1 /*
2 * Copyright (c) 2007, Oracle and/or its affiliates. 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.
22 *
23 */
24
25 # include "incls/_precompiled.incl"
26 # include "incls/_parCardTableModRefBS.cpp.incl"
27
28 void CardTableModRefBS::par_non_clean_card_iterate_work(Space* sp, MemRegion mr,
29 DirtyCardToOopClosure* dcto_cl,
30 MemRegionClosure* cl,
31 bool clear,
32 int n_threads) {
33 if (n_threads > 0) {
34 assert((n_threads == 1 && ParallelGCThreads == 0) ||
35 n_threads <= (int)ParallelGCThreads,
36 "# worker threads != # requested!");
37 // Make sure the LNC array is valid for the space.
38 jbyte** lowest_non_clean;
39 uintptr_t lowest_non_clean_base_chunk_index;
40 size_t lowest_non_clean_chunk_size;
41 get_LNC_array_for_space(sp, lowest_non_clean,
42 lowest_non_clean_base_chunk_index,
43 lowest_non_clean_chunk_size);
44
45 int n_strides = n_threads * StridesPerThread;
46 SequentialSubTasksDone* pst = sp->par_seq_tasks();
47 pst->set_par_threads(n_threads);
48 pst->set_n_tasks(n_strides);
49
50 int stride = 0;
51 while (!pst->is_task_claimed(/* reference */ stride)) {
52 process_stride(sp, mr, stride, n_strides, dcto_cl, cl, clear,
53 lowest_non_clean,
54 lowest_non_clean_base_chunk_index,
55 lowest_non_clean_chunk_size);
56 }
57 if (pst->all_tasks_completed()) {
58 // Clear lowest_non_clean array for next time.
59 intptr_t first_chunk_index = addr_to_chunk_index(mr.start());
60 uintptr_t last_chunk_index = addr_to_chunk_index(mr.last());
61 for (uintptr_t ch = first_chunk_index; ch <= last_chunk_index; ch++) {
62 intptr_t ind = ch - lowest_non_clean_base_chunk_index;
63 assert(0 <= ind && ind < (intptr_t)lowest_non_clean_chunk_size,
64 "Bounds error");
65 lowest_non_clean[ind] = NULL;
66 }
67 }
68 }
69 }
70
71 void
72 CardTableModRefBS::
73 process_stride(Space* sp,
74 MemRegion used,
75 jint stride, int n_strides,
76 DirtyCardToOopClosure* dcto_cl,
77 MemRegionClosure* cl,
78 bool clear,
79 jbyte** lowest_non_clean,
80 uintptr_t lowest_non_clean_base_chunk_index,
81 size_t lowest_non_clean_chunk_size) {
82 // We don't have to go downwards here; it wouldn't help anyway,
83 // because of parallelism.
84
85 // Find the first card address of the first chunk in the stride that is
86 // at least "bottom" of the used region.
87 jbyte* start_card = byte_for(used.start());
88 jbyte* end_card = byte_after(used.last());
89 uintptr_t start_chunk = addr_to_chunk_index(used.start());
90 uintptr_t start_chunk_stride_num = start_chunk % n_strides;
91 jbyte* chunk_card_start;
92
93 if ((uintptr_t)stride >= start_chunk_stride_num) {
94 chunk_card_start = (jbyte*)(start_card +
95 (stride - start_chunk_stride_num) *
96 CardsPerStrideChunk);
97 } else {
98 // Go ahead to the next chunk group boundary, then to the requested stride.
99 chunk_card_start = (jbyte*)(start_card +
100 (n_strides - start_chunk_stride_num + stride) *
101 CardsPerStrideChunk);
102 }
103
104 while (chunk_card_start < end_card) {
105 // We don't have to go downwards here; it wouldn't help anyway,
106 // because of parallelism. (We take care with "min_done"; see below.)
107 // Invariant: chunk_mr should be fully contained within the "used" region.
108 jbyte* chunk_card_end = chunk_card_start + CardsPerStrideChunk;
109 MemRegion chunk_mr = MemRegion(addr_for(chunk_card_start),
110 chunk_card_end >= end_card ?
111 used.end() : addr_for(chunk_card_end));
112 assert(chunk_mr.word_size() > 0, "[chunk_card_start > used_end)");
113 assert(used.contains(chunk_mr), "chunk_mr should be subset of used");
114
115 // Process the chunk.
116 process_chunk_boundaries(sp,
117 dcto_cl,
118 chunk_mr,
119 used,
120 lowest_non_clean,
121 lowest_non_clean_base_chunk_index,
122 lowest_non_clean_chunk_size);
123
124 non_clean_card_iterate_work(chunk_mr, cl, clear);
125
126 // Find the next chunk of the stride.
127 chunk_card_start += CardsPerStrideChunk * n_strides;
128 }
129 }
130
131 void
132 CardTableModRefBS::
133 process_chunk_boundaries(Space* sp,
134 DirtyCardToOopClosure* dcto_cl,
135 MemRegion chunk_mr,
136 MemRegion used,
137 jbyte** lowest_non_clean,
138 uintptr_t lowest_non_clean_base_chunk_index,
139 size_t lowest_non_clean_chunk_size)
140 {
141 // We must worry about the chunk boundaries.
142
143 // First, set our max_to_do:
144 HeapWord* max_to_do = NULL;
145 uintptr_t cur_chunk_index = addr_to_chunk_index(chunk_mr.start());
146 cur_chunk_index = cur_chunk_index - lowest_non_clean_base_chunk_index;
147
148 if (chunk_mr.end() < used.end()) {
149 // This is not the last chunk in the used region. What is the last
150 // object?
151 HeapWord* last_block = sp->block_start(chunk_mr.end());
152 assert(last_block <= chunk_mr.end(), "In case this property changes.");
153 if (last_block == chunk_mr.end()
154 || !sp->block_is_obj(last_block)) {
155 max_to_do = chunk_mr.end();
156
157 } else {
158 // It is an object and starts before the end of the current chunk.
159 // last_obj_card is the card corresponding to the start of the last object
160 // in the chunk. Note that the last object may not start in
161 // the chunk.
162 jbyte* last_obj_card = byte_for(last_block);
163 if (!card_may_have_been_dirty(*last_obj_card)) {
164 // The card containing the head is not dirty. Any marks in
165 // subsequent cards still in this chunk must have been made
166 // precisely; we can cap processing at the end.
167 max_to_do = chunk_mr.end();
168 } else {
169 // The last object must be considered dirty, and extends onto the
170 // following chunk. Look for a dirty card in that chunk that will
171 // bound our processing.
172 jbyte* limit_card = NULL;
173 size_t last_block_size = sp->block_size(last_block);
174 jbyte* last_card_of_last_obj =
175 byte_for(last_block + last_block_size - 1);
176 jbyte* first_card_of_next_chunk = byte_for(chunk_mr.end());
177 // This search potentially goes a long distance looking
178 // for the next card that will be scanned. For example,
179 // an object that is an array of primitives will not
180 // have any cards covering regions interior to the array
181 // that will need to be scanned. The scan can be terminated
182 // at the last card of the next chunk. That would leave
183 // limit_card as NULL and would result in "max_to_do"
184 // being set with the LNC value or with the end
185 // of the last block.
186 jbyte* last_card_of_next_chunk = first_card_of_next_chunk +
187 CardsPerStrideChunk;
188 assert(byte_for(chunk_mr.end()) - byte_for(chunk_mr.start())
189 == CardsPerStrideChunk, "last card of next chunk may be wrong");
190 jbyte* last_card_to_check = (jbyte*) MIN2(last_card_of_last_obj,
191 last_card_of_next_chunk);
192 for (jbyte* cur = first_card_of_next_chunk;
193 cur <= last_card_to_check; cur++) {
194 if (card_will_be_scanned(*cur)) {
195 limit_card = cur; break;
196 }
197 }
198 assert(0 <= cur_chunk_index+1 &&
199 cur_chunk_index+1 < lowest_non_clean_chunk_size,
200 "Bounds error.");
201 // LNC for the next chunk
202 jbyte* lnc_card = lowest_non_clean[cur_chunk_index+1];
203 if (limit_card == NULL) {
204 limit_card = lnc_card;
205 }
206 if (limit_card != NULL) {
207 if (lnc_card != NULL) {
208 limit_card = (jbyte*)MIN2((intptr_t)limit_card,
209 (intptr_t)lnc_card);
210 }
211 max_to_do = addr_for(limit_card);
212 } else {
213 max_to_do = last_block + last_block_size;
214 }
215 }
216 }
217 assert(max_to_do != NULL, "OOPS!");
218 } else {
219 max_to_do = used.end();
220 }
221 // Now we can set the closure we're using so it doesn't to beyond
222 // max_to_do.
223 dcto_cl->set_min_done(max_to_do);
224 #ifndef PRODUCT
225 dcto_cl->set_last_bottom(max_to_do);
226 #endif
227
228 // Now we set *our" lowest_non_clean entry.
229 // Find the object that spans our boundary, if one exists.
230 // Nothing to do on the first chunk.
231 if (chunk_mr.start() > used.start()) {
232 // first_block is the block possibly spanning the chunk start
233 HeapWord* first_block = sp->block_start(chunk_mr.start());
234 // Does the block span the start of the chunk and is it
235 // an object?
236 if (first_block < chunk_mr.start() &&
237 sp->block_is_obj(first_block)) {
238 jbyte* first_dirty_card = NULL;
239 jbyte* last_card_of_first_obj =
240 byte_for(first_block + sp->block_size(first_block) - 1);
241 jbyte* first_card_of_cur_chunk = byte_for(chunk_mr.start());
242 jbyte* last_card_of_cur_chunk = byte_for(chunk_mr.last());
243 jbyte* last_card_to_check =
244 (jbyte*) MIN2((intptr_t) last_card_of_cur_chunk,
245 (intptr_t) last_card_of_first_obj);
246 for (jbyte* cur = first_card_of_cur_chunk;
247 cur <= last_card_to_check; cur++) {
248 if (card_will_be_scanned(*cur)) {
249 first_dirty_card = cur; break;
250 }
251 }
252 if (first_dirty_card != NULL) {
253 assert(0 <= cur_chunk_index &&
254 cur_chunk_index < lowest_non_clean_chunk_size,
255 "Bounds error.");
256 lowest_non_clean[cur_chunk_index] = first_dirty_card;
257 }
258 }
259 }
260 }
261
262 void
263 CardTableModRefBS::
264 get_LNC_array_for_space(Space* sp,
265 jbyte**& lowest_non_clean,
266 uintptr_t& lowest_non_clean_base_chunk_index,
267 size_t& lowest_non_clean_chunk_size) {
268
269 int i = find_covering_region_containing(sp->bottom());
270 MemRegion covered = _covered[i];
271 size_t n_chunks = chunks_to_cover(covered);
272
273 // Only the first thread to obtain the lock will resize the
274 // LNC array for the covered region. Any later expansion can't affect
275 // the used_at_save_marks region.
276 // (I observed a bug in which the first thread to execute this would
277 // resize, and then it would cause "expand_and_allocates" that would
278 // Increase the number of chunks in the covered region. Then a second
279 // thread would come and execute this, see that the size didn't match,
280 // and free and allocate again. So the first thread would be using a
281 // freed "_lowest_non_clean" array.)
282
283 // Do a dirty read here. If we pass the conditional then take the rare
284 // event lock and do the read again in case some other thread had already
285 // succeeded and done the resize.
286 int cur_collection = Universe::heap()->total_collections();
287 if (_last_LNC_resizing_collection[i] != cur_collection) {
288 MutexLocker x(ParGCRareEvent_lock);
289 if (_last_LNC_resizing_collection[i] != cur_collection) {
290 if (_lowest_non_clean[i] == NULL ||
291 n_chunks != _lowest_non_clean_chunk_size[i]) {
292
293 // Should we delete the old?
294 if (_lowest_non_clean[i] != NULL) {
295 assert(n_chunks != _lowest_non_clean_chunk_size[i],
296 "logical consequence");
297 FREE_C_HEAP_ARRAY(CardPtr, _lowest_non_clean[i]);
298 _lowest_non_clean[i] = NULL;
299 }
300 // Now allocate a new one if necessary.
301 if (_lowest_non_clean[i] == NULL) {
302 _lowest_non_clean[i] = NEW_C_HEAP_ARRAY(CardPtr, n_chunks);
303 _lowest_non_clean_chunk_size[i] = n_chunks;
304 _lowest_non_clean_base_chunk_index[i] = addr_to_chunk_index(covered.start());
305 for (int j = 0; j < (int)n_chunks; j++)
306 _lowest_non_clean[i][j] = NULL;
307 }
308 }
309 _last_LNC_resizing_collection[i] = cur_collection;
310 }
311 }
312 // In any case, now do the initialization.
313 lowest_non_clean = _lowest_non_clean[i];
314 lowest_non_clean_base_chunk_index = _lowest_non_clean_base_chunk_index[i];
315 lowest_non_clean_chunk_size = _lowest_non_clean_chunk_size[i];
316 }