95 lines
2.3 KiB
Rust
95 lines
2.3 KiB
Rust
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#![feature(test)]
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extern crate test;
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use std::{
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alloc::{alloc_zeroed, dealloc, Layout},
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ptr::NonNull,
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};
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// AlignedBuffer is like a Box<[u8; N]> except that it is always N-byte aligned
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struct AlignedBuffer<const N: usize>(NonNull<[u8; N]>);
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impl<const N: usize> AlignedBuffer<N> {
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fn layout() -> Layout {
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Layout::from_size_align(N, N).unwrap()
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}
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fn new() -> Self {
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let p = unsafe { alloc_zeroed(Self::layout()) } as *mut [u8; N];
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Self(NonNull::new(p).unwrap())
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}
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fn buf(&mut self) -> &mut [u8; N] {
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unsafe { self.0.as_mut() }
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}
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}
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impl<const N: usize> Drop for AlignedBuffer<N> {
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fn drop(&mut self) {
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unsafe { dealloc(self.0.as_ptr() as *mut u8, Self::layout()) }
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}
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}
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// Used to benchmark the throughput of getrandom in an optimal scenario.
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// The buffer is hot, and does not require initialization.
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#[inline(always)]
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fn bench<const N: usize>(b: &mut test::Bencher) {
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let mut ab = AlignedBuffer::<N>::new();
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let buf = ab.buf();
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b.iter(|| {
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getrandom::getrandom(&mut buf[..]).unwrap();
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test::black_box(&buf);
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});
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b.bytes = N as u64;
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}
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// Used to benchmark the throughput of getrandom is a slightly less optimal
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// scenario. The buffer is still hot, but requires initialization.
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#[inline(always)]
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fn bench_with_init<const N: usize>(b: &mut test::Bencher) {
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let mut ab = AlignedBuffer::<N>::new();
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let buf = ab.buf();
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b.iter(|| {
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for byte in buf.iter_mut() {
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*byte = 0;
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}
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getrandom::getrandom(&mut buf[..]).unwrap();
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test::black_box(&buf);
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});
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b.bytes = N as u64;
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}
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// 32 bytes (256-bit) is the seed sized used for rand::thread_rng
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const SEED: usize = 32;
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// Common size of a page, 4 KiB
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const PAGE: usize = 4096;
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// Large buffer to get asymptotic performance, 2 MiB
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const LARGE: usize = 1 << 21;
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#[bench]
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fn bench_seed(b: &mut test::Bencher) {
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bench::<SEED>(b);
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}
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#[bench]
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fn bench_seed_init(b: &mut test::Bencher) {
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bench_with_init::<SEED>(b);
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}
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#[bench]
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fn bench_page(b: &mut test::Bencher) {
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bench::<PAGE>(b);
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}
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#[bench]
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fn bench_page_init(b: &mut test::Bencher) {
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bench_with_init::<PAGE>(b);
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}
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#[bench]
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fn bench_large(b: &mut test::Bencher) {
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bench::<LARGE>(b);
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}
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#[bench]
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fn bench_large_init(b: &mut test::Bencher) {
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bench_with_init::<LARGE>(b);
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}
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