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Remove random yielding

This commit is contained in:
Stjepan Glavina 2020-10-01 21:00:17 +02:00
parent c7e7fa89ed
commit 4e7cdb6a48
1 changed files with 1 additions and 21 deletions
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22
src/lib.rs
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@ -77,7 +77,7 @@ use std::os::windows::io::{AsRawSocket, FromRawSocket, RawSocket};
use futures_lite::io::{AsyncRead, AsyncWrite};
use futures_lite::stream::{self, Stream};
use futures_lite::{future, pin, ready};
use futures_lite::{future, pin};
use crate::reactor::{Reactor, Source};
@ -575,7 +575,6 @@ impl<T> Async<T> {
pub async fn read_with<R>(&self, op: impl FnMut(&T) -> io::Result<R>) -> io::Result<R> {
let mut op = op;
loop {
future::poll_fn(|cx| maybe_yield(cx)).await;
match op(self.get_ref()) {
Err(err) if err.kind() == io::ErrorKind::WouldBlock => {}
res => return res,
@ -612,7 +611,6 @@ impl<T> Async<T> {
) -> io::Result<R> {
let mut op = op;
loop {
future::poll_fn(|cx| maybe_yield(cx)).await;
match op(self.get_mut()) {
Err(err) if err.kind() == io::ErrorKind::WouldBlock => {}
res => return res,
@ -711,7 +709,6 @@ impl<T: Read> AsyncRead for Async<T> {
cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<io::Result<usize>> {
ready!(maybe_yield(cx));
match (&mut *self).get_mut().read(buf) {
Err(err) if err.kind() == io::ErrorKind::WouldBlock => {}
res => return Poll::Ready(res),
@ -725,7 +722,6 @@ impl<T: Read> AsyncRead for Async<T> {
cx: &mut Context<'_>,
bufs: &mut [IoSliceMut<'_>],
) -> Poll<io::Result<usize>> {
ready!(maybe_yield(cx));
match (&mut *self).get_mut().read_vectored(bufs) {
Err(err) if err.kind() == io::ErrorKind::WouldBlock => {}
res => return Poll::Ready(res),
@ -744,7 +740,6 @@ where
cx: &mut Context<'_>,
buf: &mut [u8],
) -> Poll<io::Result<usize>> {
ready!(maybe_yield(cx));
match (&*self).get_ref().read(buf) {
Err(err) if err.kind() == io::ErrorKind::WouldBlock => {}
res => return Poll::Ready(res),
@ -758,7 +753,6 @@ where
cx: &mut Context<'_>,
bufs: &mut [IoSliceMut<'_>],
) -> Poll<io::Result<usize>> {
ready!(maybe_yield(cx));
match (&*self).get_ref().read_vectored(bufs) {
Err(err) if err.kind() == io::ErrorKind::WouldBlock => {}
res => return Poll::Ready(res),
@ -1486,17 +1480,3 @@ async fn optimistic(fut: impl Future<Output = io::Result<()>>) -> io::Result<()>
})
.await
}
/// Yields with some small probability.
///
/// If a task is doing a lot of I/O and never gets blocked on it, it may keep the executor busy
/// forever without giving other tasks a chance to run. To prevent this kind of task starvation,
/// I/O operations yield randomly even if they are ready.
fn maybe_yield(cx: &mut Context<'_>) -> Poll<()> {
if fastrand::usize(..100) == 0 {
cx.waker().wake_by_ref();
Poll::Pending
} else {
Poll::Ready(())
}
}