Update "chunk" benchmark

benches/single_thread_with_chunks.rs

@@ -1,7 +1,6 @@
 //! Single-threaded benchmarks, writing and reading chunks.
 //!
-//! Single-threaded usage is *not* a typical use case,
-//! but the used chunk size and capacity could be.
+//! Single-threaded usage is *not* a typical use case!
 
 use std::io::{Read, Write};
 
@@ -10,7 +9,7 @@ use criterion::{AxisScale, PlotConfiguration};
 
 use rtrb::{CopyToUninit, RingBuffer};
 
-const CHUNK_SIZE: usize = 4096;
+const CHUNK_SIZE: usize = 64;
 
 fn add_function<F, M>(group: &mut criterion::BenchmarkGroup<M>, id: impl Into<String>, mut f: F)
 where
@@ -35,7 +34,7 @@ pub fn criterion_benchmark(criterion: &mut criterion::Criterion) {
     group.throughput(criterion::Throughput::Bytes(CHUNK_SIZE as u64));
     group.plot_config(PlotConfiguration::default().summary_scale(AxisScale::Logarithmic));
 
-    let (mut p, mut c) = RingBuffer::<u8>::new(1000 * CHUNK_SIZE);
+    let (mut p, mut c) = RingBuffer::<u8>::new(CHUNK_SIZE + 1);
 
     add_function(&mut group, "1-pop", |data| {
         let mut result = [0; CHUNK_SIZE];
@@ -60,8 +59,9 @@ pub fn criterion_benchmark(criterion: &mut criterion::Criterion) {
         let _ = p.write(data).unwrap();
         let chunk = c.read_chunk(data.len()).unwrap();
         let (first, second) = chunk.as_slices();
-        result.copy_from_slice(first);
-        debug_assert!(second.is_empty());
+        let mid = first.len();
+        result[..mid].copy_from_slice(first);
+        result[mid..].copy_from_slice(second);
         chunk.commit_all();
         result
     });
@@ -70,8 +70,9 @@ pub fn criterion_benchmark(criterion: &mut criterion::Criterion) {
         let mut result = [0; CHUNK_SIZE];
         let mut chunk = p.write_chunk(data.len()).unwrap();
         let (first, second) = chunk.as_mut_slices();
-        first.copy_from_slice(data);
-        debug_assert!(second.is_empty());
+        let mid = first.len();
+        first.copy_from_slice(&data[..mid]);
+        second.copy_from_slice(&data[mid..]);
         chunk.commit_all();
         let _ = c.read(&mut result).unwrap();
         result
@@ -81,8 +82,9 @@ pub fn criterion_benchmark(criterion: &mut criterion::Criterion) {
         let mut result = [0; CHUNK_SIZE];
         let mut chunk = p.write_chunk_uninit(data.len()).unwrap();
         let (first, second) = chunk.as_mut_slices();
-        data.copy_to_uninit(first);
-        debug_assert!(second.is_empty());
+        let mid = first.len();
+        data[..mid].copy_to_uninit(first);
+        data[mid..].copy_to_uninit(second);
         unsafe {
             chunk.commit_all();
         }