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Enable zerocopy for nix

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topjohnwu
2025-09-09 10:53:36 -07:00
parent 177a456d8b
commit 8d28f10a3f
2 changed files with 18 additions and 21 deletions
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2
native/src/core/Cargo.toml
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@@ -26,4 +26,4 @@ bytemuck = { workspace = true, features = ["derive"] }
thiserror = { workspace = true }
bit-set = { workspace = true }
argh = { workspace = true }
nix = { workspace = true, features = ["fs", "poll", "signal", "term"] }
nix = { workspace = true, features = ["fs", "poll", "signal", "term", "zerocopy"] }

37
native/src/core/su/pts.rs
View File

@@ -1,7 +1,7 @@
use base::{FileOrStd, LibcReturn, LoggedResult, OsResult, ResultExt, libc, warn};
use libc::{STDIN_FILENO, STDOUT_FILENO, TIOCGWINSZ, TIOCSWINSZ, c_int, ssize_t, winsize};
use libc::{STDIN_FILENO, TIOCGWINSZ, TIOCSWINSZ, c_int, winsize};
use nix::{
fcntl::OFlag,
fcntl::{OFlag, SpliceFFlags},
poll::{PollFd, PollFlags, PollTimeout, poll},
sys::signal::{SigSet, Signal, raise},
sys::signalfd::{SfdFlags, SignalFd},
@@ -10,9 +10,8 @@ use nix::{
};
use std::fs::File;
use std::io::{Read, Write};
use std::mem::{ManuallyDrop, MaybeUninit};
use std::mem::MaybeUninit;
use std::os::fd::{AsFd, AsRawFd, FromRawFd, OwnedFd, RawFd};
use std::ptr::null_mut;
use std::sync::atomic::{AtomicBool, Ordering};
static SHOULD_USE_SPLICE: AtomicBool = AtomicBool::new(true);
@@ -38,36 +37,34 @@ fn sync_winsize(ptmx: i32) {
}
}
fn splice(fd_in: RawFd, fd_out: RawFd, len: usize, flags: u32) -> OsResult<'static, ssize_t> {
unsafe { libc::splice(fd_in, null_mut(), fd_out, null_mut(), len, flags) }
fn splice(fd_in: impl AsFd, fd_out: impl AsFd, len: usize) -> OsResult<'static, usize> {
nix::fcntl::splice(fd_in, None, fd_out, None, len, SpliceFFlags::empty())
.into_os_result("splice", None, None)
}
fn pump_via_copy(infd: RawFd, outfd: RawFd) -> LoggedResult<()> {
fn pump_via_copy(mut fd_in: &File, mut fd_out: &File) -> LoggedResult<()> {
let mut buf = MaybeUninit::<[u8; 4096]>::uninit();
let buf = unsafe { buf.assume_init_mut() };
let mut infd = ManuallyDrop::new(unsafe { File::from_raw_fd(infd) });
let mut outfd = ManuallyDrop::new(unsafe { File::from_raw_fd(outfd) });
let len = infd.read(buf)?;
outfd.write_all(&buf[..len])?;
let len = fd_in.read(buf)?;
fd_out.write_all(&buf[..len])?;
Ok(())
}
fn pump_via_splice(infd: RawFd, outfd: RawFd, pipe: &(OwnedFd, OwnedFd)) -> LoggedResult<()> {
fn pump_via_splice(fd_in: &File, fd_out: &File, pipe: &(OwnedFd, OwnedFd)) -> LoggedResult<()> {
if !SHOULD_USE_SPLICE.load(Ordering::Acquire) {
return pump_via_copy(infd, outfd);
return pump_via_copy(fd_in, fd_out);
}
// The pipe capacity is by default 16 pages, let's just use 65536
let Ok(len) = splice(infd, pipe.1.as_raw_fd(), 65536_usize, 0) else {
let Ok(len) = splice(fd_in, &pipe.1, 65536) else {
// If splice failed, stop using splice and fallback to userspace copy
SHOULD_USE_SPLICE.store(false, Ordering::Release);
return pump_via_copy(infd, outfd);
return pump_via_copy(fd_in, fd_out);
};
if len == 0 {
return Ok(());
}
splice(pipe.0.as_raw_fd(), outfd, len as usize, 0)?;
splice(&pipe.0, fd_out, len)?;
Ok(())
}
@@ -96,7 +93,7 @@ fn restore_stdin(term: Termios) -> LoggedResult<()> {
.log_with_msg(|w| w.write_str("Failed to restore terminal attributes"))
}
fn pump_tty_impl(ptmx: OwnedFd, pump_stdin: bool) -> LoggedResult<()> {
fn pump_tty_impl(ptmx: File, pump_stdin: bool) -> LoggedResult<()> {
let mut signal_fd: Option<SignalFd> = None;
let raw_ptmx = ptmx.as_raw_fd();
@@ -139,9 +136,9 @@ fn pump_tty_impl(ptmx: OwnedFd, pump_stdin: bool) -> LoggedResult<()> {
if pfd.all().unwrap_or(false) {
let raw_fd = pfd.as_fd().as_raw_fd();
if raw_fd == STDIN_FILENO {
pump_via_splice(STDIN_FILENO, raw_ptmx, &pipe_fd)?;
pump_via_splice(FileOrStd::StdIn.as_file(), &ptmx, &pipe_fd)?;
} else if raw_fd == raw_ptmx {
pump_via_splice(raw_ptmx, STDOUT_FILENO, &pipe_fd)?;
pump_via_splice(&ptmx, FileOrStd::StdIn.as_file(), &pipe_fd)?;
} else if raw_fd == raw_sig {
sync_winsize(raw_ptmx);
signal_fd.as_ref().unwrap().read_signal()?;
@@ -167,7 +164,7 @@ pub fn pump_tty(ptmx: RawFd, pump_stdin: bool) {
None
};
let ptmx = unsafe { OwnedFd::from_raw_fd(ptmx) };
let ptmx = unsafe { File::from_raw_fd(ptmx) };
pump_tty_impl(ptmx, pump_stdin).ok();
if let Some(term) = old_term {