Inexplicable disk activity trying to load modules on devfs

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.

Quoted 9 lines · Daniel Jacobowitz

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.

Quoted 8 lines

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?

Quoted 17 lines · Andrew Morton

Quoted 15 lines · Daniel Jacobowitz

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.

Quoted 1 line

syslog activity from a printk, perhaps?

Nope. No log activity whatsoever.

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