1 /*
2 * Copyright (c) 2001, 2015, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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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).
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23 */
24
25 #ifndef SHARE_VM_GC_G1_CONCURRENTMARK_INLINE_HPP
26 #define SHARE_VM_GC_G1_CONCURRENTMARK_INLINE_HPP
27
28 #include "gc/g1/concurrentMark.hpp"
29 #include "gc/g1/g1CollectedHeap.inline.hpp"
30 #include "gc/shared/taskqueue.inline.hpp"
31
32 // Utility routine to set an exclusive range of cards on the given
33 // card liveness bitmap
34 inline void ConcurrentMark::set_card_bitmap_range(BitMap* card_bm,
35 BitMap::idx_t start_idx,
36 BitMap::idx_t end_idx,
37 bool is_par) {
38
39 // Set the exclusive bit range [start_idx, end_idx).
40 assert((end_idx - start_idx) > 0, "at least one card");
41 assert(end_idx <= card_bm->size(), "sanity");
42
43 // Silently clip the end index
44 end_idx = MIN2(end_idx, card_bm->size());
45
46 // For small ranges use a simple loop; otherwise use set_range or
47 // use par_at_put_range (if parallel). The range is made up of the
48 // cards that are spanned by an object/mem region so 8 cards will
49 // allow up to object sizes up to 4K to be handled using the loop.
50 if ((end_idx - start_idx) <= 8) {
51 for (BitMap::idx_t i = start_idx; i < end_idx; i += 1) {
52 if (is_par) {
53 card_bm->par_set_bit(i);
54 } else {
55 card_bm->set_bit(i);
56 }
57 }
58 } else {
59 // Note BitMap::par_at_put_range() and BitMap::set_range() are exclusive.
60 if (is_par) {
61 card_bm->par_at_put_range(start_idx, end_idx, true);
62 } else {
63 card_bm->set_range(start_idx, end_idx);
64 }
65 }
66 }
67
68 // Returns the index in the liveness accounting card bitmap
69 // for the given address
70 inline BitMap::idx_t ConcurrentMark::card_bitmap_index_for(HeapWord* addr) {
71 // Below, the term "card num" means the result of shifting an address
72 // by the card shift -- address 0 corresponds to card number 0. One
73 // must subtract the card num of the bottom of the heap to obtain a
74 // card table index.
75 intptr_t card_num = intptr_t(uintptr_t(addr) >> CardTableModRefBS::card_shift);
76 return card_num - heap_bottom_card_num();
77 }
78
79 // Counts the given memory region in the given task/worker
80 // counting data structures.
81 inline void ConcurrentMark::count_region(MemRegion mr, HeapRegion* hr,
82 size_t* marked_bytes_array,
83 BitMap* task_card_bm) {
84 G1CollectedHeap* g1h = _g1h;
85 CardTableModRefBS* ct_bs = g1h->g1_barrier_set();
86
87 HeapWord* start = mr.start();
88 HeapWord* end = mr.end();
89 size_t region_size_bytes = mr.byte_size();
90 uint index = hr->hrm_index();
91
92 assert(!hr->is_continues_humongous(), "should not be HC region");
93 assert(hr == g1h->heap_region_containing(start), "sanity");
94 assert(hr == g1h->heap_region_containing(mr.last()), "sanity");
95 assert(marked_bytes_array != NULL, "pre-condition");
96 assert(task_card_bm != NULL, "pre-condition");
97
98 // Add to the task local marked bytes for this region.
99 marked_bytes_array[index] += region_size_bytes;
100
101 BitMap::idx_t start_idx = card_bitmap_index_for(start);
102 BitMap::idx_t end_idx = card_bitmap_index_for(end);
103
104 // Note: if we're looking at the last region in heap - end
105 // could be actually just beyond the end of the heap; end_idx
106 // will then correspond to a (non-existent) card that is also
107 // just beyond the heap.
108 if (g1h->is_in_g1_reserved(end) && !ct_bs->is_card_aligned(end)) {
109 // end of region is not card aligned - increment to cover
110 // all the cards spanned by the region.
111 end_idx += 1;
112 }
113 // The card bitmap is task/worker specific => no need to use
114 // the 'par' BitMap routines.
115 // Set bits in the exclusive bit range [start_idx, end_idx).
116 set_card_bitmap_range(task_card_bm, start_idx, end_idx, false /* is_par */);
117 }
118
119 // Counts the given memory region in the task/worker counting
120 // data structures for the given worker id.
121 inline void ConcurrentMark::count_region(MemRegion mr,
122 HeapRegion* hr,
123 uint worker_id) {
124 size_t* marked_bytes_array = count_marked_bytes_array_for(worker_id);
125 BitMap* task_card_bm = count_card_bitmap_for(worker_id);
126 count_region(mr, hr, marked_bytes_array, task_card_bm);
127 }
128
129 // Counts the given object in the given task/worker counting data structures.
130 inline void ConcurrentMark::count_object(oop obj,
131 HeapRegion* hr,
132 size_t* marked_bytes_array,
133 BitMap* task_card_bm) {
134 MemRegion mr((HeapWord*)obj, obj->size());
135 count_region(mr, hr, marked_bytes_array, task_card_bm);
136 }
137
138 // Attempts to mark the given object and, if successful, counts
139 // the object in the given task/worker counting structures.
140 inline bool ConcurrentMark::par_mark_and_count(oop obj,
141 HeapRegion* hr,
142 size_t* marked_bytes_array,
143 BitMap* task_card_bm) {
144 HeapWord* addr = (HeapWord*)obj;
145 if (_nextMarkBitMap->parMark(addr)) {
146 // Update the task specific count data for the object.
147 count_object(obj, hr, marked_bytes_array, task_card_bm);
148 return true;
149 }
150 return false;
151 }
152
153 // Attempts to mark the given object and, if successful, counts
154 // the object in the task/worker counting structures for the
155 // given worker id.
156 inline bool ConcurrentMark::par_mark_and_count(oop obj,
157 size_t word_size,
158 HeapRegion* hr,
159 uint worker_id) {
160 HeapWord* addr = (HeapWord*)obj;
161 if (_nextMarkBitMap->parMark(addr)) {
162 MemRegion mr(addr, word_size);
163 count_region(mr, hr, worker_id);
164 return true;
165 }
166 return false;
167 }
168
169 template<typename Fn>
170 inline void CMMarkStack::iterate(Fn fn) {
171 assert(_saved_index == _index,
172 err_msg("saved index: %d index: %d", _saved_index, _index));
173 for (int i = 0; i < _index; ++i) {
174 fn(_base[i]);
175 }
176 }
177
178 // It scans an object and visits its children.
179 inline void CMTask::scan_object(oop obj) { process_grey_object<true>(obj); }
180
181 inline void CMTask::push(oop obj) {
182 HeapWord* objAddr = (HeapWord*) obj;
183 assert(_g1h->is_in_g1_reserved(objAddr), "invariant");
184 assert(!_g1h->is_on_master_free_list(
185 _g1h->heap_region_containing((HeapWord*) objAddr)), "invariant");
186 assert(!_g1h->is_obj_ill(obj), "invariant");
187 assert(_nextMarkBitMap->isMarked(objAddr), "invariant");
188
189 if (_cm->verbose_high()) {
190 gclog_or_tty->print_cr("[%u] pushing " PTR_FORMAT, _worker_id, p2i((void*) obj));
191 }
192
193 if (!_task_queue->push(obj)) {
194 // The local task queue looks full. We need to push some entries
195 // to the global stack.
196
197 if (_cm->verbose_medium()) {
198 gclog_or_tty->print_cr("[%u] task queue overflow, "
199 "moving entries to the global stack",
200 _worker_id);
201 }
202 move_entries_to_global_stack();
203
204 // this should succeed since, even if we overflow the global
205 // stack, we should have definitely removed some entries from the
206 // local queue. So, there must be space on it.
207 bool success = _task_queue->push(obj);
208 assert(success, "invariant");
209 }
210
211 statsOnly( size_t tmp_size = (size_t)_task_queue->size();
212 if (tmp_size > _local_max_size) {
213 _local_max_size = tmp_size;
214 }
215 ++_local_pushes );
216 }
217
218 inline bool CMTask::is_below_finger(oop obj, HeapWord* global_finger) const {
219 // If obj is above the global finger, then the mark bitmap scan
220 // will find it later, and no push is needed. Similarly, if we have
221 // a current region and obj is between the local finger and the
222 // end of the current region, then no push is needed. The tradeoff
223 // of checking both vs only checking the global finger is that the
224 // local check will be more accurate and so result in fewer pushes,
225 // but may also be a little slower.
226 HeapWord* objAddr = (HeapWord*)obj;
227 if (_finger != NULL) {
228 // We have a current region.
229
230 // Finger and region values are all NULL or all non-NULL. We
231 // use _finger to check since we immediately use its value.
232 assert(_curr_region != NULL, "invariant");
233 assert(_region_limit != NULL, "invariant");
234 assert(_region_limit <= global_finger, "invariant");
235
236 // True if obj is less than the local finger, or is between
237 // the region limit and the global finger.
238 if (objAddr < _finger) {
239 return true;
240 } else if (objAddr < _region_limit) {
241 return false;
242 } // Else check global finger.
243 }
244 // Check global finger.
245 return objAddr < global_finger;
246 }
247
248 template<bool scan>
249 inline void CMTask::process_grey_object(oop obj) {
250 assert(scan || obj->is_typeArray(), "Skipping scan of grey non-typeArray");
251 assert(_nextMarkBitMap->isMarked((HeapWord*) obj), "invariant");
252
253 if (_cm->verbose_high()) {
254 gclog_or_tty->print_cr("[%u] processing grey object " PTR_FORMAT,
255 _worker_id, p2i((void*) obj));
256 }
257
258 size_t obj_size = obj->size();
259 _words_scanned += obj_size;
260
261 if (scan) {
262 obj->oop_iterate(_cm_oop_closure);
263 }
264 statsOnly( ++_objs_scanned );
265 check_limits();
266 }
267
268
269
270 inline void CMTask::make_reference_grey(oop obj, HeapRegion* hr) {
271 if (_cm->par_mark_and_count(obj, hr, _marked_bytes_array, _card_bm)) {
272
273 if (_cm->verbose_high()) {
274 gclog_or_tty->print_cr("[%u] marked object " PTR_FORMAT,
275 _worker_id, p2i(obj));
276 }
277
278 // No OrderAccess:store_load() is needed. It is implicit in the
279 // CAS done in CMBitMap::parMark() call in the routine above.
280 HeapWord* global_finger = _cm->finger();
281
282 // We only need to push a newly grey object on the mark
283 // stack if it is in a section of memory the mark bitmap
284 // scan has already examined. Mark bitmap scanning
285 // maintains progress "fingers" for determining that.
286 //
287 // Notice that the global finger might be moving forward
288 // concurrently. This is not a problem. In the worst case, we
289 // mark the object while it is above the global finger and, by
290 // the time we read the global finger, it has moved forward
291 // past this object. In this case, the object will probably
292 // be visited when a task is scanning the region and will also
293 // be pushed on the stack. So, some duplicate work, but no
294 // correctness problems.
295 if (is_below_finger(obj, global_finger)) {
296 if (obj->is_typeArray()) {
297 // Immediately process arrays of primitive types, rather
298 // than pushing on the mark stack. This keeps us from
299 // adding humongous objects to the mark stack that might
300 // be reclaimed before the entry is processed - see
301 // selection of candidates for eager reclaim of humongous
302 // objects. The cost of the additional type test is
303 // mitigated by avoiding a trip through the mark stack,
304 // by only doing a bookkeeping update and avoiding the
305 // actual scan of the object - a typeArray contains no
306 // references, and the metadata is built-in.
307 process_grey_object<false>(obj);
308 } else {
309 if (_cm->verbose_high()) {
310 gclog_or_tty->print_cr("[%u] below a finger (local: " PTR_FORMAT
311 ", global: " PTR_FORMAT ") pushing "
312 PTR_FORMAT " on mark stack",
313 _worker_id, p2i(_finger),
314 p2i(global_finger), p2i(obj));
315 }
316 push(obj);
317 }
318 }
319 }
320 }
321
322 inline void CMTask::deal_with_reference(oop obj) {
323 if (_cm->verbose_high()) {
324 gclog_or_tty->print_cr("[%u] we're dealing with reference = " PTR_FORMAT,
325 _worker_id, p2i((void*) obj));
326 }
327
328 increment_refs_reached();
329
330 HeapWord* objAddr = (HeapWord*) obj;
331 assert(obj->is_oop_or_null(true /* ignore mark word */), err_msg("Expected an oop or NULL at " PTR_FORMAT, p2i(obj)));
332 if (_g1h->is_in_g1_reserved(objAddr)) {
333 assert(obj != NULL, "null check is implicit");
334 if (!_nextMarkBitMap->isMarked(objAddr)) {
335 // Only get the containing region if the object is not marked on the
336 // bitmap (otherwise, it's a waste of time since we won't do
337 // anything with it).
338 HeapRegion* hr = _g1h->heap_region_containing_raw(obj);
339 if (!hr->obj_allocated_since_next_marking(obj)) {
340 make_reference_grey(obj, hr);
341 }
342 }
343 }
344 }
345
346 inline void ConcurrentMark::markPrev(oop p) {
347 assert(!_prevMarkBitMap->isMarked((HeapWord*) p), "sanity");
348 // Note we are overriding the read-only view of the prev map here, via
349 // the cast.
350 ((CMBitMap*)_prevMarkBitMap)->mark((HeapWord*) p);
351 }
352
353 inline void ConcurrentMark::grayRoot(oop obj, size_t word_size,
354 uint worker_id, HeapRegion* hr) {
355 assert(obj != NULL, "pre-condition");
356 HeapWord* addr = (HeapWord*) obj;
357 if (hr == NULL) {
358 hr = _g1h->heap_region_containing_raw(addr);
359 } else {
360 assert(hr->is_in(addr), "pre-condition");
361 }
362 assert(hr != NULL, "sanity");
363 // Given that we're looking for a region that contains an object
364 // header it's impossible to get back a HC region.
365 assert(!hr->is_continues_humongous(), "sanity");
366
367 // We cannot assert that word_size == obj->size() given that obj
368 // might not be in a consistent state (another thread might be in
369 // the process of copying it). So the best thing we can do is to
370 // assert that word_size is under an upper bound which is its
371 // containing region's capacity.
372 assert(word_size * HeapWordSize <= hr->capacity(),
373 err_msg("size: " SIZE_FORMAT " capacity: " SIZE_FORMAT " " HR_FORMAT,
374 word_size * HeapWordSize, hr->capacity(),
375 HR_FORMAT_PARAMS(hr)));
376
377 if (addr < hr->next_top_at_mark_start()) {
378 if (!_nextMarkBitMap->isMarked(addr)) {
379 par_mark_and_count(obj, word_size, hr, worker_id);
380 }
381 }
382 }
383
384 #endif // SHARE_VM_GC_G1_CONCURRENTMARK_INLINE_HPP