diff -r fd16c54261b3 -r 489c9b5090e2 hotspot/src/share/vm/runtime/biasedLocking.cpp --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/hotspot/src/share/vm/runtime/biasedLocking.cpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,752 @@ + +/* + * Copyright 2005-2007 Sun Microsystems, Inc. All Rights Reserved. + * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. + * + * This code is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 only, as + * published by the Free Software Foundation. + * + * This code is distributed in the hope that it will be useful, but WITHOUT + * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or + * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License + * version 2 for more details (a copy is included in the LICENSE file that + * accompanied this code). + * + * You should have received a copy of the GNU General Public License version + * 2 along with this work; if not, write to the Free Software Foundation, + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. + * + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +# include "incls/_precompiled.incl" +# include "incls/_biasedLocking.cpp.incl" + +static bool _biased_locking_enabled = false; +BiasedLockingCounters BiasedLocking::_counters; + +static GrowableArray* _preserved_oop_stack = NULL; +static GrowableArray* _preserved_mark_stack = NULL; + +static void enable_biased_locking(klassOop k) { + Klass::cast(k)->set_prototype_header(markOopDesc::biased_locking_prototype()); +} + +class VM_EnableBiasedLocking: public VM_Operation { + public: + VM_EnableBiasedLocking() {} + VMOp_Type type() const { return VMOp_EnableBiasedLocking; } + void doit() { + // Iterate the system dictionary enabling biased locking for all + // currently loaded classes + SystemDictionary::classes_do(enable_biased_locking); + // Indicate that future instances should enable it as well + _biased_locking_enabled = true; + + if (TraceBiasedLocking) { + tty->print_cr("Biased locking enabled"); + } + } + + bool allow_nested_vm_operations() const { return false; } +}; + + +// One-shot PeriodicTask subclass for enabling biased locking +class EnableBiasedLockingTask : public PeriodicTask { + public: + EnableBiasedLockingTask(size_t interval_time) : PeriodicTask(interval_time) {} + + virtual void task() { + VM_EnableBiasedLocking op; + VMThread::execute(&op); + + // Reclaim our storage and disenroll ourself + delete this; + } +}; + + +void BiasedLocking::init() { + // If biased locking is enabled, schedule a task to fire a few + // seconds into the run which turns on biased locking for all + // currently loaded classes as well as future ones. This is a + // workaround for startup time regressions due to a large number of + // safepoints being taken during VM startup for bias revocation. + // Ideally we would have a lower cost for individual bias revocation + // and not need a mechanism like this. + if (UseBiasedLocking) { + if (BiasedLockingStartupDelay > 0) { + EnableBiasedLockingTask* task = new EnableBiasedLockingTask(BiasedLockingStartupDelay); + task->enroll(); + } else { + VM_EnableBiasedLocking op; + VMThread::execute(&op); + } + } +} + + +bool BiasedLocking::enabled() { + return _biased_locking_enabled; +} + +// Returns MonitorInfos for all objects locked on this thread in youngest to oldest order +static GrowableArray* get_or_compute_monitor_info(JavaThread* thread) { + GrowableArray* info = thread->cached_monitor_info(); + if (info != NULL) { + return info; + } + + info = new GrowableArray(); + + // It's possible for the thread to not have any Java frames on it, + // i.e., if it's the main thread and it's already returned from main() + if (thread->has_last_Java_frame()) { + RegisterMap rm(thread); + for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) { + GrowableArray *monitors = vf->monitors(); + if (monitors != NULL) { + int len = monitors->length(); + // Walk monitors youngest to oldest + for (int i = len - 1; i >= 0; i--) { + MonitorInfo* mon_info = monitors->at(i); + oop owner = mon_info->owner(); + if (owner != NULL) { + info->append(mon_info); + } + } + } + } + } + + thread->set_cached_monitor_info(info); + return info; +} + + +static BiasedLocking::Condition revoke_bias(oop obj, bool allow_rebias, bool is_bulk, JavaThread* requesting_thread) { + markOop mark = obj->mark(); + if (!mark->has_bias_pattern()) { + if (TraceBiasedLocking) { + ResourceMark rm; + tty->print_cr(" (Skipping revocation of object of type %s because it's no longer biased)", + Klass::cast(obj->klass())->external_name()); + } + return BiasedLocking::NOT_BIASED; + } + + int age = mark->age(); + markOop biased_prototype = markOopDesc::biased_locking_prototype()->set_age(age); + markOop unbiased_prototype = markOopDesc::prototype()->set_age(age); + + if (TraceBiasedLocking && (Verbose || !is_bulk)) { + ResourceMark rm; + 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, + (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); + } + + JavaThread* biased_thread = mark->biased_locker(); + if (biased_thread == NULL) { + // Object is anonymously biased. We can get here if, for + // example, we revoke the bias due to an identity hash code + // being computed for an object. + if (!allow_rebias) { + obj->set_mark(unbiased_prototype); + } + if (TraceBiasedLocking && (Verbose || !is_bulk)) { + tty->print_cr(" Revoked bias of anonymously-biased object"); + } + return BiasedLocking::BIAS_REVOKED; + } + + // Handle case where the thread toward which the object was biased has exited + bool thread_is_alive = false; + if (requesting_thread == biased_thread) { + thread_is_alive = true; + } else { + for (JavaThread* cur_thread = Threads::first(); cur_thread != NULL; cur_thread = cur_thread->next()) { + if (cur_thread == biased_thread) { + thread_is_alive = true; + break; + } + } + } + if (!thread_is_alive) { + if (allow_rebias) { + obj->set_mark(biased_prototype); + } else { + obj->set_mark(unbiased_prototype); + } + if (TraceBiasedLocking && (Verbose || !is_bulk)) { + tty->print_cr(" Revoked bias of object biased toward dead thread"); + } + return BiasedLocking::BIAS_REVOKED; + } + + // Thread owning bias is alive. + // Check to see whether it currently owns the lock and, if so, + // write down the needed displaced headers to the thread's stack. + // Otherwise, restore the object's header either to the unlocked + // or unbiased state. + GrowableArray* cached_monitor_info = get_or_compute_monitor_info(biased_thread); + BasicLock* highest_lock = NULL; + for (int i = 0; i < cached_monitor_info->length(); i++) { + MonitorInfo* mon_info = cached_monitor_info->at(i); + if (mon_info->owner() == obj) { + if (TraceBiasedLocking && Verbose) { + tty->print_cr(" mon_info->owner (" PTR_FORMAT ") == obj (" PTR_FORMAT ")", + (intptr_t) mon_info->owner(), + (intptr_t) obj); + } + // Assume recursive case and fix up highest lock later + markOop mark = markOopDesc::encode((BasicLock*) NULL); + highest_lock = mon_info->lock(); + highest_lock->set_displaced_header(mark); + } else { + if (TraceBiasedLocking && Verbose) { + tty->print_cr(" mon_info->owner (" PTR_FORMAT ") != obj (" PTR_FORMAT ")", + (intptr_t) mon_info->owner(), + (intptr_t) obj); + } + } + } + if (highest_lock != NULL) { + // Fix up highest lock to contain displaced header and point + // object at it + highest_lock->set_displaced_header(unbiased_prototype); + // Reset object header to point to displaced mark + obj->set_mark(markOopDesc::encode(highest_lock)); + assert(!obj->mark()->has_bias_pattern(), "illegal mark state: stack lock used bias bit"); + if (TraceBiasedLocking && (Verbose || !is_bulk)) { + tty->print_cr(" Revoked bias of currently-locked object"); + } + } else { + if (TraceBiasedLocking && (Verbose || !is_bulk)) { + tty->print_cr(" Revoked bias of currently-unlocked object"); + } + if (allow_rebias) { + obj->set_mark(biased_prototype); + } else { + // Store the unlocked value into the object's header. + obj->set_mark(unbiased_prototype); + } + } + + return BiasedLocking::BIAS_REVOKED; +} + + +enum HeuristicsResult { + HR_NOT_BIASED = 1, + HR_SINGLE_REVOKE = 2, + HR_BULK_REBIAS = 3, + HR_BULK_REVOKE = 4 +}; + + +static HeuristicsResult update_heuristics(oop o, bool allow_rebias) { + markOop mark = o->mark(); + if (!mark->has_bias_pattern()) { + return HR_NOT_BIASED; + } + + // Heuristics to attempt to throttle the number of revocations. + // Stages: + // 1. Revoke the biases of all objects in the heap of this type, + // but allow rebiasing of those objects if unlocked. + // 2. Revoke the biases of all objects in the heap of this type + // and don't allow rebiasing of these objects. Disable + // allocation of objects of that type with the bias bit set. + Klass* k = o->blueprint(); + jlong cur_time = os::javaTimeMillis(); + jlong last_bulk_revocation_time = k->last_biased_lock_bulk_revocation_time(); + int revocation_count = k->biased_lock_revocation_count(); + if ((revocation_count >= BiasedLockingBulkRebiasThreshold) && + (revocation_count < BiasedLockingBulkRevokeThreshold) && + (last_bulk_revocation_time != 0) && + (cur_time - last_bulk_revocation_time >= BiasedLockingDecayTime)) { + // This is the first revocation we've seen in a while of an + // object of this type since the last time we performed a bulk + // rebiasing operation. The application is allocating objects in + // bulk which are biased toward a thread and then handing them + // off to another thread. We can cope with this allocation + // pattern via the bulk rebiasing mechanism so we reset the + // klass's revocation count rather than allow it to increase + // monotonically. If we see the need to perform another bulk + // rebias operation later, we will, and if subsequently we see + // many more revocation operations in a short period of time we + // will completely disable biasing for this type. + k->set_biased_lock_revocation_count(0); + revocation_count = 0; + } + + // Make revocation count saturate just beyond BiasedLockingBulkRevokeThreshold + if (revocation_count <= BiasedLockingBulkRevokeThreshold) { + revocation_count = k->atomic_incr_biased_lock_revocation_count(); + } + + if (revocation_count == BiasedLockingBulkRevokeThreshold) { + return HR_BULK_REVOKE; + } + + if (revocation_count == BiasedLockingBulkRebiasThreshold) { + return HR_BULK_REBIAS; + } + + return HR_SINGLE_REVOKE; +} + + +static BiasedLocking::Condition bulk_revoke_or_rebias_at_safepoint(oop o, + bool bulk_rebias, + bool attempt_rebias_of_object, + JavaThread* requesting_thread) { + assert(SafepointSynchronize::is_at_safepoint(), "must be done at safepoint"); + + if (TraceBiasedLocking) { + tty->print_cr("* Beginning bulk revocation (kind == %s) because of object " + INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s", + (bulk_rebias ? "rebias" : "revoke"), + (intptr_t) o, (intptr_t) o->mark(), Klass::cast(o->klass())->external_name()); + } + + jlong cur_time = os::javaTimeMillis(); + o->blueprint()->set_last_biased_lock_bulk_revocation_time(cur_time); + + + klassOop k_o = o->klass(); + Klass* klass = Klass::cast(k_o); + + if (bulk_rebias) { + // Use the epoch in the klass of the object to implicitly revoke + // all biases of objects of this data type and force them to be + // reacquired. However, we also need to walk the stacks of all + // threads and update the headers of lightweight locked objects + // with biases to have the current epoch. + + // If the prototype header doesn't have the bias pattern, don't + // try to update the epoch -- assume another VM operation came in + // and reset the header to the unbiased state, which will + // implicitly cause all existing biases to be revoked + if (klass->prototype_header()->has_bias_pattern()) { + int prev_epoch = klass->prototype_header()->bias_epoch(); + klass->set_prototype_header(klass->prototype_header()->incr_bias_epoch()); + int cur_epoch = klass->prototype_header()->bias_epoch(); + + // Now walk all threads' stacks and adjust epochs of any biased + // and locked objects of this data type we encounter + for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { + GrowableArray* cached_monitor_info = get_or_compute_monitor_info(thr); + for (int i = 0; i < cached_monitor_info->length(); i++) { + MonitorInfo* mon_info = cached_monitor_info->at(i); + oop owner = mon_info->owner(); + markOop mark = owner->mark(); + if ((owner->klass() == k_o) && mark->has_bias_pattern()) { + // We might have encountered this object already in the case of recursive locking + assert(mark->bias_epoch() == prev_epoch || mark->bias_epoch() == cur_epoch, "error in bias epoch adjustment"); + owner->set_mark(mark->set_bias_epoch(cur_epoch)); + } + } + } + } + + // At this point we're done. All we have to do is potentially + // adjust the header of the given object to revoke its bias. + revoke_bias(o, attempt_rebias_of_object && klass->prototype_header()->has_bias_pattern(), true, requesting_thread); + } else { + if (TraceBiasedLocking) { + ResourceMark rm; + tty->print_cr("* Disabling biased locking for type %s", klass->external_name()); + } + + // Disable biased locking for this data type. Not only will this + // cause future instances to not be biased, but existing biased + // instances will notice that this implicitly caused their biases + // to be revoked. + klass->set_prototype_header(markOopDesc::prototype()); + + // Now walk all threads' stacks and forcibly revoke the biases of + // any locked and biased objects of this data type we encounter. + for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { + GrowableArray* cached_monitor_info = get_or_compute_monitor_info(thr); + for (int i = 0; i < cached_monitor_info->length(); i++) { + MonitorInfo* mon_info = cached_monitor_info->at(i); + oop owner = mon_info->owner(); + markOop mark = owner->mark(); + if ((owner->klass() == k_o) && mark->has_bias_pattern()) { + revoke_bias(owner, false, true, requesting_thread); + } + } + } + + // Must force the bias of the passed object to be forcibly revoked + // as well to ensure guarantees to callers + revoke_bias(o, false, true, requesting_thread); + } + + if (TraceBiasedLocking) { + tty->print_cr("* Ending bulk revocation"); + } + + BiasedLocking::Condition status_code = BiasedLocking::BIAS_REVOKED; + + if (attempt_rebias_of_object && + o->mark()->has_bias_pattern() && + klass->prototype_header()->has_bias_pattern()) { + markOop new_mark = markOopDesc::encode(requesting_thread, o->mark()->age(), + klass->prototype_header()->bias_epoch()); + o->set_mark(new_mark); + status_code = BiasedLocking::BIAS_REVOKED_AND_REBIASED; + if (TraceBiasedLocking) { + tty->print_cr(" Rebiased object toward thread " INTPTR_FORMAT, (intptr_t) requesting_thread); + } + } + + assert(!o->mark()->has_bias_pattern() || + (attempt_rebias_of_object && (o->mark()->biased_locker() == requesting_thread)), + "bug in bulk bias revocation"); + + return status_code; +} + + +static void clean_up_cached_monitor_info() { + // Walk the thread list clearing out the cached monitors + for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) { + thr->set_cached_monitor_info(NULL); + } +} + + +class VM_RevokeBias : public VM_Operation { +protected: + Handle* _obj; + GrowableArray* _objs; + JavaThread* _requesting_thread; + BiasedLocking::Condition _status_code; + +public: + VM_RevokeBias(Handle* obj, JavaThread* requesting_thread) + : _obj(obj) + , _objs(NULL) + , _requesting_thread(requesting_thread) + , _status_code(BiasedLocking::NOT_BIASED) {} + + VM_RevokeBias(GrowableArray* objs, JavaThread* requesting_thread) + : _obj(NULL) + , _objs(objs) + , _requesting_thread(requesting_thread) + , _status_code(BiasedLocking::NOT_BIASED) {} + + virtual VMOp_Type type() const { return VMOp_RevokeBias; } + + virtual bool doit_prologue() { + // Verify that there is actual work to do since the callers just + // give us locked object(s). If we don't find any biased objects + // there is nothing to do and we avoid a safepoint. + if (_obj != NULL) { + markOop mark = (*_obj)()->mark(); + if (mark->has_bias_pattern()) { + return true; + } + } else { + for ( int i = 0 ; i < _objs->length(); i++ ) { + markOop mark = (_objs->at(i))()->mark(); + if (mark->has_bias_pattern()) { + return true; + } + } + } + return false; + } + + virtual void doit() { + if (_obj != NULL) { + if (TraceBiasedLocking) { + tty->print_cr("Revoking bias with potentially per-thread safepoint:"); + } + _status_code = revoke_bias((*_obj)(), false, false, _requesting_thread); + clean_up_cached_monitor_info(); + return; + } else { + if (TraceBiasedLocking) { + tty->print_cr("Revoking bias with global safepoint:"); + } + BiasedLocking::revoke_at_safepoint(_objs); + } + } + + BiasedLocking::Condition status_code() const { + return _status_code; + } +}; + + +class VM_BulkRevokeBias : public VM_RevokeBias { +private: + bool _bulk_rebias; + bool _attempt_rebias_of_object; + +public: + VM_BulkRevokeBias(Handle* obj, JavaThread* requesting_thread, + bool bulk_rebias, + bool attempt_rebias_of_object) + : VM_RevokeBias(obj, requesting_thread) + , _bulk_rebias(bulk_rebias) + , _attempt_rebias_of_object(attempt_rebias_of_object) {} + + virtual VMOp_Type type() const { return VMOp_BulkRevokeBias; } + virtual bool doit_prologue() { return true; } + + virtual void doit() { + _status_code = bulk_revoke_or_rebias_at_safepoint((*_obj)(), _bulk_rebias, _attempt_rebias_of_object, _requesting_thread); + clean_up_cached_monitor_info(); + } +}; + + +BiasedLocking::Condition BiasedLocking::revoke_and_rebias(Handle obj, bool attempt_rebias, TRAPS) { + assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint"); + + // We can revoke the biases of anonymously-biased objects + // efficiently enough that we should not cause these revocations to + // update the heuristics because doing so may cause unwanted bulk + // revocations (which are expensive) to occur. + markOop mark = obj->mark(); + if (mark->is_biased_anonymously() && !attempt_rebias) { + // We are probably trying to revoke the bias of this object due to + // an identity hash code computation. Try to revoke the bias + // without a safepoint. This is possible if we can successfully + // compare-and-exchange an unbiased header into the mark word of + // the object, meaning that no other thread has raced to acquire + // the bias of the object. + markOop biased_value = mark; + markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age()); + markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark); + if (res_mark == biased_value) { + return BIAS_REVOKED; + } + } else if (mark->has_bias_pattern()) { + Klass* k = Klass::cast(obj->klass()); + markOop prototype_header = k->prototype_header(); + if (!prototype_header->has_bias_pattern()) { + // This object has a stale bias from before the bulk revocation + // for this data type occurred. It's pointless to update the + // heuristics at this point so simply update the header with a + // CAS. If we fail this race, the object's bias has been revoked + // by another thread so we simply return and let the caller deal + // with it. + markOop biased_value = mark; + markOop res_mark = (markOop) Atomic::cmpxchg_ptr(prototype_header, obj->mark_addr(), mark); + assert(!(*(obj->mark_addr()))->has_bias_pattern(), "even if we raced, should still be revoked"); + return BIAS_REVOKED; + } else if (prototype_header->bias_epoch() != mark->bias_epoch()) { + // The epoch of this biasing has expired indicating that the + // object is effectively unbiased. Depending on whether we need + // to rebias or revoke the bias of this object we can do it + // efficiently enough with a CAS that we shouldn't update the + // heuristics. This is normally done in the assembly code but we + // can reach this point due to various points in the runtime + // needing to revoke biases. + if (attempt_rebias) { + assert(THREAD->is_Java_thread(), ""); + markOop biased_value = mark; + markOop rebiased_prototype = markOopDesc::encode((JavaThread*) THREAD, mark->age(), prototype_header->bias_epoch()); + markOop res_mark = (markOop) Atomic::cmpxchg_ptr(rebiased_prototype, obj->mark_addr(), mark); + if (res_mark == biased_value) { + return BIAS_REVOKED_AND_REBIASED; + } + } else { + markOop biased_value = mark; + markOop unbiased_prototype = markOopDesc::prototype()->set_age(mark->age()); + markOop res_mark = (markOop) Atomic::cmpxchg_ptr(unbiased_prototype, obj->mark_addr(), mark); + if (res_mark == biased_value) { + return BIAS_REVOKED; + } + } + } + } + + HeuristicsResult heuristics = update_heuristics(obj(), attempt_rebias); + if (heuristics == HR_NOT_BIASED) { + return NOT_BIASED; + } else if (heuristics == HR_SINGLE_REVOKE) { + if (mark->biased_locker() == THREAD) { + // A thread is trying to revoke the bias of an object biased + // toward it, again likely due to an identity hash code + // computation. We can again avoid a safepoint in this case + // since we are only going to walk our own stack. There are no + // races with revocations occurring in other threads because we + // reach no safepoints in the revocation path. + ResourceMark rm; + if (TraceBiasedLocking) { + tty->print_cr("Revoking bias by walking my own stack:"); + } + BiasedLocking::Condition cond = revoke_bias(obj(), false, false, (JavaThread*) THREAD); + ((JavaThread*) THREAD)->set_cached_monitor_info(NULL); + assert(cond == BIAS_REVOKED, "why not?"); + return cond; + } else { + VM_RevokeBias revoke(&obj, (JavaThread*) THREAD); + VMThread::execute(&revoke); + return revoke.status_code(); + } + } + + assert((heuristics == HR_BULK_REVOKE) || + (heuristics == HR_BULK_REBIAS), "?"); + VM_BulkRevokeBias bulk_revoke(&obj, (JavaThread*) THREAD, + (heuristics == HR_BULK_REBIAS), + attempt_rebias); + VMThread::execute(&bulk_revoke); + return bulk_revoke.status_code(); +} + + +void BiasedLocking::revoke(GrowableArray* objs) { + assert(!SafepointSynchronize::is_at_safepoint(), "must not be called while at safepoint"); + if (objs->length() == 0) { + return; + } + VM_RevokeBias revoke(objs, JavaThread::current()); + VMThread::execute(&revoke); +} + + +void BiasedLocking::revoke_at_safepoint(Handle h_obj) { + assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); + oop obj = h_obj(); + HeuristicsResult heuristics = update_heuristics(obj, false); + if (heuristics == HR_SINGLE_REVOKE) { + revoke_bias(obj, false, false, NULL); + } else if ((heuristics == HR_BULK_REBIAS) || + (heuristics == HR_BULK_REVOKE)) { + bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL); + } + clean_up_cached_monitor_info(); +} + + +void BiasedLocking::revoke_at_safepoint(GrowableArray* objs) { + assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); + int len = objs->length(); + for (int i = 0; i < len; i++) { + oop obj = (objs->at(i))(); + HeuristicsResult heuristics = update_heuristics(obj, false); + if (heuristics == HR_SINGLE_REVOKE) { + revoke_bias(obj, false, false, NULL); + } else if ((heuristics == HR_BULK_REBIAS) || + (heuristics == HR_BULK_REVOKE)) { + bulk_revoke_or_rebias_at_safepoint(obj, (heuristics == HR_BULK_REBIAS), false, NULL); + } + } + clean_up_cached_monitor_info(); +} + + +void BiasedLocking::preserve_marks() { + if (!UseBiasedLocking) + return; + + assert(SafepointSynchronize::is_at_safepoint(), "must only be called while at safepoint"); + + assert(_preserved_oop_stack == NULL, "double initialization"); + assert(_preserved_mark_stack == NULL, "double initialization"); + + // In order to reduce the number of mark words preserved during GC + // due to the presence of biased locking, we reinitialize most mark + // words to the class's prototype during GC -- even those which have + // a currently valid bias owner. One important situation where we + // must not clobber a bias is when a biased object is currently + // locked. To handle this case we iterate over the currently-locked + // monitors in a prepass and, if they are biased, preserve their + // mark words here. This should be a relatively small set of objects + // especially compared to the number of objects in the heap. + _preserved_mark_stack = new (ResourceObj::C_HEAP) GrowableArray(10, true); + _preserved_oop_stack = new (ResourceObj::C_HEAP) GrowableArray(10, true); + + ResourceMark rm; + Thread* cur = Thread::current(); + for (JavaThread* thread = Threads::first(); thread != NULL; thread = thread->next()) { + if (thread->has_last_Java_frame()) { + RegisterMap rm(thread); + for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) { + GrowableArray *monitors = vf->monitors(); + if (monitors != NULL) { + int len = monitors->length(); + // Walk monitors youngest to oldest + for (int i = len - 1; i >= 0; i--) { + MonitorInfo* mon_info = monitors->at(i); + oop owner = mon_info->owner(); + if (owner != NULL) { + markOop mark = owner->mark(); + if (mark->has_bias_pattern()) { + _preserved_oop_stack->push(Handle(cur, owner)); + _preserved_mark_stack->push(mark); + } + } + } + } + } + } + } +} + + +void BiasedLocking::restore_marks() { + if (!UseBiasedLocking) + return; + + assert(_preserved_oop_stack != NULL, "double free"); + assert(_preserved_mark_stack != NULL, "double free"); + + int len = _preserved_oop_stack->length(); + for (int i = 0; i < len; i++) { + Handle owner = _preserved_oop_stack->at(i); + markOop mark = _preserved_mark_stack->at(i); + owner->set_mark(mark); + } + + delete _preserved_oop_stack; + _preserved_oop_stack = NULL; + delete _preserved_mark_stack; + _preserved_mark_stack = NULL; +} + + +int* BiasedLocking::total_entry_count_addr() { return _counters.total_entry_count_addr(); } +int* BiasedLocking::biased_lock_entry_count_addr() { return _counters.biased_lock_entry_count_addr(); } +int* BiasedLocking::anonymously_biased_lock_entry_count_addr() { return _counters.anonymously_biased_lock_entry_count_addr(); } +int* BiasedLocking::rebiased_lock_entry_count_addr() { return _counters.rebiased_lock_entry_count_addr(); } +int* BiasedLocking::revoked_lock_entry_count_addr() { return _counters.revoked_lock_entry_count_addr(); } +int* BiasedLocking::fast_path_entry_count_addr() { return _counters.fast_path_entry_count_addr(); } +int* BiasedLocking::slow_path_entry_count_addr() { return _counters.slow_path_entry_count_addr(); } + + +// BiasedLockingCounters + +int BiasedLockingCounters::slow_path_entry_count() { + if (_slow_path_entry_count != 0) { + return _slow_path_entry_count; + } + int sum = _biased_lock_entry_count + _anonymously_biased_lock_entry_count + + _rebiased_lock_entry_count + _revoked_lock_entry_count + + _fast_path_entry_count; + + return _total_entry_count - sum; +} + +void BiasedLockingCounters::print_on(outputStream* st) { + tty->print_cr("# total entries: %d", _total_entry_count); + tty->print_cr("# biased lock entries: %d", _biased_lock_entry_count); + tty->print_cr("# anonymously biased lock entries: %d", _anonymously_biased_lock_entry_count); + tty->print_cr("# rebiased lock entries: %d", _rebiased_lock_entry_count); + tty->print_cr("# revoked lock entries: %d", _revoked_lock_entry_count); + tty->print_cr("# fast path lock entries: %d", _fast_path_entry_count); + tty->print_cr("# slow path lock entries: %d", slow_path_entry_count()); +}