Linux Tune Network Stack (Buffers Size) To Increase Networking Performance Rumi, December 23, 2015 By default the Linux network stack is not configured for high speed large file transfer across WAN links. This is done to save memory resources. You can easily tune Linux network stack by increasing network buffers size for high-speed networks that connect server systems to handle more network packets. The default maximum Linux TCP buffer sizes are way too small. TCP memory is calculated automatically based on system memory; you can find the actual values by typing the following commands: $ cat /proc/sys/net/ipv4/tcp_mem The default and maximum amount for the receive socket memory: $ cat /proc/sys/net/core/rmem_default $ cat /proc/sys/net/core/rmem_max The default and maximum amount for the send socket memory: $ cat /proc/sys/net/core/wmem_default $ cat /proc/sys/net/core/wmem_max The maximum amount of option memory buffers: $ cat /proc/sys/net/core/optmem_max Tune values Set the max OS send buffer size (wmem) and receive buffer size (rmem) to 12 MB for queues on all protocols. In other words set the amount of memory that is allocated for each TCP socket when it is opened or created while transferring files: WARNING! The default value of rmem_max and wmem_max is about 128 KB in most Linux distributions, which may be enough for a low-latency general purpose network environment or for apps such as DNS / Web server. However, if the latency is large, the default size might be too small. Please note that the following settings going to increase memory usage on your server. # echo 'net.core.wmem_max=12582912' >> /etc/sysctl.conf # echo 'net.core.rmem_max=12582912' >> /etc/sysctl.conf You also need to set minimum size, initial size, and maximum size in bytes: # echo 'net.ipv4.tcp_rmem= 10240 87380 12582912' >> /etc/sysctl.conf # echo 'net.ipv4.tcp_wmem= 10240 87380 12582912' >> /etc/sysctl.conf Turn on window scaling which can be an option to enlarge the transfer window: # echo 'net.ipv4.tcp_window_scaling = 1' >> /etc/sysctl.conf Enable timestamps as defined in RFC1323: # echo 'net.ipv4.tcp_timestamps = 1' >> /etc/sysctl.conf Enable select acknowledgments: # echo 'net.ipv4.tcp_sack = 1' >> /etc/sysctl.conf By default, TCP saves various connection metrics in the route cache when the connection closes, so that connections established in the near future can use these to set initial conditions. Usually, this increases overall performance, but may sometimes cause performance degradation. If set, TCP will not cache metrics on closing connections. # echo 'net.ipv4.tcp_no_metrics_save = 1' >> /etc/sysctl.conf Set maximum number of packets, queued on the INPUT side, when the interface receives packets faster than kernel can process them. # echo 'net.core.netdev_max_backlog = 5000' >> /etc/sysctl.conf Now reload the changes: # sysctl -p Use tcpdump to view changes for eth0: # tcpdump -ni eth0 Recommend readings: Please refer to kernel documentation in Documentation /networking/ip-sysctl.txt for more information. man page sysctl Src: http://www.cyberciti.biz/faq/linux-tcp-tuning/ Related Administrations Configurations (Linux) Linux CommandsTCP Buffer
Redhat/CentOS install PHP on NginX server as fastcgi August 26, 2012 tep # 1: Enable EPEL repo ngnix is not included in the base system. Turn on EPEL repo to install nginx stable release: # rpm -Uvh http://download.fedora.redhat.com/pub/epel/5/$(uname -m)/epel-release-5-3.noarch.rpm Step # 2: Install ngnix Type the following command at a shell prompt: # yum install nginx Sample output: Loaded plugins: downloadonly,… Read More
Administrations Install gnome via tasksel on Debain 12 March 3, 2024 Tasksel is already installed on Debian 12, so you don’t need to install it. However, if for some reason tasksel is not installed on your system, you can install it via the command below sudo apt install tasksel To install Gnome via tasksel, you need first to run tasksel sudo… Read More
Install PolicyD on Zimbra 8.5 or 8.8 September 12, 2023September 12, 2023 Policyd have module quotas. This module can use for limit sending/receipt email. As example just allow sending/receipt email 200 emails/hours/users. If your email server attacked by spam or compromised password some users and used by spammer, the maximum email can be sent as many as 200 emails per hour. This policy will safe your… Read More