1 /*
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  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  *
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 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
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 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/continuationGCSupport.inline.hpp"
 34 #include "gc/shared/suspendibleThreadSet.hpp"
 35 #include "gc/shared/tlab_globals.hpp"
 36 #include "gc/shenandoah/shenandoahAsserts.hpp"
 37 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
 38 #include "gc/shenandoah/shenandoahCollectionSet.inline.hpp"
 39 #include "gc/shenandoah/shenandoahForwarding.inline.hpp"
 40 #include "gc/shenandoah/shenandoahWorkGroup.hpp"
 41 #include "gc/shenandoah/shenandoahHeapRegionSet.inline.hpp"
 42 #include "gc/shenandoah/shenandoahHeapRegion.inline.hpp"
 43 #include "gc/shenandoah/shenandoahControlThread.hpp"
 44 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
 45 #include "gc/shenandoah/shenandoahThreadLocalData.hpp"
 46 #include "oops/compressedOops.inline.hpp"
 47 #include "oops/oop.inline.hpp"
 48 #include "runtime/atomic.hpp"
 49 #include "runtime/javaThread.hpp"
 50 #include "runtime/prefetch.inline.hpp"
 51 #include "utilities/copy.hpp"
 52 #include "utilities/globalDefinitions.hpp"
 53 
 54 inline ShenandoahHeap* ShenandoahHeap::heap() {
 55   return named_heap<ShenandoahHeap>(CollectedHeap::Shenandoah);
 56 }
 57 
 58 inline ShenandoahHeapRegion* ShenandoahRegionIterator::next() {
 59   size_t new_index = Atomic::add(&_index, (size_t) 1, memory_order_relaxed);
 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 WorkerThreads* ShenandoahHeap::workers() const {
 69   return _workers;
 70 }
 71 
 72 inline WorkerThreads* ShenandoahHeap::safepoint_workers() {
 73   return _safepoint_workers;
 74 }
 75 
 76 inline void ShenandoahHeap::notify_gc_progress() {
 77   Atomic::store(&_gc_no_progress_count, (size_t) 0);
 78 
 79 }
 80 inline void ShenandoahHeap::notify_gc_no_progress() {
 81   Atomic::inc(&_gc_no_progress_count);
 82 }
 83 
 84 inline size_t ShenandoahHeap::get_gc_no_progress_count() const {
 85   return Atomic::load(&_gc_no_progress_count);
 86 }
 87 
 88 inline size_t ShenandoahHeap::heap_region_index_containing(const void* addr) const {
 89   uintptr_t region_start = ((uintptr_t) addr);
 90   uintptr_t index = (region_start - (uintptr_t) base()) >> ShenandoahHeapRegion::region_size_bytes_shift();
 91   assert(index < num_regions(), "Region index is in bounds: " PTR_FORMAT, p2i(addr));
 92   return index;
 93 }
 94 
 95 inline ShenandoahHeapRegion* ShenandoahHeap::heap_region_containing(const void* addr) const {
 96   size_t index = heap_region_index_containing(addr);
 97   ShenandoahHeapRegion* const result = get_region(index);
 98   assert(addr >= result->bottom() && addr < result->end(), "Heap region contains the address: " PTR_FORMAT, p2i(addr));
 99   return result;
100 }
101 
102 inline void ShenandoahHeap::enter_evacuation(Thread* t) {
103   _oom_evac_handler.enter_evacuation(t);
104 }
105 
106 inline void ShenandoahHeap::leave_evacuation(Thread* t) {
107   _oom_evac_handler.leave_evacuation(t);
108 }
109 
110 template <class T>
111 inline void ShenandoahHeap::update_with_forwarded(T* p) {
112   T o = RawAccess<>::oop_load(p);
113   if (!CompressedOops::is_null(o)) {
114     oop obj = CompressedOops::decode_not_null(o);
115     if (in_collection_set(obj)) {
116       // Corner case: when evacuation fails, there are objects in collection
117       // set that are not really forwarded. We can still go and try and update them
118       // (uselessly) to simplify the common path.
119       shenandoah_assert_forwarded_except(p, obj, cancelled_gc());
120       oop fwd = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
121       shenandoah_assert_not_in_cset_except(p, fwd, cancelled_gc());
122 
123       // Unconditionally store the update: no concurrent updates expected.
124       RawAccess<IS_NOT_NULL>::oop_store(p, fwd);
125     }
126   }
127 }
128 
129 template <class T>
130 inline void ShenandoahHeap::conc_update_with_forwarded(T* p) {
131   T o = RawAccess<>::oop_load(p);
132   if (!CompressedOops::is_null(o)) {
133     oop obj = CompressedOops::decode_not_null(o);
134     if (in_collection_set(obj)) {
135       // Corner case: when evacuation fails, there are objects in collection
136       // set that are not really forwarded. We can still go and try CAS-update them
137       // (uselessly) to simplify the common path.
138       shenandoah_assert_forwarded_except(p, obj, cancelled_gc());
139       oop fwd = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
140       shenandoah_assert_not_in_cset_except(p, fwd, cancelled_gc());
141 
142       // Sanity check: we should not be updating the cset regions themselves,
143       // unless we are recovering from the evacuation failure.
144       shenandoah_assert_not_in_cset_loc_except(p, !is_in(p) || cancelled_gc());
145 
146       // Either we succeed in updating the reference, or something else gets in our way.
147       // We don't care if that is another concurrent GC update, or another mutator update.
148       atomic_update_oop(fwd, p, obj);
149     }
150   }
151 }
152 
153 // Atomic updates of heap location. This is only expected to work with updating the same
154 // logical object with its forwardee. The reason why we need stronger-than-relaxed memory
155 // ordering has to do with coordination with GC barriers and mutator accesses.
156 //
157 // In essence, stronger CAS access is required to maintain the transitive chains that mutator
158 // accesses build by themselves. To illustrate this point, consider the following example.
159 //
160 // Suppose "o" is the object that has a field "x" and the reference to "o" is stored
161 // to field at "addr", which happens to be Java volatile field. Normally, the accesses to volatile
162 // field at "addr" would be matched with release/acquire barriers. This changes when GC moves
163 // the object under mutator feet.
164 //
165 // Thread 1 (Java)
166 //         // --- previous access starts here
167 //         ...
168 //   T1.1: store(&o.x, 1, mo_relaxed)
169 //   T1.2: store(&addr, o, mo_release) // volatile store
170 //
171 //         // --- new access starts here
172 //         // LRB: copy and install the new copy to fwdptr
173 //   T1.3: var copy = copy(o)
174 //   T1.4: cas(&fwd, t, copy, mo_release) // pointer-mediated publication
175 //         <access continues>
176 //
177 // Thread 2 (GC updater)
178 //   T2.1: var f = load(&fwd, mo_{consume|acquire}) // pointer-mediated acquisition
179 //   T2.2: cas(&addr, o, f, mo_release) // this method
180 //
181 // Thread 3 (Java)
182 //   T3.1: var o = load(&addr, mo_acquire) // volatile read
183 //   T3.2: if (o != null)
184 //   T3.3:   var r = load(&o.x, mo_relaxed)
185 //
186 // r is guaranteed to contain "1".
187 //
188 // Without GC involvement, there is synchronizes-with edge from T1.2 to T3.1,
189 // which guarantees this. With GC involvement, when LRB copies the object and
190 // another thread updates the reference to it, we need to have the transitive edge
191 // from T1.4 to T2.1 (that one is guaranteed by forwarding accesses), plus the edge
192 // from T2.2 to T3.1 (which is brought by this CAS).
193 //
194 // Note that we do not need to "acquire" in these methods, because we do not read the
195 // failure witnesses contents on any path, and "release" is enough.
196 //
197 
198 inline void ShenandoahHeap::atomic_update_oop(oop update, oop* addr, oop compare) {
199   assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
200   Atomic::cmpxchg(addr, compare, update, memory_order_release);
201 }
202 
203 inline void ShenandoahHeap::atomic_update_oop(oop update, narrowOop* addr, narrowOop compare) {
204   assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
205   narrowOop u = CompressedOops::encode(update);
206   Atomic::cmpxchg(addr, compare, u, memory_order_release);
207 }
208 
209 inline void ShenandoahHeap::atomic_update_oop(oop update, narrowOop* addr, oop compare) {
210   assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
211   narrowOop c = CompressedOops::encode(compare);
212   narrowOop u = CompressedOops::encode(update);
213   Atomic::cmpxchg(addr, c, u, memory_order_release);
214 }
215 
216 inline bool ShenandoahHeap::atomic_update_oop_check(oop update, oop* addr, oop compare) {
217   assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
218   return (oop) Atomic::cmpxchg(addr, compare, update, memory_order_release) == compare;
219 }
220 
221 inline bool ShenandoahHeap::atomic_update_oop_check(oop update, narrowOop* addr, narrowOop compare) {
222   assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
223   narrowOop u = CompressedOops::encode(update);
224   return (narrowOop) Atomic::cmpxchg(addr, compare, u, memory_order_release) == compare;
225 }
226 
227 inline bool ShenandoahHeap::atomic_update_oop_check(oop update, narrowOop* addr, oop compare) {
228   assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
229   narrowOop c = CompressedOops::encode(compare);
230   narrowOop u = CompressedOops::encode(update);
231   return CompressedOops::decode(Atomic::cmpxchg(addr, c, u, memory_order_release)) == compare;
232 }
233 
234 // The memory ordering discussion above does not apply for methods that store nulls:
235 // then, there is no transitive reads in mutator (as we see nulls), and we can do
236 // relaxed memory ordering there.
237 
238 inline void ShenandoahHeap::atomic_clear_oop(oop* addr, oop compare) {
239   assert(is_aligned(addr, HeapWordSize), "Address should be aligned: " PTR_FORMAT, p2i(addr));
240   Atomic::cmpxchg(addr, compare, oop(), memory_order_relaxed);
241 }
242 
243 inline void ShenandoahHeap::atomic_clear_oop(narrowOop* addr, oop compare) {
244   assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
245   narrowOop cmp = CompressedOops::encode(compare);
246   Atomic::cmpxchg(addr, cmp, narrowOop(), memory_order_relaxed);
247 }
248 
249 inline void ShenandoahHeap::atomic_clear_oop(narrowOop* addr, narrowOop compare) {
250   assert(is_aligned(addr, sizeof(narrowOop)), "Address should be aligned: " PTR_FORMAT, p2i(addr));
251   Atomic::cmpxchg(addr, compare, narrowOop(), memory_order_relaxed);
252 }
253 
254 inline bool ShenandoahHeap::cancelled_gc() const {
255   return _cancelled_gc.get() == CANCELLED;
256 }
257 
258 inline bool ShenandoahHeap::check_cancelled_gc_and_yield(bool sts_active) {
259   if (sts_active && !cancelled_gc()) {
260     if (SuspendibleThreadSet::should_yield()) {
261       SuspendibleThreadSet::yield();
262     }
263   }
264   return cancelled_gc();
265 }
266 
267 inline void ShenandoahHeap::clear_cancelled_gc() {
268   _cancelled_gc.set(CANCELLABLE);
269   _oom_evac_handler.clear();
270 }
271 
272 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
273   assert(UseTLAB, "TLABs should be enabled");
274 
275   PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
276   if (gclab == nullptr) {
277     assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
278            "Performance: thread should have GCLAB: %s", thread->name());
279     // No GCLABs in this thread, fallback to shared allocation
280     return nullptr;
281   }
282   HeapWord* obj = gclab->allocate(size);
283   if (obj != nullptr) {
284     return obj;
285   }
286   // Otherwise...
287   return allocate_from_gclab_slow(thread, size);
288 }
289 
290 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
291   oop obj = cast_to_oop(entry);
292   return !_marking_context->is_marked_strong(obj);
293 }
294 
295 inline bool ShenandoahHeap::in_collection_set(oop p) const {
296   assert(collection_set() != nullptr, "Sanity");
297   return collection_set()->is_in(p);
298 }
299 
300 inline bool ShenandoahHeap::in_collection_set_loc(void* p) const {
301   assert(collection_set() != nullptr, "Sanity");
302   return collection_set()->is_in_loc(p);
303 }
304 
305 inline bool ShenandoahHeap::is_stable() const {
306   return _gc_state.is_clear();
307 }
308 
309 inline bool ShenandoahHeap::is_idle() const {
310   return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS);
311 }
312 
313 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
314   return _gc_state.is_set(MARKING);
315 }
316 
317 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
318   return _gc_state.is_set(EVACUATION);
319 }
320 
321 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
322   return _degenerated_gc_in_progress.is_set();
323 }
324 
325 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
326   return _full_gc_in_progress.is_set();
327 }
328 
329 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
330   return _full_gc_move_in_progress.is_set();
331 }
332 
333 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
334   return _gc_state.is_set(UPDATEREFS);
335 }
336 
337 inline bool ShenandoahHeap::is_stw_gc_in_progress() const {
338   return is_full_gc_in_progress() || is_degenerated_gc_in_progress();
339 }
340 
341 inline bool ShenandoahHeap::is_concurrent_strong_root_in_progress() const {
342   return _concurrent_strong_root_in_progress.is_set();
343 }
344 
345 inline bool ShenandoahHeap::is_concurrent_weak_root_in_progress() const {
346   return _gc_state.is_set(WEAK_ROOTS);
347 }
348 
349 template<class T>
350 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
351   marked_object_iterate(region, cl, region->top());
352 }
353 
354 template<class T>
355 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
356   assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
357 
358   ShenandoahMarkingContext* const ctx = complete_marking_context();
359   assert(ctx->is_complete(), "sanity");
360 
361   HeapWord* tams = ctx->top_at_mark_start(region);
362 
363   size_t skip_bitmap_delta = 1;
364   HeapWord* start = region->bottom();
365   HeapWord* end = MIN2(tams, region->end());
366 
367   // Step 1. Scan below the TAMS based on bitmap data.
368   HeapWord* limit_bitmap = MIN2(limit, tams);
369 
370   // Try to scan the initial candidate. If the candidate is above the TAMS, it would
371   // fail the subsequent "< limit_bitmap" checks, and fall through to Step 2.
372   HeapWord* cb = ctx->get_next_marked_addr(start, end);
373 
374   intx dist = ShenandoahMarkScanPrefetch;
375   if (dist > 0) {
376     // Batched scan that prefetches the oop data, anticipating the access to
377     // either header, oop field, or forwarding pointer. Not that we cannot
378     // touch anything in oop, while it still being prefetched to get enough
379     // time for prefetch to work. This is why we try to scan the bitmap linearly,
380     // disregarding the object size. However, since we know forwarding pointer
381     // precedes the object, we can skip over it. Once we cannot trust the bitmap,
382     // there is no point for prefetching the oop contents, as oop->size() will
383     // touch it prematurely.
384 
385     // No variable-length arrays in standard C++, have enough slots to fit
386     // the prefetch distance.
387     static const int SLOT_COUNT = 256;
388     guarantee(dist <= SLOT_COUNT, "adjust slot count");
389     HeapWord* slots[SLOT_COUNT];
390 
391     int avail;
392     do {
393       avail = 0;
394       for (int c = 0; (c < dist) && (cb < limit_bitmap); c++) {
395         Prefetch::read(cb, oopDesc::mark_offset_in_bytes());
396         slots[avail++] = cb;
397         cb += skip_bitmap_delta;
398         if (cb < limit_bitmap) {
399           cb = ctx->get_next_marked_addr(cb, limit_bitmap);
400         }
401       }
402 
403       for (int c = 0; c < avail; c++) {
404         assert (slots[c] < tams,  "only objects below TAMS here: "  PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams));
405         assert (slots[c] < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit));
406         oop obj = cast_to_oop(slots[c]);
407         assert(oopDesc::is_oop(obj), "sanity");
408         assert(ctx->is_marked(obj), "object expected to be marked");
409         cl->do_object(obj);
410       }
411     } while (avail > 0);
412   } else {
413     while (cb < limit_bitmap) {
414       assert (cb < tams,  "only objects below TAMS here: "  PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams));
415       assert (cb < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit));
416       oop obj = cast_to_oop(cb);
417       assert(oopDesc::is_oop(obj), "sanity");
418       assert(ctx->is_marked(obj), "object expected to be marked");
419       cl->do_object(obj);
420       cb += skip_bitmap_delta;
421       if (cb < limit_bitmap) {
422         cb = ctx->get_next_marked_addr(cb, limit_bitmap);
423       }
424     }
425   }
426 
427   // Step 2. Accurate size-based traversal, happens past the TAMS.
428   // This restarts the scan at TAMS, which makes sure we traverse all objects,
429   // regardless of what happened at Step 1.
430   HeapWord* cs = tams;
431   while (cs < limit) {
432     assert (cs >= tams, "only objects past TAMS here: "   PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams));
433     assert (cs < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit));
434     oop obj = cast_to_oop(cs);
435     assert(oopDesc::is_oop(obj), "sanity");
436     assert(ctx->is_marked(obj), "object expected to be marked");
437     size_t size = obj->forward_safe_size();
438     cl->do_object(obj);
439     cs += size;
440   }
441 }
442 
443 template <class T>
444 class ShenandoahObjectToOopClosure : public ObjectClosure {
445   T* _cl;
446 public:
447   ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
448 
449   void do_object(oop obj) {
450     obj->oop_iterate(_cl);
451   }
452 };
453 
454 template <class T>
455 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
456   T* _cl;
457   MemRegion _bounds;
458 public:
459   ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
460     _cl(cl), _bounds(bottom, top) {}
461 
462   void do_object(oop obj) {
463     obj->oop_iterate(_cl, _bounds);
464   }
465 };
466 
467 template<class T>
468 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
469   if (region->is_humongous()) {
470     HeapWord* bottom = region->bottom();
471     if (top > bottom) {
472       region = region->humongous_start_region();
473       ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
474       marked_object_iterate(region, &objs);
475     }
476   } else {
477     ShenandoahObjectToOopClosure<T> objs(cl);
478     marked_object_iterate(region, &objs, top);
479   }
480 }
481 
482 inline ShenandoahHeapRegion* ShenandoahHeap::get_region(size_t region_idx) const {
483   if (region_idx < _num_regions) {
484     return _regions[region_idx];
485   } else {
486     return nullptr;
487   }
488 }
489 
490 inline void ShenandoahHeap::mark_complete_marking_context() {
491   _marking_context->mark_complete();
492 }
493 
494 inline void ShenandoahHeap::mark_incomplete_marking_context() {
495   _marking_context->mark_incomplete();
496 }
497 
498 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
499   assert (_marking_context->is_complete()," sanity");
500   return _marking_context;
501 }
502 
503 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
504   return _marking_context;
505 }
506 
507 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP