1 /*
2 * Copyright (c) 2010, 2012, 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.
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23 */
24
25 #include "precompiled.hpp"
26 #include "gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp"
27 #include "gc_implementation/concurrentMarkSweep/promotionInfo.hpp"
28 #include "oops/markOop.inline.hpp"
29 #include "oops/oop.inline.hpp"
30
31 /////////////////////////////////////////////////////////////////////////
32 //// PromotionInfo
33 /////////////////////////////////////////////////////////////////////////
34
35
36 //////////////////////////////////////////////////////////////////////////////
37 // We go over the list of promoted objects, removing each from the list,
38 // and applying the closure (this may, in turn, add more elements to
39 // the tail of the promoted list, and these newly added objects will
40 // also be processed) until the list is empty.
41 // To aid verification and debugging, in the non-product builds
42 // we actually forward _promoHead each time we process a promoted oop.
43 // Note that this is not necessary in general (i.e. when we don't need to
44 // call PromotionInfo::verify()) because oop_iterate can only add to the
45 // end of _promoTail, and never needs to look at _promoHead.
46
47 #define PROMOTED_OOPS_ITERATE_DEFN(OopClosureType, nv_suffix) \
48 \
49 void PromotionInfo::promoted_oops_iterate##nv_suffix(OopClosureType* cl) { \
50 NOT_PRODUCT(verify()); \
51 PromotedObject *curObj, *nextObj; \
52 for (curObj = _promoHead; curObj != NULL; curObj = nextObj) { \
53 if ((nextObj = curObj->next()) == NULL) { \
54 /* protect ourselves against additions due to closure application \
55 below by resetting the list. */ \
56 assert(_promoTail == curObj, "Should have been the tail"); \
57 _promoHead = _promoTail = NULL; \
58 } \
59 if (curObj->hasDisplacedMark()) { \
60 /* restore displaced header */ \
61 oop(curObj)->set_mark(nextDisplacedHeader()); \
62 } else { \
63 /* restore prototypical header */ \
64 oop(curObj)->init_mark(); \
65 } \
66 /* The "promoted_mark" should now not be set */ \
67 assert(!curObj->hasPromotedMark(), \
68 "Should have been cleared by restoring displaced mark-word"); \
69 NOT_PRODUCT(_promoHead = nextObj); \
70 if (cl != NULL) oop(curObj)->oop_iterate(cl); \
71 if (nextObj == NULL) { /* start at head of list reset above */ \
72 nextObj = _promoHead; \
73 } \
74 } \
75 assert(noPromotions(), "post-condition violation"); \
76 assert(_promoHead == NULL && _promoTail == NULL, "emptied promoted list");\
77 assert(_spoolHead == _spoolTail, "emptied spooling buffers"); \
78 assert(_firstIndex == _nextIndex, "empty buffer"); \
79 }
80
81 // This should have been ALL_SINCE_...() just like the others,
82 // but, because the body of the method above is somehwat longer,
83 // the MSVC compiler cannot cope; as a workaround, we split the
84 // macro into its 3 constituent parts below (see original macro
85 // definition in specializedOopClosures.hpp).
86 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES_YOUNG(PROMOTED_OOPS_ITERATE_DEFN)
87 PROMOTED_OOPS_ITERATE_DEFN(OopsInGenClosure,_v)
88
89
90 // Return the next displaced header, incrementing the pointer and
91 // recycling spool area as necessary.
92 markOop PromotionInfo::nextDisplacedHeader() {
93 assert(_spoolHead != NULL, "promotionInfo inconsistency");
94 assert(_spoolHead != _spoolTail || _firstIndex < _nextIndex,
95 "Empty spool space: no displaced header can be fetched");
96 assert(_spoolHead->bufferSize > _firstIndex, "Off by one error at head?");
97 markOop hdr = _spoolHead->displacedHdr[_firstIndex];
98 // Spool forward
99 if (++_firstIndex == _spoolHead->bufferSize) { // last location in this block
100 // forward to next block, recycling this block into spare spool buffer
101 SpoolBlock* tmp = _spoolHead->nextSpoolBlock;
102 assert(_spoolHead != _spoolTail, "Spooling storage mix-up");
103 _spoolHead->nextSpoolBlock = _spareSpool;
104 _spareSpool = _spoolHead;
105 _spoolHead = tmp;
106 _firstIndex = 1;
107 NOT_PRODUCT(
108 if (_spoolHead == NULL) { // all buffers fully consumed
109 assert(_spoolTail == NULL && _nextIndex == 1,
110 "spool buffers processing inconsistency");
111 }
112 )
113 }
114 return hdr;
115 }
116
117 void PromotionInfo::track(PromotedObject* trackOop) {
118 track(trackOop, oop(trackOop)->klass());
119 }
120
121 void PromotionInfo::track(PromotedObject* trackOop, Klass* klassOfOop) {
122 // make a copy of header as it may need to be spooled
123 markOop mark = oop(trackOop)->mark();
124 trackOop->clear_next();
125 if (mark->must_be_preserved_for_cms_scavenge(klassOfOop)) {
126 // save non-prototypical header, and mark oop
127 saveDisplacedHeader(mark);
128 trackOop->setDisplacedMark();
129 } else {
130 // we'd like to assert something like the following:
131 // assert(mark == markOopDesc::prototype(), "consistency check");
132 // ... but the above won't work because the age bits have not (yet) been
133 // cleared. The remainder of the check would be identical to the
134 // condition checked in must_be_preserved() above, so we don't really
135 // have anything useful to check here!
136 }
137 if (_promoTail != NULL) {
138 assert(_promoHead != NULL, "List consistency");
139 _promoTail->setNext(trackOop);
140 _promoTail = trackOop;
141 } else {
142 assert(_promoHead == NULL, "List consistency");
143 _promoHead = _promoTail = trackOop;
144 }
145 // Mask as newly promoted, so we can skip over such objects
146 // when scanning dirty cards
147 assert(!trackOop->hasPromotedMark(), "Should not have been marked");
148 trackOop->setPromotedMark();
149 }
150
151 // Save the given displaced header, incrementing the pointer and
152 // obtaining more spool area as necessary.
153 void PromotionInfo::saveDisplacedHeader(markOop hdr) {
154 assert(_spoolHead != NULL && _spoolTail != NULL,
155 "promotionInfo inconsistency");
156 assert(_spoolTail->bufferSize > _nextIndex, "Off by one error at tail?");
157 _spoolTail->displacedHdr[_nextIndex] = hdr;
158 // Spool forward
159 if (++_nextIndex == _spoolTail->bufferSize) { // last location in this block
160 // get a new spooling block
161 assert(_spoolTail->nextSpoolBlock == NULL, "tail should terminate spool list");
162 _splice_point = _spoolTail; // save for splicing
163 _spoolTail->nextSpoolBlock = getSpoolBlock(); // might fail
164 _spoolTail = _spoolTail->nextSpoolBlock; // might become NULL ...
165 // ... but will attempt filling before next promotion attempt
166 _nextIndex = 1;
167 }
168 }
169
170 // Ensure that spooling space exists. Return false if spooling space
171 // could not be obtained.
172 bool PromotionInfo::ensure_spooling_space_work() {
173 assert(!has_spooling_space(), "Only call when there is no spooling space");
174 // Try and obtain more spooling space
175 SpoolBlock* newSpool = getSpoolBlock();
176 assert(newSpool == NULL ||
177 (newSpool->bufferSize != 0 && newSpool->nextSpoolBlock == NULL),
178 "getSpoolBlock() sanity check");
179 if (newSpool == NULL) {
180 return false;
181 }
182 _nextIndex = 1;
183 if (_spoolTail == NULL) {
184 _spoolTail = newSpool;
185 if (_spoolHead == NULL) {
186 _spoolHead = newSpool;
187 _firstIndex = 1;
188 } else {
189 assert(_splice_point != NULL && _splice_point->nextSpoolBlock == NULL,
190 "Splice point invariant");
191 // Extra check that _splice_point is connected to list
192 #ifdef ASSERT
193 {
194 SpoolBlock* blk = _spoolHead;
195 for (; blk->nextSpoolBlock != NULL;
196 blk = blk->nextSpoolBlock);
197 assert(blk != NULL && blk == _splice_point,
198 "Splice point incorrect");
199 }
200 #endif // ASSERT
201 _splice_point->nextSpoolBlock = newSpool;
202 }
203 } else {
204 assert(_spoolHead != NULL, "spool list consistency");
205 _spoolTail->nextSpoolBlock = newSpool;
206 _spoolTail = newSpool;
207 }
208 return true;
209 }
210
211 // Get a free spool buffer from the free pool, getting a new block
212 // from the heap if necessary.
213 SpoolBlock* PromotionInfo::getSpoolBlock() {
214 SpoolBlock* res;
215 if ((res = _spareSpool) != NULL) {
216 _spareSpool = _spareSpool->nextSpoolBlock;
217 res->nextSpoolBlock = NULL;
218 } else { // spare spool exhausted, get some from heap
219 res = (SpoolBlock*)(space()->allocateScratch(refillSize()));
220 if (res != NULL) {
221 res->init();
222 }
223 }
224 assert(res == NULL || res->nextSpoolBlock == NULL, "postcondition");
225 return res;
226 }
227
228 void PromotionInfo::startTrackingPromotions() {
229 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
230 "spooling inconsistency?");
231 _firstIndex = _nextIndex = 1;
232 _tracking = true;
233 }
234
235 #define CMSPrintPromoBlockInfo 1
236
237 void PromotionInfo::stopTrackingPromotions(uint worker_id) {
238 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
239 "spooling inconsistency?");
240 _firstIndex = _nextIndex = 1;
241 _tracking = false;
242 if (CMSPrintPromoBlockInfo > 1) {
243 print_statistics(worker_id);
244 }
245 }
246
247 void PromotionInfo::print_statistics(uint worker_id) const {
248 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
249 "Else will undercount");
250 assert(CMSPrintPromoBlockInfo > 0, "Else unnecessary call");
251 // Count the number of blocks and slots in the free pool
252 size_t slots = 0;
253 size_t blocks = 0;
254 for (SpoolBlock* cur_spool = _spareSpool;
255 cur_spool != NULL;
256 cur_spool = cur_spool->nextSpoolBlock) {
257 // the first entry is just a self-pointer; indices 1 through
258 // bufferSize - 1 are occupied (thus, bufferSize - 1 slots).
259 assert((void*)cur_spool->displacedHdr == (void*)&cur_spool->displacedHdr,
260 "first entry of displacedHdr should be self-referential");
261 slots += cur_spool->bufferSize - 1;
262 blocks++;
263 }
264 if (_spoolHead != NULL) {
265 slots += _spoolHead->bufferSize - 1;
266 blocks++;
267 }
268 gclog_or_tty->print_cr(" [worker %d] promo_blocks = %d, promo_slots = %d ",
269 worker_id, blocks, slots);
270 }
271
272 // When _spoolTail is not NULL, then the slot <_spoolTail, _nextIndex>
273 // points to the next slot available for filling.
274 // The set of slots holding displaced headers are then all those in the
275 // right-open interval denoted by:
276 //
277 // [ <_spoolHead, _firstIndex>, <_spoolTail, _nextIndex> )
278 //
279 // When _spoolTail is NULL, then the set of slots with displaced headers
280 // is all those starting at the slot <_spoolHead, _firstIndex> and
281 // going up to the last slot of last block in the linked list.
282 // In this latter case, _splice_point points to the tail block of
283 // this linked list of blocks holding displaced headers.
284 void PromotionInfo::verify() const {
285 // Verify the following:
286 // 1. the number of displaced headers matches the number of promoted
287 // objects that have displaced headers
288 // 2. each promoted object lies in this space
289 debug_only(
290 PromotedObject* junk = NULL;
291 assert(junk->next_addr() == (void*)(oop(junk)->mark_addr()),
292 "Offset of PromotedObject::_next is expected to align with "
293 " the OopDesc::_mark within OopDesc");
294 )
295 // FIXME: guarantee????
296 guarantee(_spoolHead == NULL || _spoolTail != NULL ||
297 _splice_point != NULL, "list consistency");
298 guarantee(_promoHead == NULL || _promoTail != NULL, "list consistency");
299 // count the number of objects with displaced headers
300 size_t numObjsWithDisplacedHdrs = 0;
301 for (PromotedObject* curObj = _promoHead; curObj != NULL; curObj = curObj->next()) {
302 guarantee(space()->is_in_reserved((HeapWord*)curObj), "Containment");
303 // the last promoted object may fail the mark() != NULL test of is_oop().
304 guarantee(curObj->next() == NULL || oop(curObj)->is_oop(), "must be an oop");
305 if (curObj->hasDisplacedMark()) {
306 numObjsWithDisplacedHdrs++;
307 }
308 }
309 // Count the number of displaced headers
310 size_t numDisplacedHdrs = 0;
311 for (SpoolBlock* curSpool = _spoolHead;
312 curSpool != _spoolTail && curSpool != NULL;
313 curSpool = curSpool->nextSpoolBlock) {
314 // the first entry is just a self-pointer; indices 1 through
315 // bufferSize - 1 are occupied (thus, bufferSize - 1 slots).
316 guarantee((void*)curSpool->displacedHdr == (void*)&curSpool->displacedHdr,
317 "first entry of displacedHdr should be self-referential");
318 numDisplacedHdrs += curSpool->bufferSize - 1;
319 }
320 guarantee((_spoolHead == _spoolTail) == (numDisplacedHdrs == 0),
321 "internal consistency");
322 guarantee(_spoolTail != NULL || _nextIndex == 1,
323 "Inconsistency between _spoolTail and _nextIndex");
324 // We overcounted (_firstIndex-1) worth of slots in block
325 // _spoolHead and we undercounted (_nextIndex-1) worth of
326 // slots in block _spoolTail. We make an appropriate
327 // adjustment by subtracting the first and adding the
328 // second: - (_firstIndex - 1) + (_nextIndex - 1)
329 numDisplacedHdrs += (_nextIndex - _firstIndex);
330 guarantee(numDisplacedHdrs == numObjsWithDisplacedHdrs, "Displaced hdr count");
331 }
332
333 void PromotionInfo::print_on(outputStream* st) const {
334 SpoolBlock* curSpool = NULL;
335 size_t i = 0;
336 st->print_cr(" start & end indices: [" SIZE_FORMAT ", " SIZE_FORMAT ")",
337 _firstIndex, _nextIndex);
338 for (curSpool = _spoolHead; curSpool != _spoolTail && curSpool != NULL;
339 curSpool = curSpool->nextSpoolBlock) {
340 curSpool->print_on(st);
341 st->print_cr(" active ");
342 i++;
343 }
344 for (curSpool = _spoolTail; curSpool != NULL;
345 curSpool = curSpool->nextSpoolBlock) {
346 curSpool->print_on(st);
347 st->print_cr(" inactive ");
348 i++;
349 }
350 for (curSpool = _spareSpool; curSpool != NULL;
351 curSpool = curSpool->nextSpoolBlock) {
352 curSpool->print_on(st);
353 st->print_cr(" free ");
354 i++;
355 }
356 st->print_cr(" " SIZE_FORMAT " header spooling blocks", i);
357 }
358
359 void SpoolBlock::print_on(outputStream* st) const {
360 st->print("[" PTR_FORMAT "," PTR_FORMAT "), " SIZE_FORMAT " HeapWords -> " PTR_FORMAT,
361 this, (HeapWord*)displacedHdr + bufferSize,
362 bufferSize, nextSpoolBlock);
363 }