/*

 * Copyright (c) 2003, 2010, Oracle and/or its affiliates. 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 *

 */

#include "precompiled.hpp"

#include "classfile/systemDictionary.hpp"

#include "classfile/vmSymbols.hpp"

#include "oops/oop.inline.hpp"

#include "runtime/interfaceSupport.hpp"

#include "runtime/java.hpp"

#include "runtime/javaCalls.hpp"

#include "runtime/mutex.hpp"

#include "runtime/mutexLocker.hpp"

#include "services/lowMemoryDetector.hpp"

#include "services/management.hpp"

LowMemoryDetectorThread* LowMemoryDetector::_detector_thread = NULL;

volatile bool LowMemoryDetector::_enabled_for_collected_pools = false;

volatile jint LowMemoryDetector::_disabled_count = 0;

void LowMemoryDetector::initialize() {

  EXCEPTION_MARK;

  instanceKlassHandle klass (THREAD,  SystemDictionary::Thread_klass());

  instanceHandle thread_oop = klass->allocate_instance_handle(CHECK);

  const char thread_name[] = "Low Memory Detector";

  Handle string = java_lang_String::create_from_str(thread_name, CHECK);

  // Initialize thread_oop to put it into the system threadGroup

  Handle thread_group (THREAD, Universe::system_thread_group());

  JavaValue result(T_VOID);

  JavaCalls::call_special(&result, thread_oop,

                          klass,

                          thread_group,

                          string,

                          CHECK);

  {

    MutexLocker mu(Threads_lock);

    _detector_thread = new LowMemoryDetectorThread(&low_memory_detector_thread_entry);

    // At this point it may be possible that no osthread was created for the

    // JavaThread due to lack of memory. We would have to throw an exception

    // in that case. However, since this must work and we do not allow

    // exceptions anyway, check and abort if this fails.

    if (_detector_thread == NULL || _detector_thread->osthread() == NULL) {

      vm_exit_during_initialization("java.lang.OutOfMemoryError",

                                    "unable to create new native thread");

    }

    java_lang_Thread::set_thread(thread_oop(), _detector_thread);

    java_lang_Thread::set_priority(thread_oop(), NearMaxPriority);

    java_lang_Thread::set_daemon(thread_oop());

    _detector_thread->set_threadObj(thread_oop());

    Threads::add(_detector_thread);

    Thread::start(_detector_thread);

  }

}

bool LowMemoryDetector::has_pending_requests() {

  assert(LowMemory_lock->owned_by_self(), "Must own LowMemory_lock");

  bool has_requests = false;

  int num_memory_pools = MemoryService::num_memory_pools();

  for (int i = 0; i < num_memory_pools; i++) {

    MemoryPool* pool = MemoryService::get_memory_pool(i);

    SensorInfo* sensor = pool->usage_sensor();

    if (sensor != NULL) {

      has_requests = has_requests || sensor->has_pending_requests();

    }

    SensorInfo* gc_sensor = pool->gc_usage_sensor();

    if (gc_sensor != NULL) {

      has_requests = has_requests || gc_sensor->has_pending_requests();

    }

  }

  return has_requests;

}

void LowMemoryDetector::low_memory_detector_thread_entry(JavaThread* jt, TRAPS) {

  while (true) {

    bool   sensors_changed = false;

    {

      // _no_safepoint_check_flag is used here as LowMemory_lock is a

      // special lock and the VMThread may acquire this lock at safepoint.

      // Need state transition ThreadBlockInVM so that this thread

      // will be handled by safepoint correctly when this thread is

      // notified at a safepoint.

      // This ThreadBlockInVM object is not also considered to be

      // suspend-equivalent because LowMemoryDetector threads are

      // not visible to external suspension.

      ThreadBlockInVM tbivm(jt);

      MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);

      while (!(sensors_changed = has_pending_requests())) {

        // wait until one of the sensors has pending requests

        LowMemory_lock->wait(Mutex::_no_safepoint_check_flag);

      }

    }

    {

      ResourceMark rm(THREAD);

      HandleMark hm(THREAD);

      // No need to hold LowMemory_lock to call out to Java

      int num_memory_pools = MemoryService::num_memory_pools();

      for (int i = 0; i < num_memory_pools; i++) {

        MemoryPool* pool = MemoryService::get_memory_pool(i);

        SensorInfo* sensor = pool->usage_sensor();

        SensorInfo* gc_sensor = pool->gc_usage_sensor();

        if (sensor != NULL && sensor->has_pending_requests()) {

          sensor->process_pending_requests(CHECK);

        }

        if (gc_sensor != NULL && gc_sensor->has_pending_requests()) {

          gc_sensor->process_pending_requests(CHECK);

        }

      }

    }

  }

}

// This method could be called from any Java threads

// and also VMThread.

void LowMemoryDetector::detect_low_memory() {

  MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);

  bool has_pending_requests = false;

  int num_memory_pools = MemoryService::num_memory_pools();

  for (int i = 0; i < num_memory_pools; i++) {

    MemoryPool* pool = MemoryService::get_memory_pool(i);

    SensorInfo* sensor = pool->usage_sensor();

    if (sensor != NULL &&

        pool->usage_threshold()->is_high_threshold_supported() &&

        pool->usage_threshold()->high_threshold() != 0) {

      MemoryUsage usage = pool->get_memory_usage();

      sensor->set_gauge_sensor_level(usage,

                                     pool->usage_threshold());

      has_pending_requests = has_pending_requests || sensor->has_pending_requests();

    }

  }

  if (has_pending_requests) {

    LowMemory_lock->notify_all();

  }

}

// This method could be called from any Java threads

// and also VMThread.

void LowMemoryDetector::detect_low_memory(MemoryPool* pool) {

  SensorInfo* sensor = pool->usage_sensor();

  if (sensor == NULL ||

      !pool->usage_threshold()->is_high_threshold_supported() ||

      pool->usage_threshold()->high_threshold() == 0) {

    return;

  }

  {

    MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);

    MemoryUsage usage = pool->get_memory_usage();

    sensor->set_gauge_sensor_level(usage,

                                   pool->usage_threshold());

    if (sensor->has_pending_requests()) {

      // notify sensor state update

      LowMemory_lock->notify_all();

    }

  }

}

// Only called by VMThread at GC time

void LowMemoryDetector::detect_after_gc_memory(MemoryPool* pool) {

  SensorInfo* sensor = pool->gc_usage_sensor();

  if (sensor == NULL ||

      !pool->gc_usage_threshold()->is_high_threshold_supported() ||

      pool->gc_usage_threshold()->high_threshold() == 0) {

    return;

  }

  {

    MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);

    MemoryUsage usage = pool->get_last_collection_usage();

    sensor->set_counter_sensor_level(usage, pool->gc_usage_threshold());

    if (sensor->has_pending_requests()) {

      // notify sensor state update

      LowMemory_lock->notify_all();

    }

  }

}

// recompute enabled flag

void LowMemoryDetector::recompute_enabled_for_collected_pools() {

  bool enabled = false;

  int num_memory_pools = MemoryService::num_memory_pools();

  for (int i=0; i<num_memory_pools; i++) {

    MemoryPool* pool = MemoryService::get_memory_pool(i);

    if (pool->is_collected_pool() && is_enabled(pool)) {

      enabled = true;

      break;

    }

  }

  _enabled_for_collected_pools = enabled;

}

SensorInfo::SensorInfo() {

  _sensor_obj = NULL;

  _sensor_on = false;

  _sensor_count = 0;

  _pending_trigger_count = 0;

  _pending_clear_count = 0;

}

// When this method is used, the memory usage is monitored

// as a gauge attribute.  Sensor notifications (trigger or

// clear) is only emitted at the first time it crosses

// a threshold.

//

// High and low thresholds are designed to provide a

// hysteresis mechanism to avoid repeated triggering

// of notifications when the attribute value makes small oscillations

// around the high or low threshold value.

//

// The sensor will be triggered if:

//  (1) the usage is crossing above the high threshold and

//      the sensor is currently off and no pending

//      trigger requests; or

//  (2) the usage is crossing above the high threshold and

//      the sensor will be off (i.e. sensor is currently on

//      and has pending clear requests).

//

// Subsequent crossings of the high threshold value do not cause

// any triggers unless the usage becomes less than the low threshold.

//

// The sensor will be cleared if:

//  (1) the usage is crossing below the low threshold and

//      the sensor is currently on and no pending

//      clear requests; or

//  (2) the usage is crossing below the low threshold and

//      the sensor will be on (i.e. sensor is currently off

//      and has pending trigger requests).

//

// Subsequent crossings of the low threshold value do not cause

// any clears unless the usage becomes greater than or equal

// to the high threshold.

//

// If the current level is between high and low threhsold, no change.

//

void SensorInfo::set_gauge_sensor_level(MemoryUsage usage, ThresholdSupport* high_low_threshold) {

  assert(high_low_threshold->is_high_threshold_supported(), "just checking");

  bool is_over_high = high_low_threshold->is_high_threshold_crossed(usage);

  bool is_below_low = high_low_threshold->is_low_threshold_crossed(usage);

  assert(!(is_over_high && is_below_low), "Can't be both true");

  if (is_over_high &&

        ((!_sensor_on && _pending_trigger_count == 0) ||

         _pending_clear_count > 0)) {

    // low memory detected and need to increment the trigger pending count

    // if the sensor is off or will be off due to _pending_clear_ > 0

    // Request to trigger the sensor

    _pending_trigger_count++;

    _usage = usage;

    if (_pending_clear_count > 0) {

      // non-zero pending clear requests indicates that there are

      // pending requests to clear this sensor.

      // This trigger request needs to clear this clear count

      // since the resulting sensor flag should be on.

      _pending_clear_count = 0;

    }

  } else if (is_below_low &&

               ((_sensor_on && _pending_clear_count == 0) ||

                (_pending_trigger_count > 0 && _pending_clear_count == 0))) {

    // memory usage returns below the threshold

    // Request to clear the sensor if the sensor is on or will be on due to

    // _pending_trigger_count > 0 and also no clear request

    _pending_clear_count++;

  }

}

// When this method is used, the memory usage is monitored as a

// simple counter attribute.  The sensor will be triggered

// whenever the usage is crossing the threshold to keep track

// of the number of times the VM detects such a condition occurs.

//

// High and low thresholds are designed to provide a

// hysteresis mechanism to avoid repeated triggering

// of notifications when the attribute value makes small oscillations

// around the high or low threshold value.

//

// The sensor will be triggered if:

//   - the usage is crossing above the high threshold regardless

//     of the current sensor state.

//

// The sensor will be cleared if:

//  (1) the usage is crossing below the low threshold and

//      the sensor is currently on; or

//  (2) the usage is crossing below the low threshold and

//      the sensor will be on (i.e. sensor is currently off

//      and has pending trigger requests).

void SensorInfo::set_counter_sensor_level(MemoryUsage usage, ThresholdSupport* counter_threshold) {

  assert(counter_threshold->is_high_threshold_supported(), "just checking");

  bool is_over_high = counter_threshold->is_high_threshold_crossed(usage);

  bool is_below_low = counter_threshold->is_low_threshold_crossed(usage);

  assert(!(is_over_high && is_below_low), "Can't be both true");

  if (is_over_high) {

    _pending_trigger_count++;

    _usage = usage;

    _pending_clear_count = 0;

  } else if (is_below_low && (_sensor_on || _pending_trigger_count > 0)) {

    _pending_clear_count++;

  }

}

void SensorInfo::oops_do(OopClosure* f) {

  f->do_oop((oop*) &_sensor_obj);

}

void SensorInfo::process_pending_requests(TRAPS) {

  if (!has_pending_requests()) {

    return;

  }

  int pending_count = pending_trigger_count();

  if (pending_clear_count() > 0) {

    clear(pending_count, CHECK);

  } else {

    trigger(pending_count, CHECK);

  }

}

void SensorInfo::trigger(int count, TRAPS) {

  assert(count <= _pending_trigger_count, "just checking");

  if (_sensor_obj != NULL) {

    klassOop k = Management::sun_management_Sensor_klass(CHECK);

    instanceKlassHandle sensorKlass (THREAD, k);

    Handle sensor_h(THREAD, _sensor_obj);

    Handle usage_h = MemoryService::create_MemoryUsage_obj(_usage, CHECK);

    JavaValue result(T_VOID);

    JavaCallArguments args(sensor_h);

    args.push_int((int) count);

    args.push_oop(usage_h);

    JavaCalls::call_virtual(&result,

                            sensorKlass,

                            &args,

                            CHECK);

  }

  {

    // Holds LowMemory_lock and update the sensor state

    MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);

    _sensor_on = true;

    _sensor_count += count;

    _pending_trigger_count = _pending_trigger_count - count;

  }

}

void SensorInfo::clear(int count, TRAPS) {

  if (_sensor_obj != NULL) {

    klassOop k = Management::sun_management_Sensor_klass(CHECK);

    instanceKlassHandle sensorKlass (THREAD, k);

    Handle sensor(THREAD, _sensor_obj);

    JavaValue result(T_VOID);

    JavaCallArguments args(sensor);

    args.push_int((int) count);

    JavaCalls::call_virtual(&result,

                            sensorKlass,

                            &args,

                            CHECK);

  }

  {

    // Holds LowMemory_lock and update the sensor state

    MutexLockerEx ml(LowMemory_lock, Mutex::_no_safepoint_check_flag);

    _sensor_on = false;

    _pending_clear_count = 0;

    _pending_trigger_count = _pending_trigger_count - count;

  }

}

//--------------------------------------------------------------

// Non-product code

#ifndef PRODUCT

void SensorInfo::print() {

  tty->print_cr("%s count = %ld pending_triggers = %ld pending_clears = %ld",

                (_sensor_on ? "on" : "off"),

                _sensor_count, _pending_trigger_count, _pending_clear_count);

}

#endif // PRODUCT