System Health and Maintenance › System Status › Memory

Memory

The Memory section provides information about memory size, used and free bytes, and buffering statistics.

Linux may show high memory utilization when there is still ample memory available for processes to use. The reason is that the operating system uses available memory for disk caching (Cached) but will relinquish this memory to processes when needed. This is standard behavior of the Linux operating system and is done to improve performance.

When interpreting the Memory information, consider the following:

• If the Memory Free column is low but the Cached number is high and Swap Used is low or zero, then the Multi-Port Monitor is operating normally.
• If the Memory Free column is low and Cached is low and Swap Used is high (indicating that the Multi-Port Monitor is swapping), then this could indicate that some processes are using a significant amount of memory and may be impacting performance.

The Multi-Port Monitor appliance runs on 64-bit CentOS Linux. The memory information is obtained using the Linux ‘free –o’ command. The following columns are displayed:

Total

Indicates the total number of bytes of physical memory or swap space.

Used

Indicates the number of bytes of physical memory or swap space that are in use. Note that for physical memory, this number includes the number of bytes cached.

Free

Indicates the number of bytes of physical memory or swap space that are free.

Buffers

Indicates the number of bytes of physical memory used by kernel buffers.

Cached

Indicates the number of bytes of physical memory used by kernel for disk caching.

See the following articles for more information about Linux memory management:

• http://www.linuxhowtos.org/System/Linux%20Memory%20Management.htm
• http://www.itworld.com/it-managementstrategy/280695/making-sense-memory-usage-linux
• http://www.linuxintheshell.org/2012/06/05/episode-008-free-understanding-linux-memory-usage/