Erlang Term Info (Memory Consumption)

Purpose

To provide the in-memory size of Erlang terms, ignoring where the Erlang terms are stored.

Size information should match the Erlang Efficiency Guide memory information:

• Small integer: 1 word
  • On 32-bit architectures: -134217729 < i < 134217728 (28 bits)
  • On 64-bit architectures: -576460752303423489 < i < 576460752303423488 (60 bits)
• Big integer: 3..N words
• Atom: 1 word
• Float:
  • On 32-bit architectures: 4 words
  • On 64-bit architectures: 3 words
• Binary: 3..6 + data
• List: 1 word + 1 word per element + the size of each element
• Tuple: 2 words + the size of each element
• Small Map (N =< 32): 5 words + the size of all keys and values
• Large Map (N > 32): N * [1.6 .. 1.8] + the size of all keys and values
• Pid:
  • From local node: 1 word
  • From remote node: 5 words
• Port:
  • From local node: 1 word
  • From remote node: 5 words
• Reference:
  • On 32-bit architectures:
    • From local node: 5 words
    • From remote node: 7 words
  • On 64-bit architectures:
    • From local node: 4 words
    • From remote node: 6 words
• Fun: 9..13 words + size of environment
• Erlang process: 338 words when spawned (includes a heap of 233 words)

Limitations

• Binaries are not tracked to avoid counting a reference more than once (to avoid the extra latency and memory use)

License

MIT License

Contact

Michael Truog (mjtruog at protonmail dot com)

Thanks

• Sverker Eriksson erts_debug:flat_size/1 info