[Trilug-ontopic] Process priority

David Black dave at jamsoft.com
Wed May 7 19:06:50 EDT 2008

You may find using a different I/O scheduler will help.  Assuming a 2.6
kernel, here's some background: http://www.linuxjournal.com/article/6931

In recent 2.6 kernels the default I/O scheduler is cfq, and is
selectable on a per-device basis.  Here's how to change it to (for
instance) deadline for /dev/hda:

# cd /sys/block/hda/queue
# cat scheduler
noop anticipatory deadline [cfq]
# echo deadline > scheduler
# cat scheduler
noop anticipatory [deadline] cfq

The 'best' I/O scheduler depends on the kind of load the machine is
seeing.  Since there are currently only four to choose from, why not try
your test with each?


Jason Watts wrote:
> so... i discovered (it was quite obvious actually) that to run an rsync
> and an un-tar command at the same time on the same set of drives that it
> really causes the system to lag.
> My question is for the next time I need to do something like that.  how
> would I set the priority of the un-tar to a lower priority... that way
> it is only using what resources are left over that aren't being used? 
> if that's really possible  (my bottleneck was actually the spindle
> speeds of the drives)
> thanks,
> Jason
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