please educate me on memory usage

Norm Vilmer norm at
Fri Sep 24 11:46:51 PDT 2004

Gregor Mosheh wrote:
> I was looking at my top output and was surprised to
> see that the bulk of my 512 MB of memory was in use,
> since the server really has fairly little running.
> It's not a problem, but I was wanting some
> clarification on where this memory was being used, for
> my own education.
> The original goal was that I had figured that a lot of
> memory would be unused since so little is running, and
> perhaps I could allocate some more to Postgres.
> Apparently nowt, but I don't quite understand all the
> intricacies of what *is* using my memory.
> 35 processes:  1 running, 34 sleeping
> CPU states:  0.0% user,  0.0% nice,  0.0% system, 
> 0.0% interrupt,  100% idle
> Mem: 158M Active, 207M Inact, 80M Wired, 20M Cache,
> 60M Buf, 33M Free
> Swap: 2000M Total, 6848K Used, 1994M Free
> So, 158 MB of memory in use. Does that include
> anything other than process' memory, e.g. shared
> memory, kernel memory, some of the fs buffer? If I add
> up the VSZ column from 'ps aux' I get 110 MB.
> The server's only processes of interest are MySQL,
> Postgres, and Apache httpd. There are cron, sendmail,
> etc. but these are all <1M usage according to both top
> and ps.
> MySQL has VSZ 38 MB and RSS 4 MB.
> Postgres (incl stats collectors) has VSZ 25 MB and RSS
> <1 MB. There's also the shared memory: ipcs agrees
> with my postgresql.conf settings: 2 MB of shared
> memory buffers.
> Apache 1.3 has 15 processes, each using 3.6 MB VSZ and
> 1.5 MB RSS. I was of the impression that the bulk of
> this memory was shared with the parent process, no?
> So where's the rest of the memory going?
> The 80M Wired is interesting, since I don't know where
> it's going. I presume that PG's 2 MB of shared buffers
> are wired (though I saw an email today that implied
> otherwise), but how could I track down the rest of it?
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My guess would be MySQL, however I am no expert. My machine is running
apache, ntp, ipfw, and other typical stuff like syslog, sendmail, etc.
Mem: 11M Active, 122M Inact, 44M Wired, 28K Cache, 57 Buf, 292M Free.

I did optimize my machine using doc's I read on

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