1 /*
2 * Copyright (c) 2015, 2019, Red Hat, Inc. All rights reserved.
3 *
4 * This code is free software; you can redistribute it and/or modify it
5 * under the terms of the GNU General Public License version 2 only, as
6 * published by the Free Software Foundation.
7 *
8 * This code is distributed in the hope that it will be useful, but WITHOUT
9 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
10 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
11 * version 2 for more details (a copy is included in the LICENSE file that
12 * accompanied this code).
13 *
14 * You should have received a copy of the GNU General Public License version
15 * 2 along with this work; if not, write to the Free Software Foundation,
16 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
17 *
18 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
19 * or visit www.oracle.com if you need additional information or have any
20 * questions.
21 *
22 */
23
24 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHCONCURRENTMARK_INLINE_HPP
25 #define SHARE_GC_SHENANDOAH_SHENANDOAHCONCURRENTMARK_INLINE_HPP
26
27 #include "gc/shenandoah/shenandoahAsserts.hpp"
28 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
29 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
30 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
31 #include "gc/shenandoah/shenandoahStringDedup.inline.hpp"
32 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
33 #include "memory/iterator.inline.hpp"
34 #include "oops/oop.inline.hpp"
35 #include "runtime/prefetch.inline.hpp"
36
37 template <class T>
38 void ShenandoahConcurrentMark::do_task(ShenandoahObjToScanQueue* q, T* cl, jushort* live_data, ShenandoahMarkTask* task) {
39 oop obj = task->obj();
40
41 shenandoah_assert_not_forwarded_except(NULL, obj, _heap->is_concurrent_traversal_in_progress() && _heap->cancelled_gc());
42 shenandoah_assert_marked(NULL, obj);
43 shenandoah_assert_not_in_cset_except(NULL, obj, _heap->cancelled_gc());
44
45 if (task->is_not_chunked()) {
46 if (obj->is_instance()) {
47 // Case 1: Normal oop, process as usual.
48 obj->oop_iterate(cl);
49 } else if (obj->is_objArray()) {
50 // Case 2: Object array instance and no chunk is set. Must be the first
51 // time we visit it, start the chunked processing.
52 do_chunked_array_start<T>(q, cl, obj);
53 } else {
54 // Case 3: Primitive array. Do nothing, no oops there. We use the same
55 // performance tweak TypeArrayKlass::oop_oop_iterate_impl is using:
56 // We skip iterating over the klass pointer since we know that
57 // Universe::TypeArrayKlass never moves.
58 assert (obj->is_typeArray(), "should be type array");
59 }
60 // Count liveness the last: push the outstanding work to the queues first
61 count_liveness(live_data, obj);
62 } else {
63 // Case 4: Array chunk, has sensible chunk id. Process it.
64 do_chunked_array<T>(q, cl, obj, task->chunk(), task->pow());
65 }
66 }
67
68 inline void ShenandoahConcurrentMark::count_liveness(jushort* live_data, oop obj) {
69 size_t region_idx = _heap->heap_region_index_containing(obj);
70 ShenandoahHeapRegion* region = _heap->get_region(region_idx);
71 size_t size = obj->size();
72
73 if (!region->is_humongous_start()) {
74 assert(!region->is_humongous(), "Cannot have continuations here");
75 size_t max = (1 << (sizeof(jushort) * 8)) - 1;
76 if (size >= max) {
77 // too big, add to region data directly
78 region->increase_live_data_gc_words(size);
79 } else {
80 jushort cur = live_data[region_idx];
81 size_t new_val = cur + size;
82 if (new_val >= max) {
83 // overflow, flush to region data
84 region->increase_live_data_gc_words(new_val);
85 live_data[region_idx] = 0;
86 } else {
87 // still good, remember in locals
88 live_data[region_idx] = (jushort) new_val;
89 }
90 }
91 } else {
92 shenandoah_assert_in_correct_region(NULL, obj);
93 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
94
95 for (size_t i = region_idx; i < region_idx + num_regions; i++) {
96 ShenandoahHeapRegion* chain_reg = _heap->get_region(i);
97 assert(chain_reg->is_humongous(), "Expecting a humongous region");
98 chain_reg->increase_live_data_gc_words(chain_reg->used() >> LogHeapWordSize);
99 }
100 }
101 }
102
103 template <class T>
104 inline void ShenandoahConcurrentMark::do_chunked_array_start(ShenandoahObjToScanQueue* q, T* cl, oop obj) {
105 assert(obj->is_objArray(), "expect object array");
106 objArrayOop array = objArrayOop(obj);
107 int len = array->length();
108
109 if (len <= (int) ObjArrayMarkingStride*2) {
110 // A few slices only, process directly
111 array->oop_iterate_range(cl, 0, len);
112 } else {
113 int bits = log2_long((size_t) len);
114 // Compensate for non-power-of-two arrays, cover the array in excess:
115 if (len != (1 << bits)) bits++;
116
117 // Only allow full chunks on the queue. This frees do_chunked_array() from checking from/to
118 // boundaries against array->length(), touching the array header on every chunk.
119 //
120 // To do this, we cut the prefix in full-sized chunks, and submit them on the queue.
121 // If the array is not divided in chunk sizes, then there would be an irregular tail,
122 // which we will process separately.
123
124 int last_idx = 0;
125
126 int chunk = 1;
127 int pow = bits;
128
129 // Handle overflow
130 if (pow >= 31) {
131 assert (pow == 31, "sanity");
132 pow--;
133 chunk = 2;
134 last_idx = (1 << pow);
135 bool pushed = q->push(ShenandoahMarkTask(array, 1, pow));
136 assert(pushed, "overflow queue should always succeed pushing");
137 }
138
139 // Split out tasks, as suggested in ObjArrayChunkedTask docs. Record the last
140 // successful right boundary to figure out the irregular tail.
141 while ((1 << pow) > (int)ObjArrayMarkingStride &&
142 (chunk*2 < ShenandoahMarkTask::chunk_size())) {
143 pow--;
144 int left_chunk = chunk*2 - 1;
145 int right_chunk = chunk*2;
146 int left_chunk_end = left_chunk * (1 << pow);
147 if (left_chunk_end < len) {
148 bool pushed = q->push(ShenandoahMarkTask(array, left_chunk, pow));
149 assert(pushed, "overflow queue should always succeed pushing");
150 chunk = right_chunk;
151 last_idx = left_chunk_end;
152 } else {
153 chunk = left_chunk;
154 }
155 }
156
157 // Process the irregular tail, if present
158 int from = last_idx;
159 if (from < len) {
160 array->oop_iterate_range(cl, from, len);
161 }
162 }
163 }
164
165 template <class T>
166 inline void ShenandoahConcurrentMark::do_chunked_array(ShenandoahObjToScanQueue* q, T* cl, oop obj, int chunk, int pow) {
167 assert(obj->is_objArray(), "expect object array");
168 objArrayOop array = objArrayOop(obj);
169
170 assert (ObjArrayMarkingStride > 0, "sanity");
171
172 // Split out tasks, as suggested in ObjArrayChunkedTask docs. Avoid pushing tasks that
173 // are known to start beyond the array.
174 while ((1 << pow) > (int)ObjArrayMarkingStride && (chunk*2 < ShenandoahMarkTask::chunk_size())) {
175 pow--;
176 chunk *= 2;
177 bool pushed = q->push(ShenandoahMarkTask(array, chunk - 1, pow));
178 assert(pushed, "overflow queue should always succeed pushing");
179 }
180
181 int chunk_size = 1 << pow;
182
183 int from = (chunk - 1) * chunk_size;
184 int to = chunk * chunk_size;
185
186 #ifdef ASSERT
187 int len = array->length();
188 assert (0 <= from && from < len, "from is sane: %d/%d", from, len);
189 assert (0 < to && to <= len, "to is sane: %d/%d", to, len);
190 #endif
191
192 array->oop_iterate_range(cl, from, to);
193 }
194
195 class ShenandoahSATBBufferClosure : public SATBBufferClosure {
196 private:
197 ShenandoahObjToScanQueue* _queue;
198 ShenandoahHeap* _heap;
199 ShenandoahMarkingContext* const _mark_context;
200 public:
201 ShenandoahSATBBufferClosure(ShenandoahObjToScanQueue* q) :
202 _queue(q),
203 _heap(ShenandoahHeap::heap()),
204 _mark_context(_heap->marking_context())
205 {
206 }
207
208 void do_buffer(void **buffer, size_t size) {
209 if (_heap->has_forwarded_objects()) {
210 if (ShenandoahStringDedup::is_enabled()) {
211 do_buffer_impl<RESOLVE, ENQUEUE_DEDUP>(buffer, size);
212 } else {
213 do_buffer_impl<RESOLVE, NO_DEDUP>(buffer, size);
214 }
215 } else {
216 if (ShenandoahStringDedup::is_enabled()) {
217 do_buffer_impl<NONE, ENQUEUE_DEDUP>(buffer, size);
218 } else {
219 do_buffer_impl<NONE, NO_DEDUP>(buffer, size);
220 }
221 }
222 }
223
224 template<UpdateRefsMode UPDATE_REFS, StringDedupMode STRING_DEDUP>
225 void do_buffer_impl(void **buffer, size_t size) {
226 for (size_t i = 0; i < size; ++i) {
227 oop *p = (oop *) &buffer[i];
228 ShenandoahConcurrentMark::mark_through_ref<oop, UPDATE_REFS, STRING_DEDUP>(p, _heap, _queue, _mark_context);
229 }
230 }
231 };
232
233 template<class T, UpdateRefsMode UPDATE_REFS, StringDedupMode STRING_DEDUP>
234 inline void ShenandoahConcurrentMark::mark_through_ref(T *p, ShenandoahHeap* heap, ShenandoahObjToScanQueue* q, ShenandoahMarkingContext* const mark_context) {
235 T o = RawAccess<>::oop_load(p);
236 if (!CompressedOops::is_null(o)) {
237 oop obj = CompressedOops::decode_not_null(o);
238 switch (UPDATE_REFS) {
239 case NONE:
240 break;
241 case RESOLVE:
242 obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
243 break;
244 case SIMPLE:
245 // We piggy-back reference updating to the marking tasks.
246 obj = heap->update_with_forwarded_not_null(p, obj);
247 break;
248 case CONCURRENT:
249 obj = heap->maybe_update_with_forwarded_not_null(p, obj);
250 break;
251 default:
252 ShouldNotReachHere();
253 }
254
255 // Note: Only when concurrently updating references can obj become NULL here.
256 // It happens when a mutator thread beats us by writing another value. In that
257 // case we don't need to do anything else.
258 if (UPDATE_REFS != CONCURRENT || !CompressedOops::is_null(obj)) {
259 shenandoah_assert_not_forwarded(p, obj);
260 shenandoah_assert_not_in_cset_except(p, obj, heap->cancelled_gc());
261
262 if (mark_context->mark(obj)) {
263 bool pushed = q->push(ShenandoahMarkTask(obj));
264 assert(pushed, "overflow queue should always succeed pushing");
265
266 if ((STRING_DEDUP == ENQUEUE_DEDUP) && ShenandoahStringDedup::is_candidate(obj)) {
267 assert(ShenandoahStringDedup::is_enabled(), "Must be enabled");
268 ShenandoahStringDedup::enqueue_candidate(obj);
269 }
270 }
271
272 shenandoah_assert_marked(p, obj);
273 }
274 }
275 }
276
277 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHCONCURRENTMARK_INLINE_HPP