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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-17 12:02:58 +0000 |
commit | 698f8c2f01ea549d77d7dc3338a12e04c11057b9 (patch) | |
tree | 173a775858bd501c378080a10dca74132f05bc50 /vendor/once_cell/examples/bench_acquire.rs | |
parent | Initial commit. (diff) | |
download | rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.tar.xz rustc-698f8c2f01ea549d77d7dc3338a12e04c11057b9.zip |
Adding upstream version 1.64.0+dfsg1.upstream/1.64.0+dfsg1
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'vendor/once_cell/examples/bench_acquire.rs')
-rw-r--r-- | vendor/once_cell/examples/bench_acquire.rs | 39 |
1 files changed, 39 insertions, 0 deletions
diff --git a/vendor/once_cell/examples/bench_acquire.rs b/vendor/once_cell/examples/bench_acquire.rs new file mode 100644 index 000000000..151804746 --- /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<usize> = 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::<Vec<_>>(); + 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); + } + } +} |