duke@435: /*
duke@435:  * Copyright 2003-2007 Sun Microsystems, Inc.  All Rights Reserved.
duke@435:  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
duke@435:  *
duke@435:  * This code is free software; you can redistribute it and/or modify it
duke@435:  * under the terms of the GNU General Public License version 2 only, as
duke@435:  * published by the Free Software Foundation.
duke@435:  *
duke@435:  * This code is distributed in the hope that it will be useful, but WITHOUT
duke@435:  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
duke@435:  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
duke@435:  * version 2 for more details (a copy is included in the LICENSE file that
duke@435:  * accompanied this code).
duke@435:  *
duke@435:  * You should have received a copy of the GNU General Public License version
duke@435:  * 2 along with this work; if not, write to the Free Software Foundation,
duke@435:  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
duke@435:  *
duke@435:  * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
duke@435:  * CA 95054 USA or visit www.sun.com if you need additional information or
duke@435:  * have any questions.
duke@435:  *
duke@435:  */
duke@435: 
duke@435: # include "incls/_precompiled.incl"
duke@435: # include "incls/_lowMemoryDetector.cpp.incl"
duke@435: 
duke@435: LowMemoryDetectorThread* LowMemoryDetector::_detector_thread = NULL;
duke@435: volatile bool LowMemoryDetector::_enabled_for_collected_pools = false;
duke@435: volatile jint LowMemoryDetector::_disabled_count = 0;
duke@435: 
duke@435: void LowMemoryDetector::initialize() {
duke@435:   EXCEPTION_MARK;
duke@435: 
duke@435:   instanceKlassHandle klass (THREAD,  SystemDictionary::thread_klass());
duke@435:   instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);
duke@435: 
duke@435:   const char thread_name[] = "Low Memory Detector";
duke@435:   Handle string = java_lang_String::create_from_str(thread_name, CHECK);
duke@435: 
duke@435:   // Initialize thread_oop to put it into the system threadGroup
duke@435:   Handle thread_group (THREAD, Universe::system_thread_group());
duke@435:   JavaValue result(T_VOID);
duke@435:   JavaCalls::call_special(&result, thread_oop,
duke@435:                           klass,
duke@435:                           vmSymbolHandles::object_initializer_name(),
duke@435:                           vmSymbolHandles::threadgroup_string_void_signature(),
duke@435:                           thread_group,
duke@435:                           string,
duke@435:                           CHECK);
duke@435: 
duke@435:   {
duke@435:     MutexLocker mu(Threads_lock);
duke@435:     _detector_thread = new LowMemoryDetectorThread(&low_memory_detector_thread_entry);
duke@435: 
duke@435:     // At this point it may be possible that no osthread was created for the
duke@435:     // JavaThread due to lack of memory. We would have to throw an exception
duke@435:     // in that case. However, since this must work and we do not allow
duke@435:     // exceptions anyway, check and abort if this fails.
duke@435:     if (_detector_thread == NULL || _detector_thread->osthread() == NULL) {
duke@435:       vm_exit_during_initialization("java.lang.OutOfMemoryError",
duke@435:                                     "unable to create new native thread");
duke@435:     }
duke@435: 
duke@435:     java_lang_Thread::set_thread(thread_oop(), _detector_thread);
duke@435:     java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);
duke@435:     java_lang_Thread::set_daemon(thread_oop());
duke@435:     _detector_thread->set_threadObj(thread_oop());
duke@435: 
duke@435:     Threads::add(_detector_thread);
duke@435:     Thread::start(_detector_thread);
duke@435:   }
duke@435: }
duke@435: 
duke@435: bool LowMemoryDetector::has_pending_requests() {
duke@435:   assert(LowMemory_lock->owned_by_self(), "Must own LowMemory_lock");
duke@435:   bool has_requests = false;
duke@435:   int num_memory_pools = MemoryService::num_memory_pools();
duke@435:   for (int i = 0; i < num_memory_pools; i++) {
duke@435:     MemoryPool* pool = MemoryService::get_memory_pool(i);
duke@435:     SensorInfo* sensor = pool->usage_sensor();
duke@435:     if (sensor != NULL) {
duke@435:       has_requests = has_requests || sensor->has_pending_requests();
duke@435:     }
duke@435: 
duke@435:     SensorInfo* gc_sensor = pool->gc_usage_sensor();
duke@435:     if (gc_sensor != NULL) {
duke@435:       has_requests = has_requests || gc_sensor->has_pending_requests();
duke@435:     }
duke@435:   }
duke@435:   return has_requests;
duke@435: }
duke@435: 
duke@435: void LowMemoryDetector::low_memory_detector_thread_entry(JavaThread* jt, TRAPS) {
duke@435:   while (true) {
duke@435:     bool   sensors_changed = false;
duke@435: 
duke@435:     {
duke@435:       // _no_safepoint_check_flag is used here as LowMemory_lock is a
duke@435:       // special lock and the VMThread may acquire this lock at safepoint.
duke@435:       // Need state transition ThreadBlockInVM so that this thread
duke@435:       // will be handled by safepoint correctly when this thread is
duke@435:       // notified at a safepoint.
duke@435: 
duke@435:       // This ThreadBlockInVM object is not also considered to be
duke@435:       // suspend-equivalent because LowMemoryDetector threads are
duke@435:       // not visible to external suspension.
duke@435: 
duke@435:       ThreadBlockInVM tbivm(jt);
duke@435: 
duke@435:       MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
duke@435:       while (!(sensors_changed = has_pending_requests())) {
duke@435:         // wait until one of the sensors has pending requests
duke@435:         LowMemory_lock->wait(Mutex::_no_safepoint_check_flag);
duke@435:       }
duke@435:     }
duke@435: 
duke@435:     {
duke@435:       ResourceMark rm(THREAD);
duke@435:       HandleMark hm(THREAD);
duke@435: 
duke@435:       // No need to hold LowMemory_lock to call out to Java
duke@435:       int num_memory_pools = MemoryService::num_memory_pools();
duke@435:       for (int i = 0; i < num_memory_pools; i++) {
duke@435:         MemoryPool* pool = MemoryService::get_memory_pool(i);
duke@435:         SensorInfo* sensor = pool->usage_sensor();
duke@435:         SensorInfo* gc_sensor = pool->gc_usage_sensor();
duke@435:         if (sensor != NULL && sensor->has_pending_requests()) {
duke@435:           sensor->process_pending_requests(CHECK);
duke@435:         }
duke@435:         if (gc_sensor != NULL && gc_sensor->has_pending_requests()) {
duke@435:           gc_sensor->process_pending_requests(CHECK);
duke@435:         }
duke@435:       }
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: // This method could be called from any Java threads
duke@435: // and also VMThread.
duke@435: void LowMemoryDetector::detect_low_memory() {
duke@435:   MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
duke@435: 
duke@435:   bool has_pending_requests = false;
duke@435:   int num_memory_pools = MemoryService::num_memory_pools();
duke@435:   for (int i = 0; i < num_memory_pools; i++) {
duke@435:     MemoryPool* pool = MemoryService::get_memory_pool(i);
duke@435:     SensorInfo* sensor = pool->usage_sensor();
duke@435:     if (sensor != NULL &&
duke@435:         pool->usage_threshold()->is_high_threshold_supported() &&
duke@435:         pool->usage_threshold()->high_threshold() != 0) {
duke@435:       MemoryUsage usage = pool->get_memory_usage();
duke@435:       sensor->set_gauge_sensor_level(usage,
duke@435:                                      pool->usage_threshold());
duke@435:       has_pending_requests = has_pending_requests || sensor->has_pending_requests();
duke@435:     }
duke@435:   }
duke@435: 
duke@435:   if (has_pending_requests) {
duke@435:     LowMemory_lock->notify_all();
duke@435:   }
duke@435: }
duke@435: 
duke@435: // This method could be called from any Java threads
duke@435: // and also VMThread.
duke@435: void LowMemoryDetector::detect_low_memory(MemoryPool* pool) {
duke@435:   SensorInfo* sensor = pool->usage_sensor();
duke@435:   if (sensor == NULL ||
duke@435:       !pool->usage_threshold()->is_high_threshold_supported() ||
duke@435:       pool->usage_threshold()->high_threshold() == 0) {
duke@435:     return;
duke@435:   }
duke@435: 
duke@435:   {
duke@435:     MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
duke@435: 
duke@435:     MemoryUsage usage = pool->get_memory_usage();
duke@435:     sensor->set_gauge_sensor_level(usage,
duke@435:                                    pool->usage_threshold());
duke@435:     if (sensor->has_pending_requests()) {
duke@435:       // notify sensor state update
duke@435:       LowMemory_lock->notify_all();
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: // Only called by VMThread at GC time
duke@435: void LowMemoryDetector::detect_after_gc_memory(MemoryPool* pool) {
duke@435:   SensorInfo* sensor = pool->gc_usage_sensor();
duke@435:   if (sensor == NULL ||
duke@435:       !pool->gc_usage_threshold()->is_high_threshold_supported() ||
duke@435:       pool->gc_usage_threshold()->high_threshold() == 0) {
duke@435:     return;
duke@435:   }
duke@435: 
duke@435:   {
duke@435:     MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
duke@435: 
duke@435:     MemoryUsage usage = pool->get_last_collection_usage();
duke@435:     sensor->set_counter_sensor_level(usage, pool->gc_usage_threshold());
duke@435: 
duke@435:     if (sensor->has_pending_requests()) {
duke@435:       // notify sensor state update
duke@435:       LowMemory_lock->notify_all();
duke@435:     }
duke@435:   }
duke@435: }
duke@435: 
duke@435: // recompute enabled flag
duke@435: void LowMemoryDetector::recompute_enabled_for_collected_pools() {
duke@435:   bool enabled = false;
duke@435:   int num_memory_pools = MemoryService::num_memory_pools();
duke@435:   for (int i=0; i<num_memory_pools; i++) {
duke@435:     MemoryPool* pool = MemoryService::get_memory_pool(i);
duke@435:     if (pool->is_collected_pool() && is_enabled(pool)) {
duke@435:       enabled = true;
duke@435:       break;
duke@435:     }
duke@435:   }
duke@435:   _enabled_for_collected_pools = enabled;
duke@435: }
duke@435: 
duke@435: SensorInfo::SensorInfo() {
duke@435:   _sensor_obj = NULL;
duke@435:   _sensor_on = false;
duke@435:   _sensor_count = 0;
duke@435:   _pending_trigger_count = 0;
duke@435:   _pending_clear_count = 0;
duke@435: }
duke@435: 
duke@435: // When this method is used, the memory usage is monitored
duke@435: // as a gauge attribute.  Sensor notifications (trigger or
duke@435: // clear) is only emitted at the first time it crosses
duke@435: // a threshold.
duke@435: //
duke@435: // High and low thresholds are designed to provide a
duke@435: // hysteresis mechanism to avoid repeated triggering
duke@435: // of notifications when the attribute value makes small oscillations
duke@435: // around the high or low threshold value.
duke@435: //
duke@435: // The sensor will be triggered if:
duke@435: //  (1) the usage is crossing above the high threshold and
duke@435: //      the sensor is currently off and no pending
duke@435: //      trigger requests; or
duke@435: //  (2) the usage is crossing above the high threshold and
duke@435: //      the sensor will be off (i.e. sensor is currently on
duke@435: //      and has pending clear requests).
duke@435: //
duke@435: // Subsequent crossings of the high threshold value do not cause
duke@435: // any triggers unless the usage becomes less than the low threshold.
duke@435: //
duke@435: // The sensor will be cleared if:
duke@435: //  (1) the usage is crossing below the low threshold and
duke@435: //      the sensor is currently on and no pending
duke@435: //      clear requests; or
duke@435: //  (2) the usage is crossing below the low threshold and
duke@435: //      the sensor will be on (i.e. sensor is currently off
duke@435: //      and has pending trigger requests).
duke@435: //
duke@435: // Subsequent crossings of the low threshold value do not cause
duke@435: // any clears unless the usage becomes greater than or equal
duke@435: // to the high threshold.
duke@435: //
duke@435: // If the current level is between high and low threhsold, no change.
duke@435: //
duke@435: void SensorInfo::set_gauge_sensor_level(MemoryUsage usage, ThresholdSupport* high_low_threshold) {
duke@435:   assert(high_low_threshold->is_high_threshold_supported(), "just checking");
duke@435: 
duke@435:   bool is_over_high = high_low_threshold->is_high_threshold_crossed(usage);
duke@435:   bool is_below_low = high_low_threshold->is_low_threshold_crossed(usage);
duke@435: 
duke@435:   assert(!(is_over_high && is_below_low), "Can't be both true");
duke@435: 
duke@435:   if (is_over_high &&
duke@435:         ((!_sensor_on && _pending_trigger_count == 0) ||
duke@435:          _pending_clear_count > 0)) {
duke@435:     // low memory detected and need to increment the trigger pending count
duke@435:     // if the sensor is off or will be off due to _pending_clear_ > 0
duke@435:     // Request to trigger the sensor
duke@435:     _pending_trigger_count++;
duke@435:     _usage = usage;
duke@435: 
duke@435:     if (_pending_clear_count > 0) {
duke@435:       // non-zero pending clear requests indicates that there are
duke@435:       // pending requests to clear this sensor.
duke@435:       // This trigger request needs to clear this clear count
duke@435:       // since the resulting sensor flag should be on.
duke@435:       _pending_clear_count = 0;
duke@435:     }
duke@435:   } else if (is_below_low &&
duke@435:                ((_sensor_on && _pending_clear_count == 0) ||
duke@435:                 (_pending_trigger_count > 0 && _pending_clear_count == 0))) {
duke@435:     // memory usage returns below the threshold
duke@435:     // Request to clear the sensor if the sensor is on or will be on due to
duke@435:     // _pending_trigger_count > 0 and also no clear request
duke@435:     _pending_clear_count++;
duke@435:   }
duke@435: }
duke@435: 
duke@435: // When this method is used, the memory usage is monitored as a
duke@435: // simple counter attribute.  The sensor will be triggered
duke@435: // whenever the usage is crossing the threshold to keep track
duke@435: // of the number of times the VM detects such a condition occurs.
duke@435: //
duke@435: // High and low thresholds are designed to provide a
duke@435: // hysteresis mechanism to avoid repeated triggering
duke@435: // of notifications when the attribute value makes small oscillations
duke@435: // around the high or low threshold value.
duke@435: //
duke@435: // The sensor will be triggered if:
duke@435: //   - the usage is crossing above the high threshold regardless
duke@435: //     of the current sensor state.
duke@435: //
duke@435: // The sensor will be cleared if:
duke@435: //  (1) the usage is crossing below the low threshold and
duke@435: //      the sensor is currently on; or
duke@435: //  (2) the usage is crossing below the low threshold and
duke@435: //      the sensor will be on (i.e. sensor is currently off
duke@435: //      and has pending trigger requests).
duke@435: void SensorInfo::set_counter_sensor_level(MemoryUsage usage, ThresholdSupport* counter_threshold) {
duke@435:   assert(counter_threshold->is_high_threshold_supported(), "just checking");
duke@435: 
duke@435:   bool is_over_high = counter_threshold->is_high_threshold_crossed(usage);
duke@435:   bool is_below_low = counter_threshold->is_low_threshold_crossed(usage);
duke@435: 
duke@435:   assert(!(is_over_high && is_below_low), "Can't be both true");
duke@435: 
duke@435:   if (is_over_high) {
duke@435:     _pending_trigger_count++;
duke@435:     _usage = usage;
duke@435:     _pending_clear_count = 0;
duke@435:   } else if (is_below_low && (_sensor_on || _pending_trigger_count > 0)) {
duke@435:     _pending_clear_count++;
duke@435:   }
duke@435: }
duke@435: 
duke@435: void SensorInfo::oops_do(OopClosure* f) {
duke@435:   f->do_oop((oop*) &_sensor_obj);
duke@435: }
duke@435: 
duke@435: void SensorInfo::process_pending_requests(TRAPS) {
duke@435:   if (!has_pending_requests()) {
duke@435:     return;
duke@435:   }
duke@435: 
duke@435:   int pending_count = pending_trigger_count();
duke@435:   if (pending_clear_count() > 0) {
duke@435:     clear(pending_count, CHECK);
duke@435:   } else {
duke@435:     trigger(pending_count, CHECK);
duke@435:   }
duke@435: 
duke@435: }
duke@435: 
duke@435: void SensorInfo::trigger(int count, TRAPS) {
duke@435:   assert(count <= _pending_trigger_count, "just checking");
duke@435: 
duke@435:   if (_sensor_obj != NULL) {
duke@435:     klassOop k = Management::sun_management_Sensor_klass(CHECK);
duke@435:     instanceKlassHandle sensorKlass (THREAD, k);
duke@435:     Handle sensor_h(THREAD, _sensor_obj);
duke@435:     Handle usage_h = MemoryService::create_MemoryUsage_obj(_usage, CHECK);
duke@435: 
duke@435:     JavaValue result(T_VOID);
duke@435:     JavaCallArguments args(sensor_h);
duke@435:     args.push_int((int) count);
duke@435:     args.push_oop(usage_h);
duke@435: 
duke@435:     JavaCalls::call_virtual(&result,
duke@435:                             sensorKlass,
duke@435:                             vmSymbolHandles::trigger_name(),
duke@435:                             vmSymbolHandles::trigger_method_signature(),
duke@435:                             &args,
duke@435:                             CHECK);
duke@435:   }
duke@435: 
duke@435:   {
duke@435:     // Holds LowMemory_lock and update the sensor state
duke@435:     MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
duke@435:     _sensor_on = true;
duke@435:     _sensor_count += count;
duke@435:     _pending_trigger_count = _pending_trigger_count - count;
duke@435:   }
duke@435: }
duke@435: 
duke@435: void SensorInfo::clear(int count, TRAPS) {
duke@435:   if (_sensor_obj != NULL) {
duke@435:     klassOop k = Management::sun_management_Sensor_klass(CHECK);
duke@435:     instanceKlassHandle sensorKlass (THREAD, k);
duke@435:     Handle sensor(THREAD, _sensor_obj);
duke@435: 
duke@435:     JavaValue result(T_VOID);
duke@435:     JavaCallArguments args(sensor);
duke@435:     args.push_int((int) count);
duke@435:     JavaCalls::call_virtual(&result,
duke@435:                             sensorKlass,
duke@435:                             vmSymbolHandles::clear_name(),
duke@435:                             vmSymbolHandles::int_void_signature(),
duke@435:                             &args,
duke@435:                             CHECK);
duke@435:   }
duke@435: 
duke@435:   {
duke@435:     // Holds LowMemory_lock and update the sensor state
duke@435:     MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);
duke@435:     _sensor_on = false;
duke@435:     _pending_clear_count = 0;
duke@435:     _pending_trigger_count = _pending_trigger_count - count;
duke@435:   }
duke@435: }
duke@435: 
duke@435: //--------------------------------------------------------------
duke@435: // Non-product code
duke@435: 
duke@435: #ifndef PRODUCT
duke@435: void SensorInfo::print() {
duke@435:   tty->print_cr("%s count = %ld pending_triggers = %ld pending_clears = %ld",
duke@435:                 (_sensor_on ? "on" : "off"),
duke@435:                 _sensor_count, _pending_trigger_count, _pending_clear_count);
duke@435: }
duke@435: 
duke@435: #endif // PRODUCT