ageTable.hpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
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 * 2 along with this work; if not, write to the Free Software Foundation,
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#ifndef SHARE_GC_SHARED_AGETABLE_HPP
#define SHARE_GC_SHARED_AGETABLE_HPP

#include "oops/markWord.hpp"
#include "oops/oop.hpp"
#include "runtime/perfDataTypes.hpp"

/* Copyright (c) 1992, 2021, Oracle and/or its affiliates, and Stanford University.
   See the LICENSE file for license information. */

// Age table for adaptive feedback-mediated tenuring (scavenging)
//
// Note: all sizes are in oops

class AgeTable {
  friend class VMStructs;

 public:
  // constants
  enum { table_size = markWord::max_age + 1 };

  // instance variables
  size_t sizes[table_size];

  // constructor.  "global" indicates that this is the global age table
  // (as opposed to gc-thread-local)
  AgeTable(bool global = true);

  // clear table
  void clear();

  // add entry
  inline void add(oop p, size_t oop_size);

  void add(uint age, size_t oop_size) {
    assert(age > 0 && age < table_size, "invalid age of object");
    sizes[age] += oop_size;
  }

  // Merge another age table with the current one.  Used
  // for parallel young generation gc.
  void merge(AgeTable* subTable);

  // Calculate new tenuring threshold based on age information.
  uint compute_tenuring_threshold(size_t desired_survivor_size);
  void print_age_table(uint tenuring_threshold);

 private:

  PerfVariable* _perf_sizes[table_size];
};

#endif // SHARE_GC_SHARED_AGETABLE_HPP