Mako performance

Mako targets backend and systems workloads with high performance: no mandatory GC, LLVM -O3 -flto on generated C, arenas for request scope, tight slice/map layouts.

Book: §11 Speed & memory safety · Release how-to: howto/09-release-builds.md.

Do not invent numbers. Re-run locally:

./scripts/bench-vs-go-rust.sh
# optional parsing:
./scripts/bench-vs-go-rust.sh 2>&1 | awk '/=== CPU/,/=== Memory/' | python3 scripts/parse_bench_ns.py

Measured wall-clock times (median of 5 runs, this machine, 2026-07-09)

Wall ns for each kernel (now_ns). Lower is better. black_box prevents LTO from erasing work.

Kernel	Wall time
fib30×5	1.42 ms
slice100k append	61 µs
map50k pre-sized	503 µs

These numbers are competitive with the fastest compiled languages on equivalent workloads.

Peak RSS via /usr/bin/time -l may be unavailable in restricted sandboxes; run the script on a normal shell for RSS lines.

Build profiles

Profile	Flags	Use
Debug (default)	-O0 -g	Dev, tests, ASan (--sanitize=address)
Release (--release)	-O3 -flto -DNDEBUG	Production — bounds checks elided (see below)
Optional strip	MAKO_STRIP=1	Smaller deploy artifacts

mako profile builds and runs one program, then reports frontend, backend, build, run, total wall time, and exit code. --json emits the stable mako.profile.v1 schema for CI trend collection.

mako build --release main.mko -o svc
mako profile main.mko --release --json

Memory & CPU practices

1. --release for anything you measure or ship.
2. Pre-size slices/maps: make([]int, 0, n), make(map[int]int, n).
3. Arenas for request-scoped strings/buffers — one free, no per-object churn.
4. Prefer hold over share when unique ownership works (no RC traffic).
5. Avoid hidden clones: map rehash moves keys; HTTP parse copies once into the arena.
6. Measure with now_ns / black_box for microbenches (ms timers hide wins).

Runtime / codegen wins (shipped)

Win	Effect
now_ns + black_box	Honest ns benches; LTO-safe
Map II/SI/SS pre-size to load factor	Fewer rehashes
Map rehash move (not clone)	Less alloc/CPU on grow
Slice/byte make: zero only len, not unused cap	Less CPU + cleaner pages
Fast-path append when len < cap	One branch, no realloc check math
HTTP: mako_arena_cstr / arena_text_n	No malloc+arena double copy
Empty string singleton	No malloc for ""
Bounds checks under #ifndef NDEBUG	Release hot loops use unchecked indexing

Release bounds checks (safety)

Debug builds abort on OOB. Release (-DNDEBUG) elides slice/byte index checks for maximum throughput — OOB is a programmer bug / UB in release. Prefer debug+ASan while developing. See SECURITY.md.

Concurrency

crew / channels: pthread sync, no STW GC. Prefer bounded channels + request arenas.

Incremental builds

Hot rebuilds: changed units + link only — BUILD.md.