctx->is_complete(), "sanity");
358
359 HeapWord* tams = ctx->top_at_mark_start(region);
360
361 size_t skip_bitmap_delta = 1;
362 HeapWord* start = region->bottom();
363 HeapWord* end = MIN2(tams, region->end());
364
365 // Step 1. Scan below the TAMS based on bitmap data.
366 HeapWord* limit_bitmap = MIN2(limit, tams);
367
368 // Try to scan the initial candidate. If the candidate is above the TAMS, it would
369 // fail the subsequent "< limit_bitmap" checks, and fall through to Step 2.
370 HeapWord* cb = ctx->get_next_marked_addr(start, end);
371
372 intx dist = ShenandoahMarkScanPrefetch;
373 if (dist > 0) {
374 // Batched scan that prefetches the oop data, anticipating the access to
375 // either header, oop field, or forwarding pointer. Not that we cannot
376 // touch anything in oop, while it still being prefetched to get enough
377 // time for prefetch to work. This is why we try to scan the bitmap linearly,
378 // disregarding the object size. However, since we know forwarding pointer
379 // preceeds the object, we can skip over it. Once we cannot trust the bitmap,
380 // there is no point for prefetching the oop contents, as oop->size() will
381 // touch it prematurely.
382
383 // No variable-length arrays in standard C++, have enough slots to fit
384 // the prefetch distance.
385 static const int SLOT_COUNT = 256;
386 guarantee(dist <= SLOT_COUNT, "adjust slot count");
387 HeapWord* slots[SLOT_COUNT];
388
389 int avail;
390 do {
391 avail = 0;
392 for (int c = 0; (c < dist) && (cb < limit_bitmap); c++) {
393 Prefetch::read(cb, oopDesc::mark_offset_in_bytes());
394 slots[avail++] = cb;
395 cb += skip_bitmap_delta;
396 if (cb < limit_bitmap) {
397 cb = ctx->get_next_marked_addr(cb, limit_bitmap);
398 }
399 }
400
401 for (int c = 0; c < avail; c++) {
402 assert (slots[c] < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams));
403 assert (slots[c] < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit));
404 oop obj = cast_to_oop(slots[c]);
405 assert(oopDesc::is_oop(obj), "sanity");
406 assert(ctx->is_marked(obj), "object expected to be marked");
407 cl->do_object(obj);
408 }
409 } while (avail > 0);
410 } else {
411 while (cb < limit_bitmap) {
412 assert (cb < tams, "only objects below TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams));
413 assert (cb < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit));
414 oop obj = cast_to_oop(cb);
415 assert(oopDesc::is_oop(obj), "sanity");
416 assert(ctx->is_marked(obj), "object expected to be marked");
417 cl->do_object(obj);
418 cb += skip_bitmap_delta;
419 if (cb < limit_bitmap) {
420 cb = ctx->get_next_marked_addr(cb, limit_bitmap);
421 }
422 }
423 }
424
425 // Step 2. Accurate size-based traversal, happens past the TAMS.
426 // This restarts the scan at TAMS, which makes sure we traverse all objects,
427 // regardless of what happened at Step 1.
428 HeapWord* cs = tams;
429 while (cs < limit) {
430 assert (cs >= tams, "only objects past TAMS here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams));
431 assert (cs < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit));
432 oop obj = cast_to_oop(cs);
433 assert(oopDesc::is_oop(obj), "sanity");
434 assert(ctx->is_marked(obj), "object expected to be marked");
435 int size = obj->size();
436 cl->do_object(obj);
437 cs += size;
438 }
439 }
440
441 template <class T>
442 class ShenandoahObjectToOopClosure : public ObjectClosure {
443 T* _cl;
444 public:
445 ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
446
447 void do_object(oop obj) {
448 obj->oop_iterate(_cl);
449 }
450 };
451
452 template <class T>
453 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
454 T* _cl;
455 MemRegion _bounds;
456 public:
457 ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
458 _cl(cl), _bounds(bottom, top) {}
459
460 void do_object(oop obj) {
461 obj->oop_iterate(_cl, _bounds);
462 }
463 };
464
465 template<class T>
466 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
467 if (region->is_humongous()) {
468 HeapWord* bottom = region->bottom();
469 if (top > bottom) {
470 region = region->humongous_start_region();
471 ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
472 marked_object_iterate(region, &objs);
473 }
474 } else {
475 ShenandoahObjectToOopClosure<T> objs(cl);
476 marked_object_iterate(region, &objs, top);
477 }
478 }
479
480 inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
481 if (region_idx < _num_regions) {
482 return _regions[region_idx];
483 } else {
484 return NULL;
485 }
486 }
487
488 inline void ShenandoahHeap::mark_complete_marking_context() {
489 _marking_context->mark_complete();
490 }
491
492 inline void ShenandoahHeap::mark_incomplete_marking_context() {
493 _marking_context->mark_incomplete();
494 }
495
496 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
497 assert (_marking_context->is_complete()," sanity");
498 return _marking_context;
499 }
500
501 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
502 return _marking_context;
503 }
504
505 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP