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SubjectRe: DEVFSv50 and /dev/fb? (or /dev/fb/? ???)
Andrea Arcangeli writes:
> On Thu, 6 Aug 1998, Richard Gooch wrote:
>
> >No, this isn't true. Think about hot-swappable discs. Think about
> >PCMCIA. Think about USB. All cases where hardware is plugged in and
> >out and you don't reboot the kernel.
>
> So with devfs after you have connected a PCMCIA card, in some msec
> automagically the right devfs device is added to /dev/ or /devfs/?

Yup.

> >Erm, if you just move all block devices into their own subdirectory,
> >and assuming the bulk of /dev bloat is due to block devices
> >(reasonable, when you consider the zillions of possible SCSI discs
> >when we break the 16 disc limit), then searching through /dev/block is
> >nearly as long as searching /dev with everything in it.
>
> With the current inode scheme nobody force you to put all blocks device in
> the same directory. I will use /tmp/myhd to be fast.

That looks like a hack to me.

> And the device-file lookup in the case of block devices is done only at
> mount time (I hope to be right here ;-) so it' s really not importatnt and

Actually, it's done at open(2) time. That's done by mount(8), fdisk(8)
and so on. Also if you want to list the directory, it takes more time.
It gets worse if you do "ls -lF" or something, which causes a stat(2)
of each inode.

> it would be fast enough also with zillon of device in the same directory.
> In production server I mount hd once a month (the power usually go down
> once a month ;-).

Mounting isn't the only time you need to access those inodes. Also,
think about those with a small CPU: extra (noticable!) delay at boot
time is unwelcome.

Regards,

Richard....
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