Re: devfs

Albert D. Cahalan (acahalan@cs.uml.edu)
Fri, 9 Jan 1998 14:34:34 -0500 (EST)


>>> Laugh. Think 'caching' which is done right now for the current
>>> scheme. Even 1000 people logged in for 2000 inodes is a trivial
>>> number of inodes.
>>
>> Hmmm, a 64 kB /dev with linear ext2 searching. Ouch.
>> But that isn't as bad as it gets when you add SCSI.
>
> You clearly don't understand what's going on here. The directory
> search is _only_ done for a filename lookup. I.e. at the moment, only
> when someone logs in. After that the tty is referenced by
> inode. Updates are in-memory, and at very very low cost.

I expect people will want to log in.

You would slow down: lilo, most procps tools, svgalib apps,
telnetd, xterm, screen, emacs, and many shell scripts.
It is bad enough with 256 pty pairs, SCSI partitions, etc.

>>> Posix complient means nothing. Go and see what you actually need to
>>> make posix. It's bugger all. Certainly not a terribly useful system.
>>>
>>> pty's aren't minimal posix to start with, ditto devices!
>>
>> Yes, which is why an NTFS system requires a devfs. I guess you agree.
>
> Why stop at devices? What about unix pipes? what about hard links?
> The fact that NTFS is missing a bunch of features means NTFS has a
> problem. Why muck up the rest of the kernel because of NTFS
> limitations.

Get a clue about NTFS. It isn't missing a bunch of features.
The only thing missing is /dev support.

> As a sanity check: How many people would seriously want to
> run NTFS as root filesystem?

I see, _you_ don't need it so screw everyone else.
Answer 'N' in the kernel config and ignore us weirdos.

>>> This isn't an argument for devfs. This is an argument for a larger
>>> dev_t size. Before you can claim this as a reason for building a
>>> devfs, you need to detail exactly how a devfs is magically going to
>>> fix the above problem.
>>
>> Sanity check time! Let's see if your "fix" would work.
>>
>> bus 4 bits
>> unit 8 bits
>> LUN 8 bits
>> partition 6 bits
>> raw/cook/etc 2 bits
>>
>> Fine, /dev will be 4 to 8 GB. The linear search will be fun!
>> Seriously, a larger dev_t will _not_ fix this problem.
>
> This is truely nonsense. You don't need to create every possible
> device. Even in the current scheme, most people don't have a
> /dev/sdf* in there.

Really? Most people run RedHat AFAIK, which makes /dev/sdf*.

I have that device. Since ext2 directories do not get compacted,
there is no reason to remove the device without a full backup,
removal, and restore of /dev. That means a boot floppy.

Distributions need to include such devices so that people
won't call tech support and complain.

> You create the devices you need. It isn't terrible hard!

Now you are torturing newbies. Actually, great hackers shouldn't
have to bother with that either. It is a waste of their time.

> ptys need a better fix than a devfs kludge. They don't really
> belong in the device space anyway, more the unix pipe space.

Interesting. Propose a solution that won't violate standards.
You need to support ptsname() and ttyname(). Without a devfs,
you might need an ugly hack in /proc. Eeew.