NAME

       "Devel::MAT::Tool::Sizes" - calculate sizes of SV structures

DESCRIPTION

       This "Devel::MAT" tool calculates the sizes of the structures around SVs.  The individual
       size of each individual SV is given by the "size" method, though in several cases SVs can
       be considered to be part of larger structures of a combined aggregate size. This tool
       calculates those sizes and adds them to the UI.

       The structural size is calculated from the basic size of the SV, added to which for
       various types is:

       ARRAY
         Arrays add the basic size of every non-mortal element SV.

       HASH
         Hashes add the basic size of every non-mortal value SV.

       CODE
         Codes add the basic size of their padlist and constant value, and all their padnames,
         pads, constants and globrefs.

       The owned size is calculated by starting at the given SV and accumulating the set of every
       strong outref whose refcount is 1. This is the set of all SVs the original directly owns.

SV METHODS

       This tool adds the following SV methods.

   structure_set
          @svs = $sv->structure_set

       Returns the total set of the SV's structure.

   structure_size
          $size = $sv->structure_size

       Returns the size, in bytes, of the structure that the SV contains.

   owned_set
          @svs = $sv->owned_set

       Returns the set of every SV owned by the given one.

   owned_size
          $size = $sv->owned_size

       Returns the total size, in bytes, of the SVs owned by the given one.

COMMANDS

   size
       Prints the sizes of a given SV

          pmat> size defstash
          STASH(61) at 0x556e47243e10=defstash consumes:
            2.1 KiB directly
            11.2 KiB structurally
            54.2 KiB including owned referrants

   largest
          pmat> largest -owned
          STASH(61) at 0x55e4317dfe10: 54.2 KiB: of which
           |   GLOB(%*) at 0x55e43180be60: 16.9 KiB: of which
           |    |   STASH(40) at 0x55e43180bdd0: 16.7 KiB
           |    |   GLOB(&*) at 0x55e4318ad330: 2.8 KiB
           |    |   others: 15.0 KiB
           |   GLOB(%*) at 0x55e4317fdf28: 4.1 KiB: of which
           |    |   STASH(34) at 0x55e4317fdf40: 4.0 KiB bytes
          ...

       Finds and prints the largest SVs by size. The 5 largest SVs are shown.

       If counting sizes in a way that includes referred SVs, a tree is printed showing the 3
       largest SVs within these, and of those the 2 largest referred SVs again. This should help
       identify large memory occupiers.

       Takes the following named options:

       --struct
           Count SVs using the structural size.

       --owned
           Count SVs using the owned size.

       By default, only the individual SV size is counted.

AUTHOR

       Paul Evans <leonerd@leonerd.org.uk>