Free memory level in 2.6.16?

Steve Bergman
2006-10-05T07:47:51Z

Due to some problems I was having with the CentOS4.4 kernel, I just
moved a box (x86 with 4GB ram) to 2.6.16.29 from kernel.org.

All is well, but I am curious about one thing. This is a fairly memory
hungry box, serving about 40 gnome desktops via xdmcp. All VM settings
are at the default. Swappiness=60, min_free_kbytes=3831.

However, it seems to seek out about 150MB for the level of free memory
that it maintains. Typically I see somewhere between 100MB an 500MB in
swap, buffers+cache is about 500MB, and 150MB is free.

If I cat from /dev/md0 to /dev/null, the free memory does go down, to
25MB or so, but then I can watch as it seeks out about 150MB of free
memory.

To me, free memory is wasted memory. Is this a bug or a feature?

Thanks for any enlightenment.