How to get the highest RPS out of your PHP-FPM installation through tweaks, sysctls, and config options.
A common installation method for PHP is using php-fpm, typically used by Nginx and often the best method for scaling php processes for your web server. There are performance tweaks needed to the default setup for high requests per second.
/etc/sysctl.conf holds the various OS tweaks for your server. It allows you to tune the
performance of your system in general, and particularly what PHP-FPM can achieve. Add these lines
to the bottom of your sysctl.conf file:
net.ipv4.tcp_syncookies=1
net.ipv4.conf.all.rp_filter=1
net.ipv4.conf.all.secure_redirects=1
net.ipv4.conf.all.send_redirects=0
net.ipv4.conf.all.accept_source_route=0
net.ipv6.conf.all.accept_source_route=0
net.ipv4.icmp_echo_ignore_broadcasts=1
net.ipv4.tcp_timestamps=0
net.ipv4.tcp_mem=786432 1697152 1945728
net.ipv4.tcp_rmem=4096 4096 16777216
net.ipv4.tcp_wmem=4096 4096 16777216
net.core.rmem_max=16777216
net.core.wmem_max=16777216
net.ipv4.netfilter.ip_conntrack_max=999999
net.netfilter.nf_conntrack_max=999999
net.ipv4.tcp_tw_reuse=1
net.ipv4.tcp_max_orphans=262144
net.ipv4.ip_local_port_range=1000 65535
net.ipv4.tcp_fin_timeout=30
net.core.netdev_max_backlog=10000
net.core.somaxconn=60000
net.ipv4.tcp_synack_retries=3
fs.file-max=640000
The above are general network tweaks in the majority. They are designed to improve the network performance and increase the resources available and are all safe to use as defaults.
Customize your PHP-FPM installations performance by editing the /etc/php/VERSION/fpm/pool.d/www.conf file (replacing version with your version, e.g. 7.4). In particular replace these values below:
pm = dynamic
pm.max_children = 50
pm.start_servers = 5
pm.min_spare_servers = 5
pm.max_spare_servers = 20
pm.max_requests = 5000
The above configuration sets the php-fpm process scaling to dynamic, with a maximum of 50 children and allows it to scale in between. The limit of 50 is very high, but you could increase that if needed.
In order to allow PHP to have a large number of open network connections and files you must raise the system limits. Errors with wording like "too many open files" are caused by this.
Add this to the bottom of /etc/security/limits.conf and replace 'www-data' with your php-cgi user, to allow a higher
number of open files (and specifically sockets):
root soft nofile 65536
root hard nofile 65536
www-data soft nofile 65536
www-data hard nofile 65536
Add this to bottom of /etc/pam.d/common-session to allow the increased limits:
session required pam_limits.so
Add this to bottom of /etc/systemd/system.conf to set the max open files (and sockets as above):
DefaultLimitNOFILE=65536
Now reboot the system to apply your changes. It's possible to apply some of these changes without a reboot but by far the most effective will be a restart.
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