1 /*
2 * Copyright (c) 2010, 2014, 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 "memory/genOopClosures.hpp"
27 #include "gc_implementation/concurrentMarkSweep/compactibleFreeListSpace.hpp"
28 #include "gc_implementation/concurrentMarkSweep/promotionInfo.hpp"
29 #include "oops/markOop.inline.hpp"
30 #include "oops/oop.inline.hpp"
31
32 /////////////////////////////////////////////////////////////////////////
33 //// PromotionInfo
34 /////////////////////////////////////////////////////////////////////////
35
36
37 //////////////////////////////////////////////////////////////////////////////
38 // We go over the list of promoted objects, removing each from the list,
39 // and applying the closure (this may, in turn, add more elements to
40 // the tail of the promoted list, and these newly added objects will
41 // also be processed) until the list is empty.
42 // To aid verification and debugging, in the non-product builds
43 // we actually forward _promoHead each time we process a promoted oop.
44 // Note that this is not necessary in general (i.e. when we don't need to
45 // call PromotionInfo::verify()) because oop_iterate can only add to the
46 // end of _promoTail, and never needs to look at _promoHead.
47
48 #define PROMOTED_OOPS_ITERATE_DEFN(OopClosureType, nv_suffix) \
49 \
50 void PromotionInfo::promoted_oops_iterate##nv_suffix(OopClosureType* cl) { \
51 NOT_PRODUCT(verify()); \
52 PromotedObject *curObj, *nextObj; \
53 for (curObj = _promoHead; curObj != NULL; curObj = nextObj) { \
54 if ((nextObj = curObj->next()) == NULL) { \
55 /* protect ourselves against additions due to closure application \
56 below by resetting the list. */ \
57 assert(_promoTail == curObj, "Should have been the tail"); \
58 _promoHead = _promoTail = NULL; \
59 } \
60 if (curObj->hasDisplacedMark()) { \
61 /* restore displaced header */ \
62 oop(curObj)->set_mark(nextDisplacedHeader()); \
63 } else { \
64 /* restore prototypical header */ \
65 oop(curObj)->init_mark(); \
66 } \
67 /* The "promoted_mark" should now not be set */ \
68 assert(!curObj->hasPromotedMark(), \
69 "Should have been cleared by restoring displaced mark-word"); \
70 NOT_PRODUCT(_promoHead = nextObj); \
71 if (cl != NULL) oop(curObj)->oop_iterate(cl); \
72 if (nextObj == NULL) { /* start at head of list reset above */ \
73 nextObj = _promoHead; \
74 } \
75 } \
76 assert(noPromotions(), "post-condition violation"); \
77 assert(_promoHead == NULL && _promoTail == NULL, "emptied promoted list");\
78 assert(_spoolHead == _spoolTail, "emptied spooling buffers"); \
79 assert(_firstIndex == _nextIndex, "empty buffer"); \
80 }
81
82 // This should have been ALL_SINCE_...() just like the others,
83 // but, because the body of the method above is somehwat longer,
84 // the MSVC compiler cannot cope; as a workaround, we split the
85 // macro into its 3 constituent parts below (see original macro
86 // definition in specializedOopClosures.hpp).
87 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES_YOUNG(PROMOTED_OOPS_ITERATE_DEFN)
88 PROMOTED_OOPS_ITERATE_DEFN(OopsInGenClosure,_v)
89
90
91 // Return the next displaced header, incrementing the pointer and
92 // recycling spool area as necessary.
93 markOop PromotionInfo::nextDisplacedHeader() {
94 assert(_spoolHead != NULL, "promotionInfo inconsistency");
95 assert(_spoolHead != _spoolTail || _firstIndex < _nextIndex,
96 "Empty spool space: no displaced header can be fetched");
97 assert(_spoolHead->bufferSize > _firstIndex, "Off by one error at head?");
98 markOop hdr = _spoolHead->displacedHdr[_firstIndex];
99 // Spool forward
100 if (++_firstIndex == _spoolHead->bufferSize) { // last location in this block
101 // forward to next block, recycling this block into spare spool buffer
102 SpoolBlock* tmp = _spoolHead->nextSpoolBlock;
103 assert(_spoolHead != _spoolTail, "Spooling storage mix-up");
104 _spoolHead->nextSpoolBlock = _spareSpool;
105 _spareSpool = _spoolHead;
106 _spoolHead = tmp;
107 _firstIndex = 1;
108 NOT_PRODUCT(
109 if (_spoolHead == NULL) { // all buffers fully consumed
110 assert(_spoolTail == NULL && _nextIndex == 1,
111 "spool buffers processing inconsistency");
112 }
113 )
114 }
115 return hdr;
116 }
117
118 void PromotionInfo::track(PromotedObject* trackOop) {
119 track(trackOop, oop(trackOop)->klass());
120 }
121
122 void PromotionInfo::track(PromotedObject* trackOop, Klass* klassOfOop) {
123 // make a copy of header as it may need to be spooled
124 markOop mark = oop(trackOop)->mark();
125 trackOop->clear_next();
126 if (mark->must_be_preserved_for_cms_scavenge(klassOfOop)) {
127 // save non-prototypical header, and mark oop
128 saveDisplacedHeader(mark);
129 trackOop->setDisplacedMark();
130 } else {
131 // we'd like to assert something like the following:
132 // assert(mark == markOopDesc::prototype(), "consistency check");
133 // ... but the above won't work because the age bits have not (yet) been
134 // cleared. The remainder of the check would be identical to the
135 // condition checked in must_be_preserved() above, so we don't really
136 // have anything useful to check here!
137 }
138 if (_promoTail != NULL) {
139 assert(_promoHead != NULL, "List consistency");
140 _promoTail->setNext(trackOop);
141 _promoTail = trackOop;
142 } else {
143 assert(_promoHead == NULL, "List consistency");
144 _promoHead = _promoTail = trackOop;
145 }
146 // Mask as newly promoted, so we can skip over such objects
147 // when scanning dirty cards
148 assert(!trackOop->hasPromotedMark(), "Should not have been marked");
149 trackOop->setPromotedMark();
150 }
151
152 // Save the given displaced header, incrementing the pointer and
153 // obtaining more spool area as necessary.
154 void PromotionInfo::saveDisplacedHeader(markOop hdr) {
155 assert(_spoolHead != NULL && _spoolTail != NULL,
156 "promotionInfo inconsistency");
157 assert(_spoolTail->bufferSize > _nextIndex, "Off by one error at tail?");
158 _spoolTail->displacedHdr[_nextIndex] = hdr;
159 // Spool forward
160 if (++_nextIndex == _spoolTail->bufferSize) { // last location in this block
161 // get a new spooling block
162 assert(_spoolTail->nextSpoolBlock == NULL, "tail should terminate spool list");
163 _splice_point = _spoolTail; // save for splicing
164 _spoolTail->nextSpoolBlock = getSpoolBlock(); // might fail
165 _spoolTail = _spoolTail->nextSpoolBlock; // might become NULL ...
166 // ... but will attempt filling before next promotion attempt
167 _nextIndex = 1;
168 }
169 }
170
171 // Ensure that spooling space exists. Return false if spooling space
172 // could not be obtained.
173 bool PromotionInfo::ensure_spooling_space_work() {
174 assert(!has_spooling_space(), "Only call when there is no spooling space");
175 // Try and obtain more spooling space
176 SpoolBlock* newSpool = getSpoolBlock();
177 assert(newSpool == NULL ||
178 (newSpool->bufferSize != 0 && newSpool->nextSpoolBlock == NULL),
179 "getSpoolBlock() sanity check");
180 if (newSpool == NULL) {
181 return false;
182 }
183 _nextIndex = 1;
184 if (_spoolTail == NULL) {
185 _spoolTail = newSpool;
186 if (_spoolHead == NULL) {
187 _spoolHead = newSpool;
188 _firstIndex = 1;
189 } else {
190 assert(_splice_point != NULL && _splice_point->nextSpoolBlock == NULL,
191 "Splice point invariant");
192 // Extra check that _splice_point is connected to list
193 #ifdef ASSERT
194 {
195 SpoolBlock* blk = _spoolHead;
196 for (; blk->nextSpoolBlock != NULL;
197 blk = blk->nextSpoolBlock);
198 assert(blk != NULL && blk == _splice_point,
199 "Splice point incorrect");
200 }
201 #endif // ASSERT
202 _splice_point->nextSpoolBlock = newSpool;
203 }
204 } else {
205 assert(_spoolHead != NULL, "spool list consistency");
206 _spoolTail->nextSpoolBlock = newSpool;
207 _spoolTail = newSpool;
208 }
209 return true;
210 }
211
212 // Get a free spool buffer from the free pool, getting a new block
213 // from the heap if necessary.
214 SpoolBlock* PromotionInfo::getSpoolBlock() {
215 SpoolBlock* res;
216 if ((res = _spareSpool) != NULL) {
217 _spareSpool = _spareSpool->nextSpoolBlock;
218 res->nextSpoolBlock = NULL;
219 } else { // spare spool exhausted, get some from heap
220 res = (SpoolBlock*)(space()->allocateScratch(refillSize()));
221 if (res != NULL) {
222 res->init();
223 }
224 }
225 assert(res == NULL || res->nextSpoolBlock == NULL, "postcondition");
226 return res;
227 }
228
229 void PromotionInfo::startTrackingPromotions() {
230 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
231 "spooling inconsistency?");
232 _firstIndex = _nextIndex = 1;
233 _tracking = true;
234 }
235
236 #define CMSPrintPromoBlockInfo 1
237
238 void PromotionInfo::stopTrackingPromotions(uint worker_id) {
239 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
240 "spooling inconsistency?");
241 _firstIndex = _nextIndex = 1;
242 _tracking = false;
243 if (CMSPrintPromoBlockInfo > 1) {
244 print_statistics(worker_id);
245 }
246 }
247
248 void PromotionInfo::print_statistics(uint worker_id) const {
249 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
250 "Else will undercount");
251 assert(CMSPrintPromoBlockInfo > 0, "Else unnecessary call");
252 // Count the number of blocks and slots in the free pool
253 size_t slots = 0;
254 size_t blocks = 0;
255 for (SpoolBlock* cur_spool = _spareSpool;
256 cur_spool != NULL;
257 cur_spool = cur_spool->nextSpoolBlock) {
258 // the first entry is just a self-pointer; indices 1 through
259 // bufferSize - 1 are occupied (thus, bufferSize - 1 slots).
260 assert((void*)cur_spool->displacedHdr == (void*)&cur_spool->displacedHdr,
261 "first entry of displacedHdr should be self-referential");
262 slots += cur_spool->bufferSize - 1;
263 blocks++;
264 }
265 if (_spoolHead != NULL) {
266 slots += _spoolHead->bufferSize - 1;
267 blocks++;
268 }
269 gclog_or_tty->print_cr(" [worker %d] promo_blocks = " SIZE_FORMAT ", promo_slots = " SIZE_FORMAT,
270 worker_id, blocks, slots);
271 }
272
273 // When _spoolTail is not NULL, then the slot <_spoolTail, _nextIndex>
274 // points to the next slot available for filling.
275 // The set of slots holding displaced headers are then all those in the
276 // right-open interval denoted by:
277 //
278 // [ <_spoolHead, _firstIndex>, <_spoolTail, _nextIndex> )
279 //
280 // When _spoolTail is NULL, then the set of slots with displaced headers
281 // is all those starting at the slot <_spoolHead, _firstIndex> and
282 // going up to the last slot of last block in the linked list.
283 // In this latter case, _splice_point points to the tail block of
284 // this linked list of blocks holding displaced headers.
285 void PromotionInfo::verify() const {
286 // Verify the following:
287 // 1. the number of displaced headers matches the number of promoted
288 // objects that have displaced headers
289 // 2. each promoted object lies in this space
290 debug_only(
291 PromotedObject* junk = NULL;
292 assert(junk->next_addr() == (void*)(oop(junk)->mark_addr()),
293 "Offset of PromotedObject::_next is expected to align with "
294 " the OopDesc::_mark within OopDesc");
295 )
296 // FIXME: guarantee????
297 guarantee(_spoolHead == NULL || _spoolTail != NULL ||
298 _splice_point != NULL, "list consistency");
299 guarantee(_promoHead == NULL || _promoTail != NULL, "list consistency");
300 // count the number of objects with displaced headers
301 size_t numObjsWithDisplacedHdrs = 0;
302 for (PromotedObject* curObj = _promoHead; curObj != NULL; curObj = curObj->next()) {
303 guarantee(space()->is_in_reserved((HeapWord*)curObj), "Containment");
304 // the last promoted object may fail the mark() != NULL test of is_oop().
305 guarantee(curObj->next() == NULL || oop(curObj)->is_oop(), "must be an oop");
306 if (curObj->hasDisplacedMark()) {
307 numObjsWithDisplacedHdrs++;
308 }
309 }
310 // Count the number of displaced headers
311 size_t numDisplacedHdrs = 0;
312 for (SpoolBlock* curSpool = _spoolHead;
313 curSpool != _spoolTail && curSpool != NULL;
314 curSpool = curSpool->nextSpoolBlock) {
315 // the first entry is just a self-pointer; indices 1 through
316 // bufferSize - 1 are occupied (thus, bufferSize - 1 slots).
317 guarantee((void*)curSpool->displacedHdr == (void*)&curSpool->displacedHdr,
318 "first entry of displacedHdr should be self-referential");
319 numDisplacedHdrs += curSpool->bufferSize - 1;
320 }
321 guarantee((_spoolHead == _spoolTail) == (numDisplacedHdrs == 0),
322 "internal consistency");
323 guarantee(_spoolTail != NULL || _nextIndex == 1,
324 "Inconsistency between _spoolTail and _nextIndex");
325 // We overcounted (_firstIndex-1) worth of slots in block
326 // _spoolHead and we undercounted (_nextIndex-1) worth of
327 // slots in block _spoolTail. We make an appropriate
328 // adjustment by subtracting the first and adding the
329 // second: - (_firstIndex - 1) + (_nextIndex - 1)
330 numDisplacedHdrs += (_nextIndex - _firstIndex);
331 guarantee(numDisplacedHdrs == numObjsWithDisplacedHdrs, "Displaced hdr count");
332 }
333
334 void PromotionInfo::print_on(outputStream* st) const {
335 SpoolBlock* curSpool = NULL;
336 size_t i = 0;
337 st->print_cr(" start & end indices: [" SIZE_FORMAT ", " SIZE_FORMAT ")",
338 _firstIndex, _nextIndex);
339 for (curSpool = _spoolHead; curSpool != _spoolTail && curSpool != NULL;
340 curSpool = curSpool->nextSpoolBlock) {
341 curSpool->print_on(st);
342 st->print_cr(" active ");
343 i++;
344 }
345 for (curSpool = _spoolTail; curSpool != NULL;
346 curSpool = curSpool->nextSpoolBlock) {
347 curSpool->print_on(st);
348 st->print_cr(" inactive ");
349 i++;
350 }
351 for (curSpool = _spareSpool; curSpool != NULL;
352 curSpool = curSpool->nextSpoolBlock) {
353 curSpool->print_on(st);
354 st->print_cr(" free ");
355 i++;
356 }
357 st->print_cr(" " SIZE_FORMAT " header spooling blocks", i);
358 }
359
360 void SpoolBlock::print_on(outputStream* st) const {
361 st->print("[" PTR_FORMAT "," PTR_FORMAT "), " SIZE_FORMAT " HeapWords -> " PTR_FORMAT,
362 p2i(this), p2i((HeapWord*)displacedHdr + bufferSize),
363 bufferSize, p2i(nextSpoolBlock));
364 }