Memory usage

If a system is performing poorly because of lack of memory resources, it is memory bound. By viewing the contents of /proc/meminfo, you can view your memory resources and see how they are being used. /proc/swap contains information on your swap file.

Swap space is used as an extension of the systems virtual storage. Therefore, not having enough memory or swap space causes performance problems. A general guideline is that swap space should be at least twice as large as the physical memory.

A swap space can be either a file or disk partition. A disk partition offers better performance than a file does. fdisk and cfdisk are the commands that you use to create another swap partition. It is a good idea to create swap partitions on different disk drives because this distributes the I/O activities and thus reduces the chance of further bottlenecks.

The vmstat tool helps you find where performance problems might be caused. For example, if you see that high swap rates are occurring, you probably do not have enough physical or swap space. The free command displays your memory configuration; swapon -s displays your swap device configuration. A high swap rate (for example, many page faults) means that you probably need to increase your physical memory. More information about the vmstat command are provided in The vmstat command.