How to find the amount of _real_ free memory

kenneho · 03-10-2008, 07:49 AM

How can I find out how much free memory there actually is on my linux server? We going to launce an application on the server, but need to make sure that there is enough free memory for it to run.

"top" indicates that only around 1.5 GB of memory is used, while "free" says that 2.6 GB of memory is used.

Cyhaxor · 03-10-2008, 10:39 AM

try the command free... or free --help for more options..

kenneho · 03-10-2008, 11:28 AM

Quote:

Originally Posted by Cyhaxor

try the command free... or free --help for more options..

Thanks, but the problem stated in my post is that it seems as the command "free" does not seem to give the real amount of free memory. I'm sorry if I didn't make myself clear on that.

The "free" command says that 2.6 GBs of memory is used, while summarizing output from the "top" command shows that only around 1.5 GBs of memory are actually in use.

Uncle_Theodore · 03-10-2008, 11:38 AM

Quote:

Originally Posted by kenneho

Thanks, but the problem stated in my post is that it seems as the command "free" does not seem to give the real amount of free memory. I'm sorry if I didn't make myself clear on that.

The "free" command says that 2.6 GBs of memory is used, while summarizing output from the "top" command shows that only around 1.5 GBs of memory are actually in use.

So, by "free memory" you mean memory not used by applications? Look at the third line in the output of free, the one that starts with

-/+ buffers/cache:

It should give you a pretty good idea of how much memory is not used by applications.

H_TeXMeX_H · 03-10-2008, 11:58 AM

This has been posted before, but here it is again:

Code:

bash-3.1$ free
             total       used       free     shared    buffers     cached
Mem:       1033612    1013088      20524          0          0     872684
-/+ buffers/cache:     140404     893208
Swap:      1967952       2596    1965356

Your true free memory in this case is 893208 kB. This value excludes the disk cache, which will be overwritten when necessary automatically. The disk cache's purpose it speed up response time of programs that are used often by caching them, putting them in the disk cache in RAM.