jdk8-mips64-public/hotspot: src/share/vm/services/lowMemoryDetector.hpp@c18cbe5936b8 (annotated)

src/share/vm/services/lowMemoryDetector.hpp@c18cbe5936b8 (annotated)

src/share/vm/services/lowMemoryDetector.hpp

Thu, 27 May 2010 19:08:38 -0700

author: trims
date: Thu, 27 May 2010 19:08:38 -0700
changeset 1907: c18cbe5936b8
parent 435: a61af66fc99e
child 2314: f95d63e2154a
permissions: -rw-r--r--

6941466: Oracle rebranding changes for Hotspot repositories
Summary: Change all the Sun copyrights to Oracle copyright
Reviewed-by: ohair

 /*
  * 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.
  *
  */
 // Low Memory Detection Support
 // Two memory alarms in the JDK (we called them sensors).
 //   - Heap memory sensor
 //   - Non-heap memory sensor
 // When the VM detects if the memory usage of a memory pool has reached
 // or exceeded its threshold, it will trigger the sensor for the type
 // of the memory pool (heap or nonheap or both).
 //
 // If threshold == -1, no low memory detection is supported and
 // the threshold value is not allowed to be changed.
 // If threshold == 0, no low memory detection is performed for
 // that memory pool.  The threshold can be set to any non-negative
 // value.
 //
 // The default threshold of the Hotspot memory pools are:
 //   Eden space        -1
 //   Survivor space 1  -1
 //   Survivor space 2  -1
 //   Old generation    0
 //   Perm generation   0
 //   CodeCache         0
 //
 // For heap memory, detection will be performed when GC finishes
 // and also in the slow path allocation.
 // For Code cache, detection will be performed in the allocation
 // and deallocation.
 //
 // May need to deal with hysteresis effect.
 //
 class LowMemoryDetectorThread;
 class OopClosure;
 class MemoryPool;
 class ThresholdSupport : public CHeapObj {
  private:
   bool            _support_high_threshold;
   bool            _support_low_threshold;
   size_t          _high_threshold;
   size_t          _low_threshold;
  public:
   ThresholdSupport(bool support_high, bool support_low) {
     _support_high_threshold = support_high;
     _support_low_threshold = support_low;
     _high_threshold = 0;
     _low_threshold= 0;
   }
   size_t      high_threshold() const        { return _high_threshold; }
   size_t      low_threshold()  const        { return _low_threshold; }
   bool        is_high_threshold_supported() { return _support_high_threshold; }
   bool        is_low_threshold_supported()  { return _support_low_threshold; }
   bool        is_high_threshold_crossed(MemoryUsage usage) {
     if (_support_high_threshold && _high_threshold > 0) {
       return (usage.used() >= _high_threshold);
     }
     return false;
   }
   bool        is_low_threshold_crossed(MemoryUsage usage) {
     if (_support_low_threshold && _low_threshold > 0) {
       return (usage.used() < _low_threshold);
     }
     return false;
   }
   size_t      set_high_threshold(size_t new_threshold) {
     assert(_support_high_threshold, "can only be set if supported");
     assert(new_threshold >= _low_threshold, "new_threshold must be >= _low_threshold");
     size_t prev = _high_threshold;
     _high_threshold = new_threshold;
     return prev;
   }
   size_t      set_low_threshold(size_t new_threshold) {
     assert(_support_low_threshold, "can only be set if supported");
     assert(new_threshold <= _high_threshold, "new_threshold must be <= _high_threshold");
     size_t prev = _low_threshold;
     _low_threshold = new_threshold;
     return prev;
   }
 };
 class SensorInfo : public CHeapObj {
 private:
   instanceOop     _sensor_obj;
   bool            _sensor_on;
   size_t          _sensor_count;
   // before the actual sensor on flag and sensor count are set
   // we maintain the number of pending triggers and clears.
   // _pending_trigger_count means the number of pending triggers
   // and the sensor count should be incremented by the same number.
   int             _pending_trigger_count;
   // _pending_clear_count takes precedence if it's > 0 which
   // indicates the resulting sensor will be off
   // Sensor trigger requests will reset this clear count to
   // indicate the resulting flag should be on.
   int             _pending_clear_count;
   MemoryUsage     _usage;
   void clear(int count, TRAPS);
   void trigger(int count, TRAPS);
 public:
   SensorInfo();
   void set_sensor(instanceOop sensor) {
     assert(_sensor_obj == NULL, "Should be set only once");
     _sensor_obj = sensor;
   }
   bool has_pending_requests() {
     return (_pending_trigger_count > 0 || _pending_clear_count > 0);
   }
   int pending_trigger_count()      { return _pending_trigger_count; }
   int pending_clear_count()        { return _pending_clear_count; }
   // When this method is used, the memory usage is monitored
   // as a gauge attribute.  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 set_gauge_sensor_level(MemoryUsage usage, ThresholdSupport* high_low_threshold);
   // 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.
   //
   // 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 set_counter_sensor_level(MemoryUsage usage, ThresholdSupport* counter_threshold);
   void process_pending_requests(TRAPS);
   void oops_do(OopClosure* f);
 #ifndef PRODUCT
   // printing on default output stream;
   void print();
 #endif // PRODUCT
 };
 class LowMemoryDetector : public AllStatic {
 friend class LowMemoryDetectorDisabler;
 private:
   // true if any collected heap has low memory detection enabled
   static volatile bool _enabled_for_collected_pools;
   // > 0 if temporary disabed
   static volatile jint _disabled_count;
   static LowMemoryDetectorThread* _detector_thread;
   static void low_memory_detector_thread_entry(JavaThread* thread, TRAPS);
   static void check_memory_usage();
   static bool has_pending_requests();
   static bool temporary_disabled() { return _disabled_count > 0; }
   static void disable() { Atomic::inc(&_disabled_count); }
   static void enable() { Atomic::dec(&_disabled_count); }
 public:
   static void initialize();
   static void detect_low_memory();
   static void detect_low_memory(MemoryPool* pool);
   static void detect_after_gc_memory(MemoryPool* pool);
   static bool is_enabled(MemoryPool* pool) {
     // low memory detection is enabled for collected memory pools
     // iff one of the collected memory pool has a sensor and the
     // threshold set non-zero
     if (pool->usage_sensor() == NULL) {
       return false;
     } else {
       ThresholdSupport* threshold_support = pool->usage_threshold();
       return (threshold_support->is_high_threshold_supported() ?
                (threshold_support->high_threshold() > 0) : false);
     }
   }
   // indicates if low memory detection is enabled for any collected
   // memory pools
   static inline bool is_enabled_for_collected_pools() {
     return !temporary_disabled() && _enabled_for_collected_pools;
   }
   // recompute enabled flag
   static void recompute_enabled_for_collected_pools();
   // low memory detection for collected memory pools.
   static inline void detect_low_memory_for_collected_pools() {
     // no-op if low memory detection not enabled
     if (!is_enabled_for_collected_pools()) {
       return;
     }
     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 low memory detection is enabled then check if the
       // current used exceeds the high threshold
       if (pool->is_collected_pool() && is_enabled(pool)) {
         size_t used = pool->used_in_bytes();
         size_t high = pool->usage_threshold()->high_threshold();
         if (used > high) {
           detect_low_memory(pool);
         }
       }
     }
   }
 };
 class LowMemoryDetectorDisabler: public StackObj {
 public:
   LowMemoryDetectorDisabler()
   {
     LowMemoryDetector::disable();
   }
   ~LowMemoryDetectorDisabler()
   {
     assert(LowMemoryDetector::temporary_disabled(), "should be disabled!");
     LowMemoryDetector::enable();
   }
 };

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/services/lowMemoryDetector.hpp@c18cbe5936b8 (annotated)

src/share/vm/services/lowMemoryDetector.hpp