778 lines
30 KiB
C++
778 lines
30 KiB
C++
/*
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* Copyright (c) 2005, 2015, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#include "precompiled.hpp"
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#include "oops/klass.inline.hpp"
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#include "oops/markOop.hpp"
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#include "oops/oop.inline.hpp"
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#include "runtime/atomic.inline.hpp"
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#include "runtime/basicLock.hpp"
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#include "runtime/biasedLocking.hpp"
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#include "runtime/task.hpp"
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#include "runtime/vframe.hpp"
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#include "runtime/vmThread.hpp"
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#include "runtime/vm_operations.hpp"
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static bool _biased_locking_enabled = false;
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BiasedLockingCounters BiasedLocking::_counters;
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static GrowableArray<Handle>* _preserved_oop_stack = NULL;
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static GrowableArray<markOop>* _preserved_mark_stack = NULL;
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static void enable_biased_locking(Klass* k) {
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k->set_prototype_header(markOopDesc::biased_locking_prototype());
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}
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class VM_EnableBiasedLocking: public VM_Operation {
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private:
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bool _is_cheap_allocated;
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public:
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VM_EnableBiasedLocking(bool is_cheap_allocated) { _is_cheap_allocated = is_cheap_allocated; }
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VMOp_Type type() const { return VMOp_EnableBiasedLocking; }
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Mode evaluation_mode() const { return _is_cheap_allocated ? _async_safepoint : _safepoint; }
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bool is_cheap_allocated() const { return _is_cheap_allocated; }
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void doit() {
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// Iterate the system dictionary enabling biased locking for all
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// currently loaded classes
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SystemDictionary::classes_do(enable_biased_locking);
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// Indicate that future instances should enable it as well
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_biased_locking_enabled = true;
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if (TraceBiasedLocking) {
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tty->print_cr("Biased locking enabled");
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}
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}
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bool allow_nested_vm_operations() const { return false; }
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};
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// One-shot PeriodicTask subclass for enabling biased locking
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class EnableBiasedLockingTask : public PeriodicTask {
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public:
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EnableBiasedLockingTask(size_t interval_time) : PeriodicTask(interval_time) {}
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virtual void task() {
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// Use async VM operation to avoid blocking the Watcher thread.
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// VM Thread will free C heap storage.
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VM_EnableBiasedLocking *op = new VM_EnableBiasedLocking(true);
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VMThread::execute(op);
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// Reclaim our storage and disenroll ourself
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delete this;
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}
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};
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void BiasedLocking::init() {
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// If biased locking is enabled, schedule a task to fire a few
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// seconds into the run which turns on biased locking for all
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// currently loaded classes as well as future ones. This is a
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// workaround for startup time regressions due to a large number of
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// safepoints being taken during VM startup for bias revocation.
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// Ideally we would have a lower cost for individual bias revocation
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// and not need a mechanism like this.
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if (UseBiasedLocking) {
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if (BiasedLockingStartupDelay > 0) {
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EnableBiasedLockingTask* task = new EnableBiasedLockingTask(BiasedLockingStartupDelay);
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task->enroll();
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} else {
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VM_EnableBiasedLocking op(false);
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VMThread::execute(&op);
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}
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}
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}
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bool BiasedLocking::enabled() {
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return _biased_locking_enabled;
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}
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// Returns MonitorInfos for all objects locked on this thread in youngest to oldest order
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static GrowableArray<MonitorInfo*>* get_or_compute_monitor_info(JavaThread* thread) {
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GrowableArray<MonitorInfo*>* info = thread->cached_monitor_info();
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if (info != NULL) {
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return info;
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}
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info = new GrowableArray<MonitorInfo*>();
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// It's possible for the thread to not have any Java frames on it,
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// i.e., if it's the main thread and it's already returned from main()
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if (thread->has_last_Java_frame()) {
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RegisterMap rm(thread);
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for (javaVFrame* vf = thread->last_java_vframe(&rm); vf != NULL; vf = vf->java_sender()) {
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GrowableArray<MonitorInfo*> *monitors = vf->monitors();
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if (monitors != NULL) {
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int len = monitors->length();
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// Walk monitors youngest to oldest
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for (int i = len - 1; i >= 0; i--) {
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MonitorInfo* mon_info = monitors->at(i);
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if (mon_info->eliminated()) continue;
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oop owner = mon_info->owner();
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if (owner != NULL) {
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info->append(mon_info);
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}
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}
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}
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}
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}
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thread->set_cached_monitor_info(info);
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return info;
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}
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static BiasedLocking::Condition revoke_bias(oop obj, bool allow_rebias, bool is_bulk, JavaThread* requesting_thread) {
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markOop mark = obj->mark();
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if (!mark->has_bias_pattern()) {
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if (TraceBiasedLocking) {
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ResourceMark rm;
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tty->print_cr(" (Skipping revocation of object of type %s because it's no longer biased)",
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obj->klass()->external_name());
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}
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return BiasedLocking::NOT_BIASED;
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}
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uint age = mark->age();
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markOop biased_prototype = markOopDesc::biased_locking_prototype()->set_age(age);
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markOop unbiased_prototype = markOopDesc::prototype()->set_age(age);
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if (TraceBiasedLocking && (Verbose || !is_bulk)) {
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ResourceMark rm;
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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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p2i((void *)obj), (intptr_t) mark, obj->klass()->external_name(), (intptr_t) obj->klass()->prototype_header(), (allow_rebias ? 1 : 0), (intptr_t) requesting_thread);
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}
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JavaThread* biased_thread = mark->biased_locker();
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if (biased_thread == NULL) {
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// Object is anonymously biased. We can get here if, for
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// example, we revoke the bias due to an identity hash code
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// being computed for an object.
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if (!allow_rebias) {
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obj->set_mark(unbiased_prototype);
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}
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if (TraceBiasedLocking && (Verbose || !is_bulk)) {
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tty->print_cr(" Revoked bias of anonymously-biased object");
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}
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return BiasedLocking::BIAS_REVOKED;
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}
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// Handle case where the thread toward which the object was biased has exited
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bool thread_is_alive = false;
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if (requesting_thread == biased_thread) {
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thread_is_alive = true;
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} else {
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for (JavaThread* cur_thread = Threads::first(); cur_thread != NULL; cur_thread = cur_thread->next()) {
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if (cur_thread == biased_thread) {
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thread_is_alive = true;
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break;
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}
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}
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}
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if (!thread_is_alive) {
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if (allow_rebias) {
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obj->set_mark(biased_prototype);
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} else {
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obj->set_mark(unbiased_prototype);
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}
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if (TraceBiasedLocking && (Verbose || !is_bulk)) {
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tty->print_cr(" Revoked bias of object biased toward dead thread");
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}
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return BiasedLocking::BIAS_REVOKED;
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}
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// Thread owning bias is alive.
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// Check to see whether it currently owns the lock and, if so,
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// write down the needed displaced headers to the thread's stack.
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// Otherwise, restore the object's header either to the unlocked
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// or unbiased state.
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GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(biased_thread);
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BasicLock* highest_lock = NULL;
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for (int i = 0; i < cached_monitor_info->length(); i++) {
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MonitorInfo* mon_info = cached_monitor_info->at(i);
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if (mon_info->owner() == obj) {
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if (TraceBiasedLocking && Verbose) {
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tty->print_cr(" mon_info->owner (" PTR_FORMAT ") == obj (" PTR_FORMAT ")",
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p2i((void *) mon_info->owner()),
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p2i((void *) obj));
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}
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// Assume recursive case and fix up highest lock later
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markOop mark = markOopDesc::encode((BasicLock*) NULL);
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highest_lock = mon_info->lock();
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highest_lock->set_displaced_header(mark);
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} else {
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if (TraceBiasedLocking && Verbose) {
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tty->print_cr(" mon_info->owner (" PTR_FORMAT ") != obj (" PTR_FORMAT ")",
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p2i((void *) mon_info->owner()),
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p2i((void *) obj));
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}
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}
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}
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if (highest_lock != NULL) {
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// Fix up highest lock to contain displaced header and point
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// object at it
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highest_lock->set_displaced_header(unbiased_prototype);
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// Reset object header to point to displaced mark.
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// Must release storing the lock address for platforms without TSO
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// ordering (e.g. ppc).
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obj->release_set_mark(markOopDesc::encode(highest_lock));
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assert(!obj->mark()->has_bias_pattern(), "illegal mark state: stack lock used bias bit");
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if (TraceBiasedLocking && (Verbose || !is_bulk)) {
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tty->print_cr(" Revoked bias of currently-locked object");
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}
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} else {
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if (TraceBiasedLocking && (Verbose || !is_bulk)) {
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tty->print_cr(" Revoked bias of currently-unlocked object");
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}
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if (allow_rebias) {
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obj->set_mark(biased_prototype);
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} else {
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// Store the unlocked value into the object's header.
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obj->set_mark(unbiased_prototype);
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}
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}
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return BiasedLocking::BIAS_REVOKED;
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}
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enum HeuristicsResult {
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HR_NOT_BIASED = 1,
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HR_SINGLE_REVOKE = 2,
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HR_BULK_REBIAS = 3,
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HR_BULK_REVOKE = 4
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};
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static HeuristicsResult update_heuristics(oop o, bool allow_rebias) {
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markOop mark = o->mark();
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if (!mark->has_bias_pattern()) {
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return HR_NOT_BIASED;
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}
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// Heuristics to attempt to throttle the number of revocations.
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// Stages:
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// 1. Revoke the biases of all objects in the heap of this type,
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// but allow rebiasing of those objects if unlocked.
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// 2. Revoke the biases of all objects in the heap of this type
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// and don't allow rebiasing of these objects. Disable
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// allocation of objects of that type with the bias bit set.
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Klass* k = o->klass();
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jlong cur_time = os::javaTimeMillis();
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jlong last_bulk_revocation_time = k->last_biased_lock_bulk_revocation_time();
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int revocation_count = k->biased_lock_revocation_count();
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if ((revocation_count >= BiasedLockingBulkRebiasThreshold) &&
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(revocation_count < BiasedLockingBulkRevokeThreshold) &&
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(last_bulk_revocation_time != 0) &&
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(cur_time - last_bulk_revocation_time >= BiasedLockingDecayTime)) {
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// This is the first revocation we've seen in a while of an
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// object of this type since the last time we performed a bulk
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// rebiasing operation. The application is allocating objects in
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// bulk which are biased toward a thread and then handing them
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// off to another thread. We can cope with this allocation
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// pattern via the bulk rebiasing mechanism so we reset the
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// klass's revocation count rather than allow it to increase
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// monotonically. If we see the need to perform another bulk
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// rebias operation later, we will, and if subsequently we see
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// many more revocation operations in a short period of time we
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// will completely disable biasing for this type.
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k->set_biased_lock_revocation_count(0);
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revocation_count = 0;
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}
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// Make revocation count saturate just beyond BiasedLockingBulkRevokeThreshold
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if (revocation_count <= BiasedLockingBulkRevokeThreshold) {
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revocation_count = k->atomic_incr_biased_lock_revocation_count();
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}
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if (revocation_count == BiasedLockingBulkRevokeThreshold) {
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return HR_BULK_REVOKE;
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}
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if (revocation_count == BiasedLockingBulkRebiasThreshold) {
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return HR_BULK_REBIAS;
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}
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return HR_SINGLE_REVOKE;
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}
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static BiasedLocking::Condition bulk_revoke_or_rebias_at_safepoint(oop o,
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bool bulk_rebias,
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bool attempt_rebias_of_object,
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JavaThread* requesting_thread) {
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assert(SafepointSynchronize::is_at_safepoint(), "must be done at safepoint");
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if (TraceBiasedLocking) {
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tty->print_cr("* Beginning bulk revocation (kind == %s) because of object "
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INTPTR_FORMAT " , mark " INTPTR_FORMAT " , type %s",
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(bulk_rebias ? "rebias" : "revoke"),
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p2i((void *) o), (intptr_t) o->mark(), o->klass()->external_name());
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}
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jlong cur_time = os::javaTimeMillis();
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o->klass()->set_last_biased_lock_bulk_revocation_time(cur_time);
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Klass* k_o = o->klass();
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Klass* klass = k_o;
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if (bulk_rebias) {
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// Use the epoch in the klass of the object to implicitly revoke
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// all biases of objects of this data type and force them to be
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// reacquired. However, we also need to walk the stacks of all
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// threads and update the headers of lightweight locked objects
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// with biases to have the current epoch.
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// If the prototype header doesn't have the bias pattern, don't
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// try to update the epoch -- assume another VM operation came in
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// and reset the header to the unbiased state, which will
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// implicitly cause all existing biases to be revoked
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if (klass->prototype_header()->has_bias_pattern()) {
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int prev_epoch = klass->prototype_header()->bias_epoch();
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klass->set_prototype_header(klass->prototype_header()->incr_bias_epoch());
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int cur_epoch = klass->prototype_header()->bias_epoch();
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// Now walk all threads' stacks and adjust epochs of any biased
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// and locked objects of this data type we encounter
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for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
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GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr);
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for (int i = 0; i < cached_monitor_info->length(); i++) {
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MonitorInfo* mon_info = cached_monitor_info->at(i);
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oop owner = mon_info->owner();
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markOop mark = owner->mark();
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if ((owner->klass() == k_o) && mark->has_bias_pattern()) {
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// We might have encountered this object already in the case of recursive locking
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assert(mark->bias_epoch() == prev_epoch || mark->bias_epoch() == cur_epoch, "error in bias epoch adjustment");
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owner->set_mark(mark->set_bias_epoch(cur_epoch));
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}
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}
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}
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}
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// At this point we're done. All we have to do is potentially
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// adjust the header of the given object to revoke its bias.
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revoke_bias(o, attempt_rebias_of_object && klass->prototype_header()->has_bias_pattern(), true, requesting_thread);
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} else {
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if (TraceBiasedLocking) {
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ResourceMark rm;
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tty->print_cr("* Disabling biased locking for type %s", klass->external_name());
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}
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// Disable biased locking for this data type. Not only will this
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// cause future instances to not be biased, but existing biased
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// instances will notice that this implicitly caused their biases
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// to be revoked.
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klass->set_prototype_header(markOopDesc::prototype());
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// Now walk all threads' stacks and forcibly revoke the biases of
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// any locked and biased objects of this data type we encounter.
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for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
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GrowableArray<MonitorInfo*>* cached_monitor_info = get_or_compute_monitor_info(thr);
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for (int i = 0; i < cached_monitor_info->length(); i++) {
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MonitorInfo* mon_info = cached_monitor_info->at(i);
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oop owner = mon_info->owner();
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markOop mark = owner->mark();
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if ((owner->klass() == k_o) && mark->has_bias_pattern()) {
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revoke_bias(owner, false, true, requesting_thread);
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}
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}
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}
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// Must force the bias of the passed object to be forcibly revoked
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// as well to ensure guarantees to callers
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revoke_bias(o, false, true, requesting_thread);
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}
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if (TraceBiasedLocking) {
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tty->print_cr("* Ending bulk revocation");
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}
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BiasedLocking::Condition status_code = BiasedLocking::BIAS_REVOKED;
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if (attempt_rebias_of_object &&
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o->mark()->has_bias_pattern() &&
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klass->prototype_header()->has_bias_pattern()) {
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markOop new_mark = markOopDesc::encode(requesting_thread, o->mark()->age(),
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klass->prototype_header()->bias_epoch());
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o->set_mark(new_mark);
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status_code = BiasedLocking::BIAS_REVOKED_AND_REBIASED;
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if (TraceBiasedLocking) {
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tty->print_cr(" Rebiased object toward thread " INTPTR_FORMAT, (intptr_t) requesting_thread);
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}
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}
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assert(!o->mark()->has_bias_pattern() ||
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(attempt_rebias_of_object && (o->mark()->biased_locker() == requesting_thread)),
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"bug in bulk bias revocation");
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return status_code;
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}
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static void clean_up_cached_monitor_info() {
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// Walk the thread list clearing out the cached monitors
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for (JavaThread* thr = Threads::first(); thr != NULL; thr = thr->next()) {
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thr->set_cached_monitor_info(NULL);
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}
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}
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class VM_RevokeBias : public VM_Operation {
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protected:
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Handle* _obj;
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GrowableArray<Handle>* _objs;
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JavaThread* _requesting_thread;
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BiasedLocking::Condition _status_code;
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public:
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VM_RevokeBias(Handle* obj, JavaThread* requesting_thread)
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: _obj(obj)
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, _objs(NULL)
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, _requesting_thread(requesting_thread)
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, _status_code(BiasedLocking::NOT_BIASED) {}
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VM_RevokeBias(GrowableArray<Handle>* objs, JavaThread* requesting_thread)
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: _obj(NULL)
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, _objs(objs)
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, _requesting_thread(requesting_thread)
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, _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 = 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) {
|
|
Klass *k = obj->klass();
|
|
markOop prototype_header = k->prototype_header();
|
|
if (mark->biased_locker() == THREAD &&
|
|
prototype_header->bias_epoch() == mark->bias_epoch()) {
|
|
// 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.
|
|
// Also check the epoch because even if threads match, another thread
|
|
// can come in with a CAS to steal the bias of an object that has a
|
|
// stale epoch.
|
|
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, mtInternal) GrowableArray<markOop>(10, true);
|
|
_preserved_oop_stack = new (ResourceObj::C_HEAP, mtInternal) 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);
|
|
if (mon_info->owner_is_scalar_replaced()) continue;
|
|
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());
|
|
}
|