1 /*
2 * Copyright (c) 2010, 2017, 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/compressedOops.inline.hpp"
30 #include "oops/markOop.inline.hpp"
31 #include "oops/oop.hpp"
32
33 /////////////////////////////////////////////////////////////////////////
34 //// PromotionInfo
35 /////////////////////////////////////////////////////////////////////////
36
37
38 PromotedObject* PromotedObject::next() const {
39 assert(!((FreeChunk*)this)->is_free(), "Error");
40 PromotedObject* res;
41 if (UseCompressedOops) {
42 // The next pointer is a compressed oop stored in the top 32 bits
43 res = (PromotedObject*)CompressedOops::decode(_data._narrow_next);
44 } else {
45 res = (PromotedObject*)(_next & next_mask);
46 }
47 assert(oopDesc::is_oop_or_null(oop(res), true /* ignore mark word */), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(res)));
48 return res;
49 }
50
51 inline void PromotedObject::setNext(PromotedObject* x) {
52 assert(((intptr_t)x & ~next_mask) == 0, "Conflict in bit usage, "
53 "or insufficient alignment of objects");
54 if (UseCompressedOops) {
55 assert(_data._narrow_next == 0, "Overwrite?");
56 _data._narrow_next = CompressedOops::encode(oop(x));
57 } else {
58 _next |= (intptr_t)x;
59 }
60 assert(!((FreeChunk*)this)->is_free(), "Error");
61 }
62
63 //////////////////////////////////////////////////////////////////////////////
64 // We go over the list of promoted objects, removing each from the list,
65 // and applying the closure (this may, in turn, add more elements to
66 // the tail of the promoted list, and these newly added objects will
67 // also be processed) until the list is empty.
68 // To aid verification and debugging, in the non-product builds
69 // we actually forward _promoHead each time we process a promoted oop.
70 // Note that this is not necessary in general (i.e. when we don't need to
71 // call PromotionInfo::verify()) because oop_iterate can only add to the
72 // end of _promoTail, and never needs to look at _promoHead.
73
74 #define PROMOTED_OOPS_ITERATE_DEFN(OopClosureType, nv_suffix) \
75 \
76 void PromotionInfo::promoted_oops_iterate##nv_suffix(OopClosureType* cl) { \
77 NOT_PRODUCT(verify()); \
78 PromotedObject *curObj, *nextObj; \
79 for (curObj = _promoHead; curObj != NULL; curObj = nextObj) { \
80 if ((nextObj = curObj->next()) == NULL) { \
81 /* protect ourselves against additions due to closure application \
82 below by resetting the list. */ \
83 assert(_promoTail == curObj, "Should have been the tail"); \
84 _promoHead = _promoTail = NULL; \
85 } \
86 if (curObj->hasDisplacedMark()) { \
87 /* restore displaced header */ \
88 oop(curObj)->set_mark(nextDisplacedHeader()); \
89 } else { \
90 /* restore prototypical header */ \
91 oop(curObj)->init_mark(); \
92 } \
93 /* The "promoted_mark" should now not be set */ \
94 assert(!curObj->hasPromotedMark(), \
95 "Should have been cleared by restoring displaced mark-word"); \
96 NOT_PRODUCT(_promoHead = nextObj); \
97 if (cl != NULL) oop(curObj)->oop_iterate(cl); \
98 if (nextObj == NULL) { /* start at head of list reset above */ \
99 nextObj = _promoHead; \
100 } \
101 } \
102 assert(noPromotions(), "post-condition violation"); \
103 assert(_promoHead == NULL && _promoTail == NULL, "emptied promoted list");\
104 assert(_spoolHead == _spoolTail, "emptied spooling buffers"); \
105 assert(_firstIndex == _nextIndex, "empty buffer"); \
106 }
107
108 // This should have been ALL_SINCE_...() just like the others,
109 // but, because the body of the method above is somehwat longer,
110 // the MSVC compiler cannot cope; as a workaround, we split the
111 // macro into its 3 constituent parts below (see original macro
112 // definition in specializedOopClosures.hpp).
113 SPECIALIZED_SINCE_SAVE_MARKS_CLOSURES_YOUNG(PROMOTED_OOPS_ITERATE_DEFN)
114 PROMOTED_OOPS_ITERATE_DEFN(OopsInGenClosure,_v)
115
116
117 // Return the next displaced header, incrementing the pointer and
118 // recycling spool area as necessary.
119 markOop PromotionInfo::nextDisplacedHeader() {
120 assert(_spoolHead != NULL, "promotionInfo inconsistency");
121 assert(_spoolHead != _spoolTail || _firstIndex < _nextIndex,
122 "Empty spool space: no displaced header can be fetched");
123 assert(_spoolHead->bufferSize > _firstIndex, "Off by one error at head?");
124 markOop hdr = _spoolHead->displacedHdr[_firstIndex];
125 // Spool forward
126 if (++_firstIndex == _spoolHead->bufferSize) { // last location in this block
127 // forward to next block, recycling this block into spare spool buffer
128 SpoolBlock* tmp = _spoolHead->nextSpoolBlock;
129 assert(_spoolHead != _spoolTail, "Spooling storage mix-up");
130 _spoolHead->nextSpoolBlock = _spareSpool;
131 _spareSpool = _spoolHead;
132 _spoolHead = tmp;
133 _firstIndex = 1;
134 NOT_PRODUCT(
135 if (_spoolHead == NULL) { // all buffers fully consumed
136 assert(_spoolTail == NULL && _nextIndex == 1,
137 "spool buffers processing inconsistency");
138 }
139 )
140 }
141 return hdr;
142 }
143
144 void PromotionInfo::track(PromotedObject* trackOop) {
145 track(trackOop, oop(trackOop)->klass());
146 }
147
148 void PromotionInfo::track(PromotedObject* trackOop, Klass* klassOfOop) {
149 // make a copy of header as it may need to be spooled
150 markOop mark = oop(trackOop)->mark();
151 trackOop->clear_next();
152 if (mark->must_be_preserved_for_cms_scavenge(klassOfOop)) {
153 // save non-prototypical header, and mark oop
154 saveDisplacedHeader(mark);
155 trackOop->setDisplacedMark();
156 } else {
157 // we'd like to assert something like the following:
158 // assert(mark == markOopDesc::prototype(), "consistency check");
159 // ... but the above won't work because the age bits have not (yet) been
160 // cleared. The remainder of the check would be identical to the
161 // condition checked in must_be_preserved() above, so we don't really
162 // have anything useful to check here!
163 }
164 if (_promoTail != NULL) {
165 assert(_promoHead != NULL, "List consistency");
166 _promoTail->setNext(trackOop);
167 _promoTail = trackOop;
168 } else {
169 assert(_promoHead == NULL, "List consistency");
170 _promoHead = _promoTail = trackOop;
171 }
172 // Mask as newly promoted, so we can skip over such objects
173 // when scanning dirty cards
174 assert(!trackOop->hasPromotedMark(), "Should not have been marked");
175 trackOop->setPromotedMark();
176 }
177
178 // Save the given displaced header, incrementing the pointer and
179 // obtaining more spool area as necessary.
180 void PromotionInfo::saveDisplacedHeader(markOop hdr) {
181 assert(_spoolHead != NULL && _spoolTail != NULL,
182 "promotionInfo inconsistency");
183 assert(_spoolTail->bufferSize > _nextIndex, "Off by one error at tail?");
184 _spoolTail->displacedHdr[_nextIndex] = hdr;
185 // Spool forward
186 if (++_nextIndex == _spoolTail->bufferSize) { // last location in this block
187 // get a new spooling block
188 assert(_spoolTail->nextSpoolBlock == NULL, "tail should terminate spool list");
189 _splice_point = _spoolTail; // save for splicing
190 _spoolTail->nextSpoolBlock = getSpoolBlock(); // might fail
191 _spoolTail = _spoolTail->nextSpoolBlock; // might become NULL ...
192 // ... but will attempt filling before next promotion attempt
193 _nextIndex = 1;
194 }
195 }
196
197 // Ensure that spooling space exists. Return false if spooling space
198 // could not be obtained.
199 bool PromotionInfo::ensure_spooling_space_work() {
200 assert(!has_spooling_space(), "Only call when there is no spooling space");
201 // Try and obtain more spooling space
202 SpoolBlock* newSpool = getSpoolBlock();
203 assert(newSpool == NULL ||
204 (newSpool->bufferSize != 0 && newSpool->nextSpoolBlock == NULL),
205 "getSpoolBlock() sanity check");
206 if (newSpool == NULL) {
207 return false;
208 }
209 _nextIndex = 1;
210 if (_spoolTail == NULL) {
211 _spoolTail = newSpool;
212 if (_spoolHead == NULL) {
213 _spoolHead = newSpool;
214 _firstIndex = 1;
215 } else {
216 assert(_splice_point != NULL && _splice_point->nextSpoolBlock == NULL,
217 "Splice point invariant");
218 // Extra check that _splice_point is connected to list
219 #ifdef ASSERT
220 {
221 SpoolBlock* blk = _spoolHead;
222 for (; blk->nextSpoolBlock != NULL;
223 blk = blk->nextSpoolBlock);
224 assert(blk != NULL && blk == _splice_point,
225 "Splice point incorrect");
226 }
227 #endif // ASSERT
228 _splice_point->nextSpoolBlock = newSpool;
229 }
230 } else {
231 assert(_spoolHead != NULL, "spool list consistency");
232 _spoolTail->nextSpoolBlock = newSpool;
233 _spoolTail = newSpool;
234 }
235 return true;
236 }
237
238 // Get a free spool buffer from the free pool, getting a new block
239 // from the heap if necessary.
240 SpoolBlock* PromotionInfo::getSpoolBlock() {
241 SpoolBlock* res;
242 if ((res = _spareSpool) != NULL) {
243 _spareSpool = _spareSpool->nextSpoolBlock;
244 res->nextSpoolBlock = NULL;
245 } else { // spare spool exhausted, get some from heap
246 res = (SpoolBlock*)(space()->allocateScratch(refillSize()));
247 if (res != NULL) {
248 res->init();
249 }
250 }
251 assert(res == NULL || res->nextSpoolBlock == NULL, "postcondition");
252 return res;
253 }
254
255 void PromotionInfo::startTrackingPromotions() {
256 assert(noPromotions(), "sanity");
257 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
258 "spooling inconsistency?");
259 _firstIndex = _nextIndex = 1;
260 _tracking = true;
261 }
262
263 void PromotionInfo::stopTrackingPromotions() {
264 assert(noPromotions(), "we should have torn down the lists by now");
265 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
266 "spooling inconsistency?");
267 _firstIndex = _nextIndex = 1;
268 _tracking = false;
269 }
270
271 // When _spoolTail is not NULL, then the slot <_spoolTail, _nextIndex>
272 // points to the next slot available for filling.
273 // The set of slots holding displaced headers are then all those in the
274 // right-open interval denoted by:
275 //
276 // [ <_spoolHead, _firstIndex>, <_spoolTail, _nextIndex> )
277 //
278 // When _spoolTail is NULL, then the set of slots with displaced headers
279 // is all those starting at the slot <_spoolHead, _firstIndex> and
280 // going up to the last slot of last block in the linked list.
281 // In this latter case, _splice_point points to the tail block of
282 // this linked list of blocks holding displaced headers.
283 void PromotionInfo::verify() const {
284 // Verify the following:
285 // 1. the number of displaced headers matches the number of promoted
286 // objects that have displaced headers
287 // 2. each promoted object lies in this space
288 debug_only(
289 PromotedObject* junk = NULL;
290 assert(junk->next_addr() == (void*)(oop(junk)->mark_addr()),
291 "Offset of PromotedObject::_next is expected to align with "
292 " the OopDesc::_mark within OopDesc");
293 )
294 // FIXME: guarantee????
295 guarantee(_spoolHead == NULL || _spoolTail != NULL ||
296 _splice_point != NULL, "list consistency");
297 guarantee(_promoHead == NULL || _promoTail != NULL, "list consistency");
298 // count the number of objects with displaced headers
299 size_t numObjsWithDisplacedHdrs = 0;
300 for (PromotedObject* curObj = _promoHead; curObj != NULL; curObj = curObj->next()) {
301 guarantee(space()->is_in_reserved((HeapWord*)curObj), "Containment");
302 // the last promoted object may fail the mark() != NULL test of is_oop().
303 guarantee(curObj->next() == NULL || oopDesc::is_oop(oop(curObj)), "must be an oop");
304 if (curObj->hasDisplacedMark()) {
305 numObjsWithDisplacedHdrs++;
306 }
307 }
308 // Count the number of displaced headers
309 size_t numDisplacedHdrs = 0;
310 for (SpoolBlock* curSpool = _spoolHead;
311 curSpool != _spoolTail && curSpool != NULL;
312 curSpool = curSpool->nextSpoolBlock) {
313 // the first entry is just a self-pointer; indices 1 through
314 // bufferSize - 1 are occupied (thus, bufferSize - 1 slots).
315 guarantee((void*)curSpool->displacedHdr == (void*)&curSpool->displacedHdr,
316 "first entry of displacedHdr should be self-referential");
317 numDisplacedHdrs += curSpool->bufferSize - 1;
318 }
319 guarantee((_spoolHead == _spoolTail) == (numDisplacedHdrs == 0),
320 "internal consistency");
321 guarantee(_spoolTail != NULL || _nextIndex == 1,
322 "Inconsistency between _spoolTail and _nextIndex");
323 // We overcounted (_firstIndex-1) worth of slots in block
324 // _spoolHead and we undercounted (_nextIndex-1) worth of
325 // slots in block _spoolTail. We make an appropriate
326 // adjustment by subtracting the first and adding the
327 // second: - (_firstIndex - 1) + (_nextIndex - 1)
328 numDisplacedHdrs += (_nextIndex - _firstIndex);
329 guarantee(numDisplacedHdrs == numObjsWithDisplacedHdrs, "Displaced hdr count");
330 }
331
332 void PromotionInfo::print_on(outputStream* st) const {
333 SpoolBlock* curSpool = NULL;
334 size_t i = 0;
335 st->print_cr(" start & end indices: [" SIZE_FORMAT ", " SIZE_FORMAT ")",
336 _firstIndex, _nextIndex);
337 for (curSpool = _spoolHead; curSpool != _spoolTail && curSpool != NULL;
338 curSpool = curSpool->nextSpoolBlock) {
339 curSpool->print_on(st);
340 st->print_cr(" active ");
341 i++;
342 }
343 for (curSpool = _spoolTail; curSpool != NULL;
344 curSpool = curSpool->nextSpoolBlock) {
345 curSpool->print_on(st);
346 st->print_cr(" inactive ");
347 i++;
348 }
349 for (curSpool = _spareSpool; curSpool != NULL;
350 curSpool = curSpool->nextSpoolBlock) {
351 curSpool->print_on(st);
352 st->print_cr(" free ");
353 i++;
354 }
355 st->print_cr(" " SIZE_FORMAT " header spooling blocks", i);
356 }
357
358 void SpoolBlock::print_on(outputStream* st) const {
359 st->print("[" PTR_FORMAT "," PTR_FORMAT "), " SIZE_FORMAT " HeapWords -> " PTR_FORMAT,
360 p2i(this), p2i((HeapWord*)displacedHdr + bufferSize),
361 bufferSize, p2i(nextSpoolBlock));
362 }