Re: devfs: The conclusion.

H. Peter Anvin (hpa@transmeta.com)
8 Aug 1998 08:41:22 GMT


Followup to: <35CB5E99.88677E80@intermetrics.com>
By author: Pal-Kristian Engstad <engstad@intermetrics.com>
In newsgroup: linux.dev.kernel
>
> 1.) devfs is conceptually cleaner, in that the kernel devices
> control such things as major and minor device numbers.

I for one think it is not clean at all. I think it is a
Microsoft-like path-of-least-resistance hack.

> 2.) devfs reduces the number of devices in /dev to a minimum, thus
> reducing a number of inodes and some hard-disk and RAM. This
> has also the advantage that it is easy to determine which
> devices are in the system.

It stores *ALL* its inodes in RAM, whereas an on-disk /dev never
brings them in if they aren't actively used.

> 3.) devfs optionally introduces a new naming scheme, preferred by
> some linux administrators.

Not something specific to devfs. scsidev has done this for ages.

> 4.) devfs also makes it possible to mount your root on other
> filesystems, like e.g. a CD-ROM or a non-unix filesystem.

You can do that anyway.

> 5.) devfs is also claimed to be faster, in that you do not have to
> go to an external device to get major and minor device numbers.

This speed difference is at the best very slight, and might just as
well be a lose due to the loss of additional kernel RAM. Any device
used with any frequency is going to be cached in the VFS anyway.

-hpa

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