Re: [ANNOUNCE] ndevfs - a "nano" devfs
From: Oliver Neukum
Date: Wed Jun 29 2005 - 11:27:34 EST
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
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