From 1b6a04ca5504955c571d1c97504fb45ea0befee4 Mon Sep 17 00:00:00 2001 From: Valentin Popov Date: Mon, 8 Jan 2024 01:21:28 +0400 Subject: Initial vendor packages Signed-off-by: Valentin Popov --- vendor/once_cell/examples/bench_acquire.rs | 39 ++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+) create mode 100644 vendor/once_cell/examples/bench_acquire.rs (limited to 'vendor/once_cell/examples/bench_acquire.rs') diff --git a/vendor/once_cell/examples/bench_acquire.rs b/vendor/once_cell/examples/bench_acquire.rs new file mode 100644 index 0000000..1518047 --- /dev/null +++ b/vendor/once_cell/examples/bench_acquire.rs @@ -0,0 +1,39 @@ +//! Benchmark the overhead that the synchronization of `OnceCell::get` causes. +//! We do some other operations that write to memory to get an imprecise but somewhat realistic +//! measurement. + +use once_cell::sync::OnceCell; +use std::sync::atomic::{AtomicUsize, Ordering}; + +const N_THREADS: usize = 16; +const N_ROUNDS: usize = 1_000_000; + +static CELL: OnceCell = OnceCell::new(); +static OTHER: AtomicUsize = AtomicUsize::new(0); + +fn main() { + let start = std::time::Instant::now(); + let threads = + (0..N_THREADS).map(|i| std::thread::spawn(move || thread_main(i))).collect::>(); + for thread in threads { + thread.join().unwrap(); + } + println!("{:?}", start.elapsed()); + println!("{:?}", OTHER.load(Ordering::Relaxed)); +} + +#[inline(never)] +fn thread_main(i: usize) { + // The operations we do here don't really matter, as long as we do multiple writes, and + // everything is messy enough to prevent the compiler from optimizing the loop away. + let mut data = [i; 128]; + let mut accum = 0usize; + for _ in 0..N_ROUNDS { + let _value = CELL.get_or_init(|| i + 1); + let k = OTHER.fetch_add(data[accum & 0x7F] as usize, Ordering::Relaxed); + for j in data.iter_mut() { + *j = (*j).wrapping_add(accum); + accum = accum.wrapping_add(k); + } + } +} -- cgit v1.2.3