1 /*
2 * Copyright (c) 2010, 2018, 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/markWord.inline.hpp"
31 #include "oops/oop.inline.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 // Return the next displaced header, incrementing the pointer and
64 // recycling spool area as necessary.
65 markWord PromotionInfo::nextDisplacedHeader() {
66 assert(_spoolHead != NULL, "promotionInfo inconsistency");
67 assert(_spoolHead != _spoolTail || _firstIndex < _nextIndex,
68 "Empty spool space: no displaced header can be fetched");
69 assert(_spoolHead->bufferSize > _firstIndex, "Off by one error at head?");
70 markWord hdr = _spoolHead->displacedHdr[_firstIndex];
71 // Spool forward
72 if (++_firstIndex == _spoolHead->bufferSize) { // last location in this block
73 // forward to next block, recycling this block into spare spool buffer
74 SpoolBlock* tmp = _spoolHead->nextSpoolBlock;
75 assert(_spoolHead != _spoolTail, "Spooling storage mix-up");
76 _spoolHead->nextSpoolBlock = _spareSpool;
77 _spareSpool = _spoolHead;
78 _spoolHead = tmp;
79 _firstIndex = 1;
80 NOT_PRODUCT(
81 if (_spoolHead == NULL) { // all buffers fully consumed
82 assert(_spoolTail == NULL && _nextIndex == 1,
83 "spool buffers processing inconsistency");
84 }
85 )
86 }
87 return hdr;
88 }
89
90 void PromotionInfo::track(PromotedObject* trackOop) {
91 track(trackOop, oop(trackOop)->klass());
92 }
93
94 void PromotionInfo::track(PromotedObject* trackOop, Klass* klassOfOop) {
95 // make a copy of header as it may need to be spooled
96 markWord mark = oop(trackOop)->mark_raw();
97 trackOop->clear_next();
98 if (mark.must_be_preserved_for_cms_scavenge(klassOfOop)) {
99 // save non-prototypical header, and mark oop
100 saveDisplacedHeader(mark);
101 trackOop->setDisplacedMark();
102 } else {
103 // we'd like to assert something like the following:
104 // assert(mark == markWord::prototype(), "consistency check");
105 // ... but the above won't work because the age bits have not (yet) been
106 // cleared. The remainder of the check would be identical to the
107 // condition checked in must_be_preserved() above, so we don't really
108 // have anything useful to check here!
109 }
110 if (_promoTail != NULL) {
111 assert(_promoHead != NULL, "List consistency");
112 _promoTail->setNext(trackOop);
113 _promoTail = trackOop;
114 } else {
115 assert(_promoHead == NULL, "List consistency");
116 _promoHead = _promoTail = trackOop;
117 }
118 // Mask as newly promoted, so we can skip over such objects
119 // when scanning dirty cards
120 assert(!trackOop->hasPromotedMark(), "Should not have been marked");
121 trackOop->setPromotedMark();
122 }
123
124 // Save the given displaced header, incrementing the pointer and
125 // obtaining more spool area as necessary.
126 void PromotionInfo::saveDisplacedHeader(markWord hdr) {
127 assert(_spoolHead != NULL && _spoolTail != NULL,
128 "promotionInfo inconsistency");
129 assert(_spoolTail->bufferSize > _nextIndex, "Off by one error at tail?");
130 _spoolTail->displacedHdr[_nextIndex] = hdr;
131 // Spool forward
132 if (++_nextIndex == _spoolTail->bufferSize) { // last location in this block
133 // get a new spooling block
134 assert(_spoolTail->nextSpoolBlock == NULL, "tail should terminate spool list");
135 _splice_point = _spoolTail; // save for splicing
136 _spoolTail->nextSpoolBlock = getSpoolBlock(); // might fail
137 _spoolTail = _spoolTail->nextSpoolBlock; // might become NULL ...
138 // ... but will attempt filling before next promotion attempt
139 _nextIndex = 1;
140 }
141 }
142
143 // Ensure that spooling space exists. Return false if spooling space
144 // could not be obtained.
145 bool PromotionInfo::ensure_spooling_space_work() {
146 assert(!has_spooling_space(), "Only call when there is no spooling space");
147 // Try and obtain more spooling space
148 SpoolBlock* newSpool = getSpoolBlock();
149 assert(newSpool == NULL ||
150 (newSpool->bufferSize != 0 && newSpool->nextSpoolBlock == NULL),
151 "getSpoolBlock() sanity check");
152 if (newSpool == NULL) {
153 return false;
154 }
155 _nextIndex = 1;
156 if (_spoolTail == NULL) {
157 _spoolTail = newSpool;
158 if (_spoolHead == NULL) {
159 _spoolHead = newSpool;
160 _firstIndex = 1;
161 } else {
162 assert(_splice_point != NULL && _splice_point->nextSpoolBlock == NULL,
163 "Splice point invariant");
164 // Extra check that _splice_point is connected to list
165 #ifdef ASSERT
166 {
167 SpoolBlock* blk = _spoolHead;
168 for (; blk->nextSpoolBlock != NULL;
169 blk = blk->nextSpoolBlock);
170 assert(blk != NULL && blk == _splice_point,
171 "Splice point incorrect");
172 }
173 #endif // ASSERT
174 _splice_point->nextSpoolBlock = newSpool;
175 }
176 } else {
177 assert(_spoolHead != NULL, "spool list consistency");
178 _spoolTail->nextSpoolBlock = newSpool;
179 _spoolTail = newSpool;
180 }
181 return true;
182 }
183
184 // Get a free spool buffer from the free pool, getting a new block
185 // from the heap if necessary.
186 SpoolBlock* PromotionInfo::getSpoolBlock() {
187 SpoolBlock* res;
188 if ((res = _spareSpool) != NULL) {
189 _spareSpool = _spareSpool->nextSpoolBlock;
190 res->nextSpoolBlock = NULL;
191 } else { // spare spool exhausted, get some from heap
192 res = (SpoolBlock*)(space()->allocateScratch(refillSize()));
193 if (res != NULL) {
194 res->init();
195 }
196 }
197 assert(res == NULL || res->nextSpoolBlock == NULL, "postcondition");
198 return res;
199 }
200
201 void PromotionInfo::startTrackingPromotions() {
202 assert(noPromotions(), "sanity");
203 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
204 "spooling inconsistency?");
205 _firstIndex = _nextIndex = 1;
206 _tracking = true;
207 }
208
209 void PromotionInfo::stopTrackingPromotions() {
210 assert(noPromotions(), "we should have torn down the lists by now");
211 assert(_spoolHead == _spoolTail && _firstIndex == _nextIndex,
212 "spooling inconsistency?");
213 _firstIndex = _nextIndex = 1;
214 _tracking = false;
215 }
216
217 // When _spoolTail is not NULL, then the slot <_spoolTail, _nextIndex>
218 // points to the next slot available for filling.
219 // The set of slots holding displaced headers are then all those in the
220 // right-open interval denoted by:
221 //
222 // [ <_spoolHead, _firstIndex>, <_spoolTail, _nextIndex> )
223 //
224 // When _spoolTail is NULL, then the set of slots with displaced headers
225 // is all those starting at the slot <_spoolHead, _firstIndex> and
226 // going up to the last slot of last block in the linked list.
227 // In this latter case, _splice_point points to the tail block of
228 // this linked list of blocks holding displaced headers.
229 void PromotionInfo::verify() const {
230 // Verify the following:
231 // 1. the number of displaced headers matches the number of promoted
232 // objects that have displaced headers
233 // 2. each promoted object lies in this space
234 debug_only(
235 PromotedObject* junk = NULL;
236 assert(junk->next_addr() == (void*)(oop(junk)->mark_addr_raw()),
237 "Offset of PromotedObject::_next is expected to align with "
238 " the OopDesc::_mark within OopDesc");
239 )
240 // FIXME: guarantee????
241 guarantee(_spoolHead == NULL || _spoolTail != NULL ||
242 _splice_point != NULL, "list consistency");
243 guarantee(_promoHead == NULL || _promoTail != NULL, "list consistency");
244 // count the number of objects with displaced headers
245 size_t numObjsWithDisplacedHdrs = 0;
246 for (PromotedObject* curObj = _promoHead; curObj != NULL; curObj = curObj->next()) {
247 guarantee(space()->is_in_reserved((HeapWord*)curObj), "Containment");
248 // the last promoted object may fail the mark() != NULL test of is_oop().
249 guarantee(curObj->next() == NULL || oopDesc::is_oop(oop(curObj)), "must be an oop");
250 if (curObj->hasDisplacedMark()) {
251 numObjsWithDisplacedHdrs++;
252 }
253 }
254 // Count the number of displaced headers
255 size_t numDisplacedHdrs = 0;
256 for (SpoolBlock* curSpool = _spoolHead;
257 curSpool != _spoolTail && curSpool != NULL;
258 curSpool = curSpool->nextSpoolBlock) {
259 // the first entry is just a self-pointer; indices 1 through
260 // bufferSize - 1 are occupied (thus, bufferSize - 1 slots).
261 guarantee((void*)curSpool->displacedHdr == (void*)&curSpool->displacedHdr,
262 "first entry of displacedHdr should be self-referential");
263 numDisplacedHdrs += curSpool->bufferSize - 1;
264 }
265 guarantee((_spoolHead == _spoolTail) == (numDisplacedHdrs == 0),
266 "internal consistency");
267 guarantee(_spoolTail != NULL || _nextIndex == 1,
268 "Inconsistency between _spoolTail and _nextIndex");
269 // We overcounted (_firstIndex-1) worth of slots in block
270 // _spoolHead and we undercounted (_nextIndex-1) worth of
271 // slots in block _spoolTail. We make an appropriate
272 // adjustment by subtracting the first and adding the
273 // second: - (_firstIndex - 1) + (_nextIndex - 1)
274 numDisplacedHdrs += (_nextIndex - _firstIndex);
275 guarantee(numDisplacedHdrs == numObjsWithDisplacedHdrs, "Displaced hdr count");
276 }
277
278 void PromotionInfo::print_on(outputStream* st) const {
279 SpoolBlock* curSpool = NULL;
280 size_t i = 0;
281 st->print_cr(" start & end indices: [" SIZE_FORMAT ", " SIZE_FORMAT ")",
282 _firstIndex, _nextIndex);
283 for (curSpool = _spoolHead; curSpool != _spoolTail && curSpool != NULL;
284 curSpool = curSpool->nextSpoolBlock) {
285 curSpool->print_on(st);
286 st->print_cr(" active ");
287 i++;
288 }
289 for (curSpool = _spoolTail; curSpool != NULL;
290 curSpool = curSpool->nextSpoolBlock) {
291 curSpool->print_on(st);
292 st->print_cr(" inactive ");
293 i++;
294 }
295 for (curSpool = _spareSpool; curSpool != NULL;
296 curSpool = curSpool->nextSpoolBlock) {
297 curSpool->print_on(st);
298 st->print_cr(" free ");
299 i++;
300 }
301 st->print_cr(" " SIZE_FORMAT " header spooling blocks", i);
302 }
303
304 void SpoolBlock::print_on(outputStream* st) const {
305 st->print("[" PTR_FORMAT "," PTR_FORMAT "), " SIZE_FORMAT " HeapWords -> " PTR_FORMAT,
306 p2i(this), p2i((HeapWord*)displacedHdr + bufferSize),
307 bufferSize, p2i(nextSpoolBlock));
308 }