Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 2003, 2007, 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 "incls/_precompiled.incl"

 # include "incls/_lowMemoryDetector.cpp.incl"

 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,

                           vmSymbolHandles::object_initializer_name(),

                           vmSymbolHandles::threadgroup_string_void_signature(),

                           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,

                             vmSymbolHandles::trigger_name(),

                             vmSymbolHandles::trigger_method_signature(),

                             &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,

                             vmSymbolHandles::clear_name(),

                             vmSymbolHandles::int_void_signature(),

                             &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