Mercurial > hg > graal-compiler
annotate src/share/vm/runtime/biasedLocking.cpp @ 20596:4356234e712a
8041992: Fix of JDK-8034775 neglects to account for non-JIT VMs
Summary: Allow 0 compiler threads if no JIT is used.
Reviewed-by: kvn, dholmes
Contributed-by: Severin Gehwolf <sgehwolf@redhat.com>
author | anoll |
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date | Fri, 02 May 2014 06:24:39 +0200 |
parents | 78bbf4d43a14 |
children | 52b4284cb496 |
rev | line source |
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0 | 1 /* |
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2 * Copyright (c) 2005, 2014, Oracle and/or its affiliates. All rights reserved. |
0 | 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
4 * | |
5 * This code is free software; you can redistribute it and/or modify it | |
6 * under the terms of the GNU General Public License version 2 only, as | |
7 * published by the Free Software Foundation. | |
8 * | |
9 * This code is distributed in the hope that it will be useful, but WITHOUT | |
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or | |
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License | |
12 * version 2 for more details (a copy is included in the LICENSE file that | |
13 * accompanied this code). | |
14 * | |
15 * You should have received a copy of the GNU General Public License version | |
16 * 2 along with this work; if not, write to the Free Software Foundation, | |
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. | |
18 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #include "precompiled.hpp" |
26 #include "oops/klass.inline.hpp" | |
27 #include "oops/markOop.hpp" | |
28 #include "runtime/basicLock.hpp" | |
29 #include "runtime/biasedLocking.hpp" | |
30 #include "runtime/task.hpp" | |
31 #include "runtime/vframe.hpp" | |
32 #include "runtime/vmThread.hpp" | |
33 #include "runtime/vm_operations.hpp" | |
0 | 34 |
35 static bool _biased_locking_enabled = false; | |
36 BiasedLockingCounters BiasedLocking::_counters; | |
37 | |
38 static GrowableArray<Handle>* _preserved_oop_stack = NULL; | |
39 static GrowableArray<markOop>* _preserved_mark_stack = NULL; | |
40 | |
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41 static void enable_biased_locking(Klass* k) { |
6983 | 42 k->set_prototype_header(markOopDesc::biased_locking_prototype()); |
0 | 43 } |
44 | |
45 class VM_EnableBiasedLocking: public VM_Operation { | |
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46 private: |
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47 bool _is_cheap_allocated; |
0 | 48 public: |
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49 VM_EnableBiasedLocking(bool is_cheap_allocated) { _is_cheap_allocated = is_cheap_allocated; } |
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50 VMOp_Type type() const { return VMOp_EnableBiasedLocking; } |
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51 Mode evaluation_mode() const { return _is_cheap_allocated ? _async_safepoint : _safepoint; } |
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52 bool is_cheap_allocated() const { return _is_cheap_allocated; } |
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53 |
0 | 54 void doit() { |
55 // Iterate the system dictionary enabling biased locking for all | |
56 // currently loaded classes | |
57 SystemDictionary::classes_do(enable_biased_locking); | |
58 // Indicate that future instances should enable it as well | |
59 _biased_locking_enabled = true; | |
60 | |
61 if (TraceBiasedLocking) { | |
62 tty->print_cr("Biased locking enabled"); | |
63 } | |
64 } | |
65 | |
66 bool allow_nested_vm_operations() const { return false; } | |
67 }; | |
68 | |
69 | |
70 // One-shot PeriodicTask subclass for enabling biased locking | |
71 class EnableBiasedLockingTask : public PeriodicTask { | |
72 public: | |
73 EnableBiasedLockingTask(size_t interval_time) : PeriodicTask(interval_time) {} | |
74 | |
75 virtual void task() { | |
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76 // Use async VM operation to avoid blocking the Watcher thread. |
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77 // VM Thread will free C heap storage. |
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78 VM_EnableBiasedLocking *op = new VM_EnableBiasedLocking(true); |
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79 VMThread::execute(op); |
0 | 80 |
81 // Reclaim our storage and disenroll ourself | |
82 delete this; | |
83 } | |
84 }; | |
85 | |
86 | |
87 void BiasedLocking::init() { | |
88 // If biased locking is enabled, schedule a task to fire a few | |
89 // seconds into the run which turns on biased locking for all | |
90 // currently loaded classes as well as future ones. This is a | |
91 // workaround for startup time regressions due to a large number of | |
92 // safepoints being taken during VM startup for bias revocation. | |
93 // Ideally we would have a lower cost for individual bias revocation | |
94 // and not need a mechanism like this. | |
95 if (UseBiasedLocking) { | |
96 if (BiasedLockingStartupDelay > 0) { | |
97 EnableBiasedLockingTask* task = new EnableBiasedLockingTask(BiasedLockingStartupDelay); | |
98 task->enroll(); | |
99 } else { | |
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100 VM_EnableBiasedLocking op(false); |
0 | 101 VMThread::execute(&op); |
102 } | |
103 } | |
104 } | |
105 | |
106 | |
107 bool BiasedLocking::enabled() { | |
108 return _biased_locking_enabled; | |
109 } | |
110 | |
111 // Returns MonitorInfos for all objects locked on this thread in youngest to oldest order | |
112 static GrowableArray<MonitorInfo*>* get_or_compute_monitor_info(JavaThread* thread) { | |
113 GrowableArray<MonitorInfo*>* info = thread->cached_monitor_info(); | |
114 if (info != NULL) { | |
115 return info; | |
116 } | |
117 | |
118 info = new GrowableArray<MonitorInfo*>(); | |
119 | |
120 // It's possible for the thread to not have any Java frames on it, | |
121 // i.e., if it's the main thread and it's already returned from main() | |
122 if (thread->has_last_Java_frame()) { | |
123 RegisterMap rm(thread); | |
124 for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) { | |
125 GrowableArray<MonitorInfo*> *monitors = vf->monitors(); | |
126 if (monitors != NULL) { | |
127 int len = monitors->length(); | |
128 // Walk monitors youngest to oldest | |
129 for (int i = len - 1; i >= 0; i--) { | |
130 MonitorInfo* mon_info = monitors->at(i); | |
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131 if (mon_info->eliminated()) continue; |
0 | 132 oop owner = mon_info->owner(); |
133 if (owner != NULL) { | |
134 info->append(mon_info); | |
135 } | |
136 } | |
137 } | |
138 } | |
139 } | |
140 | |
141 thread->set_cached_monitor_info(info); | |
142 return info; | |
143 } | |
144 | |
145 | |
146 static BiasedLocking::Condition revoke_bias(oop obj, bool allow_rebias, bool is_bulk, JavaThread* requesting_thread) { | |
147 markOop mark = obj->mark(); | |
148 if (!mark->has_bias_pattern()) { | |
149 if (TraceBiasedLocking) { | |
150 ResourceMark rm; | |
151 tty->print_cr(" (Skipping revocation of object of type %s because it's no longer biased)", | |
6983 | 152 obj->klass()->external_name()); |
0 | 153 } |
154 return BiasedLocking::NOT_BIASED; | |
155 } | |
156 | |
6818 | 157 uint age = mark->age(); |
0 | 158 markOop biased_prototype = markOopDesc::biased_locking_prototype()->set_age(age); |
159 markOop unbiased_prototype = markOopDesc::prototype()->set_age(age); | |
160 | |
161 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
162 ResourceMark rm; | |
163 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, | |
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164 p2i((void *)obj), (intptr_t) mark, obj->klass()->external_name(), (intptr_t) obj->klass()->prototype_header(), (allow_rebias ? 1 : 0), (intptr_t) requesting_thread); |
0 | 165 } |
166 | |
167 JavaThread* biased_thread = mark->biased_locker(); | |
168 if (biased_thread == NULL) { | |
169 // Object is anonymously biased. We can get here if, for | |
170 // example, we revoke the bias due to an identity hash code | |
171 // being computed for an object. | |
172 if (!allow_rebias) { | |
173 obj->set_mark(unbiased_prototype); | |
174 } | |
175 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
176 tty->print_cr(" Revoked bias of anonymously-biased object"); | |
177 } | |
178 return BiasedLocking::BIAS_REVOKED; | |
179 } | |
180 | |
181 // Handle case where the thread toward which the object was biased has exited | |
182 bool thread_is_alive = false; | |
183 if (requesting_thread == biased_thread) { | |
184 thread_is_alive = true; | |
185 } else { | |
186 for (JavaThread* cur_thread = Threads::first(); cur_thread != NULL; cur_thread = cur_thread->next()) { | |
187 if (cur_thread == biased_thread) { | |
188 thread_is_alive = true; | |
189 break; | |
190 } | |
191 } | |
192 } | |
193 if (!thread_is_alive) { | |
194 if (allow_rebias) { | |
195 obj->set_mark(biased_prototype); | |
196 } else { | |
197 obj->set_mark(unbiased_prototype); | |
198 } | |
199 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
200 tty->print_cr(" Revoked bias of object biased toward dead thread"); | |
201 } | |
202 return BiasedLocking::BIAS_REVOKED; | |
203 } | |
204 | |
205 // Thread owning bias is alive. | |
206 // Check to see whether it currently owns the lock and, if so, | |
207 // write down the needed displaced headers to the thread's stack. | |
208 // Otherwise, restore the object's header either to the unlocked | |
209 // or unbiased state. | |
210 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(biased_thread); | |
211 BasicLock* highest_lock = NULL; | |
212 for (int i = 0; i < cached_monitor_info->length(); i++) { | |
213 MonitorInfo* mon_info = cached_monitor_info->at(i); | |
214 if (mon_info->owner() == obj) { | |
215 if (TraceBiasedLocking && Verbose) { | |
216 tty->print_cr(" mon_info->owner (" PTR_FORMAT ") == obj (" PTR_FORMAT ")", | |
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217 p2i((void *) mon_info->owner()), |
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218 p2i((void *) obj)); |
0 | 219 } |
220 // Assume recursive case and fix up highest lock later | |
221 markOop mark = markOopDesc::encode((BasicLock*) NULL); | |
222 highest_lock = mon_info->lock(); | |
223 highest_lock->set_displaced_header(mark); | |
224 } else { | |
225 if (TraceBiasedLocking && Verbose) { | |
226 tty->print_cr(" mon_info->owner (" PTR_FORMAT ") != obj (" PTR_FORMAT ")", | |
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227 p2i((void *) mon_info->owner()), |
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228 p2i((void *) obj)); |
0 | 229 } |
230 } | |
231 } | |
232 if (highest_lock != NULL) { | |
233 // Fix up highest lock to contain displaced header and point | |
234 // object at it | |
235 highest_lock->set_displaced_header(unbiased_prototype); | |
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236 // Reset object header to point to displaced mark. |
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237 // Must release storing the lock address for platforms without TSO |
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238 // ordering (e.g. ppc). |
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239 obj->release_set_mark(markOopDesc::encode(highest_lock)); |
0 | 240 assert(!obj->mark()->has_bias_pattern(), "illegal mark state: stack lock used bias bit"); |
241 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
242 tty->print_cr(" Revoked bias of currently-locked object"); | |
243 } | |
244 } else { | |
245 if (TraceBiasedLocking && (Verbose || !is_bulk)) { | |
246 tty->print_cr(" Revoked bias of currently-unlocked object"); | |
247 } | |
248 if (allow_rebias) { | |
249 obj->set_mark(biased_prototype); | |
250 } else { | |
251 // Store the unlocked value into the object's header. | |
252 obj->set_mark(unbiased_prototype); | |
253 } | |
254 } | |
255 | |
256 return BiasedLocking::BIAS_REVOKED; | |
257 } | |
258 | |
259 | |
260 enum HeuristicsResult { | |
261 HR_NOT_BIASED = 1, | |
262 HR_SINGLE_REVOKE = 2, | |
263 HR_BULK_REBIAS = 3, | |
264 HR_BULK_REVOKE = 4 | |
265 }; | |
266 | |
267 | |
268 static HeuristicsResult update_heuristics(oop o, bool allow_rebias) { | |
269 markOop mark = o->mark(); | |
270 if (!mark->has_bias_pattern()) { | |
271 return HR_NOT_BIASED; | |
272 } | |
273 | |
274 // Heuristics to attempt to throttle the number of revocations. | |
275 // Stages: | |
276 // 1. Revoke the biases of all objects in the heap of this type, | |
277 // but allow rebiasing of those objects if unlocked. | |
278 // 2. Revoke the biases of all objects in the heap of this type | |
279 // and don't allow rebiasing of these objects. Disable | |
280 // allocation of objects of that type with the bias bit set. | |
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281 Klass* k = o->klass(); |
0 | 282 jlong cur_time = os::javaTimeMillis(); |
283 jlong last_bulk_revocation_time = k->last_biased_lock_bulk_revocation_time(); | |
284 int revocation_count = k->biased_lock_revocation_count(); | |
285 if ((revocation_count >= BiasedLockingBulkRebiasThreshold) && | |
286 (revocation_count < BiasedLockingBulkRevokeThreshold) && | |
287 (last_bulk_revocation_time != 0) && | |
288 (cur_time - last_bulk_revocation_time >= BiasedLockingDecayTime)) { | |
289 // This is the first revocation we've seen in a while of an | |
290 // object of this type since the last time we performed a bulk | |
291 // rebiasing operation. The application is allocating objects in | |
292 // bulk which are biased toward a thread and then handing them | |
293 // off to another thread. We can cope with this allocation | |
294 // pattern via the bulk rebiasing mechanism so we reset the | |
295 // klass's revocation count rather than allow it to increase | |
296 // monotonically. If we see the need to perform another bulk | |
297 // rebias operation later, we will, and if subsequently we see | |
298 // many more revocation operations in a short period of time we | |
299 // will completely disable biasing for this type. | |
300 k->set_biased_lock_revocation_count(0); | |
301 revocation_count = 0; | |
302 } | |
303 | |
304 // Make revocation count saturate just beyond BiasedLockingBulkRevokeThreshold | |
305 if (revocation_count <= BiasedLockingBulkRevokeThreshold) { | |
306 revocation_count = k->atomic_incr_biased_lock_revocation_count(); | |
307 } | |
308 | |
309 if (revocation_count == BiasedLockingBulkRevokeThreshold) { | |
310 return HR_BULK_REVOKE; | |
311 } | |
312 | |
313 if (revocation_count == BiasedLockingBulkRebiasThreshold) { | |
314 return HR_BULK_REBIAS; | |
315 } | |
316 | |
317 return HR_SINGLE_REVOKE; | |
318 } | |
319 | |
320 | |
321 static BiasedLocking::Condition bulk_revoke_or_rebias_at_safepoint(oop o, | |
322 bool bulk_rebias, | |
323 bool attempt_rebias_of_object, | |
324 JavaThread* requesting_thread) { | |
325 assert(SafepointSynchronize::is_at_safepoint(), "must be done at safepoint"); | |
326 | |
327 if (TraceBiasedLocking) { | |
328 tty->print_cr("* Beginning bulk revocation (kind == %s) because of object " | |
329 INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", | |
330 (bulk_rebias ? "rebias" : "revoke"), | |
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331 p2i((void *) o), (intptr_t) o->mark(), o->klass()->external_name()); |
0 | 332 } |
333 | |
334 jlong cur_time = os::javaTimeMillis(); | |
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335 o->klass()->set_last_biased_lock_bulk_revocation_time(cur_time); |
0 | 336 |
337 | |
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338 Klass* k_o = o->klass(); |
6983 | 339 Klass* klass = k_o; |
0 | 340 |
341 if (bulk_rebias) { | |
342 // Use the epoch in the klass of the object to implicitly revoke | |
343 // all biases of objects of this data type and force them to be | |
344 // reacquired. However, we also need to walk the stacks of all | |
345 // threads and update the headers of lightweight locked objects | |
346 // with biases to have the current epoch. | |
347 | |
348 // If the prototype header doesn't have the bias pattern, don't | |
349 // try to update the epoch -- assume another VM operation came in | |
350 // and reset the header to the unbiased state, which will | |
351 // implicitly cause all existing biases to be revoked | |
352 if (klass->prototype_header()->has_bias_pattern()) { | |
353 int prev_epoch = klass->prototype_header()->bias_epoch(); | |
354 klass->set_prototype_header(klass->prototype_header()->incr_bias_epoch()); | |
355 int cur_epoch = klass->prototype_header()->bias_epoch(); | |
356 | |
357 // Now walk all threads' stacks and adjust epochs of any biased | |
358 // and locked objects of this data type we encounter | |
359 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { | |
360 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr); | |
361 for (int i = 0; i < cached_monitor_info->length(); i++) { | |
362 MonitorInfo* mon_info = cached_monitor_info->at(i); | |
363 oop owner = mon_info->owner(); | |
364 markOop mark = owner->mark(); | |
365 if ((owner->klass() == k_o) && mark->has_bias_pattern()) { | |
366 // We might have encountered this object already in the case of recursive locking | |
367 assert(mark->bias_epoch() == prev_epoch || mark->bias_epoch() == cur_epoch, "error in bias epoch adjustment"); | |
368 owner->set_mark(mark->set_bias_epoch(cur_epoch)); | |
369 } | |
370 } | |
371 } | |
372 } | |
373 | |
374 // At this point we're done. All we have to do is potentially | |
375 // adjust the header of the given object to revoke its bias. | |
376 revoke_bias(o, attempt_rebias_of_object && klass->prototype_header()->has_bias_pattern(), true, requesting_thread); | |
377 } else { | |
378 if (TraceBiasedLocking) { | |
379 ResourceMark rm; | |
380 tty->print_cr("* Disabling biased locking for type %s", klass->external_name()); | |
381 } | |
382 | |
383 // Disable biased locking for this data type. Not only will this | |
384 // cause future instances to not be biased, but existing biased | |
385 // instances will notice that this implicitly caused their biases | |
386 // to be revoked. | |
387 klass->set_prototype_header(markOopDesc::prototype()); | |
388 | |
389 // Now walk all threads' stacks and forcibly revoke the biases of | |
390 // any locked and biased objects of this data type we encounter. | |
391 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { | |
392 GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr); | |
393 for (int i = 0; i < cached_monitor_info->length(); i++) { | |
394 MonitorInfo* mon_info = cached_monitor_info->at(i); | |
395 oop owner = mon_info->owner(); | |
396 markOop mark = owner->mark(); | |
397 if ((owner->klass() == k_o) && mark->has_bias_pattern()) { | |
398 revoke_bias(owner, false, true, requesting_thread); | |
399 } | |
400 } | |
401 } | |
402 | |
403 // Must force the bias of the passed object to be forcibly revoked | |
404 // as well to ensure guarantees to callers | |
405 revoke_bias(o, false, true, requesting_thread); | |
406 } | |
407 | |
408 if (TraceBiasedLocking) { | |
409 tty->print_cr("* Ending bulk revocation"); | |
410 } | |
411 | |
412 BiasedLocking::Condition status_code = BiasedLocking::BIAS_REVOKED; | |
413 | |
414 if (attempt_rebias_of_object && | |
415 o->mark()->has_bias_pattern() && | |
416 klass->prototype_header()->has_bias_pattern()) { | |
417 markOop new_mark = markOopDesc::encode(requesting_thread, o->mark()->age(), | |
418 klass->prototype_header()->bias_epoch()); | |
419 o->set_mark(new_mark); | |
420 status_code = BiasedLocking::BIAS_REVOKED_AND_REBIASED; | |
421 if (TraceBiasedLocking) { | |
422 tty->print_cr(" Rebiased object toward thread " INTPTR_FORMAT, (intptr_t) requesting_thread); | |
423 } | |
424 } | |
425 | |
426 assert(!o->mark()->has_bias_pattern() || | |
427 (attempt_rebias_of_object && (o->mark()->biased_locker() == requesting_thread)), | |
428 "bug in bulk bias revocation"); | |
429 | |
430 return status_code; | |
431 } | |
432 | |
433 | |
434 static void clean_up_cached_monitor_info() { | |
435 // Walk the thread list clearing out the cached monitors | |
436 for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { | |
437 thr->set_cached_monitor_info(NULL); | |
438 } | |
439 } | |
440 | |
441 | |
442 class VM_RevokeBias : public VM_Operation { | |
443 protected: | |
444 Handle* _obj; | |
445 GrowableArray<Handle>* _objs; | |
446 JavaThread* _requesting_thread; | |
447 BiasedLocking::Condition _status_code; | |
448 | |
449 public: | |
450 VM_RevokeBias(Handle* obj, JavaThread* requesting_thread) | |
451 : _obj(obj) | |
452 , _objs(NULL) | |
453 , _requesting_thread(requesting_thread) | |
454 , _status_code(BiasedLocking::NOT_BIASED) {} | |
455 | |
456 VM_RevokeBias(GrowableArray<Handle>* objs, JavaThread* requesting_thread) | |
457 : _obj(NULL) | |
458 , _objs(objs) | |
459 , _requesting_thread(requesting_thread) | |
460 , _status_code(BiasedLocking::NOT_BIASED) {} | |
461 | |
462 virtual VMOp_Type type() const { return VMOp_RevokeBias; } | |
463 | |
464 virtual bool doit_prologue() { | |
465 // Verify that there is actual work to do since the callers just | |
466 // give us locked object(s). If we don't find any biased objects | |
467 // there is nothing to do and we avoid a safepoint. | |
468 if (_obj != NULL) { | |
469 markOop mark = (*_obj)()->mark(); | |
470 if (mark->has_bias_pattern()) { | |
471 return true; | |
472 } | |
473 } else { | |
474 for ( int i = 0 ; i < _objs->length(); i++ ) { | |
475 markOop mark = (_objs->at(i))()->mark(); | |
476 if (mark->has_bias_pattern()) { | |
477 return true; | |
478 } | |
479 } | |
480 } | |
481 return false; | |
482 } | |
483 | |
484 virtual void doit() { | |
485 if (_obj != NULL) { | |
486 if (TraceBiasedLocking) { | |
487 tty->print_cr("Revoking bias with potentially per-thread safepoint:"); | |
488 } | |
489 _status_code = revoke_bias((*_obj)(), false, false, _requesting_thread); | |
490 clean_up_cached_monitor_info(); | |
491 return; | |
492 } else { | |
493 if (TraceBiasedLocking) { | |
494 tty->print_cr("Revoking bias with global safepoint:"); | |
495 } | |
496 BiasedLocking::revoke_at_safepoint(_objs); | |
497 } | |
498 } | |
499 | |
500 BiasedLocking::Condition status_code() const { | |
501 return _status_code; | |
502 } | |
503 }; | |
504 | |
505 | |
506 class VM_BulkRevokeBias : public VM_RevokeBias { | |
507 private: | |
508 bool _bulk_rebias; | |
509 bool _attempt_rebias_of_object; | |
510 | |
511 public: | |
512 VM_BulkRevokeBias(Handle* obj, JavaThread* requesting_thread, | |
513 bool bulk_rebias, | |
514 bool attempt_rebias_of_object) | |
515 : VM_RevokeBias(obj, requesting_thread) | |
516 , _bulk_rebias(bulk_rebias) | |
517 , _attempt_rebias_of_object(attempt_rebias_of_object) {} | |
518 | |
519 virtual VMOp_Type type() const { return VMOp_BulkRevokeBias; } | |
520 virtual bool doit_prologue() { return true; } | |
521 | |
522 virtual void doit() { | |
523 _status_code = bulk_revoke_or_rebias_at_safepoint((*_obj)(), _bulk_rebias, _attempt_rebias_of_object, _requesting_thread); | |
524 clean_up_cached_monitor_info(); | |
525 } | |
526 }; | |
527 | |
528 | |
529 BiasedLocking::Condition BiasedLocking::revoke_and_rebias(Handle obj, bool attempt_rebias, TRAPS) { | |
530 assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint"); | |
531 | |
532 // We can revoke the biases of anonymously-biased objects | |
533 // efficiently enough that we should not cause these revocations to | |
534 // update the heuristics because doing so may cause unwanted bulk | |
535 // revocations (which are expensive) to occur. | |
536 markOop mark = obj->mark(); | |
537 if (mark->is_biased_anonymously() && !attempt_rebias) { | |
538 // We are probably trying to revoke the bias of this object due to | |
539 // an identity hash code computation. Try to revoke the bias | |
540 // without a safepoint. This is possible if we can successfully | |
541 // compare-and-exchange an unbiased header into the mark word of | |
542 // the object, meaning that no other thread has raced to acquire | |
543 // the bias of the object. | |
544 markOop biased_value = mark; | |
545 markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age()); | |
546 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark); | |
547 if (res_mark == biased_value) { | |
548 return BIAS_REVOKED; | |
549 } | |
550 } else if (mark->has_bias_pattern()) { | |
6983 | 551 Klass* k = obj->klass(); |
0 | 552 markOop prototype_header = k->prototype_header(); |
553 if (!prototype_header->has_bias_pattern()) { | |
554 // This object has a stale bias from before the bulk revocation | |
555 // for this data type occurred. It's pointless to update the | |
556 // heuristics at this point so simply update the header with a | |
557 // CAS. If we fail this race, the object's bias has been revoked | |
558 // by another thread so we simply return and let the caller deal | |
559 // with it. | |
560 markOop biased_value = mark; | |
561 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(prototype_header, obj->mark_addr(), mark); | |
562 assert(!(*(obj->mark_addr()))->has_bias_pattern(), "even if we raced, should still be revoked"); | |
563 return BIAS_REVOKED; | |
564 } else if (prototype_header->bias_epoch() != mark->bias_epoch()) { | |
565 // The epoch of this biasing has expired indicating that the | |
566 // object is effectively unbiased. Depending on whether we need | |
567 // to rebias or revoke the bias of this object we can do it | |
568 // efficiently enough with a CAS that we shouldn't update the | |
569 // heuristics. This is normally done in the assembly code but we | |
570 // can reach this point due to various points in the runtime | |
571 // needing to revoke biases. | |
572 if (attempt_rebias) { | |
573 assert(THREAD->is_Java_thread(), ""); | |
574 markOop biased_value = mark; | |
575 markOop rebiased_prototype = markOopDesc::encode((JavaThread*) THREAD, mark->age(), prototype_header->bias_epoch()); | |
576 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(rebiased_prototype, obj->mark_addr(), mark); | |
577 if (res_mark == biased_value) { | |
578 return BIAS_REVOKED_AND_REBIASED; | |
579 } | |
580 } else { | |
581 markOop biased_value = mark; | |
582 markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age()); | |
583 markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark); | |
584 if (res_mark == biased_value) { | |
585 return BIAS_REVOKED; | |
586 } | |
587 } | |
588 } | |
589 } | |
590 | |
591 HeuristicsResult heuristics = update_heuristics(obj(), attempt_rebias); | |
592 if (heuristics == HR_NOT_BIASED) { | |
593 return NOT_BIASED; | |
594 } else if (heuristics == HR_SINGLE_REVOKE) { | |
6983 | 595 Klass *k = obj->klass(); |
447
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596 markOop prototype_header = k->prototype_header(); |
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597 if (mark->biased_locker() == THREAD && |
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598 prototype_header->bias_epoch() == mark->bias_epoch()) { |
0 | 599 // A thread is trying to revoke the bias of an object biased |
600 // toward it, again likely due to an identity hash code | |
601 // computation. We can again avoid a safepoint in this case | |
602 // since we are only going to walk our own stack. There are no | |
603 // races with revocations occurring in other threads because we | |
604 // reach no safepoints in the revocation path. | |
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605 // Also check the epoch because even if threads match, another thread |
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606 // can come in with a CAS to steal the bias of an object that has a |
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607 // stale epoch. |
0 | 608 ResourceMark rm; |
609 if (TraceBiasedLocking) { | |
610 tty->print_cr("Revoking bias by walking my own stack:"); | |
611 } | |
612 BiasedLocking::Condition cond = revoke_bias(obj(), false, false, (JavaThread*) THREAD); | |
613 ((JavaThread*) THREAD)->set_cached_monitor_info(NULL); | |
614 assert(cond == BIAS_REVOKED, "why not?"); | |
615 return cond; | |
616 } else { | |
617 VM_RevokeBias revoke(&obj, (JavaThread*) THREAD); | |
618 VMThread::execute(&revoke); | |
619 return revoke.status_code(); | |
620 } | |
621 } | |
622 | |
623 assert((heuristics == HR_BULK_REVOKE) || | |
624 (heuristics == HR_BULK_REBIAS), "?"); | |
625 VM_BulkRevokeBias bulk_revoke(&obj, (JavaThread*) THREAD, | |
626 (heuristics == HR_BULK_REBIAS), | |
627 attempt_rebias); | |
628 VMThread::execute(&bulk_revoke); | |
629 return bulk_revoke.status_code(); | |
630 } | |
631 | |
632 | |
633 void BiasedLocking::revoke(GrowableArray<Handle>* objs) { | |
634 assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint"); | |
635 if (objs->length() == 0) { | |
636 return; | |
637 } | |
638 VM_RevokeBias revoke(objs, JavaThread::current()); | |
639 VMThread::execute(&revoke); | |
640 } | |
641 | |
642 | |
643 void BiasedLocking::revoke_at_safepoint(Handle h_obj) { | |
644 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); | |
645 oop obj = h_obj(); | |
646 HeuristicsResult heuristics = update_heuristics(obj, false); | |
647 if (heuristics == HR_SINGLE_REVOKE) { | |
648 revoke_bias(obj, false, false, NULL); | |
649 } else if ((heuristics == HR_BULK_REBIAS) || | |
650 (heuristics == HR_BULK_REVOKE)) { | |
651 bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL); | |
652 } | |
653 clean_up_cached_monitor_info(); | |
654 } | |
655 | |
656 | |
657 void BiasedLocking::revoke_at_safepoint(GrowableArray<Handle>* objs) { | |
658 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); | |
659 int len = objs->length(); | |
660 for (int i = 0; i < len; i++) { | |
661 oop obj = (objs->at(i))(); | |
662 HeuristicsResult heuristics = update_heuristics(obj, false); | |
663 if (heuristics == HR_SINGLE_REVOKE) { | |
664 revoke_bias(obj, false, false, NULL); | |
665 } else if ((heuristics == HR_BULK_REBIAS) || | |
666 (heuristics == HR_BULK_REVOKE)) { | |
667 bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL); | |
668 } | |
669 } | |
670 clean_up_cached_monitor_info(); | |
671 } | |
672 | |
673 | |
674 void BiasedLocking::preserve_marks() { | |
675 if (!UseBiasedLocking) | |
676 return; | |
677 | |
678 assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); | |
679 | |
680 assert(_preserved_oop_stack == NULL, "double initialization"); | |
681 assert(_preserved_mark_stack == NULL, "double initialization"); | |
682 | |
683 // In order to reduce the number of mark words preserved during GC | |
684 // due to the presence of biased locking, we reinitialize most mark | |
685 // words to the class's prototype during GC -- even those which have | |
686 // a currently valid bias owner. One important situation where we | |
687 // must not clobber a bias is when a biased object is currently | |
688 // locked. To handle this case we iterate over the currently-locked | |
689 // monitors in a prepass and, if they are biased, preserve their | |
690 // mark words here. This should be a relatively small set of objects | |
691 // especially compared to the number of objects in the heap. | |
6197 | 692 _preserved_mark_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<markOop>(10, true); |
693 _preserved_oop_stack = new (ResourceObj::C_HEAP, mtInternal) GrowableArray<Handle>(10, true); | |
0 | 694 |
695 ResourceMark rm; | |
696 Thread* cur = Thread::current(); | |
697 for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) { | |
698 if (thread->has_last_Java_frame()) { | |
699 RegisterMap rm(thread); | |
700 for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) { | |
701 GrowableArray<MonitorInfo*> *monitors = vf->monitors(); | |
702 if (monitors != NULL) { | |
703 int len = monitors->length(); | |
704 // Walk monitors youngest to oldest | |
705 for (int i = len - 1; i >= 0; i--) { | |
706 MonitorInfo* mon_info = monitors->at(i); | |
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707 if (mon_info->owner_is_scalar_replaced()) continue; |
0 | 708 oop owner = mon_info->owner(); |
709 if (owner != NULL) { | |
710 markOop mark = owner->mark(); | |
711 if (mark->has_bias_pattern()) { | |
712 _preserved_oop_stack->push(Handle(cur, owner)); | |
713 _preserved_mark_stack->push(mark); | |
714 } | |
715 } | |
716 } | |
717 } | |
718 } | |
719 } | |
720 } | |
721 } | |
722 | |
723 | |
724 void BiasedLocking::restore_marks() { | |
725 if (!UseBiasedLocking) | |
726 return; | |
727 | |
728 assert(_preserved_oop_stack != NULL, "double free"); | |
729 assert(_preserved_mark_stack != NULL, "double free"); | |
730 | |
731 int len = _preserved_oop_stack->length(); | |
732 for (int i = 0; i < len; i++) { | |
733 Handle owner = _preserved_oop_stack->at(i); | |
734 markOop mark = _preserved_mark_stack->at(i); | |
735 owner->set_mark(mark); | |
736 } | |
737 | |
738 delete _preserved_oop_stack; | |
739 _preserved_oop_stack = NULL; | |
740 delete _preserved_mark_stack; | |
741 _preserved_mark_stack = NULL; | |
742 } | |
743 | |
744 | |
745 int* BiasedLocking::total_entry_count_addr() { return _counters.total_entry_count_addr(); } | |
746 int* BiasedLocking::biased_lock_entry_count_addr() { return _counters.biased_lock_entry_count_addr(); } | |
747 int* BiasedLocking::anonymously_biased_lock_entry_count_addr() { return _counters.anonymously_biased_lock_entry_count_addr(); } | |
748 int* BiasedLocking::rebiased_lock_entry_count_addr() { return _counters.rebiased_lock_entry_count_addr(); } | |
749 int* BiasedLocking::revoked_lock_entry_count_addr() { return _counters.revoked_lock_entry_count_addr(); } | |
750 int* BiasedLocking::fast_path_entry_count_addr() { return _counters.fast_path_entry_count_addr(); } | |
751 int* BiasedLocking::slow_path_entry_count_addr() { return _counters.slow_path_entry_count_addr(); } | |
752 | |
753 | |
754 // BiasedLockingCounters | |
755 | |
756 int BiasedLockingCounters::slow_path_entry_count() { | |
757 if (_slow_path_entry_count != 0) { | |
758 return _slow_path_entry_count; | |
759 } | |
760 int sum = _biased_lock_entry_count + _anonymously_biased_lock_entry_count + | |
761 _rebiased_lock_entry_count + _revoked_lock_entry_count + | |
762 _fast_path_entry_count; | |
763 | |
764 return _total_entry_count - sum; | |
765 } | |
766 | |
767 void BiasedLockingCounters::print_on(outputStream* st) { | |
768 tty->print_cr("# total entries: %d", _total_entry_count); | |
769 tty->print_cr("# biased lock entries: %d", _biased_lock_entry_count); | |
770 tty->print_cr("# anonymously biased lock entries: %d", _anonymously_biased_lock_entry_count); | |
771 tty->print_cr("# rebiased lock entries: %d", _rebiased_lock_entry_count); | |
772 tty->print_cr("# revoked lock entries: %d", _revoked_lock_entry_count); | |
773 tty->print_cr("# fast path lock entries: %d", _fast_path_entry_count); | |
774 tty->print_cr("# slow path lock entries: %d", slow_path_entry_count()); | |
775 } |