Mercurial > hg > graal-compiler
comparison src/share/vm/runtime/biasedLocking.cpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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children | 7ee622712fcf |
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2 /* | |
3 * Copyright 2005-2007 Sun Microsystems, Inc. All Rights Reserved. | |
4 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. | |
5 * | |
6 * This code is free software; you can redistribute it and/or modify it | |
7 * under the terms of the GNU General Public License version 2 only, as | |
8 * published by the Free Software Foundation. | |
9 * | |
10 * This code is distributed in the hope that it will be useful, but WITHOUT | |
11 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
12 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
13 * version 2 for more details (a copy is included in the LICENSE file that | |
14 * accompanied this code). | |
15 * | |
16 * You should have received a copy of the GNU General Public License version | |
17 * 2 along with this work; if not, write to the Free Software Foundation, | |
18 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
19 * | |
20 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
21 * CA 95054 USA or visit www.sun.com if you need additional information or | |
22 * have any questions. | |
23 * | |
24 */ | |
25 | |
26 # include "incls/_precompiled.incl" | |
27 # include "incls/_biasedLocking.cpp.incl" | |
28 | |
29 static bool _biased_locking_enabled = false; | |
30 BiasedLockingCounters BiasedLocking::_counters; | |
31 | |
32 static GrowableArray<Handle>* _preserved_oop_stack = NULL; | |
33 static GrowableArray<markOop>* _preserved_mark_stack = NULL; | |
34 | |
35 static void enable_biased_locking(klassOop k) { | |
36 Klass::cast(k)->set_prototype_header(markOopDesc::biased_locking_prototype()); | |
37 } | |
38 | |
39 class VM_EnableBiasedLocking: public VM_Operation { | |
40 public: | |
41 VM_EnableBiasedLocking() {} | |
42 VMOp_Type type() const { return VMOp_EnableBiasedLocking; } | |
43 void doit() { | |
44 // Iterate the system dictionary enabling biased locking for all | |
45 // currently loaded classes | |
46 SystemDictionary::classes_do(enable_biased_locking); | |
47 // Indicate that future instances should enable it as well | |
48 _biased_locking_enabled = true; | |
49 | |
50 if (TraceBiasedLocking) { | |
51 tty->print_cr("Biased locking enabled"); | |
52 } | |
53 } | |
54 | |
55 bool allow_nested_vm_operations() const { return false; } | |
56 }; | |
57 | |
58 | |
59 // One-shot PeriodicTask subclass for enabling biased locking | |
60 class EnableBiasedLockingTask : public PeriodicTask { | |
61 public: | |
62 EnableBiasedLockingTask(size_t interval_time) : PeriodicTask(interval_time) {} | |
63 | |
64 virtual void task() { | |
65 VM_EnableBiasedLocking op; | |
66 VMThread::execute(&op); | |
67 | |
68 // Reclaim our storage and disenroll ourself | |
69 delete this; | |
70 } | |
71 }; | |
72 | |
73 | |
74 void BiasedLocking::init() { | |
75 // If biased locking is enabled, schedule a task to fire a few | |
76 // seconds into the run which turns on biased locking for all | |
77 // currently loaded classes as well as future ones. This is a | |
78 // workaround for startup time regressions due to a large number of | |
79 // safepoints being taken during VM startup for bias revocation. | |
80 // Ideally we would have a lower cost for individual bias revocation | |
81 // and not need a mechanism like this. | |
82 if (UseBiasedLocking) { | |
83 if (BiasedLockingStartupDelay > 0) { | |
84 EnableBiasedLockingTask* task = new EnableBiasedLockingTask(BiasedLockingStartupDelay); | |
85 task->enroll(); | |
86 } else { | |
87 VM_EnableBiasedLocking op; | |
88 VMThread::execute(&op); | |
89 } | |
90 } | |
91 } | |
92 | |
93 | |
94 bool BiasedLocking::enabled() { | |
95 return _biased_locking_enabled; | |
96 } | |
97 | |
98 // Returns MonitorInfos for all objects locked on this thread in youngest to oldest order | |
99 static GrowableArray<MonitorInfo*>* get_or_compute_monitor_info(JavaThread* thread) { | |
100 GrowableArray<MonitorInfo*>* info = thread->cached_monitor_info(); | |
101 if (info != NULL) { | |
102 return info; | |
103 } | |
104 | |
105 info = new GrowableArray<MonitorInfo*>(); | |
106 | |
107 // It's possible for the thread to not have any Java frames on it, | |
108 // i.e., if it's the main thread and it's already returned from main() | |
109 if (thread->has_last_Java_frame()) { | |
110 RegisterMap rm(thread); | |
111 for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) { | |
112 GrowableArray<MonitorInfo*> *monitors = vf->monitors(); | |
113 if (monitors != NULL) { | |
114 int len = monitors->length(); | |
115 // Walk monitors youngest to oldest | |
116 for (int i = len - 1; i >= 0; i--) { | |
117 MonitorInfo* mon_info = monitors->at(i); | |
118 oop owner = mon_info->owner(); | |
119 if (owner != NULL) { | |
120 info->append(mon_info); | |
121 } | |
122 } | |
123 } | |
124 } | |
125 } | |
126 | |
127 thread->set_cached_monitor_info(info); | |
128 return info; | |
129 } | |
130 | |
131 | |
132 static BiasedLocking::Condition revoke_bias(oop obj, bool allow_rebias, bool is_bulk, JavaThread* requesting_thread) { | |
133 markOop mark = obj->mark(); | |
134 if (!mark->has_bias_pattern()) { | |
135 if (TraceBiasedLocking) { | |
136 ResourceMark rm; | |
137 tty->print_cr(" (Skipping revocation of object of type %s because it's no longer biased)", | |
138 Klass::cast(obj->klass())->external_name()); | |
139 } | |
140 return BiasedLocking::NOT_BIASED; | |
141 } | |
142 | |
143 int age = mark->age(); | |
144 markOop biased_prototype = markOopDesc::biased_locking_prototype()->set_age(age); | |
145 markOop unbiased_prototype = markOopDesc::prototype()->set_age(age); | |
146 | |
147 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
148 ResourceMark rm; | |
149 tty->print_cr("Revoking bias of object " INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s , prototype header " INTPTR_FORMAT " , allow rebias %d , requesting thread " INTPTR_FORMAT, | |
150 (intptr_t) obj, (intptr_t) mark, Klass::cast(obj->klass())->external_name(), (intptr_t) Klass::cast(obj->klass())->prototype_header(), (allow_rebias ? 1 : 0), (intptr_t) requesting_thread); | |
151 } | |
152 | |
153 JavaThread* biased_thread = mark->biased_locker(); | |
154 if (biased_thread == NULL) { | |
155 // Object is anonymously biased. We can get here if, for | |
156 // example, we revoke the bias due to an identity hash code | |
157 // being computed for an object. | |
158 if (!allow_rebias) { | |
159 obj->set_mark(unbiased_prototype); | |
160 } | |
161 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
162 tty->print_cr(" Revoked bias of anonymously-biased object"); | |
163 } | |
164 return BiasedLocking::BIAS_REVOKED; | |
165 } | |
166 | |
167 // Handle case where the thread toward which the object was biased has exited | |
168 bool thread_is_alive = false; | |
169 if (requesting_thread == biased_thread) { | |
170 thread_is_alive = true; | |
171 } else { | |
172 for (JavaThread* cur_thread = Threads::first(); cur_thread != NULL; cur_thread = cur_thread->next()) { | |
173 if (cur_thread == biased_thread) { | |
174 thread_is_alive = true; | |
175 break; | |
176 } | |
177 } | |
178 } | |
179 if (!thread_is_alive) { | |
180 if (allow_rebias) { | |
181 obj->set_mark(biased_prototype); | |
182 } else { | |
183 obj->set_mark(unbiased_prototype); | |
184 } | |
185 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
186 tty->print_cr(" Revoked bias of object biased toward dead thread"); | |
187 } | |
188 return BiasedLocking::BIAS_REVOKED; | |
189 } | |
190 | |
191 // Thread owning bias is alive. | |
192 // Check to see whether it currently owns the lock and, if so, | |
193 // write down the needed displaced headers to the thread's stack. | |
194 // Otherwise, restore the object's header either to the unlocked | |
195 // or unbiased state. | |
196 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(biased_thread); | |
197 BasicLock* highest_lock = NULL; | |
198 for (int i = 0; i < cached_monitor_info->length(); i++) { | |
199 MonitorInfo* mon_info = cached_monitor_info->at(i); | |
200 if (mon_info->owner() == obj) { | |
201 if (TraceBiasedLocking && Verbose) { | |
202 tty->print_cr(" mon_info->owner (" PTR_FORMAT ") == obj (" PTR_FORMAT ")", | |
203 (intptr_t) mon_info->owner(), | |
204 (intptr_t) obj); | |
205 } | |
206 // Assume recursive case and fix up highest lock later | |
207 markOop mark = markOopDesc::encode((BasicLock*) NULL); | |
208 highest_lock = mon_info->lock(); | |
209 highest_lock->set_displaced_header(mark); | |
210 } else { | |
211 if (TraceBiasedLocking && Verbose) { | |
212 tty->print_cr(" mon_info->owner (" PTR_FORMAT ") != obj (" PTR_FORMAT ")", | |
213 (intptr_t) mon_info->owner(), | |
214 (intptr_t) obj); | |
215 } | |
216 } | |
217 } | |
218 if (highest_lock != NULL) { | |
219 // Fix up highest lock to contain displaced header and point | |
220 // object at it | |
221 highest_lock->set_displaced_header(unbiased_prototype); | |
222 // Reset object header to point to displaced mark | |
223 obj->set_mark(markOopDesc::encode(highest_lock)); | |
224 assert(!obj->mark()->has_bias_pattern(), "illegal mark state: stack lock used bias bit"); | |
225 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
226 tty->print_cr(" Revoked bias of currently-locked object"); | |
227 } | |
228 } else { | |
229 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
230 tty->print_cr(" Revoked bias of currently-unlocked object"); | |
231 } | |
232 if (allow_rebias) { | |
233 obj->set_mark(biased_prototype); | |
234 } else { | |
235 // Store the unlocked value into the object's header. | |
236 obj->set_mark(unbiased_prototype); | |
237 } | |
238 } | |
239 | |
240 return BiasedLocking::BIAS_REVOKED; | |
241 } | |
242 | |
243 | |
244 enum HeuristicsResult { | |
245 HR_NOT_BIASED = 1, | |
246 HR_SINGLE_REVOKE = 2, | |
247 HR_BULK_REBIAS = 3, | |
248 HR_BULK_REVOKE = 4 | |
249 }; | |
250 | |
251 | |
252 static HeuristicsResult update_heuristics(oop o, bool allow_rebias) { | |
253 markOop mark = o->mark(); | |
254 if (!mark->has_bias_pattern()) { | |
255 return HR_NOT_BIASED; | |
256 } | |
257 | |
258 // Heuristics to attempt to throttle the number of revocations. | |
259 // Stages: | |
260 // 1. Revoke the biases of all objects in the heap of this type, | |
261 // but allow rebiasing of those objects if unlocked. | |
262 // 2. Revoke the biases of all objects in the heap of this type | |
263 // and don't allow rebiasing of these objects. Disable | |
264 // allocation of objects of that type with the bias bit set. | |
265 Klass* k = o->blueprint(); | |
266 jlong cur_time = os::javaTimeMillis(); | |
267 jlong last_bulk_revocation_time = k->last_biased_lock_bulk_revocation_time(); | |
268 int revocation_count = k->biased_lock_revocation_count(); | |
269 if ((revocation_count >= BiasedLockingBulkRebiasThreshold) && | |
270 (revocation_count < BiasedLockingBulkRevokeThreshold) && | |
271 (last_bulk_revocation_time != 0) && | |
272 (cur_time - last_bulk_revocation_time >= BiasedLockingDecayTime)) { | |
273 // This is the first revocation we've seen in a while of an | |
274 // object of this type since the last time we performed a bulk | |
275 // rebiasing operation. The application is allocating objects in | |
276 // bulk which are biased toward a thread and then handing them | |
277 // off to another thread. We can cope with this allocation | |
278 // pattern via the bulk rebiasing mechanism so we reset the | |
279 // klass's revocation count rather than allow it to increase | |
280 // monotonically. If we see the need to perform another bulk | |
281 // rebias operation later, we will, and if subsequently we see | |
282 // many more revocation operations in a short period of time we | |
283 // will completely disable biasing for this type. | |
284 k->set_biased_lock_revocation_count(0); | |
285 revocation_count = 0; | |
286 } | |
287 | |
288 // Make revocation count saturate just beyond BiasedLockingBulkRevokeThreshold | |
289 if (revocation_count <= BiasedLockingBulkRevokeThreshold) { | |
290 revocation_count = k->atomic_incr_biased_lock_revocation_count(); | |
291 } | |
292 | |
293 if (revocation_count == BiasedLockingBulkRevokeThreshold) { | |
294 return HR_BULK_REVOKE; | |
295 } | |
296 | |
297 if (revocation_count == BiasedLockingBulkRebiasThreshold) { | |
298 return HR_BULK_REBIAS; | |
299 } | |
300 | |
301 return HR_SINGLE_REVOKE; | |
302 } | |
303 | |
304 | |
305 static BiasedLocking::Condition bulk_revoke_or_rebias_at_safepoint(oop o, | |
306 bool bulk_rebias, | |
307 bool attempt_rebias_of_object, | |
308 JavaThread* requesting_thread) { | |
309 assert(SafepointSynchronize::is_at_safepoint(), "must be done at safepoint"); | |
310 | |
311 if (TraceBiasedLocking) { | |
312 tty->print_cr("* Beginning bulk revocation (kind == %s) because of object " | |
313 INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
314 (bulk_rebias ? "rebias" : "revoke"), | |
315 (intptr_t) o, (intptr_t) o->mark(), Klass::cast(o->klass())->external_name()); | |
316 } | |
317 | |
318 jlong cur_time = os::javaTimeMillis(); | |
319 o->blueprint()->set_last_biased_lock_bulk_revocation_time(cur_time); | |
320 | |
321 | |
322 klassOop k_o = o->klass(); | |
323 Klass* klass = Klass::cast(k_o); | |
324 | |
325 if (bulk_rebias) { | |
326 // Use the epoch in the klass of the object to implicitly revoke | |
327 // all biases of objects of this data type and force them to be | |
328 // reacquired. However, we also need to walk the stacks of all | |
329 // threads and update the headers of lightweight locked objects | |
330 // with biases to have the current epoch. | |
331 | |
332 // If the prototype header doesn't have the bias pattern, don't | |
333 // try to update the epoch -- assume another VM operation came in | |
334 // and reset the header to the unbiased state, which will | |
335 // implicitly cause all existing biases to be revoked | |
336 if (klass->prototype_header()->has_bias_pattern()) { | |
337 int prev_epoch = klass->prototype_header()->bias_epoch(); | |
338 klass->set_prototype_header(klass->prototype_header()->incr_bias_epoch()); | |
339 int cur_epoch = klass->prototype_header()->bias_epoch(); | |
340 | |
341 // Now walk all threads' stacks and adjust epochs of any biased | |
342 // and locked objects of this data type we encounter | |
343 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { | |
344 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr); | |
345 for (int i = 0; i < cached_monitor_info->length(); i++) { | |
346 MonitorInfo* mon_info = cached_monitor_info->at(i); | |
347 oop owner = mon_info->owner(); | |
348 markOop mark = owner->mark(); | |
349 if ((owner->klass() == k_o) && mark->has_bias_pattern()) { | |
350 // We might have encountered this object already in the case of recursive locking | |
351 assert(mark->bias_epoch() == prev_epoch || mark->bias_epoch() == cur_epoch, "error in bias epoch adjustment"); | |
352 owner->set_mark(mark->set_bias_epoch(cur_epoch)); | |
353 } | |
354 } | |
355 } | |
356 } | |
357 | |
358 // At this point we're done. All we have to do is potentially | |
359 // adjust the header of the given object to revoke its bias. | |
360 revoke_bias(o, attempt_rebias_of_object && klass->prototype_header()->has_bias_pattern(), true, requesting_thread); | |
361 } else { | |
362 if (TraceBiasedLocking) { | |
363 ResourceMark rm; | |
364 tty->print_cr("* Disabling biased locking for type %s", klass->external_name()); | |
365 } | |
366 | |
367 // Disable biased locking for this data type. Not only will this | |
368 // cause future instances to not be biased, but existing biased | |
369 // instances will notice that this implicitly caused their biases | |
370 // to be revoked. | |
371 klass->set_prototype_header(markOopDesc::prototype()); | |
372 | |
373 // Now walk all threads' stacks and forcibly revoke the biases of | |
374 // any locked and biased objects of this data type we encounter. | |
375 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { | |
376 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr); | |
377 for (int i = 0; i < cached_monitor_info->length(); i++) { | |
378 MonitorInfo* mon_info = cached_monitor_info->at(i); | |
379 oop owner = mon_info->owner(); | |
380 markOop mark = owner->mark(); | |
381 if ((owner->klass() == k_o) && mark->has_bias_pattern()) { | |
382 revoke_bias(owner, false, true, requesting_thread); | |
383 } | |
384 } | |
385 } | |
386 | |
387 // Must force the bias of the passed object to be forcibly revoked | |
388 // as well to ensure guarantees to callers | |
389 revoke_bias(o, false, true, requesting_thread); | |
390 } | |
391 | |
392 if (TraceBiasedLocking) { | |
393 tty->print_cr("* Ending bulk revocation"); | |
394 } | |
395 | |
396 BiasedLocking::Condition status_code = BiasedLocking::BIAS_REVOKED; | |
397 | |
398 if (attempt_rebias_of_object && | |
399 o->mark()->has_bias_pattern() && | |
400 klass->prototype_header()->has_bias_pattern()) { | |
401 markOop new_mark = markOopDesc::encode(requesting_thread, o->mark()->age(), | |
402 klass->prototype_header()->bias_epoch()); | |
403 o->set_mark(new_mark); | |
404 status_code = BiasedLocking::BIAS_REVOKED_AND_REBIASED; | |
405 if (TraceBiasedLocking) { | |
406 tty->print_cr(" Rebiased object toward thread " INTPTR_FORMAT, (intptr_t) requesting_thread); | |
407 } | |
408 } | |
409 | |
410 assert(!o->mark()->has_bias_pattern() || | |
411 (attempt_rebias_of_object && (o->mark()->biased_locker() == requesting_thread)), | |
412 "bug in bulk bias revocation"); | |
413 | |
414 return status_code; | |
415 } | |
416 | |
417 | |
418 static void clean_up_cached_monitor_info() { | |
419 // Walk the thread list clearing out the cached monitors | |
420 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { | |
421 thr->set_cached_monitor_info(NULL); | |
422 } | |
423 } | |
424 | |
425 | |
426 class VM_RevokeBias : public VM_Operation { | |
427 protected: | |
428 Handle* _obj; | |
429 GrowableArray<Handle>* _objs; | |
430 JavaThread* _requesting_thread; | |
431 BiasedLocking::Condition _status_code; | |
432 | |
433 public: | |
434 VM_RevokeBias(Handle* obj, JavaThread* requesting_thread) | |
435 : _obj(obj) | |
436 , _objs(NULL) | |
437 , _requesting_thread(requesting_thread) | |
438 , _status_code(BiasedLocking::NOT_BIASED) {} | |
439 | |
440 VM_RevokeBias(GrowableArray<Handle>* objs, JavaThread* requesting_thread) | |
441 : _obj(NULL) | |
442 , _objs(objs) | |
443 , _requesting_thread(requesting_thread) | |
444 , _status_code(BiasedLocking::NOT_BIASED) {} | |
445 | |
446 virtual VMOp_Type type() const { return VMOp_RevokeBias; } | |
447 | |
448 virtual bool doit_prologue() { | |
449 // Verify that there is actual work to do since the callers just | |
450 // give us locked object(s). If we don't find any biased objects | |
451 // there is nothing to do and we avoid a safepoint. | |
452 if (_obj != NULL) { | |
453 markOop mark = (*_obj)()->mark(); | |
454 if (mark->has_bias_pattern()) { | |
455 return true; | |
456 } | |
457 } else { | |
458 for ( int i = 0 ; i < _objs->length(); i++ ) { | |
459 markOop mark = (_objs->at(i))()->mark(); | |
460 if (mark->has_bias_pattern()) { | |
461 return true; | |
462 } | |
463 } | |
464 } | |
465 return false; | |
466 } | |
467 | |
468 virtual void doit() { | |
469 if (_obj != NULL) { | |
470 if (TraceBiasedLocking) { | |
471 tty->print_cr("Revoking bias with potentially per-thread safepoint:"); | |
472 } | |
473 _status_code = revoke_bias((*_obj)(), false, false, _requesting_thread); | |
474 clean_up_cached_monitor_info(); | |
475 return; | |
476 } else { | |
477 if (TraceBiasedLocking) { | |
478 tty->print_cr("Revoking bias with global safepoint:"); | |
479 } | |
480 BiasedLocking::revoke_at_safepoint(_objs); | |
481 } | |
482 } | |
483 | |
484 BiasedLocking::Condition status_code() const { | |
485 return _status_code; | |
486 } | |
487 }; | |
488 | |
489 | |
490 class VM_BulkRevokeBias : public VM_RevokeBias { | |
491 private: | |
492 bool _bulk_rebias; | |
493 bool _attempt_rebias_of_object; | |
494 | |
495 public: | |
496 VM_BulkRevokeBias(Handle* obj, JavaThread* requesting_thread, | |
497 bool bulk_rebias, | |
498 bool attempt_rebias_of_object) | |
499 : VM_RevokeBias(obj, requesting_thread) | |
500 , _bulk_rebias(bulk_rebias) | |
501 , _attempt_rebias_of_object(attempt_rebias_of_object) {} | |
502 | |
503 virtual VMOp_Type type() const { return VMOp_BulkRevokeBias; } | |
504 virtual bool doit_prologue() { return true; } | |
505 | |
506 virtual void doit() { | |
507 _status_code = bulk_revoke_or_rebias_at_safepoint((*_obj)(), _bulk_rebias, _attempt_rebias_of_object, _requesting_thread); | |
508 clean_up_cached_monitor_info(); | |
509 } | |
510 }; | |
511 | |
512 | |
513 BiasedLocking::Condition BiasedLocking::revoke_and_rebias(Handle obj, bool attempt_rebias, TRAPS) { | |
514 assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint"); | |
515 | |
516 // We can revoke the biases of anonymously-biased objects | |
517 // efficiently enough that we should not cause these revocations to | |
518 // update the heuristics because doing so may cause unwanted bulk | |
519 // revocations (which are expensive) to occur. | |
520 markOop mark = obj->mark(); | |
521 if (mark->is_biased_anonymously() && !attempt_rebias) { | |
522 // We are probably trying to revoke the bias of this object due to | |
523 // an identity hash code computation. Try to revoke the bias | |
524 // without a safepoint. This is possible if we can successfully | |
525 // compare-and-exchange an unbiased header into the mark word of | |
526 // the object, meaning that no other thread has raced to acquire | |
527 // the bias of the object. | |
528 markOop biased_value = mark; | |
529 markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age()); | |
530 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark); | |
531 if (res_mark == biased_value) { | |
532 return BIAS_REVOKED; | |
533 } | |
534 } else if (mark->has_bias_pattern()) { | |
535 Klass* k = Klass::cast(obj->klass()); | |
536 markOop prototype_header = k->prototype_header(); | |
537 if (!prototype_header->has_bias_pattern()) { | |
538 // This object has a stale bias from before the bulk revocation | |
539 // for this data type occurred. It's pointless to update the | |
540 // heuristics at this point so simply update the header with a | |
541 // CAS. If we fail this race, the object's bias has been revoked | |
542 // by another thread so we simply return and let the caller deal | |
543 // with it. | |
544 markOop biased_value = mark; | |
545 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(prototype_header, obj->mark_addr(), mark); | |
546 assert(!(*(obj->mark_addr()))->has_bias_pattern(), "even if we raced, should still be revoked"); | |
547 return BIAS_REVOKED; | |
548 } else if (prototype_header->bias_epoch() != mark->bias_epoch()) { | |
549 // The epoch of this biasing has expired indicating that the | |
550 // object is effectively unbiased. Depending on whether we need | |
551 // to rebias or revoke the bias of this object we can do it | |
552 // efficiently enough with a CAS that we shouldn't update the | |
553 // heuristics. This is normally done in the assembly code but we | |
554 // can reach this point due to various points in the runtime | |
555 // needing to revoke biases. | |
556 if (attempt_rebias) { | |
557 assert(THREAD->is_Java_thread(), ""); | |
558 markOop biased_value = mark; | |
559 markOop rebiased_prototype = markOopDesc::encode((JavaThread*) THREAD, mark->age(), prototype_header->bias_epoch()); | |
560 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(rebiased_prototype, obj->mark_addr(), mark); | |
561 if (res_mark == biased_value) { | |
562 return BIAS_REVOKED_AND_REBIASED; | |
563 } | |
564 } else { | |
565 markOop biased_value = mark; | |
566 markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age()); | |
567 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark); | |
568 if (res_mark == biased_value) { | |
569 return BIAS_REVOKED; | |
570 } | |
571 } | |
572 } | |
573 } | |
574 | |
575 HeuristicsResult heuristics = update_heuristics(obj(), attempt_rebias); | |
576 if (heuristics == HR_NOT_BIASED) { | |
577 return NOT_BIASED; | |
578 } else if (heuristics == HR_SINGLE_REVOKE) { | |
579 if (mark->biased_locker() == THREAD) { | |
580 // A thread is trying to revoke the bias of an object biased | |
581 // toward it, again likely due to an identity hash code | |
582 // computation. We can again avoid a safepoint in this case | |
583 // since we are only going to walk our own stack. There are no | |
584 // races with revocations occurring in other threads because we | |
585 // reach no safepoints in the revocation path. | |
586 ResourceMark rm; | |
587 if (TraceBiasedLocking) { | |
588 tty->print_cr("Revoking bias by walking my own stack:"); | |
589 } | |
590 BiasedLocking::Condition cond = revoke_bias(obj(), false, false, (JavaThread*) THREAD); | |
591 ((JavaThread*) THREAD)->set_cached_monitor_info(NULL); | |
592 assert(cond == BIAS_REVOKED, "why not?"); | |
593 return cond; | |
594 } else { | |
595 VM_RevokeBias revoke(&obj, (JavaThread*) THREAD); | |
596 VMThread::execute(&revoke); | |
597 return revoke.status_code(); | |
598 } | |
599 } | |
600 | |
601 assert((heuristics == HR_BULK_REVOKE) || | |
602 (heuristics == HR_BULK_REBIAS), "?"); | |
603 VM_BulkRevokeBias bulk_revoke(&obj, (JavaThread*) THREAD, | |
604 (heuristics == HR_BULK_REBIAS), | |
605 attempt_rebias); | |
606 VMThread::execute(&bulk_revoke); | |
607 return bulk_revoke.status_code(); | |
608 } | |
609 | |
610 | |
611 void BiasedLocking::revoke(GrowableArray<Handle>* objs) { | |
612 assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint"); | |
613 if (objs->length() == 0) { | |
614 return; | |
615 } | |
616 VM_RevokeBias revoke(objs, JavaThread::current()); | |
617 VMThread::execute(&revoke); | |
618 } | |
619 | |
620 | |
621 void BiasedLocking::revoke_at_safepoint(Handle h_obj) { | |
622 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); | |
623 oop obj = h_obj(); | |
624 HeuristicsResult heuristics = update_heuristics(obj, false); | |
625 if (heuristics == HR_SINGLE_REVOKE) { | |
626 revoke_bias(obj, false, false, NULL); | |
627 } else if ((heuristics == HR_BULK_REBIAS) || | |
628 (heuristics == HR_BULK_REVOKE)) { | |
629 bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL); | |
630 } | |
631 clean_up_cached_monitor_info(); | |
632 } | |
633 | |
634 | |
635 void BiasedLocking::revoke_at_safepoint(GrowableArray<Handle>* objs) { | |
636 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); | |
637 int len = objs->length(); | |
638 for (int i = 0; i < len; i++) { | |
639 oop obj = (objs->at(i))(); | |
640 HeuristicsResult heuristics = update_heuristics(obj, false); | |
641 if (heuristics == HR_SINGLE_REVOKE) { | |
642 revoke_bias(obj, false, false, NULL); | |
643 } else if ((heuristics == HR_BULK_REBIAS) || | |
644 (heuristics == HR_BULK_REVOKE)) { | |
645 bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL); | |
646 } | |
647 } | |
648 clean_up_cached_monitor_info(); | |
649 } | |
650 | |
651 | |
652 void BiasedLocking::preserve_marks() { | |
653 if (!UseBiasedLocking) | |
654 return; | |
655 | |
656 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); | |
657 | |
658 assert(_preserved_oop_stack == NULL, "double initialization"); | |
659 assert(_preserved_mark_stack == NULL, "double initialization"); | |
660 | |
661 // In order to reduce the number of mark words preserved during GC | |
662 // due to the presence of biased locking, we reinitialize most mark | |
663 // words to the class's prototype during GC -- even those which have | |
664 // a currently valid bias owner. One important situation where we | |
665 // must not clobber a bias is when a biased object is currently | |
666 // locked. To handle this case we iterate over the currently-locked | |
667 // monitors in a prepass and, if they are biased, preserve their | |
668 // mark words here. This should be a relatively small set of objects | |
669 // especially compared to the number of objects in the heap. | |
670 _preserved_mark_stack = new (ResourceObj::C_HEAP) GrowableArray<markOop>(10, true); | |
671 _preserved_oop_stack = new (ResourceObj::C_HEAP) GrowableArray<Handle>(10, true); | |
672 | |
673 ResourceMark rm; | |
674 Thread* cur = Thread::current(); | |
675 for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) { | |
676 if (thread->has_last_Java_frame()) { | |
677 RegisterMap rm(thread); | |
678 for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) { | |
679 GrowableArray<MonitorInfo*> *monitors = vf->monitors(); | |
680 if (monitors != NULL) { | |
681 int len = monitors->length(); | |
682 // Walk monitors youngest to oldest | |
683 for (int i = len - 1; i >= 0; i--) { | |
684 MonitorInfo* mon_info = monitors->at(i); | |
685 oop owner = mon_info->owner(); | |
686 if (owner != NULL) { | |
687 markOop mark = owner->mark(); | |
688 if (mark->has_bias_pattern()) { | |
689 _preserved_oop_stack->push(Handle(cur, owner)); | |
690 _preserved_mark_stack->push(mark); | |
691 } | |
692 } | |
693 } | |
694 } | |
695 } | |
696 } | |
697 } | |
698 } | |
699 | |
700 | |
701 void BiasedLocking::restore_marks() { | |
702 if (!UseBiasedLocking) | |
703 return; | |
704 | |
705 assert(_preserved_oop_stack != NULL, "double free"); | |
706 assert(_preserved_mark_stack != NULL, "double free"); | |
707 | |
708 int len = _preserved_oop_stack->length(); | |
709 for (int i = 0; i < len; i++) { | |
710 Handle owner = _preserved_oop_stack->at(i); | |
711 markOop mark = _preserved_mark_stack->at(i); | |
712 owner->set_mark(mark); | |
713 } | |
714 | |
715 delete _preserved_oop_stack; | |
716 _preserved_oop_stack = NULL; | |
717 delete _preserved_mark_stack; | |
718 _preserved_mark_stack = NULL; | |
719 } | |
720 | |
721 | |
722 int* BiasedLocking::total_entry_count_addr() { return _counters.total_entry_count_addr(); } | |
723 int* BiasedLocking::biased_lock_entry_count_addr() { return _counters.biased_lock_entry_count_addr(); } | |
724 int* BiasedLocking::anonymously_biased_lock_entry_count_addr() { return _counters.anonymously_biased_lock_entry_count_addr(); } | |
725 int* BiasedLocking::rebiased_lock_entry_count_addr() { return _counters.rebiased_lock_entry_count_addr(); } | |
726 int* BiasedLocking::revoked_lock_entry_count_addr() { return _counters.revoked_lock_entry_count_addr(); } | |
727 int* BiasedLocking::fast_path_entry_count_addr() { return _counters.fast_path_entry_count_addr(); } | |
728 int* BiasedLocking::slow_path_entry_count_addr() { return _counters.slow_path_entry_count_addr(); } | |
729 | |
730 | |
731 // BiasedLockingCounters | |
732 | |
733 int BiasedLockingCounters::slow_path_entry_count() { | |
734 if (_slow_path_entry_count != 0) { | |
735 return _slow_path_entry_count; | |
736 } | |
737 int sum = _biased_lock_entry_count + _anonymously_biased_lock_entry_count + | |
738 _rebiased_lock_entry_count + _revoked_lock_entry_count + | |
739 _fast_path_entry_count; | |
740 | |
741 return _total_entry_count - sum; | |
742 } | |
743 | |
744 void BiasedLockingCounters::print_on(outputStream* st) { | |
745 tty->print_cr("# total entries: %d", _total_entry_count); | |
746 tty->print_cr("# biased lock entries: %d", _biased_lock_entry_count); | |
747 tty->print_cr("# anonymously biased lock entries: %d", _anonymously_biased_lock_entry_count); | |
748 tty->print_cr("# rebiased lock entries: %d", _rebiased_lock_entry_count); | |
749 tty->print_cr("# revoked lock entries: %d", _revoked_lock_entry_count); | |
750 tty->print_cr("# fast path lock entries: %d", _fast_path_entry_count); | |
751 tty->print_cr("# slow path lock entries: %d", slow_path_entry_count()); | |
752 } |