Re: Growing memory usage

[Christopher Wong <chris csports com>]

On Sat, 29 Dec 2001, Cameron Simpson wrote:
> On Fri, Dec 28, 2001 at 06:02:21PM -0500, Christopher Wong <chris csports com> wrote:
> | My RH 7.2 system with the latest updates and i686 kernel has been running
> | for 46 days. Puzzled by its footprint, I quit X (KDE), restarted xfs and a
> | bunch of other daemons and ran free in text mode. This is what free told
> | me:
> |              total       used       free     shared    buffers     cached
> | Mem:        126196     105440      20756          8       5432      53088
> | -/+ buffers/cache:      46920      79276
> | Swap:       265032      34216     230816
> | 
> | The largest programs running were xfs (about 3MB) and sendmail in that
> | order. In text mode with hardly anything running besides the usual
> | suspects (autofs, nfs, cron, lpd etc), Linux is using up over 46MB of RAM.
> | This does not add up.  Does anyone know why it needs so much memory?
> 
> It's probably still got your X server etc lying around in case you run
> them again.  Don't worry - the pages are "clean" and can just be tossed if
> you run something else; all linux is doing is keeping track of what they
> used to be used for in case reuse will save it sucking them back in off
> the disc (a slow process compared to just using copies already in memory).

The standard response to my query seems to be pretty much what you are
saying. That is, Linux tries to use all available RAM to speed things up,
caching executable code being one example. I am aware of that: that is
what the "buffers" and "cached" columns are for. In the above "free"  
output, those total to slightly under 60MB. Please let me direct your
attention to the second line, where it shows over 46MB of RAM in use
EXCLUSIVE of disk buffers and cache. That is the part that I am puzzled
about, which is not accounted for by caching nor the active processes.
What's in that?

There is also that additional 30MB or so of swap memory in use, but we
already know about the funny 2.4.[0-9] VM swap behavior. I'm not concerned
about that.

Chris