From 683870682c18951b2ba8400a15acfbc3fd09f17c Mon Sep 17 00:00:00 2001
From: klzgrad <kizdiv@gmail.com>
Date: Fri, 2 Oct 2020 02:46:51 +0800
Subject: [PATCH] Updated Parameter Tuning (markdown)

---
 Parameter-Tuning.md   | 35 ------------------------
 Performance-Tuning.md | 62 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 62 insertions(+), 35 deletions(-)
 delete mode 100644 Parameter-Tuning.md
 create mode 100644 Performance-Tuning.md

diff --git a/Parameter-Tuning.md b/Parameter-Tuning.md
deleted file mode 100644
index 3c3b6c9..0000000
--- a/Parameter-Tuning.md
+++ /dev/null
@@ -1,35 +0,0 @@
-## Linux kernel
-
-HTTP/2 uses a single connection per host. Most of TCP tuning is no longer needed.
-
-* Use a kernel as new as possible.
-* Use BBR congestion control (recommended).
-```
-sudo sysctl -w net.ipv4.tcp_congestion_control=bbr
-```
-* Turn off `tcp_slow_start_after_idle` (optional). This improves persistent single connection performance slightly.
-```
-sudo sysctl -w net.ipv4.tcp_slow_start_after_idle=0
-```
-
-That's it!
-
-The above two options are not important at server side, so it's OK if you cannot set them.
-
-Do not turn on TCP Fast Open. Its Linux implementation is too conservative to be useful, and its usage is rare in practice thus creating a distinct traffic feature.
-
-References: [[1]](https://hpbn.co/building-blocks-of-tcp/) [[2]](https://github.com/http2/http2-spec/wiki/Ops).
-
-## Chromium
-
-Chromium limits the number of connections per proxy to 32. New connections that exceed this limit will be stalled, but multi-tab browsing often needs more than 32 connections. Create a policy to override this limit.
-
-For Chromium on Linux:
-```
-sudo mkdir -p /etc/chromium/policies/managed
-echo '{ "MaxConnectionsPerProxy": 99 }' | sudo tee /etc/chromium/policies/managed/proxy.json
-```
-
-99 is the maximum maximum allowed by Chromium. You are recommended to use an ad-blocker to save on connections.
-
-For Chrome or other OSes, see [[1]](https://www.chromium.org/administrators/policy-templates) [[2]](https://www.chromium.org/administrators/policy-list-3#MaxConnectionsPerProxy).
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diff --git a/Performance-Tuning.md b/Performance-Tuning.md
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index 0000000..c7c07dc
--- /dev/null
+++ b/Performance-Tuning.md
@@ -0,0 +1,62 @@
+## Linux kernel
+
+### Use a kernel as new as possible
+
+HTTP/2 uses a single connection per host. Most of TCP tuning is no longer needed (e.g. `net.ipv4.tcp_wmem`).
+
+### Use BBR congestion control
+```
+sudo sysctl -w net.ipv4.tcp_congestion_control=bbr
+```
+
+### Turn off tcp_slow_start_after_idle
+```
+sudo sysctl -w net.ipv4.tcp_slow_start_after_idle=0
+```
+This setting can improve persistent single connection performance slightly.
+
+* https://hpbn.co/building-blocks-of-tcp/
+* https://github.com/http2/http2-spec/wiki/Ops
+* https://dropbox.tech/infrastructure/optimizing-web-servers-for-high-throughput-and-low-latency
+
+### (Server only) Consider setting tcp_notsent_lowat
+```
+sudo sysctl -w net.ipv4.tcp_notsent_lowat=16384
+```
+
+This setting can improve interactive latency by optimizing send buffer handling. Note that this kernel setting is useful for HTTP/2 and may be detrimental to other applications, as it applies to all applications on the server.
+
+Be cautious with this setting. Small values tend to increase server CPU usage and negatively affect throughput. You need to benchmark it to determine good settings. You can check the HTTP/2 load time in https://http2.akamai.com/demo while also downloading a large file with and without this setting.
+
+Common values range from 16KB to 128KB.
+
+* https://blog.cloudflare.com/http-2-prioritization-with-nginx/
+* https://web.archive.org/web/20170924184144/https://insouciant.org/tech/prioritization-only-works-when-theres-pending-data-to-prioritize/
+* (Benchmarking HTTP/2 Priorities) https://docs.google.com/document/d/1oLhNg1skaWD4_DtaoCxdSRN5erEXrH-KnLrMwEpOtFY/preview
+
+### Do not turn on TCP Fast Open
+
+Its Linux implementation is too conservative to be useful, and its usage is rare in practice thus creating a distinct traffic feature.
+
+* https://github.com/klzgrad/naiveproxy#why-not-use-go-node-etc-for-performance
+* https://blog.donatas.net/blog/2017/03/09/tfo/
+* https://squeeze.isobar.com/2019/04/11/the-sad-story-of-tcp-fast-open/
+
+## Chromium
+
+Chromium limits the number of connections per proxy to 32. New connections that exceed this limit will be stalled, but multi-tab browsing often needs more than 32 connections. Create a policy to override this limit.
+
+Note: This is a browser setting, not applicable to any proxies.
+
+For Chromium on Linux:
+```
+sudo mkdir -p /etc/chromium/policies/managed
+echo '{ "MaxConnectionsPerProxy": 99 }' | sudo tee /etc/chromium/policies/managed/proxy.json
+```
+You should be able to see it in chrome://policy once set up.
+
+99 is the maximum value for MaxConnectionsPerProxy allowed by Chromium. It is still too low. You are recommended to use an ad-blocker to save on connections.
+
+For Chrome or other OSes, see:
+* https://www.chromium.org/administrators/policy-templates
+* https://cloud.google.com/docs/chrome-enterprise/policies/?policy=MaxConnectionsPerProxy
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