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Immediately ACK payload in response to TCP packets that have any. 

This will lower the average software RTT by about a factor of two.
This commit is contained in:
whitequark 2017-08-25 05:50:43 +00:00
parent 5b2de544c8
commit 5396687d52
1 changed files with 28 additions and 27 deletions
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55
src/socket/tcp.rs
View File

@ -1052,8 +1052,11 @@ impl<'a> TcpSocket<'a> {
}
}
// Dequeue acknowledged octets.
// Update window length.
self.remote_win_len = repr.window_len as usize;
if ack_len > 0 {
// Dequeue acknowledged octets.
net_trace!("[{}]{}:{}: tx buffer: dequeueing {} octets (now {})",
self.debug_id, self.local_endpoint, self.remote_endpoint,
ack_len, self.tx_buffer.len() - ack_len);
@ -1066,18 +1069,21 @@ impl<'a> TcpSocket<'a> {
self.local_seq_no = ack_number;
}
// Enqueue payload octets, which is guaranteed to be in order, unless we already did.
if repr.payload.len() > 0 {
// Enqueue payload octets, which are guaranteed to be in order.
net_trace!("[{}]{}:{}: rx buffer: enqueueing {} octets (now {})",
self.debug_id, self.local_endpoint, self.remote_endpoint,
repr.payload.len(), self.rx_buffer.len() + repr.payload.len());
self.rx_buffer.enqueue_slice(repr.payload)
self.rx_buffer.enqueue_slice(repr.payload);
// Send an acknowledgement.
self.remote_last_ack = self.remote_seq_no + self.rx_buffer.len();
Ok(Some(self.ack_reply(ip_repr, &repr)))
} else {
// No data to acknowledge; the logic to acknowledge SYN and FIN flags
// resides in dispatch().
Ok(None)
}
// Update window length.
self.remote_win_len = repr.window_len as usize;
Ok(None)
}
pub(crate) fn dispatch<F, R>(&mut self, timestamp: u64, limits: &DeviceLimits,
@ -1635,10 +1641,15 @@ mod test {
ack_number: Some(LOCAL_SEQ + 1),
payload: &b"abcdef"[..],
..SEND_TEMPL
});
}, Ok(Some(TcpRepr {
seq_number: LOCAL_SEQ + 1,
ack_number: Some(REMOTE_SEQ + 1 + 6 + 1),
window_len: 58,
..RECV_TEMPL
})));
assert_eq!(s.state, State::CloseWait);
sanity!(s, TcpSocket {
remote_last_ack: REMOTE_SEQ + 1,
remote_last_ack: REMOTE_SEQ + 1 + 6 + 1,
..socket_close_wait()
});
}
@ -1847,13 +1858,12 @@ mod test {
ack_number: Some(LOCAL_SEQ + 1),
payload: &b"abcdef"[..],
..SEND_TEMPL
});
recv!(s, [TcpRepr {
}, Ok(Some(TcpRepr {
seq_number: LOCAL_SEQ + 1,
ack_number: Some(REMOTE_SEQ + 1 + 6),
window_len: 58,
..RECV_TEMPL
}]);
})));
assert_eq!(s.rx_buffer.dequeue(6), &b"abcdef"[..]);
}
@ -2583,13 +2593,12 @@ mod test {
ack_number: Some(LOCAL_SEQ + 1),
payload: &b"abcdef"[..],
..SEND_TEMPL
});
recv!(s, [TcpRepr {
}, Ok(Some(TcpRepr {
seq_number: LOCAL_SEQ + 1,
ack_number: Some(REMOTE_SEQ + 1 + 6),
window_len: 58,
..RECV_TEMPL
}]);
})));
s
}
@ -2618,13 +2627,12 @@ mod test {
ack_number: Some(LOCAL_SEQ + 1),
payload: &b"abcdef"[..],
..SEND_TEMPL
});
recv!(s, [TcpRepr {
}, Ok(Some(TcpRepr {
seq_number: LOCAL_SEQ + 1,
ack_number: Some(REMOTE_SEQ + 1 + 6),
window_len: 58,
..RECV_TEMPL
}]);
})));
send!(s, TcpRepr {
seq_number: REMOTE_SEQ + 1 + 6 + 6,
ack_number: Some(LOCAL_SEQ + 1),
@ -2884,7 +2892,6 @@ mod test {
s.remote_win_len = 6;
s.send_slice(b"abcdef").unwrap();
s.send_slice(b"123456").unwrap();
s.close();
recv!(s, time 0, Ok(TcpRepr {
seq_number: LOCAL_SEQ + 1,
ack_number: Some(REMOTE_SEQ + 1),
@ -2892,16 +2899,10 @@ mod test {
payload: &b"abcdef"[..],
..RECV_TEMPL
}), exact);
send!(s, time 0, TcpRepr {
seq_number: REMOTE_SEQ + 1,
ack_number: Some(LOCAL_SEQ + 1 + 6),
window_len: 6,
..SEND_TEMPL
});
recv!(s, time 0, Ok(TcpRepr {
control: TcpControl::Fin,
seq_number: LOCAL_SEQ + 1 + 6,
ack_number: Some(REMOTE_SEQ + 1),
push: true,
payload: &b"123456"[..],
..RECV_TEMPL
}), exact);