Further memory question [was: Clear the computer's memory?]

[Kent Borg]

On Thu, Mar 30, 2006 at 03:17:37PM +0100, R Kimber wrote:
> Yes, I know about the general principles, it's what particular
> 'thing' (s) it is that I''m trying to discover.

Ah, there I can be of less help other than to say it isn't going to be
easy.  The glib answer is "probably cache'.  For more detail, starting
with analyzing the output from "top" and comparing it before and after
will answer some questions about what applications are using memory,
and carefully watching cache and buffer sizes will answer some other
more vague questions, but the Linux memory system is complicated.
>From what I can tell those who programmed it don't find it easy to
know what all is going on.

Unlike old pre-Mac OS X days where "free" memory was equal to
"available" memory, I comfort myself by saying that knowing how much
memory is "free" isn't very meaningful, other than that a small number
is good.  When the "free" memory number is large it means:

 a. The system has not been running very long (a neutral case), or

 b. Linux is not managing to put the available memory to use (a bad
    case), or

 c. You have *so* much RAM that the Linux kernel can't (yet) find ways
    to use it all (a good case).

I have a friend who has an account on my basement server and at first
it really bugged him that there was so little free memory.  I tried to
say that was a good thing.  I don't know if he finally bought it, or
if he just quit asking about it.


-kb, the Kent who likes seeing a small free memory number.