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.
22 *
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 PRAGMA_FORMAT_MUTE_WARNINGS_FOR_GCC
32
33 /////////////////////////////////////////////////////////////////////////
34 //// PromotionInfo
35 /////////////////////////////////////////////////////////////////////////
36
37
38 //////////////////////////////////////////////////////////////////////////////
39 // We go over the list of promoted objects, removing each from the list,
40 // and applying the closure (this may, in turn, add more elements to
41 // the tail of the promoted list, and these newly added objects will
42 // also be processed) until the list is empty.
43 // To aid verification and debugging, in the non-product builds
44 // we actually forward _promoHead each time we process a promoted oop.
45 // Note that this is not necessary in general (i.e. when we don't need to
46 // call PromotionInfo::verify()) because oop_iterate can only add to the
47 // end of _promoTail, and never needs to look at _promoHead.
48
49 #define PROMOTED_OOPS_ITERATE_DEFN(OopClosureType, nv_suffix) \
50 \
51 void PromotionInfo::promoted_oops_iterate##nv_suffix(OopClosureType* cl) { \
52 NOT_PRODUCT(verify()); \
53 PromotedObject *curObj, *nextObj; \
54 for (curObj = _promoHead; curObj != NULL; curObj = nextObj) { \
55 if ((nextObj = curObj->next()) == NULL) { \
56 /* protect ourselves against additions due to closure application \
57 below by resetting the list. */ \
58 assert(_promoTail == curObj, "Should have been the tail"); \
59 _promoHead = _promoTail = NULL; \
60 } \
61 if (curObj->hasDisplacedMark()) { \
62 /* restore displaced header */ \
63 oop(curObj)->set_mark(nextDisplacedHeader()); \
64 } else { \
65 /* restore prototypical header */ \
66 oop(curObj)->init_mark(); \
67 } \
68 /* The "promoted_mark" should now not be set */ \
69 assert(!curObj->hasPromotedMark(), \
70 "Should have been cleared by restoring displaced mark-word"); \
71 NOT_PRODUCT(_promoHead = nextObj); \
72 if (cl != NULL) oop(curObj)->oop_iterate(cl); \
73 if (nextObj == NULL) { /* start at head of list reset above */ \
74 nextObj = _promoHead; \
75 } \
76 } \
77 assert(noPromotions(), "post-condition violation"); \
78 assert(_promoHead == NULL && _promoTail == NULL, "emptied promoted list");\
79 assert(_spoolHead == _spoolTail, "emptied spooling buffers"); \
80 assert(_firstIndex == _nextIndex, "empty buffer"); \
81 }
82
83 // This should have been ALL_SINCE_...() just like the others,
84 // but, because the body of the method above is somehwat longer,
85 // the MSVC compiler cannot cope; as a workaround, we split the
86 // macro into its 3 constituent parts below (see original macro
87 // definition in specializedOopClosures.hpp).
88 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES_YOUNG(PROMOTED_OOPS_ITERATE_DEFN)
89 PROMOTED_OOPS_ITERATE_DEFN(OopsInGenClosure,_v)
90
91
92 // Return the next displaced header, incrementing the pointer and
93 // recycling spool area as necessary.
94 markOop PromotionInfo::nextDisplacedHeader() {
95 assert(_spoolHead != NULL, "promotionInfo inconsistency");
96 assert(_spoolHead != _spoolTail || _firstIndex < _nextIndex,
97 "Empty spool space: no displaced header can be fetched");
98 assert(_spoolHead->bufferSize > _firstIndex, "Off by one error at head?");
99 markOop hdr = _spoolHead->displacedHdr[_firstIndex];
100 // Spool forward
101 if (++_firstIndex == _spoolHead->bufferSize) { // last location in this block
102 // forward to next block, recycling this block into spare spool buffer
103 SpoolBlock* tmp = _spoolHead->nextSpoolBlock;
104 assert(_spoolHead != _spoolTail, "Spooling storage mix-up");
105 _spoolHead->nextSpoolBlock = _spareSpool;
106 _spareSpool = _spoolHead;
107 _spoolHead = tmp;
108 _firstIndex = 1;
109 NOT_PRODUCT(
110 if (_spoolHead == NULL) { // all buffers fully consumed
111 assert(_spoolTail == NULL && _nextIndex == 1,
112 "spool buffers processing inconsistency");
113 }
114 )
115 }
116 return hdr;
117 }
118
119 void PromotionInfo::track(PromotedObject* trackOop) {
120 track(trackOop, oop(trackOop)->klass());
121 }
122
123 void PromotionInfo::track(PromotedObject* trackOop, Klass* klassOfOop) {
124 // make a copy of header as it may need to be spooled
125 markOop mark = oop(trackOop)->mark();
126 trackOop->clear_next();
127 if (mark->must_be_preserved_for_cms_scavenge(klassOfOop)) {
128 // save non-prototypical header, and mark oop
129 saveDisplacedHeader(mark);
130 trackOop->setDisplacedMark();
131 } else {
132 // we'd like to assert something like the following:
133 // assert(mark == markOopDesc::prototype(), "consistency check");
134 // ... but the above won't work because the age bits have not (yet) been
135 // cleared. The remainder of the check would be identical to the
136 // condition checked in must_be_preserved() above, so we don't really
137 // have anything useful to check here!
138 }
139 if (_promoTail != NULL) {
140 assert(_promoHead != NULL, "List consistency");
141 _promoTail->setNext(trackOop);
142 _promoTail = trackOop;
143 } else {
144 assert(_promoHead == NULL, "List consistency");
145 _promoHead = _promoTail = trackOop;
146 }
147 // Mask as newly promoted, so we can skip over such objects
148 // when scanning dirty cards
149 assert(!trackOop->hasPromotedMark(), "Should not have been marked");
150 trackOop->setPromotedMark();
151 }
152
153 // Save the given displaced header, incrementing the pointer and
154 // obtaining more spool area as necessary.
155 void PromotionInfo::saveDisplacedHeader(markOop hdr) {
156 assert(_spoolHead != NULL && _spoolTail != NULL,
157 "promotionInfo inconsistency");
158 assert(_spoolTail->bufferSize > _nextIndex, "Off by one error at tail?");
159 _spoolTail->displacedHdr[_nextIndex] = hdr;
160 // Spool forward
161 if (++_nextIndex == _spoolTail->bufferSize) { // last location in this block
162 // get a new spooling block
163 assert(_spoolTail->nextSpoolBlock == NULL, "tail should terminate spool list");
164 _splice_point = _spoolTail; // save for splicing
165 _spoolTail->nextSpoolBlock = getSpoolBlock(); // might fail
166 _spoolTail = _spoolTail->nextSpoolBlock; // might become NULL ...
167 // ... but will attempt filling before next promotion attempt
168 _nextIndex = 1;
169 }
170 }
171
172 // Ensure that spooling space exists. Return false if spooling space
173 // could not be obtained.
174 bool PromotionInfo::ensure_spooling_space_work() {
175 assert(!has_spooling_space(), "Only call when there is no spooling space");
176 // Try and obtain more spooling space
177 SpoolBlock* newSpool = getSpoolBlock();
178 assert(newSpool == NULL ||
179 (newSpool->bufferSize != 0 && newSpool->nextSpoolBlock == NULL),
180 "getSpoolBlock() sanity check");
181 if (newSpool == NULL) {
182 return false;
183 }
184 _nextIndex = 1;
185 if (_spoolTail == NULL) {
186 _spoolTail = newSpool;
187 if (_spoolHead == NULL) {
188 _spoolHead = newSpool;
189 _firstIndex = 1;
190 } else {
191 assert(_splice_point != NULL && _splice_point->nextSpoolBlock == NULL,
192 "Splice point invariant");
193 // Extra check that _splice_point is connected to list
194 #ifdef ASSERT
195 {
196 SpoolBlock* blk = _spoolHead;
197 for (; blk->nextSpoolBlock != NULL;
198 blk = blk->nextSpoolBlock);
199 assert(blk != NULL && blk == _splice_point,
200 "Splice point incorrect");
201 }
202 #endif // ASSERT
203 _splice_point->nextSpoolBlock = newSpool;
204 }
205 } else {
206 assert(_spoolHead != NULL, "spool list consistency");
207 _spoolTail->nextSpoolBlock = newSpool;
208 _spoolTail = newSpool;
209 }
210 return true;
211 }
212
213 // Get a free spool buffer from the free pool, getting a new block
214 // from the heap if necessary.
215 SpoolBlock* PromotionInfo::getSpoolBlock() {
216 SpoolBlock* res;
217 if ((res = _spareSpool) != NULL) {
218 _spareSpool = _spareSpool->nextSpoolBlock;
219 res->nextSpoolBlock = NULL;
220 } else { // spare spool exhausted, get some from heap
221 res = (SpoolBlock*)(space()->allocateScratch(refillSize()));
222 if (res != NULL) {
223 res->init();
224 }
225 }
226 assert(res == NULL || res->nextSpoolBlock == NULL, "postcondition");
227 return res;
228 }
229
230 void PromotionInfo::startTrackingPromotions() {
231 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
232 "spooling inconsistency?");
233 _firstIndex = _nextIndex = 1;
234 _tracking = true;
235 }
236
237 #define CMSPrintPromoBlockInfo 1
238
239 void PromotionInfo::stopTrackingPromotions(uint worker_id) {
240 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
241 "spooling inconsistency?");
242 _firstIndex = _nextIndex = 1;
243 _tracking = false;
244 if (CMSPrintPromoBlockInfo > 1) {
245 print_statistics(worker_id);
246 }
247 }
248
249 void PromotionInfo::print_statistics(uint worker_id) const {
250 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
251 "Else will undercount");
252 assert(CMSPrintPromoBlockInfo > 0, "Else unnecessary call");
253 // Count the number of blocks and slots in the free pool
254 size_t slots = 0;
255 size_t blocks = 0;
256 for (SpoolBlock* cur_spool = _spareSpool;
257 cur_spool != NULL;
258 cur_spool = cur_spool->nextSpoolBlock) {
259 // the first entry is just a self-pointer; indices 1 through
260 // bufferSize - 1 are occupied (thus, bufferSize - 1 slots).
261 assert((void*)cur_spool->displacedHdr == (void*)&cur_spool->displacedHdr,
262 "first entry of displacedHdr should be self-referential");
263 slots += cur_spool->bufferSize - 1;
264 blocks++;
265 }
266 if (_spoolHead != NULL) {
267 slots += _spoolHead->bufferSize - 1;
268 blocks++;
269 }
270 gclog_or_tty->print_cr(" [worker %d] promo_blocks = " SIZE_FORMAT ", promo_slots = " SIZE_FORMAT,
271 worker_id, blocks, slots);
272 }
273
274 // When _spoolTail is not NULL, then the slot <_spoolTail, _nextIndex>
275 // points to the next slot available for filling.
276 // The set of slots holding displaced headers are then all those in the
277 // right-open interval denoted by:
278 //
279 // [ <_spoolHead, _firstIndex>, <_spoolTail, _nextIndex> )
280 //
281 // When _spoolTail is NULL, then the set of slots with displaced headers
282 // is all those starting at the slot <_spoolHead, _firstIndex> and
283 // going up to the last slot of last block in the linked list.
284 // In this latter case, _splice_point points to the tail block of
285 // this linked list of blocks holding displaced headers.
286 void PromotionInfo::verify() const {
287 // Verify the following:
288 // 1. the number of displaced headers matches the number of promoted
289 // objects that have displaced headers
290 // 2. each promoted object lies in this space
291 debug_only(
292 PromotedObject* junk = NULL;
293 assert(junk->next_addr() == (void*)(oop(junk)->mark_addr()),
294 "Offset of PromotedObject::_next is expected to align with "
295 " the OopDesc::_mark within OopDesc");
296 )
297 // FIXME: guarantee????
298 guarantee(_spoolHead == NULL || _spoolTail != NULL ||
299 _splice_point != NULL, "list consistency");
300 guarantee(_promoHead == NULL || _promoTail != NULL, "list consistency");
301 // count the number of objects with displaced headers
302 size_t numObjsWithDisplacedHdrs = 0;
303 for (PromotedObject* curObj = _promoHead; curObj != NULL; curObj = curObj->next()) {
304 guarantee(space()->is_in_reserved((HeapWord*)curObj), "Containment");
305 // the last promoted object may fail the mark() != NULL test of is_oop().
306 guarantee(curObj->next() == NULL || oop(curObj)->is_oop(), "must be an oop");
307 if (curObj->hasDisplacedMark()) {
308 numObjsWithDisplacedHdrs++;
309 }
310 }
311 // Count the number of displaced headers
312 size_t numDisplacedHdrs = 0;
313 for (SpoolBlock* curSpool = _spoolHead;
314 curSpool != _spoolTail && curSpool != NULL;
315 curSpool = curSpool->nextSpoolBlock) {
316 // the first entry is just a self-pointer; indices 1 through
317 // bufferSize - 1 are occupied (thus, bufferSize - 1 slots).
318 guarantee((void*)curSpool->displacedHdr == (void*)&curSpool->displacedHdr,
319 "first entry of displacedHdr should be self-referential");
320 numDisplacedHdrs += curSpool->bufferSize - 1;
321 }
322 guarantee((_spoolHead == _spoolTail) == (numDisplacedHdrs == 0),
323 "internal consistency");
324 guarantee(_spoolTail != NULL || _nextIndex == 1,
325 "Inconsistency between _spoolTail and _nextIndex");
326 // We overcounted (_firstIndex-1) worth of slots in block
327 // _spoolHead and we undercounted (_nextIndex-1) worth of
328 // slots in block _spoolTail. We make an appropriate
329 // adjustment by subtracting the first and adding the
330 // second: - (_firstIndex - 1) + (_nextIndex - 1)
331 numDisplacedHdrs += (_nextIndex - _firstIndex);
332 guarantee(numDisplacedHdrs == numObjsWithDisplacedHdrs, "Displaced hdr count");
333 }
334
335 void PromotionInfo::print_on(outputStream* st) const {
336 SpoolBlock* curSpool = NULL;
337 size_t i = 0;
338 st->print_cr(" start & end indices: [" SIZE_FORMAT ", " SIZE_FORMAT ")",
339 _firstIndex, _nextIndex);
340 for (curSpool = _spoolHead; curSpool != _spoolTail && curSpool != NULL;
341 curSpool = curSpool->nextSpoolBlock) {
342 curSpool->print_on(st);
343 st->print_cr(" active ");
344 i++;
345 }
346 for (curSpool = _spoolTail; curSpool != NULL;
347 curSpool = curSpool->nextSpoolBlock) {
348 curSpool->print_on(st);
349 st->print_cr(" inactive ");
350 i++;
351 }
352 for (curSpool = _spareSpool; curSpool != NULL;
353 curSpool = curSpool->nextSpoolBlock) {
354 curSpool->print_on(st);
355 st->print_cr(" free ");
356 i++;
357 }
358 st->print_cr(" " SIZE_FORMAT " header spooling blocks", i);
359 }
360
361 void SpoolBlock::print_on(outputStream* st) const {
362 st->print("[" PTR_FORMAT "," PTR_FORMAT "), " SIZE_FORMAT " HeapWords -> " PTR_FORMAT,
363 this, (HeapWord*)displacedHdr + bufferSize,
364 bufferSize, nextSpoolBlock);
365 }