Mercurial > hg > graal-compiler
annotate src/share/vm/oops/markOop.hpp @ 1711:a6bff45449bc
6973570: OrderAccess::storestore() scales poorly on multi-socket x64 and sparc: cache-line ping-ponging
Summary: volatile store to static variable removed in favour of a volatile store to stack to avoid excessive cache coherency traffic; verified that the volatile store is not elided by any of our current compilers.
Reviewed-by: dholmes, dice, jcoomes, kvn
author | ysr |
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date | Tue, 10 Aug 2010 14:53:35 -0700 |
parents | c18cbe5936b8 |
children | f95d63e2154a |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 1997, 2008, Oracle and/or its affiliates. All rights reserved. |
0 | 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 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
25 // The markOop describes the header of an object. | |
26 // | |
27 // Note that the mark is not a real oop but just a word. | |
28 // It is placed in the oop hierarchy for historical reasons. | |
29 // | |
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30 // Bit-format of an object header (most significant first, big endian layout below): |
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31 // |
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32 // 32 bits: |
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33 // -------- |
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34 // hash:25 ------------>| age:4 biased_lock:1 lock:2 (normal object) |
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35 // JavaThread*:23 epoch:2 age:4 biased_lock:1 lock:2 (biased object) |
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36 // size:32 ------------------------------------------>| (CMS free block) |
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37 // PromotedObject*:29 ---------->| promo_bits:3 ----->| (CMS promoted object) |
0 | 38 // |
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39 // 64 bits: |
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40 // -------- |
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41 // unused:25 hash:31 -->| unused:1 age:4 biased_lock:1 lock:2 (normal object) |
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42 // JavaThread*:54 epoch:2 unused:1 age:4 biased_lock:1 lock:2 (biased object) |
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43 // PromotedObject*:61 --------------------->| promo_bits:3 ----->| (CMS promoted object) |
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44 // size:64 ----------------------------------------------------->| (CMS free block) |
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45 // |
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46 // unused:25 hash:31 -->| cms_free:1 age:4 biased_lock:1 lock:2 (COOPs && normal object) |
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47 // JavaThread*:54 epoch:2 cms_free:1 age:4 biased_lock:1 lock:2 (COOPs && biased object) |
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48 // narrowOop:32 unused:24 cms_free:1 unused:4 promo_bits:3 ----->| (COOPs && CMS promoted object) |
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49 // unused:21 size:35 -->| cms_free:1 unused:7 ------------------>| (COOPs && CMS free block) |
0 | 50 // |
51 // - hash contains the identity hash value: largest value is | |
52 // 31 bits, see os::random(). Also, 64-bit vm's require | |
53 // a hash value no bigger than 32 bits because they will not | |
54 // properly generate a mask larger than that: see library_call.cpp | |
55 // and c1_CodePatterns_sparc.cpp. | |
56 // | |
57 // - the biased lock pattern is used to bias a lock toward a given | |
58 // thread. When this pattern is set in the low three bits, the lock | |
59 // is either biased toward a given thread or "anonymously" biased, | |
60 // indicating that it is possible for it to be biased. When the | |
61 // lock is biased toward a given thread, locking and unlocking can | |
62 // be performed by that thread without using atomic operations. | |
63 // When a lock's bias is revoked, it reverts back to the normal | |
64 // locking scheme described below. | |
65 // | |
66 // Note that we are overloading the meaning of the "unlocked" state | |
67 // of the header. Because we steal a bit from the age we can | |
68 // guarantee that the bias pattern will never be seen for a truly | |
69 // unlocked object. | |
70 // | |
71 // Note also that the biased state contains the age bits normally | |
72 // contained in the object header. Large increases in scavenge | |
73 // times were seen when these bits were absent and an arbitrary age | |
74 // assigned to all biased objects, because they tended to consume a | |
75 // significant fraction of the eden semispaces and were not | |
76 // promoted promptly, causing an increase in the amount of copying | |
77 // performed. The runtime system aligns all JavaThread* pointers to | |
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78 // a very large value (currently 128 bytes (32bVM) or 256 bytes (64bVM)) |
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79 // to make room for the age bits & the epoch bits (used in support of |
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80 // biased locking), and for the CMS "freeness" bit in the 64bVM (+COOPs). |
0 | 81 // |
82 // [JavaThread* | epoch | age | 1 | 01] lock is biased toward given thread | |
83 // [0 | epoch | age | 1 | 01] lock is anonymously biased | |
84 // | |
85 // - the two lock bits are used to describe three states: locked/unlocked and monitor. | |
86 // | |
87 // [ptr | 00] locked ptr points to real header on stack | |
88 // [header | 0 | 01] unlocked regular object header | |
89 // [ptr | 10] monitor inflated lock (header is wapped out) | |
90 // [ptr | 11] marked used by markSweep to mark an object | |
91 // not valid at any other time | |
92 // | |
93 // We assume that stack/thread pointers have the lowest two bits cleared. | |
94 | |
95 class BasicLock; | |
96 class ObjectMonitor; | |
97 class JavaThread; | |
98 | |
99 class markOopDesc: public oopDesc { | |
100 private: | |
101 // Conversion | |
102 uintptr_t value() const { return (uintptr_t) this; } | |
103 | |
104 public: | |
105 // Constants | |
106 enum { age_bits = 4, | |
107 lock_bits = 2, | |
108 biased_lock_bits = 1, | |
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109 max_hash_bits = BitsPerWord - age_bits - lock_bits - biased_lock_bits, |
0 | 110 hash_bits = max_hash_bits > 31 ? 31 : max_hash_bits, |
187 | 111 cms_bits = LP64_ONLY(1) NOT_LP64(0), |
0 | 112 epoch_bits = 2 |
113 }; | |
114 | |
115 // The biased locking code currently requires that the age bits be | |
116 // contiguous to the lock bits. Class data sharing would prefer the | |
117 // hash bits to be lower down to provide more random hash codes for | |
118 // shared read-only symbolOop objects, because these objects' mark | |
119 // words are set to their own address with marked_value in the lock | |
120 // bit, and using lower bits would make their identity hash values | |
121 // more random. However, the performance decision was made in favor | |
122 // of the biased locking code. | |
123 | |
124 enum { lock_shift = 0, | |
125 biased_lock_shift = lock_bits, | |
126 age_shift = lock_bits + biased_lock_bits, | |
187 | 127 cms_shift = age_shift + age_bits, |
128 hash_shift = cms_shift + cms_bits, | |
0 | 129 epoch_shift = hash_shift |
130 }; | |
131 | |
132 enum { lock_mask = right_n_bits(lock_bits), | |
133 lock_mask_in_place = lock_mask << lock_shift, | |
134 biased_lock_mask = right_n_bits(lock_bits + biased_lock_bits), | |
135 biased_lock_mask_in_place= biased_lock_mask << lock_shift, | |
136 biased_lock_bit_in_place = 1 << biased_lock_shift, | |
137 age_mask = right_n_bits(age_bits), | |
138 age_mask_in_place = age_mask << age_shift, | |
139 epoch_mask = right_n_bits(epoch_bits), | |
187 | 140 epoch_mask_in_place = epoch_mask << epoch_shift, |
141 cms_mask = right_n_bits(cms_bits), | |
142 cms_mask_in_place = cms_mask << cms_shift | |
0 | 143 #ifndef _WIN64 |
144 ,hash_mask = right_n_bits(hash_bits), | |
145 hash_mask_in_place = (address_word)hash_mask << hash_shift | |
146 #endif | |
147 }; | |
148 | |
149 // Alignment of JavaThread pointers encoded in object header required by biased locking | |
150 enum { biased_lock_alignment = 2 << (epoch_shift + epoch_bits) | |
151 }; | |
152 | |
153 #ifdef _WIN64 | |
154 // These values are too big for Win64 | |
155 const static uintptr_t hash_mask = right_n_bits(hash_bits); | |
156 const static uintptr_t hash_mask_in_place = | |
157 (address_word)hash_mask << hash_shift; | |
158 #endif | |
159 | |
160 enum { locked_value = 0, | |
161 unlocked_value = 1, | |
162 monitor_value = 2, | |
163 marked_value = 3, | |
164 biased_lock_pattern = 5 | |
165 }; | |
166 | |
167 enum { no_hash = 0 }; // no hash value assigned | |
168 | |
169 enum { no_hash_in_place = (address_word)no_hash << hash_shift, | |
170 no_lock_in_place = unlocked_value | |
171 }; | |
172 | |
173 enum { max_age = age_mask }; | |
174 | |
175 enum { max_bias_epoch = epoch_mask }; | |
176 | |
177 // Biased Locking accessors. | |
178 // These must be checked by all code which calls into the | |
179 // ObjectSynchronizer and other code. The biasing is not understood | |
180 // by the lower-level CAS-based locking code, although the runtime | |
181 // fixes up biased locks to be compatible with it when a bias is | |
182 // revoked. | |
183 bool has_bias_pattern() const { | |
184 return (mask_bits(value(), biased_lock_mask_in_place) == biased_lock_pattern); | |
185 } | |
186 JavaThread* biased_locker() const { | |
187 assert(has_bias_pattern(), "should not call this otherwise"); | |
188 return (JavaThread*) ((intptr_t) (mask_bits(value(), ~(biased_lock_mask_in_place | age_mask_in_place | epoch_mask_in_place)))); | |
189 } | |
190 // Indicates that the mark has the bias bit set but that it has not | |
191 // yet been biased toward a particular thread | |
192 bool is_biased_anonymously() const { | |
193 return (has_bias_pattern() && (biased_locker() == NULL)); | |
194 } | |
195 // Indicates epoch in which this bias was acquired. If the epoch | |
196 // changes due to too many bias revocations occurring, the biases | |
197 // from the previous epochs are all considered invalid. | |
198 int bias_epoch() const { | |
199 assert(has_bias_pattern(), "should not call this otherwise"); | |
200 return (mask_bits(value(), epoch_mask_in_place) >> epoch_shift); | |
201 } | |
202 markOop set_bias_epoch(int epoch) { | |
203 assert(has_bias_pattern(), "should not call this otherwise"); | |
204 assert((epoch & (~epoch_mask)) == 0, "epoch overflow"); | |
205 return markOop(mask_bits(value(), ~epoch_mask_in_place) | (epoch << epoch_shift)); | |
206 } | |
207 markOop incr_bias_epoch() { | |
208 return set_bias_epoch((1 + bias_epoch()) & epoch_mask); | |
209 } | |
210 // Prototype mark for initialization | |
211 static markOop biased_locking_prototype() { | |
212 return markOop( biased_lock_pattern ); | |
213 } | |
214 | |
215 // lock accessors (note that these assume lock_shift == 0) | |
216 bool is_locked() const { | |
217 return (mask_bits(value(), lock_mask_in_place) != unlocked_value); | |
218 } | |
219 bool is_unlocked() const { | |
220 return (mask_bits(value(), biased_lock_mask_in_place) == unlocked_value); | |
221 } | |
222 bool is_marked() const { | |
223 return (mask_bits(value(), lock_mask_in_place) == marked_value); | |
224 } | |
225 bool is_neutral() const { return (mask_bits(value(), biased_lock_mask_in_place) == unlocked_value); } | |
226 | |
227 // Special temporary state of the markOop while being inflated. | |
228 // Code that looks at mark outside a lock need to take this into account. | |
229 bool is_being_inflated() const { return (value() == 0); } | |
230 | |
231 // Distinguished markword value - used when inflating over | |
232 // an existing stacklock. 0 indicates the markword is "BUSY". | |
233 // Lockword mutators that use a LD...CAS idiom should always | |
234 // check for and avoid overwriting a 0 value installed by some | |
235 // other thread. (They should spin or block instead. The 0 value | |
236 // is transient and *should* be short-lived). | |
237 static markOop INFLATING() { return (markOop) 0; } // inflate-in-progress | |
238 | |
239 // Should this header be preserved during GC? | |
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240 inline bool must_be_preserved(oop obj_containing_mark) const; |
0 | 241 inline bool must_be_preserved_with_bias(oop obj_containing_mark) const; |
242 | |
243 // Should this header (including its age bits) be preserved in the | |
244 // case of a promotion failure during scavenge? | |
245 // Note that we special case this situation. We want to avoid | |
246 // calling BiasedLocking::preserve_marks()/restore_marks() (which | |
247 // decrease the number of mark words that need to be preserved | |
248 // during GC) during each scavenge. During scavenges in which there | |
249 // is no promotion failure, we actually don't need to call the above | |
250 // routines at all, since we don't mutate and re-initialize the | |
251 // marks of promoted objects using init_mark(). However, during | |
252 // scavenges which result in promotion failure, we do re-initialize | |
253 // the mark words of objects, meaning that we should have called | |
254 // these mark word preservation routines. Currently there's no good | |
255 // place in which to call them in any of the scavengers (although | |
256 // guarded by appropriate locks we could make one), but the | |
257 // observation is that promotion failures are quite rare and | |
258 // reducing the number of mark words preserved during them isn't a | |
259 // high priority. | |
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260 inline bool must_be_preserved_for_promotion_failure(oop obj_containing_mark) const; |
0 | 261 inline bool must_be_preserved_with_bias_for_promotion_failure(oop obj_containing_mark) const; |
262 | |
263 // Should this header be preserved during a scavenge where CMS is | |
264 // the old generation? | |
265 // (This is basically the same body as must_be_preserved_for_promotion_failure(), | |
266 // but takes the klassOop as argument instead) | |
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267 inline bool must_be_preserved_for_cms_scavenge(klassOop klass_of_obj_containing_mark) const; |
0 | 268 inline bool must_be_preserved_with_bias_for_cms_scavenge(klassOop klass_of_obj_containing_mark) const; |
269 | |
270 // WARNING: The following routines are used EXCLUSIVELY by | |
271 // synchronization functions. They are not really gc safe. | |
272 // They must get updated if markOop layout get changed. | |
273 markOop set_unlocked() const { | |
274 return markOop(value() | unlocked_value); | |
275 } | |
276 bool has_locker() const { | |
277 return ((value() & lock_mask_in_place) == locked_value); | |
278 } | |
279 BasicLock* locker() const { | |
280 assert(has_locker(), "check"); | |
281 return (BasicLock*) value(); | |
282 } | |
283 bool has_monitor() const { | |
284 return ((value() & monitor_value) != 0); | |
285 } | |
286 ObjectMonitor* monitor() const { | |
287 assert(has_monitor(), "check"); | |
288 // Use xor instead of &~ to provide one extra tag-bit check. | |
289 return (ObjectMonitor*) (value() ^ monitor_value); | |
290 } | |
291 bool has_displaced_mark_helper() const { | |
292 return ((value() & unlocked_value) == 0); | |
293 } | |
294 markOop displaced_mark_helper() const { | |
295 assert(has_displaced_mark_helper(), "check"); | |
296 intptr_t ptr = (value() & ~monitor_value); | |
297 return *(markOop*)ptr; | |
298 } | |
299 void set_displaced_mark_helper(markOop m) const { | |
300 assert(has_displaced_mark_helper(), "check"); | |
301 intptr_t ptr = (value() & ~monitor_value); | |
302 *(markOop*)ptr = m; | |
303 } | |
304 markOop copy_set_hash(intptr_t hash) const { | |
305 intptr_t tmp = value() & (~hash_mask_in_place); | |
306 tmp |= ((hash & hash_mask) << hash_shift); | |
307 return (markOop)tmp; | |
308 } | |
309 // it is only used to be stored into BasicLock as the | |
310 // indicator that the lock is using heavyweight monitor | |
311 static markOop unused_mark() { | |
312 return (markOop) marked_value; | |
313 } | |
314 // the following two functions create the markOop to be | |
315 // stored into object header, it encodes monitor info | |
316 static markOop encode(BasicLock* lock) { | |
317 return (markOop) lock; | |
318 } | |
319 static markOop encode(ObjectMonitor* monitor) { | |
320 intptr_t tmp = (intptr_t) monitor; | |
321 return (markOop) (tmp | monitor_value); | |
322 } | |
323 static markOop encode(JavaThread* thread, int age, int bias_epoch) { | |
324 intptr_t tmp = (intptr_t) thread; | |
325 assert(UseBiasedLocking && ((tmp & (epoch_mask_in_place | age_mask_in_place | biased_lock_mask_in_place)) == 0), "misaligned JavaThread pointer"); | |
326 assert(age <= max_age, "age too large"); | |
327 assert(bias_epoch <= max_bias_epoch, "bias epoch too large"); | |
328 return (markOop) (tmp | (bias_epoch << epoch_shift) | (age << age_shift) | biased_lock_pattern); | |
329 } | |
330 | |
331 // used to encode pointers during GC | |
332 markOop clear_lock_bits() { return markOop(value() & ~lock_mask_in_place); } | |
333 | |
334 // age operations | |
335 markOop set_marked() { return markOop((value() & ~lock_mask_in_place) | marked_value); } | |
336 | |
337 int age() const { return mask_bits(value() >> age_shift, age_mask); } | |
338 markOop set_age(int v) const { | |
339 assert((v & ~age_mask) == 0, "shouldn't overflow age field"); | |
340 return markOop((value() & ~age_mask_in_place) | (((intptr_t)v & age_mask) << age_shift)); | |
341 } | |
342 markOop incr_age() const { return age() == max_age ? markOop(this) : set_age(age() + 1); } | |
343 | |
344 // hash operations | |
345 intptr_t hash() const { | |
346 return mask_bits(value() >> hash_shift, hash_mask); | |
347 } | |
348 | |
349 bool has_no_hash() const { | |
350 return hash() == no_hash; | |
351 } | |
352 | |
353 // Prototype mark for initialization | |
354 static markOop prototype() { | |
355 return markOop( no_hash_in_place | no_lock_in_place ); | |
356 } | |
357 | |
358 // Helper function for restoration of unmarked mark oops during GC | |
359 static inline markOop prototype_for_object(oop obj); | |
360 | |
361 // Debugging | |
362 void print_on(outputStream* st) const; | |
363 | |
364 // Prepare address of oop for placement into mark | |
365 inline static markOop encode_pointer_as_mark(void* p) { return markOop(p)->set_marked(); } | |
366 | |
367 // Recover address of oop from encoded form used in mark | |
368 inline void* decode_pointer() { if (UseBiasedLocking && has_bias_pattern()) return NULL; return clear_lock_bits(); } | |
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370 // see the definition in markOop.cpp for the gory details |
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371 bool should_not_be_cached() const; |
187 | 372 |
373 // These markOops indicate cms free chunk blocks and not objects. | |
374 // In 64 bit, the markOop is set to distinguish them from oops. | |
375 // These are defined in 32 bit mode for vmStructs. | |
376 const static uintptr_t cms_free_chunk_pattern = 0x1; | |
377 | |
378 // Constants for the size field. | |
379 enum { size_shift = cms_shift + cms_bits, | |
380 size_bits = 35 // need for compressed oops 32G | |
381 }; | |
382 // These values are too big for Win64 | |
383 const static uintptr_t size_mask = LP64_ONLY(right_n_bits(size_bits)) | |
384 NOT_LP64(0); | |
385 const static uintptr_t size_mask_in_place = | |
386 (address_word)size_mask << size_shift; | |
387 | |
388 #ifdef _LP64 | |
389 static markOop cms_free_prototype() { | |
390 return markOop(((intptr_t)prototype() & ~cms_mask_in_place) | | |
391 ((cms_free_chunk_pattern & cms_mask) << cms_shift)); | |
392 } | |
393 uintptr_t cms_encoding() const { | |
394 return mask_bits(value() >> cms_shift, cms_mask); | |
395 } | |
396 bool is_cms_free_chunk() const { | |
397 return is_neutral() && | |
398 (cms_encoding() & cms_free_chunk_pattern) == cms_free_chunk_pattern; | |
399 } | |
400 | |
401 size_t get_size() const { return (size_t)(value() >> size_shift); } | |
402 static markOop set_size_and_free(size_t size) { | |
403 assert((size & ~size_mask) == 0, "shouldn't overflow size field"); | |
404 return markOop(((intptr_t)cms_free_prototype() & ~size_mask_in_place) | | |
405 (((intptr_t)size & size_mask) << size_shift)); | |
406 } | |
407 #endif // _LP64 | |
0 | 408 }; |