1 files changed, 94 insertions, 0 deletions
diff --git a/third_party/rust/getrandom/benches/mod.rs b/third_party/rust/getrandom/benches/mod.rs
new file mode 100644
index 0000000000..11be47eb75
--- /dev/null
+++ b/third_party/rust/getrandom/benches/mod.rs
@@ -0,0 +1,94 @@
+#![feature(test)]
+extern crate test;
+
+use std::{
+    alloc::{alloc_zeroed, dealloc, Layout},
+    ptr::NonNull,
+};
+
+// AlignedBuffer is like a Box<[u8; N]> except that it is always N-byte aligned
+struct AlignedBuffer<const N: usize>(NonNull<[u8; N]>);
+
+impl<const N: usize> AlignedBuffer<N> {
+    fn layout() -> Layout {
+        Layout::from_size_align(N, N).unwrap()
+    }
+
+    fn new() -> Self {
+        let p = unsafe { alloc_zeroed(Self::layout()) } as *mut [u8; N];
+        Self(NonNull::new(p).unwrap())
+    }
+
+    fn buf(&mut self) -> &mut [u8; N] {
+        unsafe { self.0.as_mut() }
+    }
+}
+
+impl<const N: usize> Drop for AlignedBuffer<N> {
+    fn drop(&mut self) {
+        unsafe { dealloc(self.0.as_ptr() as *mut u8, Self::layout()) }
+    }
+}
+
+// Used to benchmark the throughput of getrandom in an optimal scenario.
+// The buffer is hot, and does not require initialization.
+#[inline(always)]
+fn bench<const N: usize>(b: &mut test::Bencher) {
+    let mut ab = AlignedBuffer::<N>::new();
+    let buf = ab.buf();
+    b.iter(|| {
+        getrandom::getrandom(&mut buf[..]).unwrap();
+        test::black_box(&buf);
+    });
+    b.bytes = N as u64;
+}
+
+// Used to benchmark the throughput of getrandom is a slightly less optimal
+// scenario. The buffer is still hot, but requires initialization.
+#[inline(always)]
+fn bench_with_init<const N: usize>(b: &mut test::Bencher) {
+    let mut ab = AlignedBuffer::<N>::new();
+    let buf = ab.buf();
+    b.iter(|| {
+        for byte in buf.iter_mut() {
+            *byte = 0;
+        }
+        getrandom::getrandom(&mut buf[..]).unwrap();
+        test::black_box(&buf);
+    });
+    b.bytes = N as u64;
+}
+
+// 32 bytes (256-bit) is the seed sized used for rand::thread_rng
+const SEED: usize = 32;
+// Common size of a page, 4 KiB
+const PAGE: usize = 4096;
+// Large buffer to get asymptotic performance, 2 MiB
+const LARGE: usize = 1 << 21;
+
+#[bench]
+fn bench_seed(b: &mut test::Bencher) {
+    bench::<SEED>(b);
+}
+#[bench]
+fn bench_seed_init(b: &mut test::Bencher) {
+    bench_with_init::<SEED>(b);
+}
+
+#[bench]
+fn bench_page(b: &mut test::Bencher) {
+    bench::<PAGE>(b);
+}
+#[bench]
+fn bench_page_init(b: &mut test::Bencher) {
+    bench_with_init::<PAGE>(b);
+}
+
+#[bench]
+fn bench_large(b: &mut test::Bencher) {
+    bench::<LARGE>(b);
+}
+#[bench]
+fn bench_large_init(b: &mut test::Bencher) {
+    bench_with_init::<LARGE>(b);
+}