1 /*
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  3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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  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  *
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 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_SHENANDOAHMARK_INLINE_HPP
 26 #define SHARE_GC_SHENANDOAH_SHENANDOAHMARK_INLINE_HPP
 27 
 28 #include "gc/shenandoah/shenandoahMark.hpp"
 29 
 30 #include "gc/shared/continuationGCSupport.inline.hpp"
 31 #include "gc/shenandoah/shenandoahAsserts.hpp"
 32 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
 33 #include "gc/shenandoah/shenandoahHeap.inline.hpp"
 34 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
 35 #include "gc/shenandoah/shenandoahOopClosures.inline.hpp"
 36 #include "gc/shenandoah/shenandoahStringDedup.inline.hpp"
 37 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
 38 #include "gc/shenandoah/shenandoahUtils.hpp"
 39 #include "memory/iterator.inline.hpp"
 40 #include "oops/compressedOops.inline.hpp"
 41 #include "oops/oop.inline.hpp"
 42 #include "runtime/prefetch.inline.hpp"
 43 #include "utilities/devirtualizer.inline.hpp"
 44 #include "utilities/powerOfTwo.hpp"
 45 
 46 template <StringDedupMode STRING_DEDUP>
 47 void ShenandoahMark::dedup_string(oop obj, StringDedup::Requests* const req) {
 48   if (STRING_DEDUP == ENQUEUE_DEDUP) {
 49     if (ShenandoahStringDedup::is_candidate(obj)) {
 50       req->add(obj);
 51     }
 52   } else if (STRING_DEDUP == ALWAYS_DEDUP) {
 53     if (ShenandoahStringDedup::is_string_candidate(obj) &&
 54         !ShenandoahStringDedup::dedup_requested(obj)) {
 55         req->add(obj);
 56     }
 57   }
 58 }
 59 
 60 template <class T, ShenandoahGenerationType GENERATION, StringDedupMode STRING_DEDUP>
 61 void ShenandoahMark::do_task(ShenandoahObjToScanQueue* q, T* cl, ShenandoahLiveData* live_data, StringDedup::Requests* const req, ShenandoahMarkTask* task) {
 62   oop obj = task->obj();
 63 
 64   shenandoah_assert_not_forwarded(nullptr, obj);
 65   shenandoah_assert_marked(nullptr, obj);
 66   shenandoah_assert_not_in_cset_except(nullptr, obj, ShenandoahHeap::heap()->cancelled_gc());
 67 
 68   // Are we in weak subgraph scan?
 69   bool weak = task->is_weak();
 70   cl->set_weak(weak);
 71 
 72   if (task->is_not_chunked()) {
 73     if (obj->is_instance()) {
 74       // Case 1: Normal oop, process as usual.
 75       if (ContinuationGCSupport::relativize_stack_chunk(obj)) {
 76           // Loom doesn't support mixing of weak marking and strong marking of
 77           // stack chunks.
 78           cl->set_weak(false);
 79       }
 80 
 81       obj->oop_iterate(cl);
 82       dedup_string<STRING_DEDUP>(obj, req);
 83     } else if (obj->is_objArray()) {
 84       // Case 2: Object array instance and no chunk is set. Must be the first
 85       // time we visit it, start the chunked processing.
 86       do_chunked_array_start<T>(q, cl, obj, weak);
 87     } else {
 88       // Case 3: Primitive array. Do nothing, no oops there. We use the same
 89       // performance tweak TypeArrayKlass::oop_oop_iterate_impl is using:
 90       // We skip iterating over the klass pointer since we know that
 91       // Universe::TypeArrayKlass never moves.
 92       assert (obj->is_typeArray(), "should be type array");
 93     }
 94     // Count liveness the last: push the outstanding work to the queues first
 95     // Avoid double-counting objects that are visited twice due to upgrade
 96     // from final- to strong mark.
 97     if (task->count_liveness()) {
 98       count_liveness<GENERATION>(live_data, obj);
 99     }
100   } else {
101     // Case 4: Array chunk, has sensible chunk id. Process it.
102     do_chunked_array<T>(q, cl, obj, task->chunk(), task->pow(), weak);
103   }
104 }
105 
106 template <ShenandoahGenerationType GENERATION>
107 inline void ShenandoahMark::count_liveness(ShenandoahLiveData* live_data, oop obj) {
108   ShenandoahHeap* const heap = ShenandoahHeap::heap();
109   size_t region_idx = heap->heap_region_index_containing(obj);
110   ShenandoahHeapRegion* region = heap->get_region(region_idx);
111   size_t size = obj->size();
112 
113   if (!region->is_humongous_start()) {
114     assert(!region->is_humongous(), "Cannot have continuations here");
115     ShenandoahLiveData cur = live_data[region_idx];
116     size_t new_val = size + cur;
117     if (new_val >= SHENANDOAH_LIVEDATA_MAX) {
118       // overflow, flush to region data
119       region->increase_live_data_gc_words(new_val);
120       live_data[region_idx] = 0;
121     } else {
122       // still good, remember in locals
123       live_data[region_idx] = (ShenandoahLiveData) new_val;
124     }
125   } else {
126     shenandoah_assert_in_correct_region(nullptr, obj);
127     size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
128 
129     for (size_t i = region_idx; i < region_idx + num_regions; i++) {
130       ShenandoahHeapRegion* chain_reg = heap->get_region(i);
131       assert(chain_reg->is_humongous(), "Expecting a humongous region");
132       chain_reg->increase_live_data_gc_words(chain_reg->used() >> LogHeapWordSize);
133     }
134   }
135 }
136 
137 template <class T>
138 inline void ShenandoahMark::do_chunked_array_start(ShenandoahObjToScanQueue* q, T* cl, oop obj, bool weak) {
139   assert(obj->is_objArray(), "expect object array");
140   objArrayOop array = objArrayOop(obj);
141   int len = array->length();
142 
143   // Mark objArray klass metadata
144   if (Devirtualizer::do_metadata(cl)) {
145     Devirtualizer::do_klass(cl, array->klass());
146   }
147 
148   if (len <= (int) ObjArrayMarkingStride*2) {
149     // A few slices only, process directly
150     array->oop_iterate_range(cl, 0, len);
151   } else {
152     int bits = log2i_graceful(len);
153     // Compensate for non-power-of-two arrays, cover the array in excess:
154     if (len != (1 << bits)) bits++;
155 
156     // Only allow full chunks on the queue. This frees do_chunked_array() from checking from/to
157     // boundaries against array->length(), touching the array header on every chunk.
158     //
159     // To do this, we cut the prefix in full-sized chunks, and submit them on the queue.
160     // If the array is not divided in chunk sizes, then there would be an irregular tail,
161     // which we will process separately.
162 
163     int last_idx = 0;
164 
165     int chunk = 1;
166     int pow = bits;
167 
168     // Handle overflow
169     if (pow >= 31) {
170       assert (pow == 31, "sanity");
171       pow--;
172       chunk = 2;
173       last_idx = (1 << pow);
174       bool pushed = q->push(ShenandoahMarkTask(array, true, weak, 1, pow));
175       assert(pushed, "overflow queue should always succeed pushing");
176     }
177 
178     // Split out tasks, as suggested in ShenandoahMarkTask docs. Record the last
179     // successful right boundary to figure out the irregular tail.
180     while ((1 << pow) > (int)ObjArrayMarkingStride &&
181            (chunk*2 < ShenandoahMarkTask::chunk_size())) {
182       pow--;
183       int left_chunk = chunk*2 - 1;
184       int right_chunk = chunk*2;
185       int left_chunk_end = left_chunk * (1 << pow);
186       if (left_chunk_end < len) {
187         bool pushed = q->push(ShenandoahMarkTask(array, true, weak, left_chunk, pow));
188         assert(pushed, "overflow queue should always succeed pushing");
189         chunk = right_chunk;
190         last_idx = left_chunk_end;
191       } else {
192         chunk = left_chunk;
193       }
194     }
195 
196     // Process the irregular tail, if present
197     int from = last_idx;
198     if (from < len) {
199       array->oop_iterate_range(cl, from, len);
200     }
201   }
202 }
203 
204 template <class T>
205 inline void ShenandoahMark::do_chunked_array(ShenandoahObjToScanQueue* q, T* cl, oop obj, int chunk, int pow, bool weak) {
206   assert(obj->is_objArray(), "expect object array");
207   objArrayOop array = objArrayOop(obj);
208 
209   assert (ObjArrayMarkingStride > 0, "sanity");
210 
211   // Split out tasks, as suggested in ShenandoahMarkTask docs. Avoid pushing tasks that
212   // are known to start beyond the array.
213   while ((1 << pow) > (int)ObjArrayMarkingStride && (chunk*2 < ShenandoahMarkTask::chunk_size())) {
214     pow--;
215     chunk *= 2;
216     bool pushed = q->push(ShenandoahMarkTask(array, true, weak, chunk - 1, pow));
217     assert(pushed, "overflow queue should always succeed pushing");
218   }
219 
220   int chunk_size = 1 << pow;
221 
222   int from = (chunk - 1) * chunk_size;
223   int to = chunk * chunk_size;
224 
225 #ifdef ASSERT
226   int len = array->length();
227   assert (0 <= from && from < len, "from is sane: %d/%d", from, len);
228   assert (0 < to && to <= len, "to is sane: %d/%d", to, len);
229 #endif
230 
231   array->oop_iterate_range(cl, from, to);
232 }
233 
234 template <ShenandoahGenerationType GENERATION>
235 class ShenandoahSATBBufferClosure : public SATBBufferClosure {
236 private:
237   ShenandoahObjToScanQueue* _queue;
238   ShenandoahHeap* _heap;
239   ShenandoahMarkingContext* const _mark_context;
240 public:
241   ShenandoahSATBBufferClosure(ShenandoahObjToScanQueue* q) :
242     _queue(q),
243     _heap(ShenandoahHeap::heap()),
244     _mark_context(_heap->marking_context())
245   {
246   }
247 
248   void do_buffer(void **buffer, size_t size) {
249     assert(size == 0 || !_heap->has_forwarded_objects(), "Forwarded objects are not expected here");
250     for (size_t i = 0; i < size; ++i) {
251       oop *p = (oop *) &buffer[i];
252       ShenandoahMark::mark_through_ref<oop, GENERATION>(p, _queue, _mark_context, false);
253     }
254   }
255 };
256 
257 template<class T, ShenandoahGenerationType GENERATION>
258 inline void ShenandoahMark::mark_through_ref(T* p, ShenandoahObjToScanQueue* q, ShenandoahMarkingContext* const mark_context, bool weak) {
259   T o = RawAccess<>::oop_load(p);
260   if (!CompressedOops::is_null(o)) {
261     oop obj = CompressedOops::decode_not_null(o);
262 
263     shenandoah_assert_not_forwarded(p, obj);
264     shenandoah_assert_not_in_cset_except(p, obj, ShenandoahHeap::heap()->cancelled_gc());
265 
266     bool skip_live = false;
267     bool marked;
268     if (weak) {
269       marked = mark_context->mark_weak(obj);
270     } else {
271       marked = mark_context->mark_strong(obj, /* was_upgraded = */ skip_live);
272     }
273     if (marked) {
274       bool pushed = q->push(ShenandoahMarkTask(obj, skip_live, weak));
275       assert(pushed, "overflow queue should always succeed pushing");
276     }
277 
278     shenandoah_assert_marked(p, obj);
279   }
280 }
281 
282 ShenandoahObjToScanQueueSet* ShenandoahMark::task_queues() const {
283   return _task_queues;
284 }
285 
286 ShenandoahObjToScanQueue* ShenandoahMark::get_queue(uint index) const {
287   return _task_queues->queue(index);
288 }
289 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHMARK_INLINE_HPP