df: add benchmarks

Author: sylvestre

.github/workflows/benchmarks.yml

@@ -28,6 +28,7 @@ jobs:
           - { package: uu_cp }
           - { package: uu_cut }
           - { package: uu_dd }
+          - { package: uu_df }
           - { package: uu_du }
           - { package: uu_expand }
           - { package: uu_fold }

Cargo.lock

@@ -25,8 +25,14 @@ thiserror = { workspace = true }
 fluent = { workspace = true }
 
 [dev-dependencies]
+divan = { workspace = true }
 tempfile = { workspace = true }
+uucore = { workspace = true, features = ["benchmark"] }
 
 [[bin]]
 name = "df"
 path = "src/main.rs"
+
+[[bench]]
+name = "df_bench"
+harness = false

src/uu/df/Cargo.toml

@@ -0,0 +1,64 @@
+// This file is part of the uutils coreutils package.
+//
+// For the full copyright and license information, please view the LICENSE
+// file that was distributed with this source code.
+
+use divan::{Bencher, black_box};
+use std::env;
+use std::fs;
+use std::path::PathBuf;
+use tempfile::TempDir;
+use uu_df::uumain;
+use uucore::benchmark::run_util_function;
+
+/// Create a deeply nested directory structure and return the path to the deepest level.
+/// Creates directories in chunks to avoid PATH_MAX limits.
+fn create_deep_directory(base_dir: &std::path::Path, depth: usize) -> PathBuf {
+    let mut current = base_dir.to_path_buf();
+    env::set_current_dir(&current).unwrap();
+
+    for _ in 0..depth {
+        current = current.join("d");
+        fs::create_dir("d").unwrap();
+        env::set_current_dir("d").unwrap();
+    }
+    current
+}
+
+/// Benchmark df running from a deeply nested directory (20000 levels).
+/// This tests the fix for issue #10117 where df was O(n²) slow in deep directories
+/// due to calling is_symlink() on relative device names like "tmpfs".
+#[divan::bench(sample_count = 300, sample_size = 1)]
+fn df_deep_directory(bencher: Bencher) {
+    const DEPTH: usize = 20000;
+
+    // Save original directory
+    let original_dir = env::current_dir().unwrap();
+
+    let temp_dir = TempDir::new().unwrap();
+    // create_deep_directory changes cwd to the deepest level
+    let _deep_path = create_deep_directory(temp_dir.path(), DEPTH);
+
+    // We're now in the deep directory, run the benchmark
+    bencher.bench(|| {
+        black_box(run_util_function(uumain, &[] as &[&str]));
+    });
+
+    // Restore original directory
+    env::set_current_dir(original_dir).unwrap();
+}
+
+/// Benchmark df with explicit path argument (baseline, not affected by cwd depth)
+#[divan::bench(sample_count = 300, sample_size = 1)]
+fn df_with_path(bencher: Bencher) {
+    let temp_dir = TempDir::new().unwrap();
+    let temp_path_str = temp_dir.path().to_str().unwrap();
+
+    bencher.bench(|| {
+        black_box(run_util_function(uumain, &[temp_path_str]));
+    });
+}
+
+fn main() {
+    divan::main();
+}