From 2ead2cea26422c00c300ccb45dee71ea7b410115 Mon Sep 17 00:00:00 2001
From: IceCodeNew <32576256+IceCodeNew@users.noreply.github.com>
Date: Tue, 12 Oct 2021 21:16:55 +0800
Subject: [PATCH] Disable TCP slow start after idle

Signed-off-by: IceCodeNew <32576256+IceCodeNew@users.noreply.github.com>
---
 sysctl.conf | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/sysctl.conf b/sysctl.conf
index dacbeb7..b394927 100644
--- a/sysctl.conf
+++ b/sysctl.conf
@@ -215,6 +215,15 @@ net.ipv4.ip_local_port_range = 1024 65535
 # - 2: enable timestamps without random offsets
 net.ipv4.tcp_timestamps = 0
 
+# Refer to: https://dropbox.tech/infrastructure/optimizing-web-servers-for-high-throughput-and-low-latency
+# the main problem with slowstart after idle is that “idle” is defined as one RTO, which is too small.
+# Refer to: https://hpbn.co/building-blocks-of-tcp/#slow-start-restart
+# Not surprisingly, SSR can have a significant impact on performance of long-lived TCP connections that may idle for bursts of time — e.g., due to user inactivity.
+# As a result, it is generally recommended to disable SSR on the server to help improve performance of long-lived HTTP connections.
+# Refer to: https://github.com/httpwg/http2-spec/wiki/Ops
+# This drops cwnd back down to initcwnd and goes back to slow start after the connection has been “idle” (defined as the RTO). This kills persistent single connection performance and should be turned off.
+net.ipv4.tcp_slow_start_after_idle = 0
+
 # enabling SACK can increase the throughput
 # but SACK is commonly exploited and rarely used
 net.ipv4.tcp_sack = 0