1 /*
2 * Copyright (c) 2015, 2021, Red Hat, Inc. All rights reserved.
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 *
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.
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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