[CentOS] VM differences between CentOS and current vanilla

Tue Oct 3 16:13:00 UTC 2006
Steve Bergman <sbergman at rueb.com>

After running into some VM problems with the new CentOS 4.4 kernel,
which I suspect are VMWare related, I built using the
FC5 .config file for 2.6.15 and "make oldconfig".

It seems to have resolved the "page allocation failure" problem.  But I
find its behavior to be a bit odd.

This is a 4GB system.

min_free_kb is at the default, which is 3841.

So I would expect Free memory to hover around 4MB.

However, instead, it seems to seek out about 150M free.

If I do a dd from /dev/md0 to /dev/null, the free memory does drop to
around 25MB.  But then, as the system is used, it drifts back to...
about 150M.

Swap varies between 100M and 500M, and buffer+cache runs around 500M.
I'm pretty sure that we access enough different data that it should be
using some of the 150M free for buffers+cache.

Swappiness is set to the default 60.

Any comments?