1 /*
2 * Copyright (c) 2015, 2018, 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_VM_GC_SHENANDOAH_SHENANDOAHCONCURRENTMARK_INLINE_HPP
25 #define SHARE_VM_GC_SHENANDOAH_SHENANDOAHCONCURRENTMARK_INLINE_HPP
26
27 #include "gc/shenandoah/shenandoahAsserts.hpp"
28 #include "gc/shenandoah/shenandoahBrooksPointer.hpp"
29 #include "gc/shenandoah/shenandoahBarrierSet.inline.hpp"
30 #include "gc/shenandoah/shenandoahConcurrentMark.hpp"
31 #include "gc/shenandoah/shenandoahMarkingContext.inline.hpp"
32 #include "gc/shenandoah/shenandoahStringDedup.hpp"
33 #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
34 #include "memory/iterator.inline.hpp"
35 #include "oops/oop.inline.hpp"
36 #include "runtime/prefetch.inline.hpp"
37
38 template <class T>
39 void ShenandoahConcurrentMark::do_task(ShenandoahObjToScanQueue* q, T* cl, jushort* live_data, ShenandoahMarkTask* task) {
40 oop obj = task->obj();
41
42 shenandoah_assert_not_forwarded_except(NULL, obj, _heap->is_concurrent_traversal_in_progress() && _heap->cancelled_gc());
43 shenandoah_assert_marked(NULL, obj);
44 shenandoah_assert_not_in_cset_except(NULL, obj, _heap->cancelled_gc());
45
46 if (task->is_not_chunked()) {
47 if (obj->is_instance()) {
48 // Case 1: Normal oop, process as usual.
49 obj->oop_iterate(cl);
50 } else if (obj->is_objArray()) {
51 // Case 2: Object array instance and no chunk is set. Must be the first
52 // time we visit it, start the chunked processing.
53 do_chunked_array_start<T>(q, cl, obj);
54 } else {
55 // Case 3: Primitive array. Do nothing, no oops there. We use the same
56 // performance tweak TypeArrayKlass::oop_oop_iterate_impl is using:
57 // We skip iterating over the klass pointer since we know that
58 // Universe::TypeArrayKlass never moves.
59 assert (obj->is_typeArray(), "should be type array");
60 }
61 // Count liveness the last: push the outstanding work to the queues first
62 count_liveness(live_data, obj);
63 } else {
64 // Case 4: Array chunk, has sensible chunk id. Process it.
65 do_chunked_array<T>(q, cl, obj, task->chunk(), task->pow());
66 }
67 }
68
69 inline void ShenandoahConcurrentMark::count_liveness(jushort* live_data, oop obj) {
70 size_t region_idx = _heap->heap_region_index_containing(obj);
71 ShenandoahHeapRegion* region = _heap->get_region(region_idx);
72 size_t size = obj->size() + ShenandoahBrooksPointer::word_size();
73
74 if (!region->is_humongous_start()) {
75 assert(!region->is_humongous(), "Cannot have continuations here");
76 size_t max = (1 << (sizeof(jushort) * 8)) - 1;
77 if (size >= max) {
78 // too big, add to region data directly
79 region->increase_live_data_gc_words(size);
80 } else {
81 jushort cur = live_data[region_idx];
82 size_t new_val = cur + size;
83 if (new_val >= max) {
84 // overflow, flush to region data
85 region->increase_live_data_gc_words(new_val);
86 live_data[region_idx] = 0;
87 } else {
88 // still good, remember in locals
89 live_data[region_idx] = (jushort) new_val;
90 }
91 }
92 } else {
93 shenandoah_assert_in_correct_region(NULL, obj);
94 size_t num_regions = ShenandoahHeapRegion::required_regions(size * HeapWordSize);
95
96 for (size_t i = region_idx; i < region_idx + num_regions; i++) {
97 ShenandoahHeapRegion* chain_reg = _heap->get_region(i);
98 assert(chain_reg->is_humongous(), "Expecting a humongous region");
99 chain_reg->increase_live_data_gc_words(chain_reg->used() >> LogHeapWordSize);
100 }
101 }
102 }
103
104 template <class T>
105 inline void ShenandoahConcurrentMark::do_chunked_array_start(ShenandoahObjToScanQueue* q, T* cl, oop obj) {
106 assert(obj->is_objArray(), "expect object array");
107 objArrayOop array = objArrayOop(obj);
108 int len = array->length();
109
110 if (len <= (int) ObjArrayMarkingStride*2) {
111 // A few slices only, process directly
112 array->oop_iterate_range(cl, 0, len);
113 } else {
114 int bits = log2_long((size_t) len);
115 // Compensate for non-power-of-two arrays, cover the array in excess:
116 if (len != (1 << bits)) bits++;
117
118 // Only allow full chunks on the queue. This frees do_chunked_array() from checking from/to
119 // boundaries against array->length(), touching the array header on every chunk.
120 //
121 // To do this, we cut the prefix in full-sized chunks, and submit them on the queue.
122 // If the array is not divided in chunk sizes, then there would be an irregular tail,
123 // which we will process separately.
124
125 int last_idx = 0;
126
127 int chunk = 1;
128 int pow = bits;
129
130 // Handle overflow
131 if (pow >= 31) {
132 assert (pow == 31, "sanity");
133 pow--;
134 chunk = 2;
135 last_idx = (1 << pow);
136 bool pushed = q->push(ShenandoahMarkTask(array, 1, pow));
137 assert(pushed, "overflow queue should always succeed pushing");
138 }
139
140 // Split out tasks, as suggested in ObjArrayChunkedTask docs. Record the last
141 // successful right boundary to figure out the irregular tail.
142 while ((1 << pow) > (int)ObjArrayMarkingStride &&
143 (chunk*2 < ShenandoahMarkTask::chunk_size())) {
144 pow--;
145 int left_chunk = chunk*2 - 1;
146 int right_chunk = chunk*2;
147 int left_chunk_end = left_chunk * (1 << pow);
148 if (left_chunk_end < len) {
149 bool pushed = q->push(ShenandoahMarkTask(array, left_chunk, pow));
150 assert(pushed, "overflow queue should always succeed pushing");
151 chunk = right_chunk;
152 last_idx = left_chunk_end;
153 } else {
154 chunk = left_chunk;
155 }
156 }
157
158 // Process the irregular tail, if present
159 int from = last_idx;
160 if (from < len) {
161 array->oop_iterate_range(cl, from, len);
162 }
163 }
164 }
165
166 template <class T>
167 inline void ShenandoahConcurrentMark::do_chunked_array(ShenandoahObjToScanQueue* q, T* cl, oop obj, int chunk, int pow) {
168 assert(obj->is_objArray(), "expect object array");
169 objArrayOop array = objArrayOop(obj);
170
171 assert (ObjArrayMarkingStride > 0, "sanity");
172
173 // Split out tasks, as suggested in ObjArrayChunkedTask docs. Avoid pushing tasks that
174 // are known to start beyond the array.
175 while ((1 << pow) > (int)ObjArrayMarkingStride && (chunk*2 < ShenandoahMarkTask::chunk_size())) {
176 pow--;
177 chunk *= 2;
178 bool pushed = q->push(ShenandoahMarkTask(array, chunk - 1, pow));
179 assert(pushed, "overflow queue should always succeed pushing");
180 }
181
182 int chunk_size = 1 << pow;
183
184 int from = (chunk - 1) * chunk_size;
185 int to = chunk * chunk_size;
186
187 #ifdef ASSERT
188 int len = array->length();
189 assert (0 <= from && from < len, "from is sane: %d/%d", from, len);
190 assert (0 < to && to <= len, "to is sane: %d/%d", to, len);
191 #endif
192
193 array->oop_iterate_range(cl, from, to);
194 }
195
196 class ShenandoahSATBBufferClosure : public SATBBufferClosure {
197 private:
198 ShenandoahObjToScanQueue* _queue;
199 ShenandoahHeap* _heap;
200 ShenandoahMarkingContext* const _mark_context;
201 public:
202 ShenandoahSATBBufferClosure(ShenandoahObjToScanQueue* q) :
203 _queue(q),
204 _heap(ShenandoahHeap::heap()),
205 _mark_context(_heap->marking_context())
206 {
207 }
208
209 void do_buffer(void **buffer, size_t size) {
210 if (_heap->has_forwarded_objects()) {
211 if (ShenandoahStringDedup::is_enabled()) {
212 do_buffer_impl<RESOLVE, ENQUEUE_DEDUP>(buffer, size);
213 } else {
214 do_buffer_impl<RESOLVE, NO_DEDUP>(buffer, size);
215 }
216 } else {
217 if (ShenandoahStringDedup::is_enabled()) {
218 do_buffer_impl<NONE, ENQUEUE_DEDUP>(buffer, size);
219 } else {
220 do_buffer_impl<NONE, NO_DEDUP>(buffer, size);
221 }
222 }
223 }
224
225 template<UpdateRefsMode UPDATE_REFS, StringDedupMode STRING_DEDUP>
226 void do_buffer_impl(void **buffer, size_t size) {
227 for (size_t i = 0; i < size; ++i) {
228 oop *p = (oop *) &buffer[i];
229 ShenandoahConcurrentMark::mark_through_ref<oop, UPDATE_REFS, STRING_DEDUP>(p, _heap, _queue, _mark_context);
230 }
231 }
232 };
233
234 template<class T, UpdateRefsMode UPDATE_REFS, StringDedupMode STRING_DEDUP>
235 inline void ShenandoahConcurrentMark::mark_through_ref(T *p, ShenandoahHeap* heap, ShenandoahObjToScanQueue* q, ShenandoahMarkingContext* const mark_context) {
236 T o = RawAccess<>::oop_load(p);
237 if (!CompressedOops::is_null(o)) {
238 oop obj = CompressedOops::decode_not_null(o);
239 switch (UPDATE_REFS) {
240 case NONE:
241 break;
242 case RESOLVE:
243 obj = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
244 break;
245 case SIMPLE:
246 // We piggy-back reference updating to the marking tasks.
247 obj = heap->update_with_forwarded_not_null(p, obj);
248 break;
249 case CONCURRENT:
250 obj = heap->maybe_update_with_forwarded_not_null(p, obj);
251 break;
252 default:
253 ShouldNotReachHere();
254 }
255
256 // Note: Only when concurrently updating references can obj become NULL here.
257 // It happens when a mutator thread beats us by writing another value. In that
258 // case we don't need to do anything else.
259 if (UPDATE_REFS != CONCURRENT || !CompressedOops::is_null(obj)) {
260 shenandoah_assert_not_forwarded(p, obj);
261 shenandoah_assert_not_in_cset_except(p, obj, heap->cancelled_gc());
262
263 if (mark_context->mark(obj)) {
264 bool pushed = q->push(ShenandoahMarkTask(obj));
265 assert(pushed, "overflow queue should always succeed pushing");
266
267 if ((STRING_DEDUP == ENQUEUE_DEDUP) && ShenandoahStringDedup::is_candidate(obj)) {
268 assert(ShenandoahStringDedup::is_enabled(), "Must be enabled");
269 ShenandoahStringDedup::enqueue_candidate(obj);
270 }
271 }
272
273 shenandoah_assert_marked(p, obj);
274 }
275 }
276 }
277
278 #endif // SHARE_VM_GC_SHENANDOAH_SHENANDOAHCONCURRENTMARK_INLINE_HPP