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annotate src/share/vm/gc_implementation/shared/parGCAllocBuffer.cpp @ 19083:09292c24d555
LSStackSlotAllocator: hide inner class.
author | Josef Eisl <josef.eisl@jku.at> |
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date | Sat, 31 Jan 2015 11:07:15 +0100 |
parents | 52b4284cb496 |
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0 | 1 /* |
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2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #include "precompiled.hpp" |
6595 | 26 #include "gc_implementation/shared/parGCAllocBuffer.hpp" |
1972 | 27 #include "memory/sharedHeap.hpp" |
28 #include "oops/arrayOop.hpp" | |
29 #include "oops/oop.inline.hpp" | |
0 | 30 |
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31 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC |
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32 |
0 | 33 ParGCAllocBuffer::ParGCAllocBuffer(size_t desired_plab_sz_) : |
34 _word_sz(desired_plab_sz_), _bottom(NULL), _top(NULL), | |
35 _end(NULL), _hard_end(NULL), | |
36 _retained(false), _retained_filler(), | |
37 _allocated(0), _wasted(0) | |
38 { | |
39 assert (min_size() > AlignmentReserve, "Inconsistency!"); | |
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40 // arrayOopDesc::header_size depends on command line initialization. |
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41 FillerHeaderSize = align_object_size(arrayOopDesc::header_size(T_INT)); |
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42 AlignmentReserve = oopDesc::header_size() > MinObjAlignment ? FillerHeaderSize : 0; |
0 | 43 } |
44 | |
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45 size_t ParGCAllocBuffer::FillerHeaderSize; |
0 | 46 |
47 // If the minimum object size is greater than MinObjAlignment, we can | |
48 // end up with a shard at the end of the buffer that's smaller than | |
49 // the smallest object. We can't allow that because the buffer must | |
50 // look like it's full of objects when we retire it, so we make | |
51 // sure we have enough space for a filler int array object. | |
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52 size_t ParGCAllocBuffer::AlignmentReserve; |
0 | 53 |
54 void ParGCAllocBuffer::retire(bool end_of_gc, bool retain) { | |
55 assert(!retain || end_of_gc, "Can only retain at GC end."); | |
56 if (_retained) { | |
57 // If the buffer had been retained shorten the previous filler object. | |
58 assert(_retained_filler.end() <= _top, "INVARIANT"); | |
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59 CollectedHeap::fill_with_object(_retained_filler); |
0 | 60 // Wasted space book-keeping, otherwise (normally) done in invalidate() |
61 _wasted += _retained_filler.word_size(); | |
62 _retained = false; | |
63 } | |
64 assert(!end_of_gc || !_retained, "At this point, end_of_gc ==> !_retained."); | |
65 if (_top < _hard_end) { | |
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66 CollectedHeap::fill_with_object(_top, _hard_end); |
0 | 67 if (!retain) { |
68 invalidate(); | |
69 } else { | |
70 // Is there wasted space we'd like to retain for the next GC? | |
71 if (pointer_delta(_end, _top) > FillerHeaderSize) { | |
72 _retained = true; | |
73 _retained_filler = MemRegion(_top, FillerHeaderSize); | |
74 _top = _top + FillerHeaderSize; | |
75 } else { | |
76 invalidate(); | |
77 } | |
78 } | |
79 } | |
80 } | |
81 | |
82 void ParGCAllocBuffer::flush_stats(PLABStats* stats) { | |
83 assert(ResizePLAB, "Wasted work"); | |
84 stats->add_allocated(_allocated); | |
85 stats->add_wasted(_wasted); | |
86 stats->add_unused(pointer_delta(_end, _top)); | |
87 } | |
88 | |
89 // Compute desired plab size and latch result for later | |
90 // use. This should be called once at the end of parallel | |
91 // scavenge; it clears the sensor accumulators. | |
6819 | 92 void PLABStats::adjust_desired_plab_sz(uint no_of_gc_workers) { |
0 | 93 assert(ResizePLAB, "Not set"); |
17727 | 94 |
95 assert(is_object_aligned(max_size()) && min_size() <= max_size(), | |
96 "PLAB clipping computation may be incorrect"); | |
97 | |
0 | 98 if (_allocated == 0) { |
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99 assert(_unused == 0, |
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100 err_msg("Inconsistency in PLAB stats: " |
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101 "_allocated: "SIZE_FORMAT", " |
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102 "_wasted: "SIZE_FORMAT", " |
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103 "_unused: "SIZE_FORMAT", " |
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104 "_used : "SIZE_FORMAT, |
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105 _allocated, _wasted, _unused, _used)); |
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106 |
0 | 107 _allocated = 1; |
108 } | |
109 double wasted_frac = (double)_unused/(double)_allocated; | |
110 size_t target_refills = (size_t)((wasted_frac*TargetSurvivorRatio)/ | |
111 TargetPLABWastePct); | |
112 if (target_refills == 0) { | |
113 target_refills = 1; | |
114 } | |
115 _used = _allocated - _wasted - _unused; | |
6819 | 116 size_t plab_sz = _used/(target_refills*no_of_gc_workers); |
0 | 117 if (PrintPLAB) gclog_or_tty->print(" (plab_sz = %d ", plab_sz); |
118 // Take historical weighted average | |
119 _filter.sample(plab_sz); | |
120 // Clip from above and below, and align to object boundary | |
121 plab_sz = MAX2(min_size(), (size_t)_filter.average()); | |
122 plab_sz = MIN2(max_size(), plab_sz); | |
123 plab_sz = align_object_size(plab_sz); | |
124 // Latch the result | |
125 if (PrintPLAB) gclog_or_tty->print(" desired_plab_sz = %d) ", plab_sz); | |
6595 | 126 _desired_plab_sz = plab_sz; |
0 | 127 // Now clear the accumulators for next round: |
128 // note this needs to be fixed in the case where we | |
129 // are retaining across scavenges. FIX ME !!! XXX | |
130 _allocated = 0; | |
131 _wasted = 0; | |
132 _unused = 0; | |
133 } | |
134 | |
135 #ifndef PRODUCT | |
136 void ParGCAllocBuffer::print() { | |
137 gclog_or_tty->print("parGCAllocBuffer: _bottom: %p _top: %p _end: %p _hard_end: %p" | |
138 "_retained: %c _retained_filler: [%p,%p)\n", | |
139 _bottom, _top, _end, _hard_end, | |
140 "FT"[_retained], _retained_filler.start(), _retained_filler.end()); | |
141 } | |
142 #endif // !PRODUCT | |
143 | |
144 const size_t ParGCAllocBufferWithBOT::ChunkSizeInWords = | |
145 MIN2(CardTableModRefBS::par_chunk_heapword_alignment(), | |
146 ((size_t)Generation::GenGrain)/HeapWordSize); | |
147 const size_t ParGCAllocBufferWithBOT::ChunkSizeInBytes = | |
148 MIN2(CardTableModRefBS::par_chunk_heapword_alignment() * HeapWordSize, | |
149 (size_t)Generation::GenGrain); | |
150 | |
151 ParGCAllocBufferWithBOT::ParGCAllocBufferWithBOT(size_t word_sz, | |
152 BlockOffsetSharedArray* bsa) : | |
153 ParGCAllocBuffer(word_sz), | |
154 _bsa(bsa), | |
155 _bt(bsa, MemRegion(_bottom, _hard_end)), | |
156 _true_end(_hard_end) | |
157 {} | |
158 | |
159 // The buffer comes with its own BOT, with a shared (obviously) underlying | |
160 // BlockOffsetSharedArray. We manipulate this BOT in the normal way | |
161 // as we would for any contiguous space. However, on accasion we | |
162 // need to do some buffer surgery at the extremities before we | |
163 // start using the body of the buffer for allocations. Such surgery | |
164 // (as explained elsewhere) is to prevent allocation on a card that | |
165 // is in the process of being walked concurrently by another GC thread. | |
166 // When such surgery happens at a point that is far removed (to the | |
167 // right of the current allocation point, top), we use the "contig" | |
168 // parameter below to directly manipulate the shared array without | |
169 // modifying the _next_threshold state in the BOT. | |
170 void ParGCAllocBufferWithBOT::fill_region_with_block(MemRegion mr, | |
171 bool contig) { | |
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172 CollectedHeap::fill_with_object(mr); |
0 | 173 if (contig) { |
174 _bt.alloc_block(mr.start(), mr.end()); | |
175 } else { | |
176 _bt.BlockOffsetArray::alloc_block(mr.start(), mr.end()); | |
177 } | |
178 } | |
179 | |
180 HeapWord* ParGCAllocBufferWithBOT::allocate_slow(size_t word_sz) { | |
181 HeapWord* res = NULL; | |
182 if (_true_end > _hard_end) { | |
183 assert((HeapWord*)align_size_down(intptr_t(_hard_end), | |
184 ChunkSizeInBytes) == _hard_end, | |
185 "or else _true_end should be equal to _hard_end"); | |
186 assert(_retained, "or else _true_end should be equal to _hard_end"); | |
187 assert(_retained_filler.end() <= _top, "INVARIANT"); | |
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188 CollectedHeap::fill_with_object(_retained_filler); |
0 | 189 if (_top < _hard_end) { |
190 fill_region_with_block(MemRegion(_top, _hard_end), true); | |
191 } | |
192 HeapWord* next_hard_end = MIN2(_true_end, _hard_end + ChunkSizeInWords); | |
193 _retained_filler = MemRegion(_hard_end, FillerHeaderSize); | |
194 _bt.alloc_block(_retained_filler.start(), _retained_filler.word_size()); | |
195 _top = _retained_filler.end(); | |
196 _hard_end = next_hard_end; | |
197 _end = _hard_end - AlignmentReserve; | |
198 res = ParGCAllocBuffer::allocate(word_sz); | |
199 if (res != NULL) { | |
200 _bt.alloc_block(res, word_sz); | |
201 } | |
202 } | |
203 return res; | |
204 } | |
205 | |
206 void | |
207 ParGCAllocBufferWithBOT::undo_allocation(HeapWord* obj, size_t word_sz) { | |
208 ParGCAllocBuffer::undo_allocation(obj, word_sz); | |
209 // This may back us up beyond the previous threshold, so reset. | |
210 _bt.set_region(MemRegion(_top, _hard_end)); | |
211 _bt.initialize_threshold(); | |
212 } | |
213 | |
214 void ParGCAllocBufferWithBOT::retire(bool end_of_gc, bool retain) { | |
215 assert(!retain || end_of_gc, "Can only retain at GC end."); | |
216 if (_retained) { | |
217 // We're about to make the retained_filler into a block. | |
218 _bt.BlockOffsetArray::alloc_block(_retained_filler.start(), | |
219 _retained_filler.end()); | |
220 } | |
221 // Reset _hard_end to _true_end (and update _end) | |
222 if (retain && _hard_end != NULL) { | |
223 assert(_hard_end <= _true_end, "Invariant."); | |
224 _hard_end = _true_end; | |
225 _end = MAX2(_top, _hard_end - AlignmentReserve); | |
226 assert(_end <= _hard_end, "Invariant."); | |
227 } | |
228 _true_end = _hard_end; | |
229 HeapWord* pre_top = _top; | |
230 | |
231 ParGCAllocBuffer::retire(end_of_gc, retain); | |
232 // Now any old _retained_filler is cut back to size, the free part is | |
233 // filled with a filler object, and top is past the header of that | |
234 // object. | |
235 | |
236 if (retain && _top < _end) { | |
237 assert(end_of_gc && retain, "Or else retain should be false."); | |
238 // If the lab does not start on a card boundary, we don't want to | |
239 // allocate onto that card, since that might lead to concurrent | |
240 // allocation and card scanning, which we don't support. So we fill | |
241 // the first card with a garbage object. | |
242 size_t first_card_index = _bsa->index_for(pre_top); | |
243 HeapWord* first_card_start = _bsa->address_for_index(first_card_index); | |
244 if (first_card_start < pre_top) { | |
245 HeapWord* second_card_start = | |
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246 _bsa->inc_by_region_size(first_card_start); |
0 | 247 |
248 // Ensure enough room to fill with the smallest block | |
249 second_card_start = MAX2(second_card_start, pre_top + AlignmentReserve); | |
250 | |
251 // If the end is already in the first card, don't go beyond it! | |
252 // Or if the remainder is too small for a filler object, gobble it up. | |
253 if (_hard_end < second_card_start || | |
254 pointer_delta(_hard_end, second_card_start) < AlignmentReserve) { | |
255 second_card_start = _hard_end; | |
256 } | |
257 if (pre_top < second_card_start) { | |
258 MemRegion first_card_suffix(pre_top, second_card_start); | |
259 fill_region_with_block(first_card_suffix, true); | |
260 } | |
261 pre_top = second_card_start; | |
262 _top = pre_top; | |
263 _end = MAX2(_top, _hard_end - AlignmentReserve); | |
264 } | |
265 | |
266 // If the lab does not end on a card boundary, we don't want to | |
267 // allocate onto that card, since that might lead to concurrent | |
268 // allocation and card scanning, which we don't support. So we fill | |
269 // the last card with a garbage object. | |
270 size_t last_card_index = _bsa->index_for(_hard_end); | |
271 HeapWord* last_card_start = _bsa->address_for_index(last_card_index); | |
272 if (last_card_start < _hard_end) { | |
273 | |
274 // Ensure enough room to fill with the smallest block | |
275 last_card_start = MIN2(last_card_start, _hard_end - AlignmentReserve); | |
276 | |
277 // If the top is already in the last card, don't go back beyond it! | |
278 // Or if the remainder is too small for a filler object, gobble it up. | |
279 if (_top > last_card_start || | |
280 pointer_delta(last_card_start, _top) < AlignmentReserve) { | |
281 last_card_start = _top; | |
282 } | |
283 if (last_card_start < _hard_end) { | |
284 MemRegion last_card_prefix(last_card_start, _hard_end); | |
285 fill_region_with_block(last_card_prefix, false); | |
286 } | |
287 _hard_end = last_card_start; | |
288 _end = MAX2(_top, _hard_end - AlignmentReserve); | |
289 _true_end = _hard_end; | |
290 assert(_end <= _hard_end, "Invariant."); | |
291 } | |
292 | |
293 // At this point: | |
294 // 1) we had a filler object from the original top to hard_end. | |
295 // 2) We've filled in any partial cards at the front and back. | |
296 if (pre_top < _hard_end) { | |
297 // Now we can reset the _bt to do allocation in the given area. | |
298 MemRegion new_filler(pre_top, _hard_end); | |
299 fill_region_with_block(new_filler, false); | |
300 _top = pre_top + ParGCAllocBuffer::FillerHeaderSize; | |
301 // If there's no space left, don't retain. | |
302 if (_top >= _end) { | |
303 _retained = false; | |
304 invalidate(); | |
305 return; | |
306 } | |
307 _retained_filler = MemRegion(pre_top, _top); | |
308 _bt.set_region(MemRegion(_top, _hard_end)); | |
309 _bt.initialize_threshold(); | |
310 assert(_bt.threshold() > _top, "initialize_threshold failed!"); | |
311 | |
312 // There may be other reasons for queries into the middle of the | |
313 // filler object. When such queries are done in parallel with | |
314 // allocation, bad things can happen, if the query involves object | |
315 // iteration. So we ensure that such queries do not involve object | |
316 // iteration, by putting another filler object on the boundaries of | |
317 // such queries. One such is the object spanning a parallel card | |
318 // chunk boundary. | |
319 | |
320 // "chunk_boundary" is the address of the first chunk boundary less | |
321 // than "hard_end". | |
322 HeapWord* chunk_boundary = | |
323 (HeapWord*)align_size_down(intptr_t(_hard_end-1), ChunkSizeInBytes); | |
324 assert(chunk_boundary < _hard_end, "Or else above did not work."); | |
325 assert(pointer_delta(_true_end, chunk_boundary) >= AlignmentReserve, | |
326 "Consequence of last card handling above."); | |
327 | |
328 if (_top <= chunk_boundary) { | |
329 assert(_true_end == _hard_end, "Invariant."); | |
330 while (_top <= chunk_boundary) { | |
331 assert(pointer_delta(_hard_end, chunk_boundary) >= AlignmentReserve, | |
332 "Consequence of last card handling above."); | |
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333 _bt.BlockOffsetArray::alloc_block(chunk_boundary, _hard_end); |
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334 CollectedHeap::fill_with_object(chunk_boundary, _hard_end); |
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335 _hard_end = chunk_boundary; |
0 | 336 chunk_boundary -= ChunkSizeInWords; |
337 } | |
338 _end = _hard_end - AlignmentReserve; | |
339 assert(_top <= _end, "Invariant."); | |
340 // Now reset the initial filler chunk so it doesn't overlap with | |
341 // the one(s) inserted above. | |
342 MemRegion new_filler(pre_top, _hard_end); | |
343 fill_region_with_block(new_filler, false); | |
344 } | |
345 } else { | |
346 _retained = false; | |
347 invalidate(); | |
348 } | |
349 } else { | |
350 assert(!end_of_gc || | |
351 (!_retained && _true_end == _hard_end), "Checking."); | |
352 } | |
353 assert(_end <= _hard_end, "Invariant."); | |
354 assert(_top < _end || _top == _hard_end, "Invariant"); | |
355 } |