On Sun, Oct 10, 2010 at 11:17:37PM +0400, Dmitry-T wrote:
quoted text
> My test OpenBSD:
> 
> load from livecd bsdanywhere46-amd64
> 
> in different consoles:
> 
> dd if=/dev/wd0c of=/dev/null bs=1m
> dd if=/dev/wd0c of=/dev/null bs=1m
> dd if=/dev/wd0c of=/dev/null bs=1m
> iostat
> top
> 
> run:
> dd if=/dev/urandom of=/dev/null
> and disk read speed jump from 22Mb/s to 0.9Mb/s!
> 
> renice 20 for last dd - throughput not change!
> renice -20 for first three dd  - throughput not change!
> For check renice, run renice -20 for last dd - OpenBSD froze, even mouse.
> 
> It is not secure. One script or program may load CPU and 
> database or another servers lost speed in disk operations.
> 
> In Linux (test on 2.6.35 libre) renice work correct...
> Why renice not work in OpenBSD?
> 

This is not how scheduling priorities work. You try to renice I/O bound
processes. The scheduler priority only matters when processes are CPU
bound.

I also don't get it why people always use /dev/*random as input
source for tests -- random numbers are not for free. 

-- 
:wq Claudio