Fri, 09 May 2008 08:55:13 -0700
6670684: 4/5 SA command universe did not print out CMS space information
Summary: Forward port of Yumin's fix for 6670684 from HSX-11; Yumin verified the port was correct.
Reviewed-by: dcubed
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 */
26 # include "incls/_precompiled.incl"
27 # include "incls/_biasedLocking.cpp.incl"
29 static bool _biased_locking_enabled = false;
30 BiasedLockingCounters BiasedLocking::_counters;
32 static GrowableArray<Handle>* _preserved_oop_stack = NULL;
33 static GrowableArray<markOop>* _preserved_mark_stack = NULL;
35 static void enable_biased_locking(klassOop k) {
36 Klass::cast(k)->set_prototype_header(markOopDesc::biased_locking_prototype());
37 }
39 class VM_EnableBiasedLocking: public VM_Operation {
40 public:
41 VM_EnableBiasedLocking() {}
42 VMOp_Type type() const { return VMOp_EnableBiasedLocking; }
43 Mode evaluation_mode() const { return _async_safepoint; }
44 bool is_cheap_allocated() const { return true; }
46 void doit() {
47 // Iterate the system dictionary enabling biased locking for all
48 // currently loaded classes
49 SystemDictionary::classes_do(enable_biased_locking);
50 // Indicate that future instances should enable it as well
51 _biased_locking_enabled = true;
53 if (TraceBiasedLocking) {
54 tty->print_cr("Biased locking enabled");
55 }
56 }
58 bool allow_nested_vm_operations() const { return false; }
59 };
62 // One-shot PeriodicTask subclass for enabling biased locking
63 class EnableBiasedLockingTask : public PeriodicTask {
64 public:
65 EnableBiasedLockingTask(size_t interval_time) : PeriodicTask(interval_time) {}
67 virtual void task() {
68 // Use async VM operation to avoid blocking the Watcher thread.
69 // VM Thread will free C heap storage.
70 VM_EnableBiasedLocking *op = new VM_EnableBiasedLocking();
71 VMThread::execute(op);
73 // Reclaim our storage and disenroll ourself
74 delete this;
75 }
76 };
79 void BiasedLocking::init() {
80 // If biased locking is enabled, schedule a task to fire a few
81 // seconds into the run which turns on biased locking for all
82 // currently loaded classes as well as future ones. This is a
83 // workaround for startup time regressions due to a large number of
84 // safepoints being taken during VM startup for bias revocation.
85 // Ideally we would have a lower cost for individual bias revocation
86 // and not need a mechanism like this.
87 if (UseBiasedLocking) {
88 if (BiasedLockingStartupDelay > 0) {
89 EnableBiasedLockingTask* task = new EnableBiasedLockingTask(BiasedLockingStartupDelay);
90 task->enroll();
91 } else {
92 VM_EnableBiasedLocking op;
93 VMThread::execute(&op);
94 }
95 }
96 }
99 bool BiasedLocking::enabled() {
100 return _biased_locking_enabled;
101 }
103 // Returns MonitorInfos for all objects locked on this thread in youngest to oldest order
104 static GrowableArray<MonitorInfo*>* get_or_compute_monitor_info(JavaThread* thread) {
105 GrowableArray<MonitorInfo*>* info = thread->cached_monitor_info();
106 if (info != NULL) {
107 return info;
108 }
110 info = new GrowableArray<MonitorInfo*>();
112 // It's possible for the thread to not have any Java frames on it,
113 // i.e., if it's the main thread and it's already returned from main()
114 if (thread->has_last_Java_frame()) {
115 RegisterMap rm(thread);
116 for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) {
117 GrowableArray<MonitorInfo*> *monitors = vf->monitors();
118 if (monitors != NULL) {
119 int len = monitors->length();
120 // Walk monitors youngest to oldest
121 for (int i = len - 1; i >= 0; i--) {
122 MonitorInfo* mon_info = monitors->at(i);
123 oop owner = mon_info->owner();
124 if (owner != NULL) {
125 info->append(mon_info);
126 }
127 }
128 }
129 }
130 }
132 thread->set_cached_monitor_info(info);
133 return info;
134 }
137 static BiasedLocking::Condition revoke_bias(oop obj, bool allow_rebias, bool is_bulk, JavaThread* requesting_thread) {
138 markOop mark = obj->mark();
139 if (!mark->has_bias_pattern()) {
140 if (TraceBiasedLocking) {
141 ResourceMark rm;
142 tty->print_cr(" (Skipping revocation of object of type %s because it's no longer biased)",
143 Klass::cast(obj->klass())->external_name());
144 }
145 return BiasedLocking::NOT_BIASED;
146 }
148 int age = mark->age();
149 markOop biased_prototype = markOopDesc::biased_locking_prototype()->set_age(age);
150 markOop unbiased_prototype = markOopDesc::prototype()->set_age(age);
152 if (TraceBiasedLocking && (Verbose || !is_bulk)) {
153 ResourceMark rm;
154 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,
155 (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);
156 }
158 JavaThread* biased_thread = mark->biased_locker();
159 if (biased_thread == NULL) {
160 // Object is anonymously biased. We can get here if, for
161 // example, we revoke the bias due to an identity hash code
162 // being computed for an object.
163 if (!allow_rebias) {
164 obj->set_mark(unbiased_prototype);
165 }
166 if (TraceBiasedLocking && (Verbose || !is_bulk)) {
167 tty->print_cr(" Revoked bias of anonymously-biased object");
168 }
169 return BiasedLocking::BIAS_REVOKED;
170 }
172 // Handle case where the thread toward which the object was biased has exited
173 bool thread_is_alive = false;
174 if (requesting_thread == biased_thread) {
175 thread_is_alive = true;
176 } else {
177 for (JavaThread* cur_thread = Threads::first(); cur_thread != NULL; cur_thread = cur_thread->next()) {
178 if (cur_thread == biased_thread) {
179 thread_is_alive = true;
180 break;
181 }
182 }
183 }
184 if (!thread_is_alive) {
185 if (allow_rebias) {
186 obj->set_mark(biased_prototype);
187 } else {
188 obj->set_mark(unbiased_prototype);
189 }
190 if (TraceBiasedLocking && (Verbose || !is_bulk)) {
191 tty->print_cr(" Revoked bias of object biased toward dead thread");
192 }
193 return BiasedLocking::BIAS_REVOKED;
194 }
196 // Thread owning bias is alive.
197 // Check to see whether it currently owns the lock and, if so,
198 // write down the needed displaced headers to the thread's stack.
199 // Otherwise, restore the object's header either to the unlocked
200 // or unbiased state.
201 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(biased_thread);
202 BasicLock* highest_lock = NULL;
203 for (int i = 0; i < cached_monitor_info->length(); i++) {
204 MonitorInfo* mon_info = cached_monitor_info->at(i);
205 if (mon_info->owner() == obj) {
206 if (TraceBiasedLocking && Verbose) {
207 tty->print_cr(" mon_info->owner (" PTR_FORMAT ") == obj (" PTR_FORMAT ")",
208 (intptr_t) mon_info->owner(),
209 (intptr_t) obj);
210 }
211 // Assume recursive case and fix up highest lock later
212 markOop mark = markOopDesc::encode((BasicLock*) NULL);
213 highest_lock = mon_info->lock();
214 highest_lock->set_displaced_header(mark);
215 } else {
216 if (TraceBiasedLocking && Verbose) {
217 tty->print_cr(" mon_info->owner (" PTR_FORMAT ") != obj (" PTR_FORMAT ")",
218 (intptr_t) mon_info->owner(),
219 (intptr_t) obj);
220 }
221 }
222 }
223 if (highest_lock != NULL) {
224 // Fix up highest lock to contain displaced header and point
225 // object at it
226 highest_lock->set_displaced_header(unbiased_prototype);
227 // Reset object header to point to displaced mark
228 obj->set_mark(markOopDesc::encode(highest_lock));
229 assert(!obj->mark()->has_bias_pattern(), "illegal mark state: stack lock used bias bit");
230 if (TraceBiasedLocking && (Verbose || !is_bulk)) {
231 tty->print_cr(" Revoked bias of currently-locked object");
232 }
233 } else {
234 if (TraceBiasedLocking && (Verbose || !is_bulk)) {
235 tty->print_cr(" Revoked bias of currently-unlocked object");
236 }
237 if (allow_rebias) {
238 obj->set_mark(biased_prototype);
239 } else {
240 // Store the unlocked value into the object's header.
241 obj->set_mark(unbiased_prototype);
242 }
243 }
245 return BiasedLocking::BIAS_REVOKED;
246 }
249 enum HeuristicsResult {
250 HR_NOT_BIASED = 1,
251 HR_SINGLE_REVOKE = 2,
252 HR_BULK_REBIAS = 3,
253 HR_BULK_REVOKE = 4
254 };
257 static HeuristicsResult update_heuristics(oop o, bool allow_rebias) {
258 markOop mark = o->mark();
259 if (!mark->has_bias_pattern()) {
260 return HR_NOT_BIASED;
261 }
263 // Heuristics to attempt to throttle the number of revocations.
264 // Stages:
265 // 1. Revoke the biases of all objects in the heap of this type,
266 // but allow rebiasing of those objects if unlocked.
267 // 2. Revoke the biases of all objects in the heap of this type
268 // and don't allow rebiasing of these objects. Disable
269 // allocation of objects of that type with the bias bit set.
270 Klass* k = o->blueprint();
271 jlong cur_time = os::javaTimeMillis();
272 jlong last_bulk_revocation_time = k->last_biased_lock_bulk_revocation_time();
273 int revocation_count = k->biased_lock_revocation_count();
274 if ((revocation_count >= BiasedLockingBulkRebiasThreshold) &&
275 (revocation_count < BiasedLockingBulkRevokeThreshold) &&
276 (last_bulk_revocation_time != 0) &&
277 (cur_time - last_bulk_revocation_time >= BiasedLockingDecayTime)) {
278 // This is the first revocation we've seen in a while of an
279 // object of this type since the last time we performed a bulk
280 // rebiasing operation. The application is allocating objects in
281 // bulk which are biased toward a thread and then handing them
282 // off to another thread. We can cope with this allocation
283 // pattern via the bulk rebiasing mechanism so we reset the
284 // klass's revocation count rather than allow it to increase
285 // monotonically. If we see the need to perform another bulk
286 // rebias operation later, we will, and if subsequently we see
287 // many more revocation operations in a short period of time we
288 // will completely disable biasing for this type.
289 k->set_biased_lock_revocation_count(0);
290 revocation_count = 0;
291 }
293 // Make revocation count saturate just beyond BiasedLockingBulkRevokeThreshold
294 if (revocation_count <= BiasedLockingBulkRevokeThreshold) {
295 revocation_count = k->atomic_incr_biased_lock_revocation_count();
296 }
298 if (revocation_count == BiasedLockingBulkRevokeThreshold) {
299 return HR_BULK_REVOKE;
300 }
302 if (revocation_count == BiasedLockingBulkRebiasThreshold) {
303 return HR_BULK_REBIAS;
304 }
306 return HR_SINGLE_REVOKE;
307 }
310 static BiasedLocking::Condition bulk_revoke_or_rebias_at_safepoint(oop o,
311 bool bulk_rebias,
312 bool attempt_rebias_of_object,
313 JavaThread* requesting_thread) {
314 assert(SafepointSynchronize::is_at_safepoint(), "must be done at safepoint");
316 if (TraceBiasedLocking) {
317 tty->print_cr("* Beginning bulk revocation (kind == %s) because of object "
318 INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s",
319 (bulk_rebias ? "rebias" : "revoke"),
320 (intptr_t) o, (intptr_t) o->mark(), Klass::cast(o->klass())->external_name());
321 }
323 jlong cur_time = os::javaTimeMillis();
324 o->blueprint()->set_last_biased_lock_bulk_revocation_time(cur_time);
327 klassOop k_o = o->klass();
328 Klass* klass = Klass::cast(k_o);
330 if (bulk_rebias) {
331 // Use the epoch in the klass of the object to implicitly revoke
332 // all biases of objects of this data type and force them to be
333 // reacquired. However, we also need to walk the stacks of all
334 // threads and update the headers of lightweight locked objects
335 // with biases to have the current epoch.
337 // If the prototype header doesn't have the bias pattern, don't
338 // try to update the epoch -- assume another VM operation came in
339 // and reset the header to the unbiased state, which will
340 // implicitly cause all existing biases to be revoked
341 if (klass->prototype_header()->has_bias_pattern()) {
342 int prev_epoch = klass->prototype_header()->bias_epoch();
343 klass->set_prototype_header(klass->prototype_header()->incr_bias_epoch());
344 int cur_epoch = klass->prototype_header()->bias_epoch();
346 // Now walk all threads' stacks and adjust epochs of any biased
347 // and locked objects of this data type we encounter
348 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
349 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr);
350 for (int i = 0; i < cached_monitor_info->length(); i++) {
351 MonitorInfo* mon_info = cached_monitor_info->at(i);
352 oop owner = mon_info->owner();
353 markOop mark = owner->mark();
354 if ((owner->klass() == k_o) && mark->has_bias_pattern()) {
355 // We might have encountered this object already in the case of recursive locking
356 assert(mark->bias_epoch() == prev_epoch || mark->bias_epoch() == cur_epoch, "error in bias epoch adjustment");
357 owner->set_mark(mark->set_bias_epoch(cur_epoch));
358 }
359 }
360 }
361 }
363 // At this point we're done. All we have to do is potentially
364 // adjust the header of the given object to revoke its bias.
365 revoke_bias(o, attempt_rebias_of_object && klass->prototype_header()->has_bias_pattern(), true, requesting_thread);
366 } else {
367 if (TraceBiasedLocking) {
368 ResourceMark rm;
369 tty->print_cr("* Disabling biased locking for type %s", klass->external_name());
370 }
372 // Disable biased locking for this data type. Not only will this
373 // cause future instances to not be biased, but existing biased
374 // instances will notice that this implicitly caused their biases
375 // to be revoked.
376 klass->set_prototype_header(markOopDesc::prototype());
378 // Now walk all threads' stacks and forcibly revoke the biases of
379 // any locked and biased objects of this data type we encounter.
380 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
381 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr);
382 for (int i = 0; i < cached_monitor_info->length(); i++) {
383 MonitorInfo* mon_info = cached_monitor_info->at(i);
384 oop owner = mon_info->owner();
385 markOop mark = owner->mark();
386 if ((owner->klass() == k_o) && mark->has_bias_pattern()) {
387 revoke_bias(owner, false, true, requesting_thread);
388 }
389 }
390 }
392 // Must force the bias of the passed object to be forcibly revoked
393 // as well to ensure guarantees to callers
394 revoke_bias(o, false, true, requesting_thread);
395 }
397 if (TraceBiasedLocking) {
398 tty->print_cr("* Ending bulk revocation");
399 }
401 BiasedLocking::Condition status_code = BiasedLocking::BIAS_REVOKED;
403 if (attempt_rebias_of_object &&
404 o->mark()->has_bias_pattern() &&
405 klass->prototype_header()->has_bias_pattern()) {
406 markOop new_mark = markOopDesc::encode(requesting_thread, o->mark()->age(),
407 klass->prototype_header()->bias_epoch());
408 o->set_mark(new_mark);
409 status_code = BiasedLocking::BIAS_REVOKED_AND_REBIASED;
410 if (TraceBiasedLocking) {
411 tty->print_cr(" Rebiased object toward thread " INTPTR_FORMAT, (intptr_t) requesting_thread);
412 }
413 }
415 assert(!o->mark()->has_bias_pattern() ||
416 (attempt_rebias_of_object && (o->mark()->biased_locker() == requesting_thread)),
417 "bug in bulk bias revocation");
419 return status_code;
420 }
423 static void clean_up_cached_monitor_info() {
424 // Walk the thread list clearing out the cached monitors
425 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
426 thr->set_cached_monitor_info(NULL);
427 }
428 }
431 class VM_RevokeBias : public VM_Operation {
432 protected:
433 Handle* _obj;
434 GrowableArray<Handle>* _objs;
435 JavaThread* _requesting_thread;
436 BiasedLocking::Condition _status_code;
438 public:
439 VM_RevokeBias(Handle* obj, JavaThread* requesting_thread)
440 : _obj(obj)
441 , _objs(NULL)
442 , _requesting_thread(requesting_thread)
443 , _status_code(BiasedLocking::NOT_BIASED) {}
445 VM_RevokeBias(GrowableArray<Handle>* objs, JavaThread* requesting_thread)
446 : _obj(NULL)
447 , _objs(objs)
448 , _requesting_thread(requesting_thread)
449 , _status_code(BiasedLocking::NOT_BIASED) {}
451 virtual VMOp_Type type() const { return VMOp_RevokeBias; }
453 virtual bool doit_prologue() {
454 // Verify that there is actual work to do since the callers just
455 // give us locked object(s). If we don't find any biased objects
456 // there is nothing to do and we avoid a safepoint.
457 if (_obj != NULL) {
458 markOop mark = (*_obj)()->mark();
459 if (mark->has_bias_pattern()) {
460 return true;
461 }
462 } else {
463 for ( int i = 0 ; i < _objs->length(); i++ ) {
464 markOop mark = (_objs->at(i))()->mark();
465 if (mark->has_bias_pattern()) {
466 return true;
467 }
468 }
469 }
470 return false;
471 }
473 virtual void doit() {
474 if (_obj != NULL) {
475 if (TraceBiasedLocking) {
476 tty->print_cr("Revoking bias with potentially per-thread safepoint:");
477 }
478 _status_code = revoke_bias((*_obj)(), false, false, _requesting_thread);
479 clean_up_cached_monitor_info();
480 return;
481 } else {
482 if (TraceBiasedLocking) {
483 tty->print_cr("Revoking bias with global safepoint:");
484 }
485 BiasedLocking::revoke_at_safepoint(_objs);
486 }
487 }
489 BiasedLocking::Condition status_code() const {
490 return _status_code;
491 }
492 };
495 class VM_BulkRevokeBias : public VM_RevokeBias {
496 private:
497 bool _bulk_rebias;
498 bool _attempt_rebias_of_object;
500 public:
501 VM_BulkRevokeBias(Handle* obj, JavaThread* requesting_thread,
502 bool bulk_rebias,
503 bool attempt_rebias_of_object)
504 : VM_RevokeBias(obj, requesting_thread)
505 , _bulk_rebias(bulk_rebias)
506 , _attempt_rebias_of_object(attempt_rebias_of_object) {}
508 virtual VMOp_Type type() const { return VMOp_BulkRevokeBias; }
509 virtual bool doit_prologue() { return true; }
511 virtual void doit() {
512 _status_code = bulk_revoke_or_rebias_at_safepoint((*_obj)(), _bulk_rebias, _attempt_rebias_of_object, _requesting_thread);
513 clean_up_cached_monitor_info();
514 }
515 };
518 BiasedLocking::Condition BiasedLocking::revoke_and_rebias(Handle obj, bool attempt_rebias, TRAPS) {
519 assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint");
521 // We can revoke the biases of anonymously-biased objects
522 // efficiently enough that we should not cause these revocations to
523 // update the heuristics because doing so may cause unwanted bulk
524 // revocations (which are expensive) to occur.
525 markOop mark = obj->mark();
526 if (mark->is_biased_anonymously() && !attempt_rebias) {
527 // We are probably trying to revoke the bias of this object due to
528 // an identity hash code computation. Try to revoke the bias
529 // without a safepoint. This is possible if we can successfully
530 // compare-and-exchange an unbiased header into the mark word of
531 // the object, meaning that no other thread has raced to acquire
532 // the bias of the object.
533 markOop biased_value = mark;
534 markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age());
535 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark);
536 if (res_mark == biased_value) {
537 return BIAS_REVOKED;
538 }
539 } else if (mark->has_bias_pattern()) {
540 Klass* k = Klass::cast(obj->klass());
541 markOop prototype_header = k->prototype_header();
542 if (!prototype_header->has_bias_pattern()) {
543 // This object has a stale bias from before the bulk revocation
544 // for this data type occurred. It's pointless to update the
545 // heuristics at this point so simply update the header with a
546 // CAS. If we fail this race, the object's bias has been revoked
547 // by another thread so we simply return and let the caller deal
548 // with it.
549 markOop biased_value = mark;
550 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(prototype_header, obj->mark_addr(), mark);
551 assert(!(*(obj->mark_addr()))->has_bias_pattern(), "even if we raced, should still be revoked");
552 return BIAS_REVOKED;
553 } else if (prototype_header->bias_epoch() != mark->bias_epoch()) {
554 // The epoch of this biasing has expired indicating that the
555 // object is effectively unbiased. Depending on whether we need
556 // to rebias or revoke the bias of this object we can do it
557 // efficiently enough with a CAS that we shouldn't update the
558 // heuristics. This is normally done in the assembly code but we
559 // can reach this point due to various points in the runtime
560 // needing to revoke biases.
561 if (attempt_rebias) {
562 assert(THREAD->is_Java_thread(), "");
563 markOop biased_value = mark;
564 markOop rebiased_prototype = markOopDesc::encode((JavaThread*) THREAD, mark->age(), prototype_header->bias_epoch());
565 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(rebiased_prototype, obj->mark_addr(), mark);
566 if (res_mark == biased_value) {
567 return BIAS_REVOKED_AND_REBIASED;
568 }
569 } else {
570 markOop biased_value = mark;
571 markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age());
572 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark);
573 if (res_mark == biased_value) {
574 return BIAS_REVOKED;
575 }
576 }
577 }
578 }
580 HeuristicsResult heuristics = update_heuristics(obj(), attempt_rebias);
581 if (heuristics == HR_NOT_BIASED) {
582 return NOT_BIASED;
583 } else if (heuristics == HR_SINGLE_REVOKE) {
584 if (mark->biased_locker() == THREAD) {
585 // A thread is trying to revoke the bias of an object biased
586 // toward it, again likely due to an identity hash code
587 // computation. We can again avoid a safepoint in this case
588 // since we are only going to walk our own stack. There are no
589 // races with revocations occurring in other threads because we
590 // reach no safepoints in the revocation path.
591 ResourceMark rm;
592 if (TraceBiasedLocking) {
593 tty->print_cr("Revoking bias by walking my own stack:");
594 }
595 BiasedLocking::Condition cond = revoke_bias(obj(), false, false, (JavaThread*) THREAD);
596 ((JavaThread*) THREAD)->set_cached_monitor_info(NULL);
597 assert(cond == BIAS_REVOKED, "why not?");
598 return cond;
599 } else {
600 VM_RevokeBias revoke(&obj, (JavaThread*) THREAD);
601 VMThread::execute(&revoke);
602 return revoke.status_code();
603 }
604 }
606 assert((heuristics == HR_BULK_REVOKE) ||
607 (heuristics == HR_BULK_REBIAS), "?");
608 VM_BulkRevokeBias bulk_revoke(&obj, (JavaThread*) THREAD,
609 (heuristics == HR_BULK_REBIAS),
610 attempt_rebias);
611 VMThread::execute(&bulk_revoke);
612 return bulk_revoke.status_code();
613 }
616 void BiasedLocking::revoke(GrowableArray<Handle>* objs) {
617 assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint");
618 if (objs->length() == 0) {
619 return;
620 }
621 VM_RevokeBias revoke(objs, JavaThread::current());
622 VMThread::execute(&revoke);
623 }
626 void BiasedLocking::revoke_at_safepoint(Handle h_obj) {
627 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint");
628 oop obj = h_obj();
629 HeuristicsResult heuristics = update_heuristics(obj, false);
630 if (heuristics == HR_SINGLE_REVOKE) {
631 revoke_bias(obj, false, false, NULL);
632 } else if ((heuristics == HR_BULK_REBIAS) ||
633 (heuristics == HR_BULK_REVOKE)) {
634 bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL);
635 }
636 clean_up_cached_monitor_info();
637 }
640 void BiasedLocking::revoke_at_safepoint(GrowableArray<Handle>* objs) {
641 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint");
642 int len = objs->length();
643 for (int i = 0; i < len; i++) {
644 oop obj = (objs->at(i))();
645 HeuristicsResult heuristics = update_heuristics(obj, false);
646 if (heuristics == HR_SINGLE_REVOKE) {
647 revoke_bias(obj, false, false, NULL);
648 } else if ((heuristics == HR_BULK_REBIAS) ||
649 (heuristics == HR_BULK_REVOKE)) {
650 bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL);
651 }
652 }
653 clean_up_cached_monitor_info();
654 }
657 void BiasedLocking::preserve_marks() {
658 if (!UseBiasedLocking)
659 return;
661 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint");
663 assert(_preserved_oop_stack == NULL, "double initialization");
664 assert(_preserved_mark_stack == NULL, "double initialization");
666 // In order to reduce the number of mark words preserved during GC
667 // due to the presence of biased locking, we reinitialize most mark
668 // words to the class's prototype during GC -- even those which have
669 // a currently valid bias owner. One important situation where we
670 // must not clobber a bias is when a biased object is currently
671 // locked. To handle this case we iterate over the currently-locked
672 // monitors in a prepass and, if they are biased, preserve their
673 // mark words here. This should be a relatively small set of objects
674 // especially compared to the number of objects in the heap.
675 _preserved_mark_stack = new (ResourceObj::C_HEAP) GrowableArray<markOop>(10, true);
676 _preserved_oop_stack = new (ResourceObj::C_HEAP) GrowableArray<Handle>(10, true);
678 ResourceMark rm;
679 Thread* cur = Thread::current();
680 for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) {
681 if (thread->has_last_Java_frame()) {
682 RegisterMap rm(thread);
683 for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) {
684 GrowableArray<MonitorInfo*> *monitors = vf->monitors();
685 if (monitors != NULL) {
686 int len = monitors->length();
687 // Walk monitors youngest to oldest
688 for (int i = len - 1; i >= 0; i--) {
689 MonitorInfo* mon_info = monitors->at(i);
690 oop owner = mon_info->owner();
691 if (owner != NULL) {
692 markOop mark = owner->mark();
693 if (mark->has_bias_pattern()) {
694 _preserved_oop_stack->push(Handle(cur, owner));
695 _preserved_mark_stack->push(mark);
696 }
697 }
698 }
699 }
700 }
701 }
702 }
703 }
706 void BiasedLocking::restore_marks() {
707 if (!UseBiasedLocking)
708 return;
710 assert(_preserved_oop_stack != NULL, "double free");
711 assert(_preserved_mark_stack != NULL, "double free");
713 int len = _preserved_oop_stack->length();
714 for (int i = 0; i < len; i++) {
715 Handle owner = _preserved_oop_stack->at(i);
716 markOop mark = _preserved_mark_stack->at(i);
717 owner->set_mark(mark);
718 }
720 delete _preserved_oop_stack;
721 _preserved_oop_stack = NULL;
722 delete _preserved_mark_stack;
723 _preserved_mark_stack = NULL;
724 }
727 int* BiasedLocking::total_entry_count_addr() { return _counters.total_entry_count_addr(); }
728 int* BiasedLocking::biased_lock_entry_count_addr() { return _counters.biased_lock_entry_count_addr(); }
729 int* BiasedLocking::anonymously_biased_lock_entry_count_addr() { return _counters.anonymously_biased_lock_entry_count_addr(); }
730 int* BiasedLocking::rebiased_lock_entry_count_addr() { return _counters.rebiased_lock_entry_count_addr(); }
731 int* BiasedLocking::revoked_lock_entry_count_addr() { return _counters.revoked_lock_entry_count_addr(); }
732 int* BiasedLocking::fast_path_entry_count_addr() { return _counters.fast_path_entry_count_addr(); }
733 int* BiasedLocking::slow_path_entry_count_addr() { return _counters.slow_path_entry_count_addr(); }
736 // BiasedLockingCounters
738 int BiasedLockingCounters::slow_path_entry_count() {
739 if (_slow_path_entry_count != 0) {
740 return _slow_path_entry_count;
741 }
742 int sum = _biased_lock_entry_count + _anonymously_biased_lock_entry_count +
743 _rebiased_lock_entry_count + _revoked_lock_entry_count +
744 _fast_path_entry_count;
746 return _total_entry_count - sum;
747 }
749 void BiasedLockingCounters::print_on(outputStream* st) {
750 tty->print_cr("# total entries: %d", _total_entry_count);
751 tty->print_cr("# biased lock entries: %d", _biased_lock_entry_count);
752 tty->print_cr("# anonymously biased lock entries: %d", _anonymously_biased_lock_entry_count);
753 tty->print_cr("# rebiased lock entries: %d", _rebiased_lock_entry_count);
754 tty->print_cr("# revoked lock entries: %d", _revoked_lock_entry_count);
755 tty->print_cr("# fast path lock entries: %d", _fast_path_entry_count);
756 tty->print_cr("# slow path lock entries: %d", slow_path_entry_count());
757 }