Re: Inexplicable disk activity trying to load modules on devfs

From: Richard Gooch (
Date: Tue Jun 25 2002 - 22:37:11 EST

Borsenkow Andrej writes:
> >>
> >> 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.
> >>
> >
> >
> >syslog activity from a printk, perhaps?
> No. It is most probably devfsd trying to load sound modules.
> This is exactly the reason Mandrake does not enable devfs in
> kernel-secure. You can badly hit your system by doing in a loop ls
> /dev/foo for some device foo that is configured for module
> autoloading.
> It is very fascist decision; the slightly more forgiving way is to
> disable devfsd module autoloading (or disable devfsd entirely, just
> run it once after all drivers are loaded to execute actions) but
> then you lose support for hot plugging and some people do use
> kernel-secure on desktops.

Or you can use the IGNORE action to selectively disable loading of
some modules (whether or not they exist).

Another option is to write a shared object extension to devfsd which
has rate-limiting. All the mechanisms you need are there or can be
built on top of the existing infrastructure.


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This archive was generated by hypermail 2b29 : Sun Jun 30 2002 - 22:00:11 EST