Messages in this thread | | | Subject | Re: devfs | From | "Michael O'Reilly" <> | Date | 09 Jan 1998 13:01:11 +0800 |
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"Albert D. Cahalan" <acahalan@cs.uml.edu> writes: > > 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.
> > 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.
As a sanity check: How many people would seriously want to run NTFS as root filesystem?
> > 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.
You create the devices you need. It isn't terrible hard!
So far, the only reasons I've seen for a devfs are: #1. NTFS doesn't have devices. #2. Some people want fixed scsi device numbering. #3. Ptys are a bit of a kludge, and people would like to be able to securely use them w/o being root.
#1 is furphy. #2 There already exists a working solution for this in userspace. Find it and use it! #3 ptys need a better fix than a devfs kludge. They don't really belong in the device space anyway, more the unix pipe space.
Michael.
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