topic Re: Need assistance on interpreting memory usage data in Operating System - Linux

Need assistance on interpreting memory usage data

Debbie Fleith — Tue, 07 Nov 2006 13:45:07 GMT

Can someone give me more information about how to interpret how much memory I have un-used/available for applications on my Linux server?

"top" shows this (and appears that I don't have much free memory left):

Mem: 2055236k av, 2031852k used, 23384k free

"free" shows this:
total used free shared buffers cached
Mem: 2055236 2032884 22352 0 206704 1531700
-/+ buffers/cache: 294480 1760756
Swap: 4096532 0 4096532

Re: Need assistance on interpreting memory usage data

Ivan Ferreira — Tue, 07 Nov 2006 13:52:47 GMT

Normal, please see:

https://www.redhat.com/advice/tips/meminfo.html

Linux will always try to use all available memory, if not for applications, for buffers/cache.

From the output of free command, you can see how much memory is used as buffers/cache. So the memory used by your application is what you see in +/- buffers/cache.

Re: Need assistance on interpreting memory usage data

Mike Stroyan — Wed, 08 Nov 2006 17:37:03 GMT

One surprise to watch out for is that shared memory and tmpfs files are reported as part of the "Cached" total in /proc/meminfo and top. That can make it seem that there is a lot of pagecache in use and easily freed when much of that memory is actually shared memory or tmpfs files that would need to be swapped out to release their RAM. You can see the amount of system V shared memory in RAM using "ipcs -u". There is no easy way to see the amount of tmpfs RAM. The total amount in RAM and swap can be seeing looking at the output of "df".