#!/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 = 50

# minimum free memory
vm.min_free_kbytes = 1000000

# follow mellanox best practices https://community.mellanox.com/s/article/linux-sysctl-tuning
# the following changes are recommended for improving IPv4 traffic performance by Mellanox

# disable the TCP timestamps option for better CPU utilization
net.ipv4.tcp_timestamps = 0

# enable the TCP selective acks option for better throughput
net.ipv4.tcp_sack = 1

# increase the maximum length of processor input queues
net.core.netdev_max_backlog = 250000

# increase the TCP maximum and default buffer sizes using setsockopt()
net.core.rmem_max = 4194304
net.core.wmem_max = 4194304
net.core.rmem_default = 4194304
net.core.wmem_default = 4194304
net.core.optmem_max = 4194304

# increase memory thresholds to prevent packet dropping:
net.ipv4.tcp_rmem = 4096 87380 4194304
net.ipv4.tcp_wmem = 4096 65536 4194304

# enable low latency mode for TCP:
net.ipv4.tcp_low_latency = 1

# the following variable is used to tell the kernel how much of the socket buffer
# space should be used for TCP window size, and how much to save for an application
# buffer. A value of 1 means the socket buffer will be divided evenly between.
# TCP windows size and application.
net.ipv4.tcp_adv_win_scale = 1

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

# maximum number of packets queued
net.core.netdev_max_backlog = 10000

# queue length of completely established sockets waiting for accept
net.ipv4.tcp_max_syn_backlog = 4096

# time to wait (seconds) for FIN packet
net.ipv4.tcp_fin_timeout = 15

# 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
