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