Mercurial > hg > graal-compiler
annotate src/share/vm/runtime/biasedLocking.cpp @ 1476:1f81c0d18c75
Build also release version of VM. Fix towards making SpecJVM2008 run.
author | Thomas Wuerthinger <wuerthinger@ssw.jku.at> |
---|---|
date | Fri, 26 Nov 2010 12:12:35 +0100 |
parents | bd02caa94611 |
children | c18cbe5936b8 |
rev | line source |
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0 | 1 /* |
844 | 2 * Copyright 2005-2009 Sun Microsystems, Inc. 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 * | |
19 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, | |
20 * CA 95054 USA or visit www.sun.com if you need additional information or | |
21 * have any questions. | |
22 * | |
23 */ | |
24 | |
25 # include "incls/_precompiled.incl" | |
26 # include "incls/_biasedLocking.cpp.incl" | |
27 | |
28 static bool _biased_locking_enabled = false; | |
29 BiasedLockingCounters BiasedLocking::_counters; | |
30 | |
31 static GrowableArray<Handle>* _preserved_oop_stack = NULL; | |
32 static GrowableArray<markOop>* _preserved_mark_stack = NULL; | |
33 | |
34 static void enable_biased_locking(klassOop k) { | |
35 Klass::cast(k)->set_prototype_header(markOopDesc::biased_locking_prototype()); | |
36 } | |
37 | |
38 class VM_EnableBiasedLocking: public VM_Operation { | |
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39 private: |
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40 bool _is_cheap_allocated; |
0 | 41 public: |
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42 VM_EnableBiasedLocking(bool is_cheap_allocated) { _is_cheap_allocated = is_cheap_allocated; } |
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43 VMOp_Type type() const { return VMOp_EnableBiasedLocking; } |
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44 Mode evaluation_mode() const { return _is_cheap_allocated ? _async_safepoint : _safepoint; } |
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45 bool is_cheap_allocated() const { return _is_cheap_allocated; } |
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46 |
0 | 47 void doit() { |
48 // Iterate the system dictionary enabling biased locking for all | |
49 // currently loaded classes | |
50 SystemDictionary::classes_do(enable_biased_locking); | |
51 // Indicate that future instances should enable it as well | |
52 _biased_locking_enabled = true; | |
53 | |
54 if (TraceBiasedLocking) { | |
55 tty->print_cr("Biased locking enabled"); | |
56 } | |
57 } | |
58 | |
59 bool allow_nested_vm_operations() const { return false; } | |
60 }; | |
61 | |
62 | |
63 // One-shot PeriodicTask subclass for enabling biased locking | |
64 class EnableBiasedLockingTask : public PeriodicTask { | |
65 public: | |
66 EnableBiasedLockingTask(size_t interval_time) : PeriodicTask(interval_time) {} | |
67 | |
68 virtual void task() { | |
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69 // Use async VM operation to avoid blocking the Watcher thread. |
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70 // VM Thread will free C heap storage. |
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71 VM_EnableBiasedLocking *op = new VM_EnableBiasedLocking(true); |
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72 VMThread::execute(op); |
0 | 73 |
74 // Reclaim our storage and disenroll ourself | |
75 delete this; | |
76 } | |
77 }; | |
78 | |
79 | |
80 void BiasedLocking::init() { | |
81 // If biased locking is enabled, schedule a task to fire a few | |
82 // seconds into the run which turns on biased locking for all | |
83 // currently loaded classes as well as future ones. This is a | |
84 // workaround for startup time regressions due to a large number of | |
85 // safepoints being taken during VM startup for bias revocation. | |
86 // Ideally we would have a lower cost for individual bias revocation | |
87 // and not need a mechanism like this. | |
88 if (UseBiasedLocking) { | |
89 if (BiasedLockingStartupDelay > 0) { | |
90 EnableBiasedLockingTask* task = new EnableBiasedLockingTask(BiasedLockingStartupDelay); | |
91 task->enroll(); | |
92 } else { | |
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93 VM_EnableBiasedLocking op(false); |
0 | 94 VMThread::execute(&op); |
95 } | |
96 } | |
97 } | |
98 | |
99 | |
100 bool BiasedLocking::enabled() { | |
101 return _biased_locking_enabled; | |
102 } | |
103 | |
104 // Returns MonitorInfos for all objects locked on this thread in youngest to oldest order | |
105 static GrowableArray<MonitorInfo*>* get_or_compute_monitor_info(JavaThread* thread) { | |
106 GrowableArray<MonitorInfo*>* info = thread->cached_monitor_info(); | |
107 if (info != NULL) { | |
108 return info; | |
109 } | |
110 | |
111 info = new GrowableArray<MonitorInfo*>(); | |
112 | |
113 // It's possible for the thread to not have any Java frames on it, | |
114 // i.e., if it's the main thread and it's already returned from main() | |
115 if (thread->has_last_Java_frame()) { | |
116 RegisterMap rm(thread); | |
117 for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) { | |
118 GrowableArray<MonitorInfo*> *monitors = vf->monitors(); | |
119 if (monitors != NULL) { | |
120 int len = monitors->length(); | |
121 // Walk monitors youngest to oldest | |
122 for (int i = len - 1; i >= 0; i--) { | |
123 MonitorInfo* mon_info = monitors->at(i); | |
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124 if (mon_info->owner_is_scalar_replaced()) continue; |
0 | 125 oop owner = mon_info->owner(); |
126 if (owner != NULL) { | |
127 info->append(mon_info); | |
128 } | |
129 } | |
130 } | |
131 } | |
132 } | |
133 | |
134 thread->set_cached_monitor_info(info); | |
135 return info; | |
136 } | |
137 | |
138 | |
139 static BiasedLocking::Condition revoke_bias(oop obj, bool allow_rebias, bool is_bulk, JavaThread* requesting_thread) { | |
140 markOop mark = obj->mark(); | |
141 if (!mark->has_bias_pattern()) { | |
142 if (TraceBiasedLocking) { | |
143 ResourceMark rm; | |
144 tty->print_cr(" (Skipping revocation of object of type %s because it's no longer biased)", | |
145 Klass::cast(obj->klass())->external_name()); | |
146 } | |
147 return BiasedLocking::NOT_BIASED; | |
148 } | |
149 | |
150 int age = mark->age(); | |
151 markOop biased_prototype = markOopDesc::biased_locking_prototype()->set_age(age); | |
152 markOop unbiased_prototype = markOopDesc::prototype()->set_age(age); | |
153 | |
154 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
155 ResourceMark rm; | |
156 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, | |
157 (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); | |
158 } | |
159 | |
160 JavaThread* biased_thread = mark->biased_locker(); | |
161 if (biased_thread == NULL) { | |
162 // Object is anonymously biased. We can get here if, for | |
163 // example, we revoke the bias due to an identity hash code | |
164 // being computed for an object. | |
165 if (!allow_rebias) { | |
166 obj->set_mark(unbiased_prototype); | |
167 } | |
168 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
169 tty->print_cr(" Revoked bias of anonymously-biased object"); | |
170 } | |
171 return BiasedLocking::BIAS_REVOKED; | |
172 } | |
173 | |
174 // Handle case where the thread toward which the object was biased has exited | |
175 bool thread_is_alive = false; | |
176 if (requesting_thread == biased_thread) { | |
177 thread_is_alive = true; | |
178 } else { | |
179 for (JavaThread* cur_thread = Threads::first(); cur_thread != NULL; cur_thread = cur_thread->next()) { | |
180 if (cur_thread == biased_thread) { | |
181 thread_is_alive = true; | |
182 break; | |
183 } | |
184 } | |
185 } | |
186 if (!thread_is_alive) { | |
187 if (allow_rebias) { | |
188 obj->set_mark(biased_prototype); | |
189 } else { | |
190 obj->set_mark(unbiased_prototype); | |
191 } | |
192 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
193 tty->print_cr(" Revoked bias of object biased toward dead thread"); | |
194 } | |
195 return BiasedLocking::BIAS_REVOKED; | |
196 } | |
197 | |
198 // Thread owning bias is alive. | |
199 // Check to see whether it currently owns the lock and, if so, | |
200 // write down the needed displaced headers to the thread's stack. | |
201 // Otherwise, restore the object's header either to the unlocked | |
202 // or unbiased state. | |
203 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(biased_thread); | |
204 BasicLock* highest_lock = NULL; | |
205 for (int i = 0; i < cached_monitor_info->length(); i++) { | |
206 MonitorInfo* mon_info = cached_monitor_info->at(i); | |
207 if (mon_info->owner() == obj) { | |
208 if (TraceBiasedLocking && Verbose) { | |
209 tty->print_cr(" mon_info->owner (" PTR_FORMAT ") == obj (" PTR_FORMAT ")", | |
210 (intptr_t) mon_info->owner(), | |
211 (intptr_t) obj); | |
212 } | |
213 // Assume recursive case and fix up highest lock later | |
214 markOop mark = markOopDesc::encode((BasicLock*) NULL); | |
215 highest_lock = mon_info->lock(); | |
216 highest_lock->set_displaced_header(mark); | |
217 } else { | |
218 if (TraceBiasedLocking && Verbose) { | |
219 tty->print_cr(" mon_info->owner (" PTR_FORMAT ") != obj (" PTR_FORMAT ")", | |
220 (intptr_t) mon_info->owner(), | |
221 (intptr_t) obj); | |
222 } | |
223 } | |
224 } | |
225 if (highest_lock != NULL) { | |
226 // Fix up highest lock to contain displaced header and point | |
227 // object at it | |
228 highest_lock->set_displaced_header(unbiased_prototype); | |
229 // Reset object header to point to displaced mark | |
230 obj->set_mark(markOopDesc::encode(highest_lock)); | |
231 assert(!obj->mark()->has_bias_pattern(), "illegal mark state: stack lock used bias bit"); | |
232 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
233 tty->print_cr(" Revoked bias of currently-locked object"); | |
234 } | |
235 } else { | |
236 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
237 tty->print_cr(" Revoked bias of currently-unlocked object"); | |
238 } | |
239 if (allow_rebias) { | |
240 obj->set_mark(biased_prototype); | |
241 } else { | |
242 // Store the unlocked value into the object's header. | |
243 obj->set_mark(unbiased_prototype); | |
244 } | |
245 } | |
246 | |
247 return BiasedLocking::BIAS_REVOKED; | |
248 } | |
249 | |
250 | |
251 enum HeuristicsResult { | |
252 HR_NOT_BIASED = 1, | |
253 HR_SINGLE_REVOKE = 2, | |
254 HR_BULK_REBIAS = 3, | |
255 HR_BULK_REVOKE = 4 | |
256 }; | |
257 | |
258 | |
259 static HeuristicsResult update_heuristics(oop o, bool allow_rebias) { | |
260 markOop mark = o->mark(); | |
261 if (!mark->has_bias_pattern()) { | |
262 return HR_NOT_BIASED; | |
263 } | |
264 | |
265 // Heuristics to attempt to throttle the number of revocations. | |
266 // Stages: | |
267 // 1. Revoke the biases of all objects in the heap of this type, | |
268 // but allow rebiasing of those objects if unlocked. | |
269 // 2. Revoke the biases of all objects in the heap of this type | |
270 // and don't allow rebiasing of these objects. Disable | |
271 // allocation of objects of that type with the bias bit set. | |
272 Klass* k = o->blueprint(); | |
273 jlong cur_time = os::javaTimeMillis(); | |
274 jlong last_bulk_revocation_time = k->last_biased_lock_bulk_revocation_time(); | |
275 int revocation_count = k->biased_lock_revocation_count(); | |
276 if ((revocation_count >= BiasedLockingBulkRebiasThreshold) && | |
277 (revocation_count < BiasedLockingBulkRevokeThreshold) && | |
278 (last_bulk_revocation_time != 0) && | |
279 (cur_time - last_bulk_revocation_time >= BiasedLockingDecayTime)) { | |
280 // This is the first revocation we've seen in a while of an | |
281 // object of this type since the last time we performed a bulk | |
282 // rebiasing operation. The application is allocating objects in | |
283 // bulk which are biased toward a thread and then handing them | |
284 // off to another thread. We can cope with this allocation | |
285 // pattern via the bulk rebiasing mechanism so we reset the | |
286 // klass's revocation count rather than allow it to increase | |
287 // monotonically. If we see the need to perform another bulk | |
288 // rebias operation later, we will, and if subsequently we see | |
289 // many more revocation operations in a short period of time we | |
290 // will completely disable biasing for this type. | |
291 k->set_biased_lock_revocation_count(0); | |
292 revocation_count = 0; | |
293 } | |
294 | |
295 // Make revocation count saturate just beyond BiasedLockingBulkRevokeThreshold | |
296 if (revocation_count <= BiasedLockingBulkRevokeThreshold) { | |
297 revocation_count = k->atomic_incr_biased_lock_revocation_count(); | |
298 } | |
299 | |
300 if (revocation_count == BiasedLockingBulkRevokeThreshold) { | |
301 return HR_BULK_REVOKE; | |
302 } | |
303 | |
304 if (revocation_count == BiasedLockingBulkRebiasThreshold) { | |
305 return HR_BULK_REBIAS; | |
306 } | |
307 | |
308 return HR_SINGLE_REVOKE; | |
309 } | |
310 | |
311 | |
312 static BiasedLocking::Condition bulk_revoke_or_rebias_at_safepoint(oop o, | |
313 bool bulk_rebias, | |
314 bool attempt_rebias_of_object, | |
315 JavaThread* requesting_thread) { | |
316 assert(SafepointSynchronize::is_at_safepoint(), "must be done at safepoint"); | |
317 | |
318 if (TraceBiasedLocking) { | |
319 tty->print_cr("* Beginning bulk revocation (kind == %s) because of object " | |
320 INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
321 (bulk_rebias ? "rebias" : "revoke"), | |
322 (intptr_t) o, (intptr_t) o->mark(), Klass::cast(o->klass())->external_name()); | |
323 } | |
324 | |
325 jlong cur_time = os::javaTimeMillis(); | |
326 o->blueprint()->set_last_biased_lock_bulk_revocation_time(cur_time); | |
327 | |
328 | |
329 klassOop k_o = o->klass(); | |
330 Klass* klass = Klass::cast(k_o); | |
331 | |
332 if (bulk_rebias) { | |
333 // Use the epoch in the klass of the object to implicitly revoke | |
334 // all biases of objects of this data type and force them to be | |
335 // reacquired. However, we also need to walk the stacks of all | |
336 // threads and update the headers of lightweight locked objects | |
337 // with biases to have the current epoch. | |
338 | |
339 // If the prototype header doesn't have the bias pattern, don't | |
340 // try to update the epoch -- assume another VM operation came in | |
341 // and reset the header to the unbiased state, which will | |
342 // implicitly cause all existing biases to be revoked | |
343 if (klass->prototype_header()->has_bias_pattern()) { | |
344 int prev_epoch = klass->prototype_header()->bias_epoch(); | |
345 klass->set_prototype_header(klass->prototype_header()->incr_bias_epoch()); | |
346 int cur_epoch = klass->prototype_header()->bias_epoch(); | |
347 | |
348 // Now walk all threads' stacks and adjust epochs of any biased | |
349 // and locked objects of this data type we encounter | |
350 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { | |
351 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr); | |
352 for (int i = 0; i < cached_monitor_info->length(); i++) { | |
353 MonitorInfo* mon_info = cached_monitor_info->at(i); | |
354 oop owner = mon_info->owner(); | |
355 markOop mark = owner->mark(); | |
356 if ((owner->klass() == k_o) && mark->has_bias_pattern()) { | |
357 // We might have encountered this object already in the case of recursive locking | |
358 assert(mark->bias_epoch() == prev_epoch || mark->bias_epoch() == cur_epoch, "error in bias epoch adjustment"); | |
359 owner->set_mark(mark->set_bias_epoch(cur_epoch)); | |
360 } | |
361 } | |
362 } | |
363 } | |
364 | |
365 // At this point we're done. All we have to do is potentially | |
366 // adjust the header of the given object to revoke its bias. | |
367 revoke_bias(o, attempt_rebias_of_object && klass->prototype_header()->has_bias_pattern(), true, requesting_thread); | |
368 } else { | |
369 if (TraceBiasedLocking) { | |
370 ResourceMark rm; | |
371 tty->print_cr("* Disabling biased locking for type %s", klass->external_name()); | |
372 } | |
373 | |
374 // Disable biased locking for this data type. Not only will this | |
375 // cause future instances to not be biased, but existing biased | |
376 // instances will notice that this implicitly caused their biases | |
377 // to be revoked. | |
378 klass->set_prototype_header(markOopDesc::prototype()); | |
379 | |
380 // Now walk all threads' stacks and forcibly revoke the biases of | |
381 // any locked and biased objects of this data type we encounter. | |
382 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { | |
383 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr); | |
384 for (int i = 0; i < cached_monitor_info->length(); i++) { | |
385 MonitorInfo* mon_info = cached_monitor_info->at(i); | |
386 oop owner = mon_info->owner(); | |
387 markOop mark = owner->mark(); | |
388 if ((owner->klass() == k_o) && mark->has_bias_pattern()) { | |
389 revoke_bias(owner, false, true, requesting_thread); | |
390 } | |
391 } | |
392 } | |
393 | |
394 // Must force the bias of the passed object to be forcibly revoked | |
395 // as well to ensure guarantees to callers | |
396 revoke_bias(o, false, true, requesting_thread); | |
397 } | |
398 | |
399 if (TraceBiasedLocking) { | |
400 tty->print_cr("* Ending bulk revocation"); | |
401 } | |
402 | |
403 BiasedLocking::Condition status_code = BiasedLocking::BIAS_REVOKED; | |
404 | |
405 if (attempt_rebias_of_object && | |
406 o->mark()->has_bias_pattern() && | |
407 klass->prototype_header()->has_bias_pattern()) { | |
408 markOop new_mark = markOopDesc::encode(requesting_thread, o->mark()->age(), | |
409 klass->prototype_header()->bias_epoch()); | |
410 o->set_mark(new_mark); | |
411 status_code = BiasedLocking::BIAS_REVOKED_AND_REBIASED; | |
412 if (TraceBiasedLocking) { | |
413 tty->print_cr(" Rebiased object toward thread " INTPTR_FORMAT, (intptr_t) requesting_thread); | |
414 } | |
415 } | |
416 | |
417 assert(!o->mark()->has_bias_pattern() || | |
418 (attempt_rebias_of_object && (o->mark()->biased_locker() == requesting_thread)), | |
419 "bug in bulk bias revocation"); | |
420 | |
421 return status_code; | |
422 } | |
423 | |
424 | |
425 static void clean_up_cached_monitor_info() { | |
426 // Walk the thread list clearing out the cached monitors | |
427 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { | |
428 thr->set_cached_monitor_info(NULL); | |
429 } | |
430 } | |
431 | |
432 | |
433 class VM_RevokeBias : public VM_Operation { | |
434 protected: | |
435 Handle* _obj; | |
436 GrowableArray<Handle>* _objs; | |
437 JavaThread* _requesting_thread; | |
438 BiasedLocking::Condition _status_code; | |
439 | |
440 public: | |
441 VM_RevokeBias(Handle* obj, JavaThread* requesting_thread) | |
442 : _obj(obj) | |
443 , _objs(NULL) | |
444 , _requesting_thread(requesting_thread) | |
445 , _status_code(BiasedLocking::NOT_BIASED) {} | |
446 | |
447 VM_RevokeBias(GrowableArray<Handle>* objs, JavaThread* requesting_thread) | |
448 : _obj(NULL) | |
449 , _objs(objs) | |
450 , _requesting_thread(requesting_thread) | |
451 , _status_code(BiasedLocking::NOT_BIASED) {} | |
452 | |
453 virtual VMOp_Type type() const { return VMOp_RevokeBias; } | |
454 | |
455 virtual bool doit_prologue() { | |
456 // Verify that there is actual work to do since the callers just | |
457 // give us locked object(s). If we don't find any biased objects | |
458 // there is nothing to do and we avoid a safepoint. | |
459 if (_obj != NULL) { | |
460 markOop mark = (*_obj)()->mark(); | |
461 if (mark->has_bias_pattern()) { | |
462 return true; | |
463 } | |
464 } else { | |
465 for ( int i = 0 ; i < _objs->length(); i++ ) { | |
466 markOop mark = (_objs->at(i))()->mark(); | |
467 if (mark->has_bias_pattern()) { | |
468 return true; | |
469 } | |
470 } | |
471 } | |
472 return false; | |
473 } | |
474 | |
475 virtual void doit() { | |
476 if (_obj != NULL) { | |
477 if (TraceBiasedLocking) { | |
478 tty->print_cr("Revoking bias with potentially per-thread safepoint:"); | |
479 } | |
480 _status_code = revoke_bias((*_obj)(), false, false, _requesting_thread); | |
481 clean_up_cached_monitor_info(); | |
482 return; | |
483 } else { | |
484 if (TraceBiasedLocking) { | |
485 tty->print_cr("Revoking bias with global safepoint:"); | |
486 } | |
487 BiasedLocking::revoke_at_safepoint(_objs); | |
488 } | |
489 } | |
490 | |
491 BiasedLocking::Condition status_code() const { | |
492 return _status_code; | |
493 } | |
494 }; | |
495 | |
496 | |
497 class VM_BulkRevokeBias : public VM_RevokeBias { | |
498 private: | |
499 bool _bulk_rebias; | |
500 bool _attempt_rebias_of_object; | |
501 | |
502 public: | |
503 VM_BulkRevokeBias(Handle* obj, JavaThread* requesting_thread, | |
504 bool bulk_rebias, | |
505 bool attempt_rebias_of_object) | |
506 : VM_RevokeBias(obj, requesting_thread) | |
507 , _bulk_rebias(bulk_rebias) | |
508 , _attempt_rebias_of_object(attempt_rebias_of_object) {} | |
509 | |
510 virtual VMOp_Type type() const { return VMOp_BulkRevokeBias; } | |
511 virtual bool doit_prologue() { return true; } | |
512 | |
513 virtual void doit() { | |
514 _status_code = bulk_revoke_or_rebias_at_safepoint((*_obj)(), _bulk_rebias, _attempt_rebias_of_object, _requesting_thread); | |
515 clean_up_cached_monitor_info(); | |
516 } | |
517 }; | |
518 | |
519 | |
520 BiasedLocking::Condition BiasedLocking::revoke_and_rebias(Handle obj, bool attempt_rebias, TRAPS) { | |
521 assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint"); | |
522 | |
523 // We can revoke the biases of anonymously-biased objects | |
524 // efficiently enough that we should not cause these revocations to | |
525 // update the heuristics because doing so may cause unwanted bulk | |
526 // revocations (which are expensive) to occur. | |
527 markOop mark = obj->mark(); | |
528 if (mark->is_biased_anonymously() && !attempt_rebias) { | |
529 // We are probably trying to revoke the bias of this object due to | |
530 // an identity hash code computation. Try to revoke the bias | |
531 // without a safepoint. This is possible if we can successfully | |
532 // compare-and-exchange an unbiased header into the mark word of | |
533 // the object, meaning that no other thread has raced to acquire | |
534 // the bias of the object. | |
535 markOop biased_value = mark; | |
536 markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age()); | |
537 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark); | |
538 if (res_mark == biased_value) { | |
539 return BIAS_REVOKED; | |
540 } | |
541 } else if (mark->has_bias_pattern()) { | |
542 Klass* k = Klass::cast(obj->klass()); | |
543 markOop prototype_header = k->prototype_header(); | |
544 if (!prototype_header->has_bias_pattern()) { | |
545 // This object has a stale bias from before the bulk revocation | |
546 // for this data type occurred. It's pointless to update the | |
547 // heuristics at this point so simply update the header with a | |
548 // CAS. If we fail this race, the object's bias has been revoked | |
549 // by another thread so we simply return and let the caller deal | |
550 // with it. | |
551 markOop biased_value = mark; | |
552 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(prototype_header, obj->mark_addr(), mark); | |
553 assert(!(*(obj->mark_addr()))->has_bias_pattern(), "even if we raced, should still be revoked"); | |
554 return BIAS_REVOKED; | |
555 } else if (prototype_header->bias_epoch() != mark->bias_epoch()) { | |
556 // The epoch of this biasing has expired indicating that the | |
557 // object is effectively unbiased. Depending on whether we need | |
558 // to rebias or revoke the bias of this object we can do it | |
559 // efficiently enough with a CAS that we shouldn't update the | |
560 // heuristics. This is normally done in the assembly code but we | |
561 // can reach this point due to various points in the runtime | |
562 // needing to revoke biases. | |
563 if (attempt_rebias) { | |
564 assert(THREAD->is_Java_thread(), ""); | |
565 markOop biased_value = mark; | |
566 markOop rebiased_prototype = markOopDesc::encode((JavaThread*) THREAD, mark->age(), prototype_header->bias_epoch()); | |
567 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(rebiased_prototype, obj->mark_addr(), mark); | |
568 if (res_mark == biased_value) { | |
569 return BIAS_REVOKED_AND_REBIASED; | |
570 } | |
571 } else { | |
572 markOop biased_value = mark; | |
573 markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age()); | |
574 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark); | |
575 if (res_mark == biased_value) { | |
576 return BIAS_REVOKED; | |
577 } | |
578 } | |
579 } | |
580 } | |
581 | |
582 HeuristicsResult heuristics = update_heuristics(obj(), attempt_rebias); | |
583 if (heuristics == HR_NOT_BIASED) { | |
584 return NOT_BIASED; | |
585 } else if (heuristics == HR_SINGLE_REVOKE) { | |
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586 Klass *k = Klass::cast(obj->klass()); |
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587 markOop prototype_header = k->prototype_header(); |
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588 if (mark->biased_locker() == THREAD && |
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589 prototype_header->bias_epoch() == mark->bias_epoch()) { |
0 | 590 // A thread is trying to revoke the bias of an object biased |
591 // toward it, again likely due to an identity hash code | |
592 // computation. We can again avoid a safepoint in this case | |
593 // since we are only going to walk our own stack. There are no | |
594 // races with revocations occurring in other threads because we | |
595 // reach no safepoints in the revocation path. | |
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596 // Also check the epoch because even if threads match, another thread |
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597 // can come in with a CAS to steal the bias of an object that has a |
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598 // stale epoch. |
0 | 599 ResourceMark rm; |
600 if (TraceBiasedLocking) { | |
601 tty->print_cr("Revoking bias by walking my own stack:"); | |
602 } | |
603 BiasedLocking::Condition cond = revoke_bias(obj(), false, false, (JavaThread*) THREAD); | |
604 ((JavaThread*) THREAD)->set_cached_monitor_info(NULL); | |
605 assert(cond == BIAS_REVOKED, "why not?"); | |
606 return cond; | |
607 } else { | |
608 VM_RevokeBias revoke(&obj, (JavaThread*) THREAD); | |
609 VMThread::execute(&revoke); | |
610 return revoke.status_code(); | |
611 } | |
612 } | |
613 | |
614 assert((heuristics == HR_BULK_REVOKE) || | |
615 (heuristics == HR_BULK_REBIAS), "?"); | |
616 VM_BulkRevokeBias bulk_revoke(&obj, (JavaThread*) THREAD, | |
617 (heuristics == HR_BULK_REBIAS), | |
618 attempt_rebias); | |
619 VMThread::execute(&bulk_revoke); | |
620 return bulk_revoke.status_code(); | |
621 } | |
622 | |
623 | |
624 void BiasedLocking::revoke(GrowableArray<Handle>* objs) { | |
625 assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint"); | |
626 if (objs->length() == 0) { | |
627 return; | |
628 } | |
629 VM_RevokeBias revoke(objs, JavaThread::current()); | |
630 VMThread::execute(&revoke); | |
631 } | |
632 | |
633 | |
634 void BiasedLocking::revoke_at_safepoint(Handle h_obj) { | |
635 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); | |
636 oop obj = h_obj(); | |
637 HeuristicsResult heuristics = update_heuristics(obj, false); | |
638 if (heuristics == HR_SINGLE_REVOKE) { | |
639 revoke_bias(obj, false, false, NULL); | |
640 } else if ((heuristics == HR_BULK_REBIAS) || | |
641 (heuristics == HR_BULK_REVOKE)) { | |
642 bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL); | |
643 } | |
644 clean_up_cached_monitor_info(); | |
645 } | |
646 | |
647 | |
648 void BiasedLocking::revoke_at_safepoint(GrowableArray<Handle>* objs) { | |
649 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); | |
650 int len = objs->length(); | |
651 for (int i = 0; i < len; i++) { | |
652 oop obj = (objs->at(i))(); | |
653 HeuristicsResult heuristics = update_heuristics(obj, false); | |
654 if (heuristics == HR_SINGLE_REVOKE) { | |
655 revoke_bias(obj, false, false, NULL); | |
656 } else if ((heuristics == HR_BULK_REBIAS) || | |
657 (heuristics == HR_BULK_REVOKE)) { | |
658 bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL); | |
659 } | |
660 } | |
661 clean_up_cached_monitor_info(); | |
662 } | |
663 | |
664 | |
665 void BiasedLocking::preserve_marks() { | |
666 if (!UseBiasedLocking) | |
667 return; | |
668 | |
669 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); | |
670 | |
671 assert(_preserved_oop_stack == NULL, "double initialization"); | |
672 assert(_preserved_mark_stack == NULL, "double initialization"); | |
673 | |
674 // In order to reduce the number of mark words preserved during GC | |
675 // due to the presence of biased locking, we reinitialize most mark | |
676 // words to the class's prototype during GC -- even those which have | |
677 // a currently valid bias owner. One important situation where we | |
678 // must not clobber a bias is when a biased object is currently | |
679 // locked. To handle this case we iterate over the currently-locked | |
680 // monitors in a prepass and, if they are biased, preserve their | |
681 // mark words here. This should be a relatively small set of objects | |
682 // especially compared to the number of objects in the heap. | |
683 _preserved_mark_stack = new (ResourceObj::C_HEAP) GrowableArray<markOop>(10, true); | |
684 _preserved_oop_stack = new (ResourceObj::C_HEAP) GrowableArray<Handle>(10, true); | |
685 | |
686 ResourceMark rm; | |
687 Thread* cur = Thread::current(); | |
688 for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) { | |
689 if (thread->has_last_Java_frame()) { | |
690 RegisterMap rm(thread); | |
691 for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) { | |
692 GrowableArray<MonitorInfo*> *monitors = vf->monitors(); | |
693 if (monitors != NULL) { | |
694 int len = monitors->length(); | |
695 // Walk monitors youngest to oldest | |
696 for (int i = len - 1; i >= 0; i--) { | |
697 MonitorInfo* mon_info = monitors->at(i); | |
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698 if (mon_info->owner_is_scalar_replaced()) continue; |
0 | 699 oop owner = mon_info->owner(); |
700 if (owner != NULL) { | |
701 markOop mark = owner->mark(); | |
702 if (mark->has_bias_pattern()) { | |
703 _preserved_oop_stack->push(Handle(cur, owner)); | |
704 _preserved_mark_stack->push(mark); | |
705 } | |
706 } | |
707 } | |
708 } | |
709 } | |
710 } | |
711 } | |
712 } | |
713 | |
714 | |
715 void BiasedLocking::restore_marks() { | |
716 if (!UseBiasedLocking) | |
717 return; | |
718 | |
719 assert(_preserved_oop_stack != NULL, "double free"); | |
720 assert(_preserved_mark_stack != NULL, "double free"); | |
721 | |
722 int len = _preserved_oop_stack->length(); | |
723 for (int i = 0; i < len; i++) { | |
724 Handle owner = _preserved_oop_stack->at(i); | |
725 markOop mark = _preserved_mark_stack->at(i); | |
726 owner->set_mark(mark); | |
727 } | |
728 | |
729 delete _preserved_oop_stack; | |
730 _preserved_oop_stack = NULL; | |
731 delete _preserved_mark_stack; | |
732 _preserved_mark_stack = NULL; | |
733 } | |
734 | |
735 | |
736 int* BiasedLocking::total_entry_count_addr() { return _counters.total_entry_count_addr(); } | |
737 int* BiasedLocking::biased_lock_entry_count_addr() { return _counters.biased_lock_entry_count_addr(); } | |
738 int* BiasedLocking::anonymously_biased_lock_entry_count_addr() { return _counters.anonymously_biased_lock_entry_count_addr(); } | |
739 int* BiasedLocking::rebiased_lock_entry_count_addr() { return _counters.rebiased_lock_entry_count_addr(); } | |
740 int* BiasedLocking::revoked_lock_entry_count_addr() { return _counters.revoked_lock_entry_count_addr(); } | |
741 int* BiasedLocking::fast_path_entry_count_addr() { return _counters.fast_path_entry_count_addr(); } | |
742 int* BiasedLocking::slow_path_entry_count_addr() { return _counters.slow_path_entry_count_addr(); } | |
743 | |
744 | |
745 // BiasedLockingCounters | |
746 | |
747 int BiasedLockingCounters::slow_path_entry_count() { | |
748 if (_slow_path_entry_count != 0) { | |
749 return _slow_path_entry_count; | |
750 } | |
751 int sum = _biased_lock_entry_count + _anonymously_biased_lock_entry_count + | |
752 _rebiased_lock_entry_count + _revoked_lock_entry_count + | |
753 _fast_path_entry_count; | |
754 | |
755 return _total_entry_count - sum; | |
756 } | |
757 | |
758 void BiasedLockingCounters::print_on(outputStream* st) { | |
759 tty->print_cr("# total entries: %d", _total_entry_count); | |
760 tty->print_cr("# biased lock entries: %d", _biased_lock_entry_count); | |
761 tty->print_cr("# anonymously biased lock entries: %d", _anonymously_biased_lock_entry_count); | |
762 tty->print_cr("# rebiased lock entries: %d", _rebiased_lock_entry_count); | |
763 tty->print_cr("# revoked lock entries: %d", _revoked_lock_entry_count); | |
764 tty->print_cr("# fast path lock entries: %d", _fast_path_entry_count); | |
765 tty->print_cr("# slow path lock entries: %d", slow_path_entry_count()); | |
766 } |