Add Additional benchmarks and buffer size

Signed-off-by: Joe Richey <joerichey@google.com>

benches/mod.rs

@@ -7,6 +7,7 @@ use std::mem::MaybeUninit;
 // The buffer is hot, and does not require initialization.
 #[inline(always)]
 fn bench_getrandom<const N: usize>(b: &mut test::Bencher) {
+    b.bytes = N as u64;
     b.iter(|| {
         let mut buf = [0u8; N];
         getrandom::getrandom(&mut buf[..]).unwrap();
@@ -18,6 +19,7 @@ fn bench_getrandom<const N: usize>(b: &mut test::Bencher) {
 // scenario. The buffer is still hot, but requires initialization.
 #[inline(always)]
 fn bench_getrandom_uninit<const N: usize>(b: &mut test::Bencher) {
+    b.bytes = N as u64;
     b.iter(|| {
         // TODO: When the feature `maybe_uninit_as_bytes` is available, use:
         // ```
@@ -48,6 +50,9 @@ macro_rules! bench {
     };
 }
 
+// 16 bytes (128 bits) is the size of an 128-bit AES key/nonce.
+bench!(aes128, 128 / 8);
+
 // 32 bytes (256 bits) is the seed sized used for rand::thread_rng
 // and the `random` value in a ClientHello/ServerHello for TLS.
 // This is also the size of a 256-bit AES/HMAC/P-256/Curve25519 key
@@ -56,3 +61,8 @@ bench!(p256, 256 / 8);
 
 // A P-384/HMAC-384 key and/or nonce.
 bench!(p384, 384 / 8);
+
+// Initializing larger buffers is not the primary use case of this library, as
+// this should normally be done by a userspace CSPRNG. However, we have a test
+// here to see the effects of a lower (amortized) syscall overhead.
+bench!(page, 4096);