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Cat splice perf #10835

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0a70ae7
cat: optimize splice usage based on file size
FidelSch Feb 9, 2026
d027529
cat: increase file splice threshold to 16KB
FidelSch Feb 9, 2026
70afe03
lint(cat): unused variables
FidelSch Feb 9, 2026
04ad03d
cat: bypass clap when possible
FidelSch Feb 9, 2026
4102ac3
Merge branch 'main' into cat-splice-perf
sylvestre Feb 10, 2026
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135 changes: 86 additions & 49 deletions src/uu/cat/src/cat.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -26,6 +26,7 @@ use uucore::{fast_inc::fast_inc_one, format_usage};
/// Linux splice support
#[cfg(any(target_os = "linux", target_os = "android"))]
mod splice;
const FILE_SPLICE_SIZE_THRESHOLD: u64 = 1024 * 16; // 16KB

// Allocate 32 digits for the line number.
// An estimate is that we can print about 1e8 lines/seconds, so 32 digits
Expand Down Expand Up @@ -218,54 +219,79 @@ mod options {

#[uucore::main]
pub fn uumain(args: impl uucore::Args) -> UResult<()> {
let matches = uucore::clap_localization::handle_clap_result(uu_app(), args)?;
let args: Vec<OsString> = args.collect();
let mut files: Vec<OsString>;
let options;

let number_mode = if matches.get_flag(options::NUMBER_NONBLANK) {
NumberingMode::NonEmpty
} else if matches.get_flag(options::NUMBER) {
NumberingMode::All
if args.len() > 1
&& args
.iter()
.skip(1)
.all(|a| !a.to_string_lossy().starts_with('-') || a == "-")
{
// No options, just files.
// Skip clap parsing
files = args.into_iter().skip(1).collect();
if files.is_empty() {
files.push(OsString::from("-"));
}
options = OutputOptions {
show_ends: false,
number: NumberingMode::None,
show_nonprint: false,
show_tabs: false,
squeeze_blank: false,
};
} else {
NumberingMode::None
};
let matches = uucore::clap_localization::handle_clap_result(uu_app(), args)?;

let show_nonprint = [
options::SHOW_ALL.to_owned(),
options::SHOW_NONPRINTING_ENDS.to_owned(),
options::SHOW_NONPRINTING_TABS.to_owned(),
options::SHOW_NONPRINTING.to_owned(),
]
.iter()
.any(|v| matches.get_flag(v));

let show_ends = [
options::SHOW_ENDS.to_owned(),
options::SHOW_ALL.to_owned(),
options::SHOW_NONPRINTING_ENDS.to_owned(),
]
.iter()
.any(|v| matches.get_flag(v));

let show_tabs = [
options::SHOW_ALL.to_owned(),
options::SHOW_TABS.to_owned(),
options::SHOW_NONPRINTING_TABS.to_owned(),
]
.iter()
.any(|v| matches.get_flag(v));

let squeeze_blank = matches.get_flag(options::SQUEEZE_BLANK);
let files: Vec<OsString> = match matches.get_many::<OsString>(options::FILE) {
Some(v) => v.cloned().collect(),
None => vec![OsString::from("-")],
};
let number_mode = if matches.get_flag(options::NUMBER_NONBLANK) {
NumberingMode::NonEmpty
} else if matches.get_flag(options::NUMBER) {
NumberingMode::All
} else {
NumberingMode::None
};

let options = OutputOptions {
show_ends,
number: number_mode,
show_nonprint,
show_tabs,
squeeze_blank,
};
let show_nonprint = [
options::SHOW_ALL.to_owned(),
options::SHOW_NONPRINTING_ENDS.to_owned(),
options::SHOW_NONPRINTING_TABS.to_owned(),
options::SHOW_NONPRINTING.to_owned(),
]
.iter()
.any(|v| matches.get_flag(v));

let show_ends = [
options::SHOW_ENDS.to_owned(),
options::SHOW_ALL.to_owned(),
options::SHOW_NONPRINTING_ENDS.to_owned(),
]
.iter()
.any(|v| matches.get_flag(v));

let show_tabs = [
options::SHOW_ALL.to_owned(),
options::SHOW_TABS.to_owned(),
options::SHOW_NONPRINTING_TABS.to_owned(),
]
.iter()
.any(|v| matches.get_flag(v));

let squeeze_blank = matches.get_flag(options::SQUEEZE_BLANK);
files = match matches.get_many::<OsString>(options::FILE) {
Some(v) => v.cloned().collect(),
None => vec![OsString::from("-")],
};

options = OutputOptions {
show_ends,
number: number_mode,
show_nonprint,
show_tabs,
squeeze_blank,
};
}
cat_files(&files, &options)
}

Expand Down Expand Up @@ -359,9 +385,10 @@ fn cat_handle<R: FdReadable>(
handle: &mut InputHandle<R>,
options: &OutputOptions,
state: &mut OutputState,
skip_splice: bool,
) -> CatResult<()> {
if options.can_write_fast() {
write_fast(handle)
write_fast(handle, skip_splice)
} else {
write_lines(handle, options, state)
}
Expand All @@ -378,7 +405,7 @@ fn cat_path(path: &OsString, options: &OutputOptions, state: &mut OutputState) -
reader: stdin,
is_interactive: io::stdin().is_terminal(),
};
cat_handle(&mut handle, options, state)
cat_handle(&mut handle, options, state, false)
}
InputType::Directory => Err(CatError::IsDirectory),
#[cfg(unix)]
Expand All @@ -388,11 +415,20 @@ fn cat_path(path: &OsString, options: &OutputOptions, state: &mut OutputState) -
if is_unsafe_overwrite(&file, &io::stdout()) {
return Err(CatError::OutputIsInput);
}

// Skip splice if file is small enough
let metadata = file.metadata();
let skip_splice = if let Ok(metadata) = metadata {
metadata.len() <= FILE_SPLICE_SIZE_THRESHOLD
} else {
false
};

let mut handle = InputHandle {
reader: file,
is_interactive: false,
};
cat_handle(&mut handle, options, state)
cat_handle(&mut handle, options, state, skip_splice)
}
}
}
Expand Down Expand Up @@ -474,14 +510,15 @@ fn get_input_type(path: &OsString) -> CatResult<InputType> {

/// Writes handle to stdout with no configuration. This allows a
/// simple memory copy.
fn write_fast<R: FdReadable>(handle: &mut InputHandle<R>) -> CatResult<()> {
#[allow(unused_variables)]
fn write_fast<R: FdReadable>(handle: &mut InputHandle<R>, skip_splice: bool) -> CatResult<()> {
let stdout = io::stdout();
let mut stdout_lock = stdout.lock();
#[cfg(any(target_os = "linux", target_os = "android"))]
{
// If we're on Linux or Android, try to use the splice() system call
// for faster writing. If it works, we're done.
if !splice::write_fast_using_splice(handle, &stdout_lock)? {
if !skip_splice && !splice::write_fast_using_splice(handle, &stdout_lock)? {
return Ok(());
}
}
Expand Down
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