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perf(lib): re-enable writev support (#2338)

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Tokio's `AsyncWrite` trait once again has support for vectored writes in
Tokio 0.3.4 (see tokio-rs/tokio#3149).

This branch re-enables vectored writes in Hyper for HTTP/1. Using
vectored writes in HTTP/2 will require an upstream change in the `h2`
crate as well.

I've removed the adaptive write buffer implementation
that attempts to detect whether vectored IO is or is not available,
since the Tokio 0.3.4 `AsyncWrite` trait exposes this directly via the
`is_write_vectored` method. Now, we just ask the IO whether or not it
supports vectored writes, and configure the buffer accordingly. This
makes the implementation somewhat simpler.

This also removes `http1_writev()` methods from the builders. These are
no longer necessary, as Hyper can now determine whether or not
to use vectored writes based on `is_write_vectored`, rather than trying
to auto-detect it.

Closes #2320 

BREAKING CHANGE: Removed `http1_writev` methods from `client::Builder`,
  `client::conn::Builder`, `server::Builder`, and `server::conn::Builder`.
  
  Vectored writes are now enabled based on whether the `AsyncWrite`
  implementation in use supports them, rather than though adaptive
  detection. To explicitly disable vectored writes, users may wrap the IO
  in a newtype that implements `AsyncRead` and `AsyncWrite` and returns
  `false` from its `AsyncWrite::is_write_vectored` method.
This commit is contained in:
Eliza Weisman
2020-11-24 10:31:48 -08:00
committed by GitHub
parent 121c33132c
commit d6aadb8300
10 changed files with 94 additions and 216 deletions
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158
src/proto/h1/io.rs
View File

@@ -1,4 +1,3 @@
use std::cell::Cell;
use std::cmp;
use std::fmt;
use std::io::{self, IoSlice};
@@ -57,13 +56,14 @@ where
B: Buf,
{
pub fn new(io: T) -> Buffered<T, B> {
let write_buf = WriteBuf::new(&io);
Buffered {
flush_pipeline: false,
io,
read_blocked: false,
read_buf: BytesMut::with_capacity(0),
read_buf_strategy: ReadStrategy::default(),
write_buf: WriteBuf::new(),
write_buf,
}
}
@@ -98,13 +98,6 @@ where
self.write_buf.set_strategy(WriteStrategy::Flatten);
}
pub fn set_write_strategy_queue(&mut self) {
// this should always be called only at construction time,
// so this assert is here to catch myself
debug_assert!(self.write_buf.queue.bufs_cnt() == 0);
self.write_buf.set_strategy(WriteStrategy::Queue);
}
pub fn read_buf(&self) -> &[u8] {
self.read_buf.as_ref()
}
@@ -237,13 +230,13 @@ where
if let WriteStrategy::Flatten = self.write_buf.strategy {
return self.poll_flush_flattened(cx);
}
loop {
// TODO(eliza): this basically ignores all of `WriteBuf`...put
// back vectored IO and `poll_write_buf` when the appropriate Tokio
// changes land...
let n = ready!(Pin::new(&mut self.io)
// .poll_write_buf(cx, &mut self.write_buf.auto()))?;
.poll_write(cx, self.write_buf.auto().bytes()))?;
let n = {
let mut iovs = [IoSlice::new(&[]); crate::common::io::MAX_WRITEV_BUFS];
let len = self.write_buf.bytes_vectored(&mut iovs);
ready!(Pin::new(&mut self.io).poll_write_vectored(cx, &iovs[..len]))?
};
// TODO(eliza): we have to do this manually because
// `poll_write_buf` doesn't exist in Tokio 0.3 yet...when
// `poll_write_buf` comes back, the manual advance will need to leave!
@@ -462,12 +455,17 @@ pub(super) struct WriteBuf<B> {
}
impl<B: Buf> WriteBuf<B> {
fn new() -> WriteBuf<B> {
fn new(io: &impl AsyncWrite) -> WriteBuf<B> {
let strategy = if io.is_write_vectored() {
WriteStrategy::Queue
} else {
WriteStrategy::Flatten
};
WriteBuf {
headers: Cursor::new(Vec::with_capacity(INIT_BUFFER_SIZE)),
max_buf_size: DEFAULT_MAX_BUFFER_SIZE,
queue: BufList::new(),
strategy: WriteStrategy::Auto,
strategy,
}
}
}
@@ -480,12 +478,6 @@ where
self.strategy = strategy;
}
// TODO(eliza): put back writev!
#[inline]
fn auto(&mut self) -> WriteBufAuto<'_, B> {
WriteBufAuto::new(self)
}
pub(super) fn buffer<BB: Buf + Into<B>>(&mut self, mut buf: BB) {
debug_assert!(buf.has_remaining());
match self.strategy {
@@ -505,7 +497,7 @@ where
buf.advance(adv);
}
}
WriteStrategy::Auto | WriteStrategy::Queue => {
WriteStrategy::Queue => {
self.queue.push(buf.into());
}
}
@@ -514,7 +506,7 @@ where
fn can_buffer(&self) -> bool {
match self.strategy {
WriteStrategy::Flatten => self.remaining() < self.max_buf_size,
WriteStrategy::Auto | WriteStrategy::Queue => {
WriteStrategy::Queue => {
self.queue.bufs_cnt() < MAX_BUF_LIST_BUFFERS && self.remaining() < self.max_buf_size
}
}
@@ -573,65 +565,8 @@ impl<B: Buf> Buf for WriteBuf<B> {
}
}
/// Detects when wrapped `WriteBuf` is used for vectored IO, and
/// adjusts the `WriteBuf` strategy if not.
struct WriteBufAuto<'a, B: Buf> {
bytes_called: Cell<bool>,
bytes_vec_called: Cell<bool>,
inner: &'a mut WriteBuf<B>,
}
impl<'a, B: Buf> WriteBufAuto<'a, B> {
fn new(inner: &'a mut WriteBuf<B>) -> WriteBufAuto<'a, B> {
WriteBufAuto {
bytes_called: Cell::new(false),
bytes_vec_called: Cell::new(false),
inner,
}
}
}
impl<'a, B: Buf> Buf for WriteBufAuto<'a, B> {
#[inline]
fn remaining(&self) -> usize {
self.inner.remaining()
}
#[inline]
fn bytes(&self) -> &[u8] {
self.bytes_called.set(true);
self.inner.bytes()
}
#[inline]
fn advance(&mut self, cnt: usize) {
self.inner.advance(cnt)
}
#[inline]
fn bytes_vectored<'t>(&'t self, dst: &mut [IoSlice<'t>]) -> usize {
self.bytes_vec_called.set(true);
self.inner.bytes_vectored(dst)
}
}
impl<'a, B: Buf + 'a> Drop for WriteBufAuto<'a, B> {
fn drop(&mut self) {
if let WriteStrategy::Auto = self.inner.strategy {
if self.bytes_vec_called.get() {
self.inner.strategy = WriteStrategy::Queue;
} else if self.bytes_called.get() {
trace!("detected no usage of vectored write, flattening");
self.inner.strategy = WriteStrategy::Flatten;
self.inner.headers.bytes.put(&mut self.inner.queue);
}
}
}
}
#[derive(Debug)]
enum WriteStrategy {
Auto,
Flatten,
Queue,
}
@@ -643,8 +578,8 @@ mod tests {
use tokio_test::io::Builder as Mock;
#[cfg(feature = "nightly")]
use test::Bencher;
// #[cfg(feature = "nightly")]
// use test::Bencher;
/*
impl<T: Read> MemRead for AsyncIo<T> {
@@ -873,33 +808,6 @@ mod tests {
buffered.flush().await.expect("flush");
}
#[tokio::test]
async fn write_buf_auto_flatten() {
let _ = pretty_env_logger::try_init();
let mock = Mock::new()
// Expects write_buf to only consume first buffer
.write(b"hello ")
// And then the Auto strategy will have flattened
.write(b"world, it's hyper!")
.build();
let mut buffered = Buffered::<_, Cursor<Vec<u8>>>::new(mock);
// we have 4 buffers, but hope to detect that vectored IO isn't
// being used, and switch to flattening automatically,
// resulting in only 2 writes
buffered.headers_buf().extend(b"hello ");
buffered.buffer(Cursor::new(b"world, ".to_vec()));
buffered.buffer(Cursor::new(b"it's ".to_vec()));
buffered.buffer(Cursor::new(b"hyper!".to_vec()));
assert_eq!(buffered.write_buf.queue.bufs_cnt(), 3);
buffered.flush().await.expect("flush");
assert_eq!(buffered.write_buf.queue.bufs_cnt(), 0);
}
#[tokio::test]
async fn write_buf_queue_disable_auto() {
let _ = pretty_env_logger::try_init();
@@ -928,19 +836,19 @@ mod tests {
assert_eq!(buffered.write_buf.queue.bufs_cnt(), 0);
}
#[cfg(feature = "nightly")]
#[bench]
fn bench_write_buf_flatten_buffer_chunk(b: &mut Bencher) {
let s = "Hello, World!";
b.bytes = s.len() as u64;
// #[cfg(feature = "nightly")]
// #[bench]
// fn bench_write_buf_flatten_buffer_chunk(b: &mut Bencher) {
// let s = "Hello, World!";
// b.bytes = s.len() as u64;
let mut write_buf = WriteBuf::<bytes::Bytes>::new();
write_buf.set_strategy(WriteStrategy::Flatten);
b.iter(|| {
let chunk = bytes::Bytes::from(s);
write_buf.buffer(chunk);
::test::black_box(&write_buf);
write_buf.headers.bytes.clear();
})
}
// let mut write_buf = WriteBuf::<bytes::Bytes>::new();
// write_buf.set_strategy(WriteStrategy::Flatten);
// b.iter(|| {
// let chunk = bytes::Bytes::from(s);
// write_buf.buffer(chunk);
// ::test::black_box(&write_buf);
// write_buf.headers.bytes.clear();
// })
// }
}