vm/memory/referencePolicy.hpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
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 * published by the Free Software Foundation.
 *
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 * 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.
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#ifndef SHARE_VM_MEMORY_REFERENCEPOLICY_HPP
#define SHARE_VM_MEMORY_REFERENCEPOLICY_HPP

// referencePolicy is used to determine when soft reference objects
// should be cleared.


class ReferencePolicy : public CHeapObj<mtGC> {
 public:
  virtual bool should_clear_reference(oop p, jlong timestamp_clock) {
    ShouldNotReachHere();
    return true;
  }

  // Capture state (of-the-VM) information needed to evaluate the policy
  virtual void setup() { /* do nothing */ }
};

class NeverClearPolicy : public ReferencePolicy {
 public:
  virtual bool should_clear_reference(oop p, jlong timestamp_clock) {
    return false;
  }
};

class AlwaysClearPolicy : public ReferencePolicy {
 public:
  virtual bool should_clear_reference(oop p, jlong timestamp_clock) {
    return true;
  }
};

class LRUCurrentHeapPolicy : public ReferencePolicy {
 private:
  jlong _max_interval;

 public:
  LRUCurrentHeapPolicy();

  // Capture state (of-the-VM) information needed to evaluate the policy
  void setup();
  virtual bool should_clear_reference(oop p, jlong timestamp_clock);
};

class LRUMaxHeapPolicy : public ReferencePolicy {
 private:
  jlong _max_interval;

 public:
  LRUMaxHeapPolicy();

  // Capture state (of-the-VM) information needed to evaluate the policy
  void setup();
  virtual bool should_clear_reference(oop p, jlong timestamp_clock);
};

#endif // SHARE_VM_MEMORY_REFERENCEPOLICY_HPP