truffle: src/share/vm/runtime/biasedLocking.cpp comparison

comparison src/share/vm/runtime/biasedLocking.cpp @ 0:a61af66fc99e jdk7-b24

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author	duke
date	Sat, 01 Dec 2007 00:00:00 +0000
parents
children	7ee622712fcf

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--1:000000000000
+:a61af66fc99e
+/*
+* 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<Handle>*  _preserved_oop_stack  = NULL;
+static GrowableArray<markOop>* _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<MonitorInfo*>* get_or_compute_monitor_info(JavaThread* thread) {
+GrowableArray<MonitorInfo*>* info = thread->cached_monitor_info();
+if (info != NULL) {
+return info;
+}
+info = new GrowableArray<MonitorInfo*>();
+// 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<MonitorInfo*> *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<MonitorInfo*>* 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<MonitorInfo*>* 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<MonitorInfo*>* 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<Handle>* _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<Handle>* 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<Handle>* 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<Handle>* 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<markOop>(10, true);
+_preserved_oop_stack = new (ResourceObj::C_HEAP) GrowableArray<Handle>(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<MonitorInfo*> *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());
+}

Mercurial > hg > truffle

comparison src/share/vm/runtime/biasedLocking.cpp @ 0:a61af66fc99e jdk7-b24