bench: reduce memory variance in cp and numfmt benchmarks (#10283)

src/uu/cp/benches/cp_bench.rs

@@ -82,20 +82,25 @@ fn cp_preserve_metadata(
 
 #[divan::bench(args = [16])]
 fn cp_large_file(bencher: Bencher, size_mb: usize) {
-    let temp_dir = TempDir::new().unwrap();
-    let source = temp_dir.path().join("source.bin");
-    let dest = temp_dir.path().join("dest.bin");
+    bencher
+        .with_inputs(|| {
+            let temp_dir = TempDir::new().unwrap();
+            let source = temp_dir.path().join("source.bin");
+            binary_data::create_file(&source, size_mb, b'x');
+            (temp_dir, source)
+        })
+        .counter(divan::counter::BytesCount::new(size_mb * 1024 * 1024))
+        .bench_values(|(temp_dir, source)| {
+            // Use unique destination name to avoid filesystem allocation variance
+            let dest = temp_dir.path().join(format!(
+                "dest_{}.bin",
+                std::ptr::addr_of!(temp_dir) as usize
+            ));
+            let source_str = source.to_str().unwrap();
+            let dest_str = dest.to_str().unwrap();
 
-    binary_data::create_file(&source, size_mb, b'x');
-
-    let source_str = source.to_str().unwrap();
-    let dest_str = dest.to_str().unwrap();
-
-    bencher.bench(|| {
-        fs_utils::remove_path(&dest);
-
-        black_box(run_util_function(uumain, &[source_str, dest_str]));
-    });
+            black_box(run_util_function(uumain, &[source_str, dest_str]));
+        });
 }
 
 fn main() {

src/uu/numfmt/benches/numfmt_bench.rs

@@ -63,19 +63,22 @@ fn numfmt_from_si(bencher: Bencher, count: usize) {
 /// Benchmark large numbers with SI formatting
 #[divan::bench(args = [10_000])]
 fn numfmt_large_numbers_si(bencher: Bencher, count: usize) {
-    // Generate numbers that all produce uniform SI output lengths (all in 1-9M range)
-    // This avoids variance from variable output string lengths
-    let numbers: Vec<String> = (1..=count)
-        .map(|n| ((n % 9) + 1) * 1_000_000)
-        .map(|n| n.to_string())
-        .collect();
-    let mut args = vec!["--to=si"];
-    let number_refs: Vec<&str> = numbers.iter().map(|s| s.as_str()).collect();
-    args.extend(number_refs);
-
-    bencher.bench(|| {
-        black_box(run_util_function(uumain, &args));
-    });
+    bencher
+        .with_inputs(|| {
+            // Generate numbers that all produce uniform SI output lengths (all in 1-9M range)
+            // This avoids variance from variable output string lengths
+            let numbers: Vec<String> = (1..=count)
+                .map(|n| ((n % 9) + 1) * 1_000_000)
+                .map(|n| n.to_string())
+                .collect();
+            let mut args: Vec<String> = vec!["--to=si".to_string()];
+            args.extend(numbers);
+            args
+        })
+        .bench_values(|args| {
+            let arg_refs: Vec<&str> = args.iter().map(|s| s.as_str()).collect();
+            black_box(run_util_function(uumain, &arg_refs));
+        });
 }
 
 /// Benchmark different padding widths