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Re: speedup device flushing with devfs
From: |
David Schweikert |
Subject: |
Re: speedup device flushing with devfs |
Date: |
Sun, 15 Dec 2002 10:22:58 +0100 |
User-agent: |
Mutt/1.4i |
On Sun, Dec 15, 2002 at 10:06:53 +1100, Andrew Clausen wrote:
> > I made a strace and I did see that parted does try to open
> > part1, part2, ... part15, in that directory, which in turn triggers
> > devfs module probing.
>
> Hmmm. What kind of module probing? Rescanning the partition table?
> (I don't have devfs here...)
My Debian-default modules.conf has:
alias /dev/ide/host*/bus*/target*/lun*/* /dev/ide
probeall /dev/ide ide-probe-mod ide-disk ide-cd ide-tape
ide-floppy
It means every time you try to open for example
/dev/ide/host0/bus0/target0/lun0/partN then it will try to load
ide-probe-mod ide-disk ide-cd ide-tape ide-floppy, which I guess in turn
probe the hardware to see if it is installed. All of this takes a lot of
time.
> > With the following simple patch, the time required is down to 0.05
> > seconds. Is this a good thing or am I going to destroy my disks?
>
> Why not structure the loop around scanning the directory, rather than
> around iterating through partition numbers?
Being not so confident with the code, I didn't want to change the
behaviour for non-devfs installations. I also wanted to be able to
use _device_get_part_path, etc. The cost of scanning the directory
15 times is really low in any case, so I think that the code as is more
readable and not really unoptimal.
Cheers
David
--
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__| |___ David Schweikert <address@hidden>
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