1 /*
2 * Copyright (c) 2015, 2022, 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.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
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 shenandoah_assert_not_forwarded(nullptr, obj);
64 shenandoah_assert_marked(nullptr, obj);
65 shenandoah_assert_not_in_cset_except(nullptr, obj, ShenandoahHeap::heap()->cancelled_gc());
66
67 // Are we in weak subgraph scan?
68 bool weak = task->is_weak();
69 cl->set_weak(weak);
70
71 if (task->is_not_chunked()) {
72 if (obj->is_instance()) {
73 // Case 1: Normal oop, process as usual.
74 if (ContinuationGCSupport::relativize_stack_chunk(obj)) {
75 // Loom doesn't support mixing of weak marking and strong marking of
76 // stack chunks.
77 cl->set_weak(false);
78 }
79
80 obj->oop_iterate(cl);
81 dedup_string<STRING_DEDUP>(obj, req);
82 } else if (obj->is_objArray()) {
83 // Case 2: Object array instance and no chunk is set. Must be the first
84 // time we visit it, start the chunked processing.
85 do_chunked_array_start<T>(q, cl, obj, weak);
86 } else {
87 // Case 3: Primitive array. Do nothing, no oops there. We use the same
88 // performance tweak TypeArrayKlass::oop_oop_iterate_impl is using:
89 // We skip iterating over the klass pointer since we know that
90 // Universe::TypeArrayKlass never moves.
91 assert (obj->is_typeArray(), "should be type array");
92 }
93 // Count liveness the last: push the outstanding work to the queues first
94 // Avoid double-counting objects that are visited twice due to upgrade
95 // from final- to strong mark.
96 if (task->count_liveness()) {
97 count_liveness(live_data, obj);
98 }
99 } else {
100 // Case 4: Array chunk, has sensible chunk id. Process it.
101 do_chunked_array<T>(q, cl, obj, task->chunk(), task->pow(), weak);
102 }
103 }
104
105 inline void ShenandoahMark::count_liveness(ShenandoahLiveData* live_data, oop obj) {
106 ShenandoahHeap* const heap = ShenandoahHeap::heap();
107 size_t region_idx = heap->heap_region_index_containing(obj);
108 ShenandoahHeapRegion* region = heap->get_region(region_idx);
109 size_t size = obj->size();
110
111 if (!region->is_humongous_start()) {
112 assert(!region->is_humongous(), "Cannot have continuations here");
113 ShenandoahLiveData cur = live_data[region_idx];
114 size_t new_val = size + cur;
115 if (new_val >= SHENANDOAH_LIVEDATA_MAX) {
116 // overflow, flush to region data
117 region->increase_live_data_gc_words(new_val);
118 live_data[region_idx] = 0;
119 } else {
120 // still good, remember in locals
121 live_data[region_idx] = (ShenandoahLiveData) new_val;
122 }
123 } else {
124 shenandoah_assert_in_correct_region(nullptr, obj);
125 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
126
127 for (size_t i = region_idx; i < region_idx + num_regions; i++) {
128 ShenandoahHeapRegion* chain_reg = heap->get_region(i);
129 assert(chain_reg->is_humongous(), "Expecting a humongous region");
130 chain_reg->increase_live_data_gc_words(chain_reg->used() >> LogHeapWordSize);
131 }
132 }
133 }
134
135 template <class T>
136 inline void ShenandoahMark::do_chunked_array_start(ShenandoahObjToScanQueue* q, T* cl, oop obj, bool weak) {
137 assert(obj->is_objArray(), "expect object array");
138 objArrayOop array = objArrayOop(obj);
139 int len = array->length();
140
141 // Mark objArray klass metadata
142 if (Devirtualizer::do_metadata(cl)) {
143 Devirtualizer::do_klass(cl, array->klass());
144 }
145
146 if (len <= (int) ObjArrayMarkingStride*2) {
147 // A few slices only, process directly
148 array->oop_iterate_range(cl, 0, len);
149 } else {
150 int bits = log2i_graceful(len);
151 // Compensate for non-power-of-two arrays, cover the array in excess:
152 if (len != (1 << bits)) bits++;
153
154 // Only allow full chunks on the queue. This frees do_chunked_array() from checking from/to
155 // boundaries against array->length(), touching the array header on every chunk.
156 //
157 // To do this, we cut the prefix in full-sized chunks, and submit them on the queue.
158 // If the array is not divided in chunk sizes, then there would be an irregular tail,
159 // which we will process separately.
160
161 int last_idx = 0;
162
163 int chunk = 1;
164 int pow = bits;
165
166 // Handle overflow
167 if (pow >= 31) {
168 assert (pow == 31, "sanity");
169 pow--;
170 chunk = 2;
171 last_idx = (1 << pow);
172 bool pushed = q->push(ShenandoahMarkTask(array, true, weak, 1, pow));
173 assert(pushed, "overflow queue should always succeed pushing");
174 }
175
176 // Split out tasks, as suggested in ShenandoahMarkTask docs. Record the last
177 // successful right boundary to figure out the irregular tail.
178 while ((1 << pow) > (int)ObjArrayMarkingStride &&
179 (chunk*2 < ShenandoahMarkTask::chunk_size())) {
180 pow--;
181 int left_chunk = chunk*2 - 1;
182 int right_chunk = chunk*2;
183 int left_chunk_end = left_chunk * (1 << pow);
184 if (left_chunk_end < len) {
185 bool pushed = q->push(ShenandoahMarkTask(array, true, weak, left_chunk, pow));
186 assert(pushed, "overflow queue should always succeed pushing");
187 chunk = right_chunk;
188 last_idx = left_chunk_end;
189 } else {
190 chunk = left_chunk;
191 }
192 }
193
194 // Process the irregular tail, if present
195 int from = last_idx;
196 if (from < len) {
197 array->oop_iterate_range(cl, from, len);
198 }
199 }
200 }
201
202 template <class T>
203 inline void ShenandoahMark::do_chunked_array(ShenandoahObjToScanQueue* q, T* cl, oop obj, int chunk, int pow, bool weak) {
204 assert(obj->is_objArray(), "expect object array");
205 objArrayOop array = objArrayOop(obj);
206
207 assert (ObjArrayMarkingStride > 0, "sanity");
208
209 // Split out tasks, as suggested in ShenandoahMarkTask docs. Avoid pushing tasks that
210 // are known to start beyond the array.
211 while ((1 << pow) > (int)ObjArrayMarkingStride && (chunk*2 < ShenandoahMarkTask::chunk_size())) {
212 pow--;
213 chunk *= 2;
214 bool pushed = q->push(ShenandoahMarkTask(array, true, weak, chunk - 1, pow));
215 assert(pushed, "overflow queue should always succeed pushing");
216 }
217
218 int chunk_size = 1 << pow;
219
220 int from = (chunk - 1) * chunk_size;
221 int to = chunk * chunk_size;
222
223 #ifdef ASSERT
224 int len = array->length();
225 assert (0 <= from && from < len, "from is sane: %d/%d", from, len);
226 assert (0 < to && to <= len, "to is sane: %d/%d", to, len);
227 #endif
228
229 array->oop_iterate_range(cl, from, to);
230 }
231
232 class ShenandoahSATBBufferClosure : public SATBBufferClosure {
233 private:
234 ShenandoahObjToScanQueue* _queue;
235 ShenandoahHeap* _heap;
236 ShenandoahMarkingContext* const _mark_context;
237 public:
238 ShenandoahSATBBufferClosure(ShenandoahObjToScanQueue* q) :
239 _queue(q),
240 _heap(ShenandoahHeap::heap()),
241 _mark_context(_heap->marking_context())
242 {
243 }
244
245 void do_buffer(void **buffer, size_t size) {
246 assert(size == 0 || !_heap->has_forwarded_objects(), "Forwarded objects are not expected here");
247 for (size_t i = 0; i < size; ++i) {
248 oop *p = (oop *) &buffer[i];
249 ShenandoahMark::mark_through_ref<oop>(p, _queue, _mark_context, false);
250 }
251 }
252 };
253
254 template<class T>
255 inline void ShenandoahMark::mark_through_ref(T* p, ShenandoahObjToScanQueue* q, ShenandoahMarkingContext* const mark_context, bool weak) {
256 T o = RawAccess<>::oop_load(p);
257 if (!CompressedOops::is_null(o)) {
258 oop obj = CompressedOops::decode_not_null(o);
259
260 shenandoah_assert_not_forwarded(p, obj);
261 shenandoah_assert_not_in_cset_except(p, obj, ShenandoahHeap::heap()->cancelled_gc());
262
263 bool skip_live = false;
264 bool marked;
265 if (weak) {
266 marked = mark_context->mark_weak(obj);
267 } else {
268 marked = mark_context->mark_strong(obj, /* was_upgraded = */ skip_live);
269 }
270 if (marked) {
271 bool pushed = q->push(ShenandoahMarkTask(obj, skip_live, weak));
272 assert(pushed, "overflow queue should always succeed pushing");
273 }
274
275 shenandoah_assert_marked(p, obj);
276 }
277 }
278
279 ShenandoahObjToScanQueueSet* ShenandoahMark::task_queues() const {
280 return _task_queues;
281 }
282
283 ShenandoahObjToScanQueue* ShenandoahMark::get_queue(uint index) const {
284 return _task_queues->queue(index);
285 }
286 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHMARK_INLINE_HPP