Why is not all memory used?

[Timothy A. Seufert]

At 10:43 PM +0100 6/30/02, Iain Stevenson wrote:
>--On Sunday, June 30, 2002 1:46 pm -0700 "Timothy A. Seufert" 
><tas@mindspring.com> wrote:
>
>>  Have you started and subsequently quit any big memory chewers?  This just
>>  looks like what happens after a large program that forced a lot of
>>  swapping has quit: stuff that got swapped out to make room for the
>>  monster is still swapped out (it will not be swapped back in until there
>>  is a need for it), and now there's a big chunk of physical RAM free which
>>  the monster had been occupying. --
>
>That's possible at the moment because I have been running a number of
>fairly chunky applications.  However, I used to get seemingly better
>memory utilisation out of the 320M - the 'free' memory always seemed to
>be next to nothing - rather than the 218592 now.

If you haven't done anything that would increase RAM use since the 
big consumers exited, there's no reason for the system to refill the 
freed memory.  The kernel is reactive to your workload, not proactive.

Try looking at it while the system is under its heavy load condition. 
You should see full usage under load.  If you don't, that's when you 
should start worrying.

>Previous discussions on the list (and elsewhere) seem to suggest that
>Linux always keeps almost all of the memory active.  Has the memory
>handling changed a lot recently?

Not that I know of, but it's easy to fool yourself looking at just 
one snapshot.  The amount of memory in use depends on a lot of 
factors and can be very dynamic.
-- 
Tim Seufert