findr/PERFORMANCE_IDEAS.md

Performance Ideas

Current state after regex→glob migration. findr beats fd in 3/4 cases.

Benchmark results (2026-06-17)

Case	fd	findr	Ratio
1 -E .jj	172ms	135ms	1.27x faster
2 -H	1.184s	1.097s	1.08x faster
3 -HI	1.251s	1.670s	1.34x slower
4 -E .git	274ms	202ms	1.36x faster

Case 3 (-HI) skips gitignore entirely, so it's pure I/O + allocation. System time is 2x fd's (12.1s vs 5.5s), pointing to syscall/allocation overhead.

Completed

1. Per-thread result buffers — each thread accumulates locally, merges once at exit. Eliminates per-result mutex contention.
2. Lean path join — join_path/join_path_dir use stack buffer + copy + single alloc instead of strings.Builder + fmt.sbprintf + clone.
3. Regex→glob migration — replaced regex NFA with backtracking glob matcher. Eliminated 27% of CPU spent on add_thread/is_ignored. Biggest win.

Remaining ideas

1. Larger getdents buffer (8KB → 64KB+) Fewer syscalls per directory with many entries. Low effort.

2. Eliminate entry name cloning strings.clone(name) in read_dir_entries heap-allocates per dirent. Names are valid in the getdents buffer during process_dir, so the clone may be unnecessary. Low effort.

3. Arena allocator per thread Bump allocator for all transient strings, free once at exit. Bigger change, helps everywhere.

4. Batched channel (fd's approach) Replace global results array with buffered channel of batches. Enables streaming output and sorting like fd does.