Question about Virtual Memory

From: James Fillman (
Date: Tue May 07 2002 - 12:27:09 EST

Hash: SHA1

I'm trying to understand how the 2.4 kernel behaves with respect to
caching. I'm running the 2.4.17 kernel on an i686. The server is running
heartbeat, apache, tomcat, and a java based message routing application. 99%
of the work is comming from the java application which produces a lot of disk
and network I/O.
Am I correct in saying that the kernel will cache disk writes to memory if
there is ample free RAM? Then syncing it to disk at a later time?

With the above mentioned applications NOT running, %swapused = 0, disk cache
= 0. I've observed that when the applications start up, the kernel slowly
starts allocating free RAM for caching. It will stabalize with ~6MB of RAM
free. That's fine. But what I don't understand is that at the same time, swap
usage starts to increase and after a day or so, stabalizes at ~15MB. What is
being swapped out? Is the VMM utilizing swap when it's caching?

James Fillman
Version: GnuPG v1.0.6 (GNU/Linux)
Comment: For info see

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

This archive was generated by hypermail 2b29 : Tue May 07 2002 - 22:00:30 EST