Hongwei Li wrote:
> I have a similar question as 2 above. My system: 2.6.10-1.741_FC3
> The free command displays the free physical memory decreasing continuesly
> every minute or so:
>
> # free
> total used free shared buffers cached
> Mem: 1035788 1017952 17836 0 296172 81224
> -/+ buffers/cache: 640556 395232
> Swap: 1052216 8120 1044096
>
> # free
> total used free shared buffers cached
> Mem: 1035788 1017980 17808 0 296228 81244
> -/+ buffers/cache: 640508 395280
> Swap: 1052216 8120 1044096
>
> # free
> total used free shared buffers cached
> Mem: 1035788 1018100 17688 0 296260 81300
> -/+ buffers/cache: 640540 395248
> Swap: 1052216 8120 1044096
>
> Is it normal? I don't know what will happen if the free memory goes to
> zero, but it seems that, in my system, it never goes to zero.
*Thoroughly* normal.
Linux, like modern Unix and NT, is written around the assumption that
free memory is unused memory. If it's buffering or caching the hard
drive, that could speed things up. This is generally a Good Thing.
Linux keeps around a little free memory in case it needs it in a hurry:
if it needs more, it reclaims the memory it used on hard drive buffers
and cache. Normally, it can just "forget" about what that memory was
doing before.
Linux can also use the swap file to keep relatively unused "pages" of
memory: if you want to use more than 1 GB of memory, the least used
pages will be written into swap. Sometimes Linux will write back
"program" memory to swap (or elsewhere) in order to keep frequently-read
files in cache.
(Yes, this is still oversimplified).
Happy?
James.
--
James Wilkinson | Never drink coke in a moving lift: the motion and the
Exeter Devon UK | chemicals in coke produce hallucinations. People tend
E-mail address: james | to change into lizards and attack without warning, and
@westexe.demon.co.uk | large bats usually fly in the window. Additionally,
| you begin to believe that lifts have windows.
