Re: [ANNOUNCE] ndevfs - a "nano" devfs

[Oliver Neukum <oliver@neukum.org>]

Am Mittwoch, 29. Juni 2005 18:06 schrieben Sie:
> On Wed, Jun 29, 2005 at 08:41:29AM +0200, Oliver Neukum wrote:
> > What devfs and udev can do, and a static dev cannot, is names independent
> > of order of detection.
> 
> devfs can not do that.

Why not?

> > As for ressources, it is an illusion to think that user space means
> > less ressources. A demon means page tables and a kernel stack. That
> > 12K unswappable memory in the best case.
> 
> You don't have to run the udevd process if you are worried about an

What about events arriving out of order?

> extra process in your kernel tables.  Although this is the first time I
> have heard anyone voice the "oh no, not another userspace task running"
> point :)

Well, you should have. 16K is a more realistic figure. Tasks have their cost.
In fact:
root         1  0.0  0.0    684   248 ?        S    16:58   0:01 init [5]
root         2  0.0  0.0      0     0 ?        SN   16:58   0:00 [ksoftirqd/0]
root         3  0.0  0.0      0     0 ?        S<   16:58   0:00 [events/0]
root         4  0.0  0.0      0     0 ?        S<   16:58   0:00 [khelper]
root         5  0.0  0.0      0     0 ?        S<   16:58   0:00 [kthread]
<snip>
root      3424  0.0  0.1   2032   632 tty3     Ss+  16:59   0:00 /sbin/mingetty tty3
root      3425  0.0  0.1   2032   632 tty4     Ss+  16:59   0:00 /sbin/mingetty tty4
root      3426  0.0  0.1   2032   632 tty5     Ss+  16:59   0:00 /sbin/mingetty tty5
root      3427  0.0  0.1   2032   632 tty6     Ss+  16:59   0:00 /sbin/mingetty tty6

Counting this I arrive at 51*16K = 816K. That's a whole lot of unswappable
memory. Thinking user space cheap is an automatic reflex these days. It's
sometimes misleading like all blind reflexes.
It makes me feel a fool for caring about __init and __exit.

	Regards
		Oliver