Inexplicable disk activity trying to load modules on devfs

From: Daniel Jacobowitz (
Date: Sat Jun 15 2002 - 17:22:44 EST

I just booted into 2.4.19-pre10-ac2 for the first time, and noticed
something very odd: my disk activity light was flashing at about
half-second intervals, very regularly, and I could hear the disk
moving. I was only able to track it down to which disk controller, via
/proc/interrupts (are there any tools for monitoring VFS activity?
They'd be really useful). Eventually I hunted down the program causing
it: xmms.

The reason turned out to be that I hadn't remembered to build my sound
driver for this kernel version. Every half-second xmms tried to open
/dev/mixer (and failed, ENOENT). Every time it did that there was
actual disk activity. Easily reproducible without xmms. Reproducible
on any non-existant device in devfs, but not for nonexisting files on
other filesystems. Is something bypassing the normal disk cache
mechanisms here? That doesn't seem right at all.

Daniel Jacobowitz                           Debian GNU/Linux Developer
MontaVista Software                         Carnegie Mellon University
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