1 /*
2 * Copyright (c) 2015, 2022, Red Hat, Inc. All rights reserved.
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
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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
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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/shenandoahStringDedup.inline.hpp"
36 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
37 #include "gc/shenandoah/shenandoahUtils.hpp"
38 #include "memory/iterator.inline.hpp"
39 #include "oops/compressedOops.inline.hpp"
40 #include "oops/oop.inline.hpp"
41 #include "runtime/prefetch.inline.hpp"
42 #include "utilities/devirtualizer.inline.hpp"
43 #include "utilities/powerOfTwo.hpp"
44
45 template <StringDedupMode STRING_DEDUP>
46 void ShenandoahMark::dedup_string(oop obj, StringDedup::Requests* const req) {
47 if (STRING_DEDUP == ENQUEUE_DEDUP) {
48 if (ShenandoahStringDedup::is_candidate(obj)) {
49 req->add(obj);
50 }
51 } else if (STRING_DEDUP == ALWAYS_DEDUP) {
52 if (ShenandoahStringDedup::is_string_candidate(obj) &&
53 !ShenandoahStringDedup::dedup_requested(obj)) {
54 req->add(obj);
55 }
56 }
57 }
58
59 template <class T, StringDedupMode STRING_DEDUP>
60 void ShenandoahMark::do_task(ShenandoahObjToScanQueue* q, T* cl, ShenandoahLiveData* live_data, StringDedup::Requests* const req, ShenandoahMarkTask* task) {
61 oop obj = task->obj();
62
63 // TODO: This will push array chunks into the mark queue with no regard for
64 // generations. I don't think it will break anything, but the young generation
65 // scan might end up processing some old generation array chunks.
66
67 shenandoah_assert_not_forwarded(nullptr, obj);
68 shenandoah_assert_marked(nullptr, obj);
69 shenandoah_assert_not_in_cset_except(nullptr, obj, ShenandoahHeap::heap()->cancelled_gc());
70
71 // Are we in weak subgraph scan?
72 bool weak = task->is_weak();
73 cl->set_weak(weak);
74
75 if (task->is_not_chunked()) {
76 if (obj->is_instance()) {
77 // Case 1: Normal oop, process as usual.
78 if (ContinuationGCSupport::relativize_stack_chunk(obj)) {
79 // Loom doesn't support mixing of weak marking and strong marking of
80 // stack chunks.
81 cl->set_weak(false);
82 }
83
84 obj->oop_iterate(cl);
85 dedup_string<STRING_DEDUP>(obj, req);
86 } else if (obj->is_objArray()) {
87 // Case 2: Object array instance and no chunk is set. Must be the first
88 // time we visit it, start the chunked processing.
89 do_chunked_array_start<T>(q, cl, obj, weak);
90 } else {
91 // Case 3: Primitive array. Do nothing, no oops there. We use the same
92 // performance tweak TypeArrayKlass::oop_oop_iterate_impl is using:
93 // We skip iterating over the klass pointer since we know that
94 // Universe::TypeArrayKlass never moves.
95 assert (obj->is_typeArray(), "should be type array");
96 }
97 // Count liveness the last: push the outstanding work to the queues first
98 // Avoid double-counting objects that are visited twice due to upgrade
99 // from final- to strong mark.
100 if (task->count_liveness()) {
101 count_liveness(live_data, obj);
102 }
103 } else {
104 // Case 4: Array chunk, has sensible chunk id. Process it.
105 do_chunked_array<T>(q, cl, obj, task->chunk(), task->pow(), weak);
106 }
107 }
108
109 inline void ShenandoahMark::count_liveness(ShenandoahLiveData* live_data, oop obj) {
110 ShenandoahHeap* const heap = ShenandoahHeap::heap();
111 size_t region_idx = heap->heap_region_index_containing(obj);
112 ShenandoahHeapRegion* region = heap->get_region(region_idx);
113 size_t size = obj->size();
114
115 if (!region->is_humongous_start()) {
116 assert(!region->is_humongous(), "Cannot have continuations here");
117 assert(region->affiliation() != FREE, "Do not count live data within Free Regular Region " SIZE_FORMAT, region_idx);
118 ShenandoahLiveData cur = live_data[region_idx];
119 size_t new_val = size + cur;
120 if (new_val >= SHENANDOAH_LIVEDATA_MAX) {
121 // overflow, flush to region data
122 region->increase_live_data_gc_words(new_val);
123 live_data[region_idx] = 0;
124 } else {
125 // still good, remember in locals
126 live_data[region_idx] = (ShenandoahLiveData) new_val;
127 }
128 } else {
129 shenandoah_assert_in_correct_region(nullptr, obj);
130 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
131
132 assert(region->affiliation() != FREE, "Do not count live data within FREE Humongous Start Region " SIZE_FORMAT, region_idx);
133 for (size_t i = region_idx; i < region_idx + num_regions; i++) {
134 ShenandoahHeapRegion* chain_reg = heap->get_region(i);
135 assert(chain_reg->is_humongous(), "Expecting a humongous region");
136 assert(chain_reg->affiliation() != FREE, "Do not count live data within FREE Humongous Continuation Region " SIZE_FORMAT, i);
137 chain_reg->increase_live_data_gc_words(chain_reg->used() >> LogHeapWordSize);
138 }
139 }
140 }
141
142 template <class T>
143 inline void ShenandoahMark::do_chunked_array_start(ShenandoahObjToScanQueue* q, T* cl, oop obj, bool weak) {
144 assert(obj->is_objArray(), "expect object array");
145 objArrayOop array = objArrayOop(obj);
146 int len = array->length();
147
148 // Mark objArray klass metadata
149 if (Devirtualizer::do_metadata(cl)) {
150 Devirtualizer::do_klass(cl, array->klass());
151 }
152
153 if (len <= (int) ObjArrayMarkingStride*2) {
154 // A few slices only, process directly
155 array->oop_iterate_range(cl, 0, len);
156 } else {
157 int bits = log2i_graceful(len);
158 // Compensate for non-power-of-two arrays, cover the array in excess:
159 if (len != (1 << bits)) bits++;
160
161 // Only allow full chunks on the queue. This frees do_chunked_array() from checking from/to
162 // boundaries against array->length(), touching the array header on every chunk.
163 //
164 // To do this, we cut the prefix in full-sized chunks, and submit them on the queue.
165 // If the array is not divided in chunk sizes, then there would be an irregular tail,
166 // which we will process separately.
167
168 int last_idx = 0;
169
170 int chunk = 1;
171 int pow = bits;
172
173 // Handle overflow
174 if (pow >= 31) {
175 assert (pow == 31, "sanity");
176 pow--;
177 chunk = 2;
178 last_idx = (1 << pow);
179 bool pushed = q->push(ShenandoahMarkTask(array, true, weak, 1, pow));
180 assert(pushed, "overflow queue should always succeed pushing");
181 }
182
183 // Split out tasks, as suggested in ShenandoahMarkTask docs. Record the last
184 // successful right boundary to figure out the irregular tail.
185 while ((1 << pow) > (int)ObjArrayMarkingStride &&
186 (chunk*2 < ShenandoahMarkTask::chunk_size())) {
187 pow--;
188 int left_chunk = chunk*2 - 1;
189 int right_chunk = chunk*2;
190 int left_chunk_end = left_chunk * (1 << pow);
191 if (left_chunk_end < len) {
192 bool pushed = q->push(ShenandoahMarkTask(array, true, weak, left_chunk, pow));
193 assert(pushed, "overflow queue should always succeed pushing");
194 chunk = right_chunk;
195 last_idx = left_chunk_end;
196 } else {
197 chunk = left_chunk;
198 }
199 }
200
201 // Process the irregular tail, if present
202 int from = last_idx;
203 if (from < len) {
204 array->oop_iterate_range(cl, from, len);
205 }
206 }
207 }
208
209 template <class T>
210 inline void ShenandoahMark::do_chunked_array(ShenandoahObjToScanQueue* q, T* cl, oop obj, int chunk, int pow, bool weak) {
211 assert(obj->is_objArray(), "expect object array");
212 objArrayOop array = objArrayOop(obj);
213
214 assert (ObjArrayMarkingStride > 0, "sanity");
215
216 // Split out tasks, as suggested in ShenandoahMarkTask docs. Avoid pushing tasks that
217 // are known to start beyond the array.
218 while ((1 << pow) > (int)ObjArrayMarkingStride && (chunk*2 < ShenandoahMarkTask::chunk_size())) {
219 pow--;
220 chunk *= 2;
221 bool pushed = q->push(ShenandoahMarkTask(array, true, weak, chunk - 1, pow));
222 assert(pushed, "overflow queue should always succeed pushing");
223 }
224
225 int chunk_size = 1 << pow;
226
227 int from = (chunk - 1) * chunk_size;
228 int to = chunk * chunk_size;
229
230 #ifdef ASSERT
231 int len = array->length();
232 assert (0 <= from && from < len, "from is sane: %d/%d", from, len);
233 assert (0 < to && to <= len, "to is sane: %d/%d", to, len);
234 #endif
235
236 array->oop_iterate_range(cl, from, to);
237 }
238
239 template <GenerationMode GENERATION>
240 class ShenandoahSATBBufferClosure : public SATBBufferClosure {
241 private:
242 ShenandoahObjToScanQueue* _queue;
243 ShenandoahObjToScanQueue* _old;
244 ShenandoahHeap* _heap;
245 ShenandoahMarkingContext* const _mark_context;
246 public:
247 ShenandoahSATBBufferClosure(ShenandoahObjToScanQueue* q, ShenandoahObjToScanQueue* old) :
248 _queue(q),
249 _old(old),
250 _heap(ShenandoahHeap::heap()),
251 _mark_context(_heap->marking_context())
252 {
253 }
254
255 void do_buffer(void **buffer, size_t size) {
256 assert(size == 0 || !_heap->has_forwarded_objects() || _heap->is_concurrent_old_mark_in_progress(), "Forwarded objects are not expected here");
257 for (size_t i = 0; i < size; ++i) {
258 oop *p = (oop *) &buffer[i];
259 ShenandoahMark::mark_through_ref<oop, GENERATION>(p, _queue, _old, _mark_context, false);
260 }
261 }
262 };
263
264 template<GenerationMode GENERATION>
265 bool ShenandoahMark::in_generation(oop obj) {
266 // Each in-line expansion of in_generation() resolves GENERATION at compile time.
267 if (GENERATION == YOUNG)
268 return ShenandoahHeap::heap()->is_in_young(obj);
269 else if (GENERATION == OLD)
270 return ShenandoahHeap::heap()->is_in_old(obj);
271 else if (GENERATION == GLOBAL)
272 return true;
273 else
274 return false;
275 }
276
277 template<class T, GenerationMode GENERATION>
278 inline void ShenandoahMark::mark_through_ref(T *p, ShenandoahObjToScanQueue* q, ShenandoahObjToScanQueue* old, ShenandoahMarkingContext* const mark_context, bool weak) {
279 T o = RawAccess<>::oop_load(p);
280 if (!CompressedOops::is_null(o)) {
281 oop obj = CompressedOops::decode_not_null(o);
282
283 ShenandoahHeap* heap = ShenandoahHeap::heap();
284 shenandoah_assert_not_forwarded(p, obj);
285 shenandoah_assert_not_in_cset_except(p, obj, heap->cancelled_gc());
286 if (in_generation<GENERATION>(obj)) {
287 mark_ref(q, mark_context, weak, obj);
288 shenandoah_assert_marked(p, obj);
289 if (heap->mode()->is_generational()) {
290 // TODO: As implemented herein, GLOBAL collections reconstruct the card table during GLOBAL concurrent
291 // marking. Note that the card table is cleaned at init_mark time so it needs to be reconstructed to support
292 // future young-gen collections. It might be better to reconstruct card table in
293 // ShenandoahHeapRegion::global_oop_iterate_and_fill_dead. We could either mark all live memory as dirty, or could
294 // use the GLOBAL update-refs scanning of pointers to determine precisely which cards to flag as dirty.
295 if (GENERATION == YOUNG && heap->is_in_old(p)) {
296 // Mark card as dirty because remembered set scanning still finds interesting pointer.
297 heap->mark_card_as_dirty((HeapWord*)p);
298 } else if (GENERATION == GLOBAL && heap->is_in_old(p) && heap->is_in_young(obj)) {
299 // Mark card as dirty because GLOBAL marking finds interesting pointer.
300 heap->mark_card_as_dirty((HeapWord*)p);
301 }
302 }
303 } else if (old != nullptr) {
304 // Young mark, bootstrapping old or concurrent with old marking.
305 mark_ref(old, mark_context, weak, obj);
306 shenandoah_assert_marked(p, obj);
307 } else if (GENERATION == OLD) {
308 // Old mark, found a young pointer.
309 // TODO: Rethink this: may be redundant with dirtying of cards identified during young-gen remembered set scanning
310 // and by mutator write barriers. Assert
311 if (heap->is_in(p)) {
312 assert(heap->is_in_young(obj), "Expected young object.");
313 heap->mark_card_as_dirty(p);
314 }
315 }
316 }
317 }
318
319 inline void ShenandoahMark::mark_ref(ShenandoahObjToScanQueue* q,
320 ShenandoahMarkingContext* const mark_context,
321 bool weak, oop obj) {
322 bool skip_live = false;
323 bool marked;
324 if (weak) {
325 marked = mark_context->mark_weak(obj);
326 } else {
327 marked = mark_context->mark_strong(obj, /* was_upgraded = */ skip_live);
328 }
329 if (marked) {
330 bool pushed = q->push(ShenandoahMarkTask(obj, skip_live, weak));
331 assert(pushed, "overflow queue should always succeed pushing");
332 }
333 }
334
335 ShenandoahObjToScanQueueSet* ShenandoahMark::task_queues() const {
336 return _task_queues;
337 }
338
339 ShenandoahObjToScanQueue* ShenandoahMark::get_queue(uint index) const {
340 return _task_queues->queue(index);
341 }
342
343 ShenandoahObjToScanQueue* ShenandoahMark::get_old_queue(uint index) const {
344 if (_old_gen_task_queues != nullptr) {
345 return _old_gen_task_queues->queue(index);
346 }
347 return nullptr;
348 }
349
350 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHMARK_INLINE_HPP