1 /*
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  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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  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).
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 17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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 19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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 24 
 25 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHMARK_INLINE_HPP
 26 #define SHARE_GC_SHENANDOAH_SHENANDOAHMARK_INLINE_HPP
 27 
 28 #include "gc/shenandoah/shenandoahMark.hpp"
 29 
 30 #include "gc/shenandoah/shenandoahAsserts.hpp"
 31 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
 32 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
 33 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
 34 #include "gc/shenandoah/shenandoahStringDedup.inline.hpp"
 35 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
 36 #include "gc/shenandoah/shenandoahUtils.hpp"
 37 #include "memory/iterator.inline.hpp"
 38 #include "oops/compressedOops.inline.hpp"
 39 #include "oops/oop.inline.hpp"
 40 #include "runtime/prefetch.inline.hpp"
 41 #include "utilities/powerOfTwo.hpp"
 42 
 43 template <StringDedupMode STRING_DEDUP>
 44 void ShenandoahMark::dedup_string(oop obj, StringDedup::Requests* const req) {
 45   if (STRING_DEDUP == ENQUEUE_DEDUP) {
 46     if (ShenandoahStringDedup::is_candidate(obj)) {
 47       req->add(obj);
 48     }
 49   } else if (STRING_DEDUP == ALWAYS_DEDUP) {
 50     if (ShenandoahStringDedup::is_string_candidate(obj) &&
 51         !ShenandoahStringDedup::dedup_requested(obj)) {
 52         req->add(obj);
 53     }
 54   }
 55 }
 56 
 57 template <class T, StringDedupMode STRING_DEDUP>
 58 void ShenandoahMark::do_task(ShenandoahObjToScanQueue* q, T* cl, ShenandoahLiveData* live_data, StringDedup::Requests* const req, ShenandoahMarkTask* task) {
 59   oop obj = task->obj();
 60 
 61   // TODO: This will push array chunks into the mark queue with no regard for
 62   // generations. I don't think it will break anything, but the young generation
 63   // scan might end up processing some old generation array chunks.
 64 
 65   shenandoah_assert_not_forwarded(NULL, obj);
 66   shenandoah_assert_marked(NULL, obj);
 67   shenandoah_assert_not_in_cset_except(NULL, obj, ShenandoahHeap::heap()->cancelled_gc());
 68 
 69   // Are we in weak subgraph scan?
 70   bool weak = task->is_weak();
 71   cl->set_weak(weak);
 72 
 73   if (task->is_not_chunked()) {
 74     if (obj->is_instance()) {
 75       // Case 1: Normal oop, process as usual.
 76       obj->oop_iterate(cl);
 77       dedup_string<STRING_DEDUP>(obj, req);
 78     } else if (obj->is_objArray()) {
 79       // Case 2: Object array instance and no chunk is set. Must be the first
 80       // time we visit it, start the chunked processing.
 81       do_chunked_array_start<T>(q, cl, obj, weak);
 82     } else {
 83       // Case 3: Primitive array. Do nothing, no oops there. We use the same
 84       // performance tweak TypeArrayKlass::oop_oop_iterate_impl is using:
 85       // We skip iterating over the klass pointer since we know that
 86       // Universe::TypeArrayKlass never moves.
 87       assert (obj->is_typeArray(), "should be type array");
 88     }
 89     // Count liveness the last: push the outstanding work to the queues first
 90     // Avoid double-counting objects that are visited twice due to upgrade
 91     // from final- to strong mark.
 92     if (task->count_liveness()) {
 93       count_liveness(live_data, obj);
 94     }
 95   } else {
 96     // Case 4: Array chunk, has sensible chunk id. Process it.
 97     do_chunked_array<T>(q, cl, obj, task->chunk(), task->pow(), weak);
 98   }
 99 }
100 
101 inline void ShenandoahMark::count_liveness(ShenandoahLiveData* live_data, oop obj) {
102   ShenandoahHeap* const heap = ShenandoahHeap::heap();
103   size_t region_idx = heap->heap_region_index_containing(obj);
104   ShenandoahHeapRegion* region = heap->get_region(region_idx);
105   size_t size = obj->size();
106 
107   if (!region->is_humongous_start()) {
108     assert(!region->is_humongous(), "Cannot have continuations here");
109     assert(region->affiliation() != FREE, "Do not count live data within Free Regular Region " SIZE_FORMAT, region_idx);
110     ShenandoahLiveData cur = live_data[region_idx];
111     size_t new_val = size + cur;
112     if (new_val >= SHENANDOAH_LIVEDATA_MAX) {
113       // overflow, flush to region data
114       region->increase_live_data_gc_words(new_val);
115       live_data[region_idx] = 0;
116     } else {
117       // still good, remember in locals
118       live_data[region_idx] = (ShenandoahLiveData) new_val;
119     }
120   } else {
121     shenandoah_assert_in_correct_region(NULL, obj);
122     size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
123 
124     assert(region->affiliation() != FREE, "Do not count live data within FREE Humongous Start Region " SIZE_FORMAT, region_idx);
125     for (size_t i = region_idx; i < region_idx + num_regions; i++) {
126       ShenandoahHeapRegion* chain_reg = heap->get_region(i);
127       assert(chain_reg->is_humongous(), "Expecting a humongous region");
128       assert(chain_reg->affiliation() != FREE, "Do not count live data within FREE Humongous Continuation Region " SIZE_FORMAT, i);
129       chain_reg->increase_live_data_gc_words(chain_reg->used() >> LogHeapWordSize);
130     }
131   }
132 }
133 
134 template <class T>
135 inline void ShenandoahMark::do_chunked_array_start(ShenandoahObjToScanQueue* q, T* cl, oop obj, bool weak) {
136   assert(obj->is_objArray(), "expect object array");
137   objArrayOop array = objArrayOop(obj);
138   int len = array->length();
139 
140   // Mark objArray klass metadata
141   if (Devirtualizer::do_metadata(cl)) {
142     Devirtualizer::do_klass(cl, array->klass());
143   }
144 
145   if (len <= (int) ObjArrayMarkingStride*2) {
146     // A few slices only, process directly
147     array->oop_iterate_range(cl, 0, len);
148   } else {
149     int bits = log2i_graceful(len);
150     // Compensate for non-power-of-two arrays, cover the array in excess:
151     if (len != (1 << bits)) bits++;
152 
153     // Only allow full chunks on the queue. This frees do_chunked_array() from checking from/to
154     // boundaries against array->length(), touching the array header on every chunk.
155     //
156     // To do this, we cut the prefix in full-sized chunks, and submit them on the queue.
157     // If the array is not divided in chunk sizes, then there would be an irregular tail,
158     // which we will process separately.
159 
160     int last_idx = 0;
161 
162     int chunk = 1;
163     int pow = bits;
164 
165     // Handle overflow
166     if (pow >= 31) {
167       assert (pow == 31, "sanity");
168       pow--;
169       chunk = 2;
170       last_idx = (1 << pow);
171       bool pushed = q->push(ShenandoahMarkTask(array, true, weak, 1, pow));
172       assert(pushed, "overflow queue should always succeed pushing");
173     }
174 
175     // Split out tasks, as suggested in ShenandoahMarkTask docs. Record the last
176     // successful right boundary to figure out the irregular tail.
177     while ((1 << pow) > (int)ObjArrayMarkingStride &&
178            (chunk*2 < ShenandoahMarkTask::chunk_size())) {
179       pow--;
180       int left_chunk = chunk*2 - 1;
181       int right_chunk = chunk*2;
182       int left_chunk_end = left_chunk * (1 << pow);
183       if (left_chunk_end < len) {
184         bool pushed = q->push(ShenandoahMarkTask(array, true, weak, left_chunk, pow));
185         assert(pushed, "overflow queue should always succeed pushing");
186         chunk = right_chunk;
187         last_idx = left_chunk_end;
188       } else {
189         chunk = left_chunk;
190       }
191     }
192 
193     // Process the irregular tail, if present
194     int from = last_idx;
195     if (from < len) {
196       array->oop_iterate_range(cl, from, len);
197     }
198   }
199 }
200 
201 template <class T>
202 inline void ShenandoahMark::do_chunked_array(ShenandoahObjToScanQueue* q, T* cl, oop obj, int chunk, int pow, bool weak) {
203   assert(obj->is_objArray(), "expect object array");
204   objArrayOop array = objArrayOop(obj);
205 
206   assert (ObjArrayMarkingStride > 0, "sanity");
207 
208   // Split out tasks, as suggested in ShenandoahMarkTask docs. Avoid pushing tasks that
209   // are known to start beyond the array.
210   while ((1 << pow) > (int)ObjArrayMarkingStride && (chunk*2 < ShenandoahMarkTask::chunk_size())) {
211     pow--;
212     chunk *= 2;
213     bool pushed = q->push(ShenandoahMarkTask(array, true, weak, chunk - 1, pow));
214     assert(pushed, "overflow queue should always succeed pushing");
215   }
216 
217   int chunk_size = 1 << pow;
218 
219   int from = (chunk - 1) * chunk_size;
220   int to = chunk * chunk_size;
221 
222 #ifdef ASSERT
223   int len = array->length();
224   assert (0 <= from && from < len, "from is sane: %d/%d", from, len);
225   assert (0 < to && to <= len, "to is sane: %d/%d", to, len);
226 #endif
227 
228   array->oop_iterate_range(cl, from, to);
229 }
230 
231 template <GenerationMode GENERATION>
232 class ShenandoahSATBBufferClosure : public SATBBufferClosure {
233 private:
234   ShenandoahObjToScanQueue* _queue;
235   ShenandoahObjToScanQueue* _old;
236   ShenandoahHeap* _heap;
237   ShenandoahMarkingContext* const _mark_context;
238 public:
239   ShenandoahSATBBufferClosure(ShenandoahObjToScanQueue* q, ShenandoahObjToScanQueue* old) :
240     _queue(q),
241     _old(old),
242     _heap(ShenandoahHeap::heap()),
243     _mark_context(_heap->marking_context())
244   {
245   }
246 
247   void do_buffer(void **buffer, size_t size) {
248     assert(size == 0 || !_heap->has_forwarded_objects() || _heap->is_concurrent_old_mark_in_progress(), "Forwarded objects are not expected here");
249     for (size_t i = 0; i < size; ++i) {
250       oop *p = (oop *) &buffer[i];
251       ShenandoahMark::mark_through_ref<oop, GENERATION>(p, _queue, _old, _mark_context, false);
252     }
253   }
254 };
255 
256 template<GenerationMode GENERATION>
257 bool ShenandoahMark::in_generation(oop obj) {
258   // Each in-line expansion of in_generation() resolves GENERATION at compile time.
259   if (GENERATION == YOUNG)
260     return ShenandoahHeap::heap()->is_in_young(obj);
261   else if (GENERATION == OLD)
262     return ShenandoahHeap::heap()->is_in_old(obj);
263   else if (GENERATION == GLOBAL)
264     return true;
265   else
266     return false;
267 }
268 
269 template<class T, GenerationMode GENERATION>
270 inline void ShenandoahMark::mark_through_ref(T *p, ShenandoahObjToScanQueue* q, ShenandoahObjToScanQueue* old, ShenandoahMarkingContext* const mark_context, bool weak) {
271   T o = RawAccess<>::oop_load(p);
272   if (!CompressedOops::is_null(o)) {
273     oop obj = CompressedOops::decode_not_null(o);
274 
275     ShenandoahHeap* heap = ShenandoahHeap::heap();
276     shenandoah_assert_not_forwarded(p, obj);
277     shenandoah_assert_not_in_cset_except(p, obj, heap->cancelled_gc());
278     if (in_generation<GENERATION>(obj)) {
279       mark_ref(q, mark_context, weak, obj);
280       shenandoah_assert_marked(p, obj);
281       if (heap->mode()->is_generational()) {
282         // TODO: As implemented herein, GLOBAL collections reconstruct the card table during GLOBAL concurrent
283         // marking. Note that the card table is cleaned at init_mark time so it needs to be reconstructed to support
284         // future young-gen collections.  It might be better to reconstruct card table in
285         // ShenandoahHeapRegion::global_oop_iterate_and_fill_dead.  We could either mark all live memory as dirty, or could
286         // use the GLOBAL update-refs scanning of pointers to determine precisely which cards to flag as dirty.
287         if (GENERATION == YOUNG && heap->is_in_old(p)) {
288           // Mark card as dirty because remembered set scanning still finds interesting pointer.
289           heap->mark_card_as_dirty((HeapWord*)p);
290         } else if (GENERATION == GLOBAL && heap->is_in_old(p) && heap->is_in_young(obj)) {
291           // Mark card as dirty because GLOBAL marking finds interesting pointer.
292           heap->mark_card_as_dirty((HeapWord*)p);
293         }
294       }
295     } else if (old != nullptr) {
296       // Young mark, bootstrapping old or concurrent with old marking.
297       mark_ref(old, mark_context, weak, obj);
298       shenandoah_assert_marked(p, obj);
299     } else if (GENERATION == OLD) {
300       // Old mark, found a young pointer.
301       // TODO:  Rethink this: may be redundant with dirtying of cards identified during young-gen remembered set scanning
302       // and by mutator write barriers.  Assert
303       assert(heap->is_in_young(obj), "Expected young object.");
304       heap->mark_card_as_dirty(p);
305     }
306   }
307 }
308 
309 inline void ShenandoahMark::mark_ref(ShenandoahObjToScanQueue* q,
310                               ShenandoahMarkingContext* const mark_context,
311                               bool weak, oop obj) {
312   bool skip_live = false;
313   bool marked;
314   if (weak) {
315     marked = mark_context->mark_weak(obj);
316   } else {
317     marked = mark_context->mark_strong(obj, /* was_upgraded = */ skip_live);
318   }
319   if (marked) {
320     bool pushed = q->push(ShenandoahMarkTask(obj, skip_live, weak));
321     assert(pushed, "overflow queue should always succeed pushing");
322   }
323 }
324 
325 ShenandoahObjToScanQueueSet* ShenandoahMark::task_queues() const {
326   return _task_queues;
327 }
328 
329 ShenandoahObjToScanQueue* ShenandoahMark::get_queue(uint index) const {
330   return _task_queues->queue(index);
331 }
332 
333 ShenandoahObjToScanQueue* ShenandoahMark::get_old_queue(uint index) const {
334   if (_old_gen_task_queues != nullptr) {
335     return _old_gen_task_queues->queue(index);
336   }
337   return nullptr;
338 }
339 
340 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHMARK_INLINE_HPP