[KLUG Members] Memory problems

[Jamie McCarthy]

adam@morrison-ind.com (Adam Tauno Williams) writes:

>              total       used       free     shared    buffers     cached
> Mem:        517260     512028       5232     149724      52232     362952
> -/+ buffers/cache:      96844     420416

> Perfectly normal.  420Mb is being used to cache I/O,  which is
> all good.

Mind if I go off on a tangent here?  Apparently "cached" is *mostly*
or *usually* just disk cache.  I gather disk cache is like disk
buffer except one is a cache of what's been read, and the other's a
cache of what's been written (I'm not sure which is which).

But "cached" can also refer to other ways that RAM is being used
besides mirroring disk sectors.  I know this because a machine with
4 GB of RAM that's running MySQL under heavy load is getting to the
point where the kernel needs to kill the "mysqld" process because it
runs out of RAM... even though there are about 3 GB of RAM listed in
the "cached" category in "free"'s output.

This leaves little footprints in /var/log/messages like:

Dec  1 12:34:56 myhost kernel: Out of Memory: Killed process 23798 (mysqld-max).

So... does anyone know what gets "cached" besides disk?
--
 Jamie McCarthy
 jamie@mccarthy.vg