Udev cause of disk IO slowdown?

Udev cause of disk IO slowdown?

[Ake]

Hi!
I'm experiencing something that looks like a severe slowdown of disk IO
when going through udev (compared to when going through devfs handled
/dev). Interrupts and context switches goes up by a factor of 4 when
removing background noise.

Has anyone seen this?

This is a debian 2.6.5 kernel with udev 0.24 from debian.
Using devfs mounted /dev i get around 90-100MB/s from /dev/sdb doing
dd if=/dev/sdb of=/dev/null bsÅ92k
but using udev as /dev handler i get only 15MB/s

The devfs vs udev change is the ONLY difference here (guaranteed).

-- 
Ake Sandgren, HPC2N, Umea University, S-90187 Umea, Sweden
Internet: ake@hpc2n.umu.se	Phone: +46 90 7866134 Fax: +46 90 7866126
Mobile: +46 70 7716134 WWW: http://www.hpc2n.umu.se


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Re: Udev cause of disk IO slowdown?

[Harald Hoyer]

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this sounds completly bogus :) a device node is a device node...

Ake wrote:
> Hi!
> I'm experiencing something that looks like a severe slowdown of disk IO
> when going through udev (compared to when going through devfs handled
> /dev). Interrupts and context switches goes up by a factor of 4 when
> removing background noise.
> 
> Has anyone seen this?
> 
> This is a debian 2.6.5 kernel with udev 0.24 from debian.
> Using devfs mounted /dev i get around 90-100MB/s from /dev/sdb doing
> dd if=/dev/sdb of=/dev/null bs=8192k
> but using udev as /dev handler i get only 15MB/s
> 
> The devfs vs udev change is the ONLY difference here (guaranteed).
> 


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