This experiment is a bit weird. If you look at
https://github.com/matklad/lock-bench, this was run on a machine with 8 logical CPUs, but the test is using 32 threads. It's not that surprising that running 4x as many threads as there are CPUs doesn't make sense for spin locks.
I did a quick test on my Mac using 4 threads instead. At "heavy contention" the spin lock is actually 22% faster than parking_lot::Mutex. At "extreme contention", the spin lock is 22% slower than parking_lot::Mutex.
Heavy contention run:
$ cargo run --release 4 64 10000 100
Finished release [optimized] target(s) in 0.01s
Running `target/release/lock-bench 4 64 10000 100`
Options {
n_threads: 4,
n_locks: 64,
n_ops: 10000,
n_rounds: 100,
}
std::sync::Mutex avg 2.822382ms min 1.459601ms max 3.342966ms
parking_lot::Mutex avg 1.070323ms min 760.52µs max 1.212874ms
spin::Mutex avg 879.457µs min 681.836µs max 990.38µs
AmdSpinlock avg 915.096µs min 445.494µs max 1.003548ms
std::sync::Mutex avg 2.832905ms min 2.227285ms max 3.46791ms
parking_lot::Mutex avg 1.059368ms min 507.346µs max 1.263203ms
spin::Mutex avg 873.197µs min 432.016µs max 1.062487ms
AmdSpinlock avg 916.393µs min 568.889µs max 1.024317ms
Extreme contention run:
$ cargo run --release 4 2 10000 100
Finished release [optimized] target(s) in 0.01s
Running `target/release/lock-bench 4 2 10000 100`
Options {
n_threads: 4,
n_locks: 2,
n_ops: 10000,
n_rounds: 100,
}
std::sync::Mutex avg 4.552701ms min 2.699316ms max 5.42634ms
parking_lot::Mutex avg 2.802124ms min 1.398002ms max 4.798426ms
spin::Mutex avg 3.596568ms min 1.66903ms max 4.290803ms
AmdSpinlock avg 3.470115ms min 1.707714ms max 4.118536ms
std::sync::Mutex avg 4.486896ms min 2.536907ms max 5.821404ms
parking_lot::Mutex avg 2.712171ms min 1.508037ms max 5.44592ms
spin::Mutex avg 3.563192ms min 1.700003ms max 4.264851ms
AmdSpinlock avg 3.643592ms min 2.208522ms max 4.856297ms