The “bdflush” parameters
The “buffermem” parameters
The buffermem file is also closely related to the operation of the virtual memory (VM) subsystem of the Linux kernel. The value in this file 7proc/sys/vm/buffermem” controls how much memory should be used for buffer memory (in percentage). It is important to note that the percentage is calculated as a percentage of total system memory.
The default setup for the “buffermem” parameters under Red Hat Linux is: “2 10 60″
• To change the values of buffermem, type the following command on your terminal:
Under Red Hat Linux 6.1
[root@deep /]# echo “80 10 60″ >/proc/sys/vm/buffermem
You may add the above commands to the 7etc/rc.d/rc.local” script file and you’ll not have to type it again the next time you reboot your system.
Under Red Hat Linux 6.2
Edit the “/etc/sysdl.conf file and add the following line:
# Improve virtual memory performance vm. buffermem = 80 10 60
You must restart your network for the change to take effect. The command to restart the network is the following:
• To restart all networks devices manually on your system, use the following command: [root@deep /]# /etc/rc.d/init.d/network restart
Setting network parameters [ OK ]
Bringing up interface lo [ OK ]
Bringing up interface ethO [ OK ]
Bringing up interface eth1 [ OK ]
In our example above, according to the7usr/src/linux/Documentation/sysctl/vm.txt” file, the first parameter (80 %) means to use a minimum of 80 percent of memory for the buffer cache; the minimum percentage of memory that should be spent on buffer memory.
The last two parameters (10 and 60) are unused by the system so we don’t need to change the defaults.
NOTE: Look at 7usr/src/linux/Documentation/sysctl/vm.txt” for more information on how to improve kernel parameters related to virtual memory.
The “ip_local_port_range” parameters
The ip_local_port_range 7proc/sys/net/ipv4/ip_local_port_range” defines the local port range that is used by TCP and UDP traffic to choose the local port. You will see in the parameters of this file two numbers: The first number is the first local port allowed for TCP and UDP traffic on the server, the second is the last local port number. For high-usage systems you may change its default parameters to 32768-61000 (first-last).
The default setup for the “ip_local_port_range” parameters under Red Hat Linux is: “1024 4999″
• To change the values of ip_local_port_range, type the following command on your terminal:
Under Red Hat Linux 6.1