1 /*
2 * Copyright (c) 2010, 2016, 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/cms/compactibleFreeListSpace.hpp"
27 #include "gc/cms/promotionInfo.hpp"
28 #include "gc/shared/genOopClosures.hpp"
29 #include "oops/markOop.inline.hpp"
30 #include "oops/oop.inline.hpp"
31
32 /////////////////////////////////////////////////////////////////////////
33 //// PromotionInfo
34 /////////////////////////////////////////////////////////////////////////
35
36
37 PromotedObject* PromotedObject::next() const {
38 assert(!((FreeChunk*)this)->is_free(), "Error");
39 PromotedObject* res;
40 if (UseCompressedOops) {
41 // The next pointer is a compressed oop stored in the top 32 bits
42 res = (PromotedObject*)oopDesc::decode_heap_oop(_data._narrow_next);
43 } else {
44 res = (PromotedObject*)(_next & next_mask);
45 }
46 assert(oop(res)->is_oop_or_null(true /* ignore mark word */), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(res)));
47 return res;
48 }
49
50 inline void PromotedObject::setNext(PromotedObject* x) {
51 assert(((intptr_t)x & ~next_mask) == 0, "Conflict in bit usage, "
52 "or insufficient alignment of objects");
53 if (UseCompressedOops) {
54 assert(_data._narrow_next == 0, "Overwrite?");
55 _data._narrow_next = oopDesc::encode_heap_oop(oop(x));
56 } else {
57 _next |= (intptr_t)x;
58 }
59 assert(!((FreeChunk*)this)->is_free(), "Error");
60 }
61
62 //////////////////////////////////////////////////////////////////////////////
63 // We go over the list of promoted objects, removing each from the list,
64 // and applying the closure (this may, in turn, add more elements to
65 // the tail of the promoted list, and these newly added objects will
66 // also be processed) until the list is empty.
67 // To aid verification and debugging, in the non-product builds
68 // we actually forward _promoHead each time we process a promoted oop.
69 // Note that this is not necessary in general (i.e. when we don't need to
70 // call PromotionInfo::verify()) because oop_iterate can only add to the
71 // end of _promoTail, and never needs to look at _promoHead.
72
73 #define PROMOTED_OOPS_ITERATE_DEFN(OopClosureType, nv_suffix) \
74 \
75 void PromotionInfo::promoted_oops_iterate##nv_suffix(OopClosureType* cl) { \
76 NOT_PRODUCT(verify()); \
77 PromotedObject *curObj, *nextObj; \
78 for (curObj = _promoHead; curObj != NULL; curObj = nextObj) { \
79 if ((nextObj = curObj->next()) == NULL) { \
80 /* protect ourselves against additions due to closure application \
81 below by resetting the list. */ \
82 assert(_promoTail == curObj, "Should have been the tail"); \
83 _promoHead = _promoTail = NULL; \
84 } \
85 if (curObj->hasDisplacedMark()) { \
86 /* restore displaced header */ \
87 oop(curObj)->set_mark(nextDisplacedHeader()); \
88 } else { \
89 /* restore prototypical header */ \
90 oop(curObj)->init_mark(); \
91 } \
92 /* The "promoted_mark" should now not be set */ \
93 assert(!curObj->hasPromotedMark(), \
94 "Should have been cleared by restoring displaced mark-word"); \
95 NOT_PRODUCT(_promoHead = nextObj); \
96 if (cl != NULL) oop(curObj)->oop_iterate(cl); \
97 if (nextObj == NULL) { /* start at head of list reset above */ \
98 nextObj = _promoHead; \
99 } \
100 } \
101 assert(noPromotions(), "post-condition violation"); \
102 assert(_promoHead == NULL && _promoTail == NULL, "emptied promoted list");\
103 assert(_spoolHead == _spoolTail, "emptied spooling buffers"); \
104 assert(_firstIndex == _nextIndex, "empty buffer"); \
105 }
106
107 // This should have been ALL_SINCE_...() just like the others,
108 // but, because the body of the method above is somehwat longer,
109 // the MSVC compiler cannot cope; as a workaround, we split the
110 // macro into its 3 constituent parts below (see original macro
111 // definition in specializedOopClosures.hpp).
112 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES_YOUNG(PROMOTED_OOPS_ITERATE_DEFN)
113 PROMOTED_OOPS_ITERATE_DEFN(OopsInGenClosure,_v)
114
115
116 // Return the next displaced header, incrementing the pointer and
117 // recycling spool area as necessary.
118 markOop PromotionInfo::nextDisplacedHeader() {
119 assert(_spoolHead != NULL, "promotionInfo inconsistency");
120 assert(_spoolHead != _spoolTail || _firstIndex < _nextIndex,
121 "Empty spool space: no displaced header can be fetched");
122 assert(_spoolHead->bufferSize > _firstIndex, "Off by one error at head?");
123 markOop hdr = _spoolHead->displacedHdr[_firstIndex];
124 // Spool forward
125 if (++_firstIndex == _spoolHead->bufferSize) { // last location in this block
126 // forward to next block, recycling this block into spare spool buffer
127 SpoolBlock* tmp = _spoolHead->nextSpoolBlock;
128 assert(_spoolHead != _spoolTail, "Spooling storage mix-up");
129 _spoolHead->nextSpoolBlock = _spareSpool;
130 _spareSpool = _spoolHead;
131 _spoolHead = tmp;
132 _firstIndex = 1;
133 NOT_PRODUCT(
134 if (_spoolHead == NULL) { // all buffers fully consumed
135 assert(_spoolTail == NULL && _nextIndex == 1,
136 "spool buffers processing inconsistency");
137 }
138 )
139 }
140 return hdr;
141 }
142
143 void PromotionInfo::track(PromotedObject* trackOop) {
144 track(trackOop, oop(trackOop)->klass());
145 }
146
147 void PromotionInfo::track(PromotedObject* trackOop, Klass* klassOfOop) {
148 // make a copy of header as it may need to be spooled
149 markOop mark = oop(trackOop)->mark();
150 trackOop->clear_next();
151 if (mark->must_be_preserved_for_cms_scavenge(klassOfOop)) {
152 // save non-prototypical header, and mark oop
153 saveDisplacedHeader(mark);
154 trackOop->setDisplacedMark();
155 } else {
156 // we'd like to assert something like the following:
157 // assert(mark == markOopDesc::prototype(), "consistency check");
158 // ... but the above won't work because the age bits have not (yet) been
159 // cleared. The remainder of the check would be identical to the
160 // condition checked in must_be_preserved() above, so we don't really
161 // have anything useful to check here!
162 }
163 if (_promoTail != NULL) {
164 assert(_promoHead != NULL, "List consistency");
165 _promoTail->setNext(trackOop);
166 _promoTail = trackOop;
167 } else {
168 assert(_promoHead == NULL, "List consistency");
169 _promoHead = _promoTail = trackOop;
170 }
171 // Mask as newly promoted, so we can skip over such objects
172 // when scanning dirty cards
173 assert(!trackOop->hasPromotedMark(), "Should not have been marked");
174 trackOop->setPromotedMark();
175 }
176
177 // Save the given displaced header, incrementing the pointer and
178 // obtaining more spool area as necessary.
179 void PromotionInfo::saveDisplacedHeader(markOop hdr) {
180 assert(_spoolHead != NULL && _spoolTail != NULL,
181 "promotionInfo inconsistency");
182 assert(_spoolTail->bufferSize > _nextIndex, "Off by one error at tail?");
183 _spoolTail->displacedHdr[_nextIndex] = hdr;
184 // Spool forward
185 if (++_nextIndex == _spoolTail->bufferSize) { // last location in this block
186 // get a new spooling block
187 assert(_spoolTail->nextSpoolBlock == NULL, "tail should terminate spool list");
188 _splice_point = _spoolTail; // save for splicing
189 _spoolTail->nextSpoolBlock = getSpoolBlock(); // might fail
190 _spoolTail = _spoolTail->nextSpoolBlock; // might become NULL ...
191 // ... but will attempt filling before next promotion attempt
192 _nextIndex = 1;
193 }
194 }
195
196 // Ensure that spooling space exists. Return false if spooling space
197 // could not be obtained.
198 bool PromotionInfo::ensure_spooling_space_work() {
199 assert(!has_spooling_space(), "Only call when there is no spooling space");
200 // Try and obtain more spooling space
201 SpoolBlock* newSpool = getSpoolBlock();
202 assert(newSpool == NULL ||
203 (newSpool->bufferSize != 0 && newSpool->nextSpoolBlock == NULL),
204 "getSpoolBlock() sanity check");
205 if (newSpool == NULL) {
206 return false;
207 }
208 _nextIndex = 1;
209 if (_spoolTail == NULL) {
210 _spoolTail = newSpool;
211 if (_spoolHead == NULL) {
212 _spoolHead = newSpool;
213 _firstIndex = 1;
214 } else {
215 assert(_splice_point != NULL && _splice_point->nextSpoolBlock == NULL,
216 "Splice point invariant");
217 // Extra check that _splice_point is connected to list
218 #ifdef ASSERT
219 {
220 SpoolBlock* blk = _spoolHead;
221 for (; blk->nextSpoolBlock != NULL;
222 blk = blk->nextSpoolBlock);
223 assert(blk != NULL && blk == _splice_point,
224 "Splice point incorrect");
225 }
226 #endif // ASSERT
227 _splice_point->nextSpoolBlock = newSpool;
228 }
229 } else {
230 assert(_spoolHead != NULL, "spool list consistency");
231 _spoolTail->nextSpoolBlock = newSpool;
232 _spoolTail = newSpool;
233 }
234 return true;
235 }
236
237 // Get a free spool buffer from the free pool, getting a new block
238 // from the heap if necessary.
239 SpoolBlock* PromotionInfo::getSpoolBlock() {
240 SpoolBlock* res;
241 if ((res = _spareSpool) != NULL) {
242 _spareSpool = _spareSpool->nextSpoolBlock;
243 res->nextSpoolBlock = NULL;
244 } else { // spare spool exhausted, get some from heap
245 res = (SpoolBlock*)(space()->allocateScratch(refillSize()));
246 if (res != NULL) {
247 res->init();
248 }
249 }
250 assert(res == NULL || res->nextSpoolBlock == NULL, "postcondition");
251 return res;
252 }
253
254 void PromotionInfo::startTrackingPromotions() {
255 assert(noPromotions(), "sanity");
256 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
257 "spooling inconsistency?");
258 _firstIndex = _nextIndex = 1;
259 _tracking = true;
260 }
261
262 void PromotionInfo::stopTrackingPromotions() {
263 assert(noPromotions(), "we should have torn down the lists by now");
264 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
265 "spooling inconsistency?");
266 _firstIndex = _nextIndex = 1;
267 _tracking = false;
268 }
269
270 // When _spoolTail is not NULL, then the slot <_spoolTail, _nextIndex>
271 // points to the next slot available for filling.
272 // The set of slots holding displaced headers are then all those in the
273 // right-open interval denoted by:
274 //
275 // [ <_spoolHead, _firstIndex>, <_spoolTail, _nextIndex> )
276 //
277 // When _spoolTail is NULL, then the set of slots with displaced headers
278 // is all those starting at the slot <_spoolHead, _firstIndex> and
279 // going up to the last slot of last block in the linked list.
280 // In this latter case, _splice_point points to the tail block of
281 // this linked list of blocks holding displaced headers.
282 void PromotionInfo::verify() const {
283 // Verify the following:
284 // 1. the number of displaced headers matches the number of promoted
285 // objects that have displaced headers
286 // 2. each promoted object lies in this space
287 debug_only(
288 PromotedObject* junk = NULL;
289 assert(junk->next_addr() == (void*)(oop(junk)->mark_addr()),
290 "Offset of PromotedObject::_next is expected to align with "
291 " the OopDesc::_mark within OopDesc");
292 )
293 // FIXME: guarantee????
294 guarantee(_spoolHead == NULL || _spoolTail != NULL ||
295 _splice_point != NULL, "list consistency");
296 guarantee(_promoHead == NULL || _promoTail != NULL, "list consistency");
297 // count the number of objects with displaced headers
298 size_t numObjsWithDisplacedHdrs = 0;
299 for (PromotedObject* curObj = _promoHead; curObj != NULL; curObj = curObj->next()) {
300 guarantee(space()->is_in_reserved((HeapWord*)curObj), "Containment");
301 // the last promoted object may fail the mark() != NULL test of is_oop().
302 guarantee(curObj->next() == NULL || oop(curObj)->is_oop(), "must be an oop");
303 if (curObj->hasDisplacedMark()) {
304 numObjsWithDisplacedHdrs++;
305 }
306 }
307 // Count the number of displaced headers
308 size_t numDisplacedHdrs = 0;
309 for (SpoolBlock* curSpool = _spoolHead;
310 curSpool != _spoolTail && curSpool != NULL;
311 curSpool = curSpool->nextSpoolBlock) {
312 // the first entry is just a self-pointer; indices 1 through
313 // bufferSize - 1 are occupied (thus, bufferSize - 1 slots).
314 guarantee((void*)curSpool->displacedHdr == (void*)&curSpool->displacedHdr,
315 "first entry of displacedHdr should be self-referential");
316 numDisplacedHdrs += curSpool->bufferSize - 1;
317 }
318 guarantee((_spoolHead == _spoolTail) == (numDisplacedHdrs == 0),
319 "internal consistency");
320 guarantee(_spoolTail != NULL || _nextIndex == 1,
321 "Inconsistency between _spoolTail and _nextIndex");
322 // We overcounted (_firstIndex-1) worth of slots in block
323 // _spoolHead and we undercounted (_nextIndex-1) worth of
324 // slots in block _spoolTail. We make an appropriate
325 // adjustment by subtracting the first and adding the
326 // second: - (_firstIndex - 1) + (_nextIndex - 1)
327 numDisplacedHdrs += (_nextIndex - _firstIndex);
328 guarantee(numDisplacedHdrs == numObjsWithDisplacedHdrs, "Displaced hdr count");
329 }
330
331 void PromotionInfo::print_on(outputStream* st) const {
332 SpoolBlock* curSpool = NULL;
333 size_t i = 0;
334 st->print_cr(" start & end indices: [" SIZE_FORMAT ", " SIZE_FORMAT ")",
335 _firstIndex, _nextIndex);
336 for (curSpool = _spoolHead; curSpool != _spoolTail && curSpool != NULL;
337 curSpool = curSpool->nextSpoolBlock) {
338 curSpool->print_on(st);
339 st->print_cr(" active ");
340 i++;
341 }
342 for (curSpool = _spoolTail; curSpool != NULL;
343 curSpool = curSpool->nextSpoolBlock) {
344 curSpool->print_on(st);
345 st->print_cr(" inactive ");
346 i++;
347 }
348 for (curSpool = _spareSpool; curSpool != NULL;
349 curSpool = curSpool->nextSpoolBlock) {
350 curSpool->print_on(st);
351 st->print_cr(" free ");
352 i++;
353 }
354 st->print_cr(" " SIZE_FORMAT " header spooling blocks", i);
355 }
356
357 void SpoolBlock::print_on(outputStream* st) const {
358 st->print("[" PTR_FORMAT "," PTR_FORMAT "), " SIZE_FORMAT " HeapWords -> " PTR_FORMAT,
359 p2i(this), p2i((HeapWord*)displacedHdr + bufferSize),
360 bufferSize, p2i(nextSpoolBlock));
361 }