
  [;1m-spec memory() -> [{Type, Size}][0m
  [;1m                when Type :: memory_type(), Size :: non_neg_integer().[0m

  Returns a list with information about memory dynamically allocated
  by the Erlang emulator.

  Each list element is a tuple [;;4m{Type, Size}[0m. The first element [;;4m[0m
  [;;4mType[0m is an atom describing memory type. The second element [;;4mSize[0m
  is the memory size in bytes.

  Memory types:

   • [;;4mtotal[0m - The total amount of memory currently allocated.
     This is the same as the sum of the memory size for [;;4m[0m
     [;;4mprocesses[0m and [;;4msystem[0m.

   • [;;4mprocesses[0m - The total amount of memory currently allocated
     for the Erlang processes.

   • [;;4mprocesses_used[0m - The total amount of memory currently used
     by the Erlang processes. This is part of the memory
     presented as [;;4mprocesses[0m memory.

   • [;;4msystem[0m - The total amount of memory currently allocated for
     the emulator that is not directly related to any Erlang
     process. Memory presented as [;;4mprocesses[0m is not included in
     this memory. [;;4minstrument[0m can be used to get a more detailed
     breakdown of what memory is part of this type.

   • [;;4matom[0m - The total amount of memory currently allocated for
     atoms. This memory is part of the memory presented as [;;4m[0m
     [;;4msystem[0m memory.

   • [;;4matom_used[0m - The total amount of memory currently used for
     atoms. This memory is part of the memory presented as [;;4matom[0m
     memory.

   • [;;4mbinary[0m - The total amount of memory currently allocated for
     binaries. This memory is part of the memory presented as [;;4m[0m
     [;;4msystem[0m memory.

   • [;;4mcode[0m - The total amount of memory currently allocated for
     Erlang code. This memory is part of the memory presented as [;;4m[0m
     [;;4msystem[0m memory.

   • [;;4mets[0m - The total amount of memory currently allocated for
     ETS tables. This memory is part of the memory presented as [;;4m[0m
     [;;4msystem[0m memory.

   • [;;4mmaximum[0m - The maximum total amount of memory allocated
     since the emulator was started. This tuple is only present
     when the emulator is run with instrumentation.

     For information on how to run the emulator with
     instrumentation, see [;;4minstrument[0m and/or [;;4merl(1)[0m.

  [;;4mNote[0m

    The [;;4msystem[0m value is not complete. Some allocated memory that
    is to be part of this value is not. When the emulator is run
    with instrumentation, the [;;4msystem[0m value is more accurate, but
    memory directly allocated for [;;4mmalloc[0m (and friends) is still
    not part of the [;;4msystem[0m value. Direct calls to [;;4mmalloc[0m are
    only done from OS-specific runtime libraries and perhaps from
    user-implemented Erlang drivers that do not use the memory
    allocation functions in the driver interface. As the [;;4mtotal[0m
    value is the sum of [;;4mprocesses[0m and [;;4msystem[0m, the error in [;;4m[0m
    [;;4msystem[0m propagates to the [;;4mtotal[0m value. The different amounts
    of memory that are summed are not gathered atomically, which
    introduces an error in the result.

  The different values have the following relation to each other.
  Values beginning with an uppercase letter is not part of the
  result.

    total      = processes + system
    processes  = processes_used + ProcessesNotUsed
    system     = atom + binary + code + ets + OtherSystem
    atom       = atom_used + AtomNotUsed
    RealTotal  = processes + RealSystem
    RealSystem = system + MissedSystem

  More tuples in the returned list can be added in a future release.

  [;;4mNote[0m

    The [;;4mtotal[0m value is supposed to be the total amount of memory
    dynamically allocated by the emulator. Shared libraries, the
    code of the emulator itself, and the emulator stacks are not
    supposed to be included. That is, the [;;4mtotal[0m value is not
    supposed to be equal to the total size of all pages mapped to
    the emulator. Also, because of fragmentation and
    prereservation of memory areas, the size of the memory
    segments containing the dynamically allocated memory blocks
    can be much larger than the total size of the dynamically
    allocated memory blocks.

  [;;4mChange[0m

    As from ERTS 5.6.4, [;;4merlang:memory/0[0m requires that all [;;4m[0m
    [;;4merts_alloc(3)[0m allocators are enabled (default behavior).

  Failure: [;;4mnotsup[0m if an [;;4merts_alloc(3)[0m allocator has been
  disabled.
