From a53001260e34459f5d74d0c165d1813be4078679 Mon Sep 17 00:00:00 2001
From: Karl Rikte <karl.rikte@gmail.com>
Date: Sat, 13 Jan 2024 00:19:35 +0100
Subject: [PATCH] Improve response times

When the network interface can't make any progress, it's probably
a good idea to yeild the task so that the wifi task may run and
proceed with actually sending/receiving data.

This seems to greatly improve response times, especially with low
tick_rate_hz values. At 100Hz, ping time goes down from 25ms to
<2ms. A simple http server test saw a response time reduction from
45ms to 6ms. At 1000Hz tick rate the gains are diminishing but
there are some small gains. I ran my tests on esp32s3.

This might also increase throughput. I have not tested that.
It also may have some unforseen adverse effects.

Ideally, we would have a more fine grained return value from
interface.poll() than a bool so we have a better idea if yeilding
is appropriate or not.
---
 esp-wifi/src/wifi_interface.rs | 13 ++++++++++---
 1 file changed, 10 insertions(+), 3 deletions(-)

diff --git a/esp-wifi/src/wifi_interface.rs b/esp-wifi/src/wifi_interface.rs
index 8af82416..bf293f44 100644
--- a/esp-wifi/src/wifi_interface.rs
+++ b/esp-wifi/src/wifi_interface.rs
@@ -443,6 +443,7 @@ impl<'a, MODE: WifiDeviceMode> WifiStack<'a, MODE> {
                     sockets,
                 )
             }) {
+                crate::timer::yield_task();
                 break;
             }
         }
@@ -713,7 +714,9 @@ impl<'s, 'n: 's, MODE: WifiDeviceMode> Read for Socket<'s, 'n, MODE> {
             use smoltcp::socket::tcp::RecvError;
 
             loop {
-                interface.poll(timestamp(), device, sockets);
+                if interface.poll(timestamp(), device, sockets) == false {
+                    crate::timer::yield_task();
+                }
                 let socket = sockets.get_mut::<TcpSocket>(self.socket_handle);
 
                 match socket.recv_slice(buf) {
@@ -733,11 +736,14 @@ impl<'s, 'n: 's, MODE: WifiDeviceMode> Write for Socket<'s, 'n, MODE> {
         loop {
             let (may_send, is_open, can_send) =
                 self.network.with_mut(|interface, device, sockets| {
-                    interface.poll(
+                    if interface.poll(
                         Instant::from_millis((self.network.current_millis_fn)() as i64),
                         device,
                         sockets,
-                    );
+                    ) == false
+                    {
+                        crate::timer::yield_task();
+                    }
 
                     let socket = sockets.get_mut::<TcpSocket>(self.socket_handle);
 
@@ -784,6 +790,7 @@ impl<'s, 'n: 's, MODE: WifiDeviceMode> Write for Socket<'s, 'n, MODE> {
             });
 
             if let false = res {
+                crate::timer::yield_task();
                 break;
             }
         }