sysctl tuning for HAproxy

gistfile1.txt

net.core.somaxconn = 32768
net.ipv4.conf.all.send_redirects = 1
net.ipv4.ip_nonlocal_bind = 1
net.ipv4.tcp_abort_on_overflow = 0
net.ipv4.tcp_fin_timeout = 10
net.ipv4.tcp_keepalive_time = 300
net.ipv4.tcp_max_orphans = 262144
net.ipv4.tcp_max_syn_backlog = 16384
net.ipv4.tcp_max_tw_buckets = 262144
net.ipv4.tcp_mem = 200000    280000    300000
net.ipv4.tcp_reordering = 3
net.ipv4.tcp_rmem = 4096    87380    4120928
net.ipv4.tcp_synack_retries = 3
net.ipv4.tcp_syncookies = 1
net.ipv4.tcp_syn_retries = 5
net.ipv4.tcp_timestamps = 0
net.ipv4.tcp_tw_recycle = 1
net.ipv4.tcp_tw_reuse = 1
net.ipv4.tcp_wmem = 4096    16384    4120928

net.ipv4.netfilter.ip_conntrack_max = 10485760
net.ipv4.netfilter.ip_conntrack_tcp_timeout_fin_wait = 30
net.ipv4.netfilter.ip_conntrack_tcp_timeout_time_wait = 15
net.netfilter.nf_conntrack_max = 10485760
net.netfilter.nf_conntrack_tcp_timeout_fin_wait = 30
net.netfilter.nf_conntrack_tcp_timeout_time_wait = 15

Seriously; do not use net.ipv4.tcp_tw_recycle, it will easily break your setup. See http://vincent.bernat.im/en/blog/2014-tcp-time-wait-state-linux.html for details.

You probably don't want to disable net.ipv4.tcp_timestamps.

It's important to have that turned on in fast networks because it's used to detect sequence number wrapping (PAWS). It also makes the TCP congestion control algorithms work better. There are a lot of tuning guides out there that recommend turning it off, but they're often old or just cargo-culting outdated advice from a long time ago.

It's usually not necessary to set net.ipv4.tcp_mem. The kernel choses sane values for most use cases. Also, be advised it's specified in pages not bytes.

To echo the comment above, enabling net.ipv4.tcp_tw_recycle can cause problems -- especially on public-facing load balancers.

which of the above settings will have the biggest impact to my server?

ref: https://www.slideshare.net/haproxytech/haproxy-best-practice slide 13

net.ipv4.ip_local_port_range="1025 65534"
net.ipv4.tcp_max_syn_backlog = 100000
net.core.netdev_max_backlog = 100000
net.core.somaxconn = 65534
ipv4.tcp_rmem = "4096 16060 64060"
ipv4.tcp_wmem = "4096 16384 262144"

optional

tcp_slow_start_after_idle = 0
net.netfilter.nf_conntrack_max = 131072

from https://www.slideshare.net/haproxytech/haproxy-best-practice slide 13

Updated documentation
https://www.haproxy.com/documentation/hapee/latest/getting-started/system-tuning/