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.
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  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
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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/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 && !cancelled_gc()) {
166     if (SuspendibleThreadSet::should_yield()) {
167       SuspendibleThreadSet::yield();
168     }
169   }
170   return cancelled_gc();
171 }
172 
173 inline void ShenandoahHeap::clear_cancelled_gc() {
174   _cancelled_gc.set(CANCELLABLE);
175   _oom_evac_handler.clear();
176 }
177 
178 inline HeapWord* ShenandoahHeap::allocate_from_gclab(Thread* thread, size_t size) {
179   assert(UseTLAB, "TLABs should be enabled");
180 
181   PLAB* gclab = ShenandoahThreadLocalData::gclab(thread);
182   if (gclab == NULL) {
183     assert(!thread->is_Java_thread() && !thread->is_Worker_thread(),
184            "Performance: thread should have GCLAB: %s", thread->name());
185     // No GCLABs in this thread, fallback to shared allocation
186     return NULL;
187   }
188   HeapWord* obj = gclab->allocate(size);
189   if (obj != NULL) {
190     return obj;
191   }
192   // Otherwise...
193   return allocate_from_gclab_slow(thread, size);
194 }
195 
196 inline oop ShenandoahHeap::evacuate_object(oop p, Thread* thread) {
197   if (ShenandoahThreadLocalData::is_oom_during_evac(Thread::current())) {
198     // This thread went through the OOM during evac protocol and it is safe to return
199     // the forward pointer. It must not attempt to evacuate any more.
200     return ShenandoahBarrierSet::resolve_forwarded(p);
201   }
202 
203   assert(ShenandoahThreadLocalData::is_evac_allowed(thread), "must be enclosed in oom-evac scope");
204 
205   size_t size = p->forward_safe_size();
206 
207   assert(!heap_region_containing(p)->is_humongous(), "never evacuate humongous objects");
208 
209   bool alloc_from_gclab = true;
210   HeapWord* copy = NULL;
211 
212 #ifdef ASSERT
213   if (ShenandoahOOMDuringEvacALot &&
214       (os::random() & 1) == 0) { // Simulate OOM every ~2nd slow-path call
215         copy = NULL;
216   } else {
217 #endif
218     if (UseTLAB) {
219       copy = allocate_from_gclab(thread, size);
220     }
221     if (copy == NULL) {
222       ShenandoahAllocRequest req = ShenandoahAllocRequest::for_shared_gc(size);
223       copy = allocate_memory(req);
224       alloc_from_gclab = false;
225     }
226 #ifdef ASSERT
227   }
228 #endif
229 
230   if (copy == NULL) {
231     control_thread()->handle_alloc_failure_evac(size);
232 
233     _oom_evac_handler.handle_out_of_memory_during_evacuation();
234 
235     return ShenandoahBarrierSet::resolve_forwarded(p);
236   }
237 
238   // Copy the object:
239   Copy::aligned_disjoint_words(cast_from_oop<HeapWord*>(p), copy, size);
240 
241   // Try to install the new forwarding pointer.
242   oop copy_val = cast_to_oop(copy);
243   oop result = ShenandoahForwarding::try_update_forwardee(p, copy_val);
244   if (result == copy_val) {
245     // Successfully evacuated. Our copy is now the public one!
246     shenandoah_assert_correct(NULL, copy_val);
247     return copy_val;
248   }  else {
249     // Failed to evacuate. We need to deal with the object that is left behind. Since this
250     // new allocation is certainly after TAMS, it will be considered live in the next cycle.
251     // But if it happens to contain references to evacuated regions, those references would
252     // not get updated for this stale copy during this cycle, and we will crash while scanning
253     // it the next cycle.
254     //
255     // For GCLAB allocations, it is enough to rollback the allocation ptr. Either the next
256     // object will overwrite this stale copy, or the filler object on LAB retirement will
257     // do this. For non-GCLAB allocations, we have no way to retract the allocation, and
258     // have to explicitly overwrite the copy with the filler object. With that overwrite,
259     // we have to keep the fwdptr initialized and pointing to our (stale) copy.
260     if (alloc_from_gclab) {
261       ShenandoahThreadLocalData::gclab(thread)->undo_allocation(copy, size);
262     } else {
263       fill_with_object(copy, size);
264       shenandoah_assert_correct(NULL, copy_val);
265     }
266     shenandoah_assert_correct(NULL, result);
267     return result;
268   }
269 }
270 
271 inline bool ShenandoahHeap::requires_marking(const void* entry) const {
272   oop obj = cast_to_oop(entry);
273   return !_marking_context->is_marked_strong(obj);
274 }
275 
276 inline bool ShenandoahHeap::in_collection_set(oop p) const {
277   assert(collection_set() != NULL, "Sanity");
278   return collection_set()->is_in(p);
279 }
280 
281 inline bool ShenandoahHeap::in_collection_set_loc(void* p) const {
282   assert(collection_set() != NULL, "Sanity");
283   return collection_set()->is_in_loc(p);
284 }
285 
286 inline bool ShenandoahHeap::is_stable() const {
287   return _gc_state.is_clear();
288 }
289 
290 inline bool ShenandoahHeap::is_idle() const {
291   return _gc_state.is_unset(MARKING | EVACUATION | UPDATEREFS);
292 }
293 
294 inline bool ShenandoahHeap::is_concurrent_mark_in_progress() const {
295   return _gc_state.is_set(MARKING);
296 }
297 
298 inline bool ShenandoahHeap::is_evacuation_in_progress() const {
299   return _gc_state.is_set(EVACUATION);
300 }
301 
302 inline bool ShenandoahHeap::is_gc_in_progress_mask(uint mask) const {
303   return _gc_state.is_set(mask);
304 }
305 
306 inline bool ShenandoahHeap::is_degenerated_gc_in_progress() const {
307   return _degenerated_gc_in_progress.is_set();
308 }
309 
310 inline bool ShenandoahHeap::is_full_gc_in_progress() const {
311   return _full_gc_in_progress.is_set();
312 }
313 
314 inline bool ShenandoahHeap::is_full_gc_move_in_progress() const {
315   return _full_gc_move_in_progress.is_set();
316 }
317 
318 inline bool ShenandoahHeap::is_update_refs_in_progress() const {
319   return _gc_state.is_set(UPDATEREFS);
320 }
321 
322 inline bool ShenandoahHeap::is_stw_gc_in_progress() const {
323   return is_full_gc_in_progress() || is_degenerated_gc_in_progress();
324 }
325 
326 inline bool ShenandoahHeap::is_concurrent_strong_root_in_progress() const {
327   return _concurrent_strong_root_in_progress.is_set();
328 }
329 
330 inline bool ShenandoahHeap::is_concurrent_weak_root_in_progress() const {
331   return _gc_state.is_set(WEAK_ROOTS);
332 }
333 
334 template<class T>
335 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl) {
336   marked_object_iterate(region, cl, region->top());
337 }
338 
339 template<class T>
340 inline void ShenandoahHeap::marked_object_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* limit) {
341   assert(! region->is_humongous_continuation(), "no humongous continuation regions here");
342 
343   ShenandoahMarkingContext* const ctx = complete_marking_context();
344   assert(ctx->is_complete(), "sanity");
345 
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 = ctx->get_next_marked_addr(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 = ctx->get_next_marked_addr(cb, limit_bitmap);
385         }
386       }
387 
388       for (int c = 0; c < avail; c++) {
389         assert (slots[c] < tams,  "only objects below TAMS here: "  PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(tams));
390         assert (slots[c] < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(slots[c]), p2i(limit));
391         oop obj = cast_to_oop(slots[c]);
392         assert(oopDesc::is_oop(obj), "sanity");
393         assert(ctx->is_marked(obj), "object expected to be marked");
394         cl->do_object(obj);
395       }
396     } while (avail > 0);
397   } else {
398     while (cb < limit_bitmap) {
399       assert (cb < tams,  "only objects below TAMS here: "  PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(tams));
400       assert (cb < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cb), p2i(limit));
401       oop obj = cast_to_oop(cb);
402       assert(oopDesc::is_oop(obj), "sanity");
403       assert(ctx->is_marked(obj), "object expected to be marked");
404       cl->do_object(obj);
405       cb += skip_bitmap_delta;
406       if (cb < limit_bitmap) {
407         cb = ctx->get_next_marked_addr(cb, limit_bitmap);
408       }
409     }
410   }
411 
412   // Step 2. Accurate size-based traversal, happens past the TAMS.
413   // This restarts the scan at TAMS, which makes sure we traverse all objects,
414   // regardless of what happened at Step 1.
415   HeapWord* cs = tams;
416   while (cs < limit) {
417     assert (cs >= tams, "only objects past TAMS here: "   PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(tams));
418     assert (cs < limit, "only objects below limit here: " PTR_FORMAT " (" PTR_FORMAT ")", p2i(cs), p2i(limit));
419     oop obj = cast_to_oop(cs);
420     assert(oopDesc::is_oop(obj), "sanity");
421     assert(ctx->is_marked(obj), "object expected to be marked");
422     size_t size = obj->forward_safe_size();
423     cl->do_object(obj);
424     cs += size;
425   }
426 }
427 
428 template <class T>
429 class ShenandoahObjectToOopClosure : public ObjectClosure {
430   T* _cl;
431 public:
432   ShenandoahObjectToOopClosure(T* cl) : _cl(cl) {}
433 
434   void do_object(oop obj) {
435     obj->oop_iterate(_cl);
436   }
437 };
438 
439 template <class T>
440 class ShenandoahObjectToOopBoundedClosure : public ObjectClosure {
441   T* _cl;
442   MemRegion _bounds;
443 public:
444   ShenandoahObjectToOopBoundedClosure(T* cl, HeapWord* bottom, HeapWord* top) :
445     _cl(cl), _bounds(bottom, top) {}
446 
447   void do_object(oop obj) {
448     obj->oop_iterate(_cl, _bounds);
449   }
450 };
451 
452 template<class T>
453 inline void ShenandoahHeap::marked_object_oop_iterate(ShenandoahHeapRegion* region, T* cl, HeapWord* top) {
454   if (region->is_humongous()) {
455     HeapWord* bottom = region->bottom();
456     if (top > bottom) {
457       region = region->humongous_start_region();
458       ShenandoahObjectToOopBoundedClosure<T> objs(cl, bottom, top);
459       marked_object_iterate(region, &objs);
460     }
461   } else {
462     ShenandoahObjectToOopClosure<T> objs(cl);
463     marked_object_iterate(region, &objs, top);
464   }
465 }
466 
467 inline ShenandoahHeapRegion* const ShenandoahHeap::get_region(size_t region_idx) const {
468   if (region_idx < _num_regions) {
469     return _regions[region_idx];
470   } else {
471     return NULL;
472   }
473 }
474 
475 inline void ShenandoahHeap::mark_complete_marking_context() {
476   _marking_context->mark_complete();
477 }
478 
479 inline void ShenandoahHeap::mark_incomplete_marking_context() {
480   _marking_context->mark_incomplete();
481 }
482 
483 inline ShenandoahMarkingContext* ShenandoahHeap::complete_marking_context() const {
484   assert (_marking_context->is_complete()," sanity");
485   return _marking_context;
486 }
487 
488 inline ShenandoahMarkingContext* ShenandoahHeap::marking_context() const {
489   return _marking_context;
490 }
491 
492 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHHEAP_INLINE_HPP