Package com.carrotsearch.hppc

Class RamUsageEstimator

java.lang.Object
com.carrotsearch.hppc.RamUsageEstimator
public class RamUsageEstimator
extends java.lang.Object
Helper class that helps estimate memory usage

Mostly forked from Lucene tag releases/lucene-solr/8.5.1

  • Field Summary

    Fields 
    Modifier and Type Field Description
    static boolean COMPRESSED_REFS_ENABLED
    True, iff compressed references (oops) are enabled by this JVM
    static int NUM_BYTES_ARRAY_HEADER
    Number of bytes to represent an array header (no content, but with alignments).
    static int NUM_BYTES_OBJECT_ALIGNMENT
    A constant specifying the object alignment boundary inside the JVM.
    static int NUM_BYTES_OBJECT_HEADER
    Number of bytes to represent an object header (no fields, no alignments).
    static int NUM_BYTES_OBJECT_REF
    Number of bytes this JVM uses to represent an object reference.
    static long ONE_GB
    One gigabyte bytes.
    static long ONE_KB
    One kilobyte bytes.
    static long ONE_MB
    One megabyte bytes.
    static java.util.Map<java.lang.Class<?>,​java.lang.Integer> primitiveSizes
    Sizes of primitive classes.

  • Method Summary

    Modifier and Type Method Description
    static long alignObjectSize​(long size)
    Aligns an object size to be the next multiple of NUM_BYTES_OBJECT_ALIGNMENT.
    static long shallowSizeOfArray​(java.lang.Object array)
    Return shallow size of any array.
    static long shallowUsedSizeOfArray​(java.lang.Object array, int usedSize)
    Return used part of shallow size of any array.

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Field Details

    • ONE_KB

      public static final long ONE_KB
      One kilobyte bytes.
      See Also:
      Constant Field Values

    • ONE_MB

      public static final long ONE_MB
      One megabyte bytes.
      See Also:
      Constant Field Values

    • ONE_GB

      public static final long ONE_GB
      One gigabyte bytes.
      See Also:
      Constant Field Values

    • COMPRESSED_REFS_ENABLED

      public static final boolean COMPRESSED_REFS_ENABLED
      True, iff compressed references (oops) are enabled by this JVM

    • NUM_BYTES_OBJECT_REF

      public static final int NUM_BYTES_OBJECT_REF
      Number of bytes this JVM uses to represent an object reference.

    • NUM_BYTES_OBJECT_HEADER

      public static final int NUM_BYTES_OBJECT_HEADER
      Number of bytes to represent an object header (no fields, no alignments).

    • NUM_BYTES_ARRAY_HEADER

      public static final int NUM_BYTES_ARRAY_HEADER
      Number of bytes to represent an array header (no content, but with alignments).

    • NUM_BYTES_OBJECT_ALIGNMENT

      public static final int NUM_BYTES_OBJECT_ALIGNMENT
      A constant specifying the object alignment boundary inside the JVM. Objects will always take a full multiple of this constant, possibly wasting some space.

    • primitiveSizes

      public static final java.util.Map<java.lang.Class<?>,​java.lang.Integer> primitiveSizes
      Sizes of primitive classes.

  • Method Details

    • alignObjectSize

      public static long alignObjectSize​(long size)
      Aligns an object size to be the next multiple of NUM_BYTES_OBJECT_ALIGNMENT.

    • shallowUsedSizeOfArray

      public static long shallowUsedSizeOfArray​(java.lang.Object array, int usedSize)
      Return used part of shallow size of any array.
      Parameters:
      usedSize - Size that array is actually used

    • shallowSizeOfArray

      public static long shallowSizeOfArray​(java.lang.Object array)
      Return shallow size of any array.