cat: improve splice fast-path

Author: oech3

.vscode/cspell.dictionaries/workspace.wordlist.txt

@@ -374,6 +374,7 @@ weblate
 algs
 wasm
 wasip
+SETPIPE
 
 # * stty terminal flags
 brkint

src/uu/cat/src/splice.rs

@@ -7,9 +7,8 @@ use super::{CatResult, FdReadable, InputHandle};
 use nix::unistd;
 use std::os::{fd::AsFd, unix::io::AsRawFd};
 
-use uucore::pipes::{pipe, splice, splice_exact};
+use uucore::pipes::{MAX_ROOTLESS_PIPE_SIZE, pipe, splice, splice_exact};
 
-const SPLICE_SIZE: usize = 1024 * 128;
 const BUF_SIZE: usize = 1024 * 16;
 
 /// This function is called from `write_fast()` on Linux and Android. The
@@ -24,10 +23,16 @@ pub(super) fn write_fast_using_splice<R: FdReadable, S: AsRawFd + AsFd>(
     handle: &InputHandle<R>,
     write_fd: &S,
 ) -> CatResult<bool> {
+    use nix::fcntl::{FcntlArg, fcntl};
     let (pipe_rd, pipe_wr) = pipe()?;
+    // improve performance
+    let _ = fcntl(
+        write_fd,
+        FcntlArg::F_SETPIPE_SZ(MAX_ROOTLESS_PIPE_SIZE as i32),
+    );
 
     loop {
-        match splice(&handle.reader, &pipe_wr, SPLICE_SIZE) {
+        match splice(&handle.reader, &pipe_wr, MAX_ROOTLESS_PIPE_SIZE) {
             Ok(n) => {
                 if n == 0 {
                     return Ok(false);

src/uucore/src/lib/features/pipes.rs

@@ -4,21 +4,26 @@
 // file that was distributed with this source code.
 
 //! Thin zero-copy-related wrappers around functions from the `rustix` crate.
+
 #[cfg(any(target_os = "linux", target_os = "android"))]
 use std::fs::File;
 #[cfg(any(target_os = "linux", target_os = "android"))]
 use std::os::fd::AsFd;
-
 #[cfg(any(target_os = "linux", target_os = "android"))]
 use rustix::pipe::SpliceFlags;
+pub const MAX_ROOTLESS_PIPE_SIZE: usize = 1024 * 1024;
 
 /// A wrapper around [`rustix::pipe::pipe`] that ensures the pipe is cleaned up.
 ///
 /// Returns two `File` objects: everything written to the second can be read
 /// from the first.
+/// This is used only for resolving the limitation for splice: one of a input or output should be pipe
 #[cfg(any(target_os = "linux", target_os = "android"))]
 pub fn pipe() -> std::io::Result<(File, File)> {
     let (read, write) = rustix::pipe::pipe()?;
+    // improve performance for splice
+    let _ = fcntl(&read, FcntlArg::F_SETPIPE_SZ(MAX_ROOTLESS_PIPE_SIZE as i32));
+
     Ok((File::from(read), File::from(write)))
 }