reduce the recursion to its core, keep no state

Byron · Jun 1, 2021 · 247cf38 · 247cf38
1 parent a6afcfe
commit 247cf38
Showing 1 changed file with 39 additions and 54 deletions.
diff --git a/benches/walk_benchmark.rs b/benches/walk_benchmark.rs
@@ -32,74 +32,59 @@ fn checkout_linux_if_needed() {
     }
 }
 
-#[derive(Default)]
-struct FsTree {
-    children: Vec<FsTree>,
-    metadata: Option<std::fs::Metadata>,
-}
+fn recursive_descent(
+    root: impl AsRef<Path>,
+    file_type: Option<std::fs::FileType>,
+    get_file_metadata: bool,
+) {
+    let root = root.as_ref();
+    let (_metadata, is_dir) = file_type
+        .map(|ft| {
+            (
+                if !ft.is_dir() && get_file_metadata {
+                    std::fs::symlink_metadata(root).ok()
+                } else {
+                    None
+                },
+                ft.is_dir(),
+            )
+        })
+        .or_else(|| {
+            std::fs::symlink_metadata(root)
+                .map(|m| {
+                    let is_dir = m.file_type().is_dir();
+                    (Some(m), is_dir)
+                })
+                .ok()
+        })
+        .unwrap_or((None, false));
 
-impl FsTree {
-    fn recursive_descent(
-        root: impl AsRef<Path>,
-        file_type: Option<std::fs::FileType>,
-        get_file_metadata: bool,
-    ) -> Self {
-        let root = root.as_ref();
-        let (metadata, is_dir) = file_type
-            .map(|ft| {
-                (
-                    if !ft.is_dir() && get_file_metadata {
-                        std::fs::symlink_metadata(root).ok()
-                    } else {
-                        None
-                    },
-                    ft.is_dir(),
-                )
-            })
-            .or_else(|| {
-                std::fs::symlink_metadata(root)
-                    .map(|m| {
-                        let is_dir = m.file_type().is_dir();
-                        (Some(m), is_dir)
+    if is_dir {
+        std::fs::read_dir(root)
+            .map(|iter| {
+                iter.filter_map(Result::ok)
+                    .collect::<Vec<_>>()
+                    .into_par_iter()
+                    .map(|entry| {
+                        recursive_descent(entry.path(), entry.file_type().ok(), get_file_metadata)
                     })
-                    .ok()
+                    .for_each(|_| {})
             })
-            .unwrap_or((None, false));
-
-        let children: Vec<_> = if is_dir {
-            std::fs::read_dir(root)
-                .map(|iter| {
-                    iter.filter_map(Result::ok)
-                        .collect::<Vec<_>>()
-                        .into_par_iter()
-                        .map(|entry| {
-                            FsTree::recursive_descent(
-                                entry.path(),
-                                entry.file_type().ok(),
-                                get_file_metadata,
-                            )
-                        })
-                        .collect()
-                })
-                .unwrap_or_default()
-        } else {
-            Vec::new()
-        };
-        FsTree { children, metadata }
-    }
+            .unwrap_or_default()
+    };
 }
 
 fn walk_benches(c: &mut Criterion) {
     checkout_linux_if_needed();
 
     c.bench_function(
         "simple recursive NO file metadata (unsorted, n threads)",
-        |b| b.iter(|| black_box(FsTree::recursive_descent(linux_dir(), None, false))),
+        |b| b.iter(|| black_box(recursive_descent(linux_dir(), None, false))),
     );
 
     c.bench_function(
         "simple recursive WITH file metadata (unsorted, n threads)",
-        |b| b.iter(|| black_box(FsTree::recursive_descent(linux_dir(), None, true))),
+        |b| b.iter(|| black_box(recursive_descent(linux_dir(), None, true))),
     );
 
     c.bench_function("jwalk (unsorted, n threads)", |b| {