#!/bin/bash

cat > sysctl.conf <EOF
# maximum number of open files/file descriptors
fs.file-max = 4194303

# use as little swap space as possible
vm.swappiness = 1

# prioritize application RAM against disk/swap cache
vm.vfs_cache_pressure = 10

# minimum free memory
vm.min_free_kbytes = 1000000

# maximum receive socket buffer (bytes)
net.core.rmem_max = 268435456

# maximum send buffer socket buffer (bytes)
net.core.wmem_max = 268435456

# default receive buffer socket size (bytes)
net.core.rmem_default = 67108864

# default send buffer socket size (bytes)
net.core.wmem_default = 67108864

# maximum number of packets in one poll cycle
net.core.netdev_budget = 1200

# maximum ancillary buffer size per socket
net.core.optmem_max = 134217728

# maximum number of incoming connections
net.core.somaxconn = 65535

# maximum number of packets queued
net.core.netdev_max_backlog = 250000

# maximum read buffer space
net.ipv4.tcp_rmem = 67108864 134217728 268435456

# maximum write buffer space
net.ipv4.tcp_wmem = 67108864 134217728 268435456

# enable low latency mode
net.ipv4.tcp_low_latency = 1

# socket buffer portion used for TCP window
net.ipv4.tcp_adv_win_scale = 1

# queue length of completely established sockets waiting for accept
net.ipv4.tcp_max_syn_backlog = 30000

# maximum number of sockets in TIME_WAIT state
net.ipv4.tcp_max_tw_buckets = 2000000

# reuse sockets in TIME_WAIT state when safe
net.ipv4.tcp_tw_reuse = 1

# time to wait (seconds) for FIN packet
net.ipv4.tcp_fin_timeout = 5

# disable icmp send redirects
net.ipv4.conf.all.send_redirects = 0

# disable icmp accept redirect
net.ipv4.conf.all.accept_redirects = 0

# drop packets with LSR or SSR
net.ipv4.conf.all.accept_source_route = 0

# MTU discovery, only enable when ICMP blackhole detected
net.ipv4.tcp_mtu_probing = 1

EOF

echo "Enabling system level tuning params"
sysctl --quiet --load sysctl.conf && rm -f sysctl.conf

# `Transparent Hugepage Support`*: This is a Linux kernel feature intended to improve
# performance by making more efficient use of processor’s memory-mapping hardware.
# But this may cause https://blogs.oracle.com/linux/performance-issues-with-transparent-huge-pages-thp
# for non-optimized applications. As most Linux distributions set it to `enabled=always` by default,
# we recommend changing this to `enabled=madvise`. This will allow applications optimized
# for transparent hugepages to obtain the performance benefits, while preventing the
# associated problems otherwise. Also, set `transparent_hugepage=madvise` on your kernel
# command line (e.g. in /etc/default/grub) to persistently set this value.

echo "Enabling THP madvise"
echo madvise | sudo tee /sys/kernel/mm/transparent_hugepage/enabled