[ltp] Renice disk ?

[Richard Neill]

Charles E. "Rick" Taylor, IV wrote:
> On Wed, 2005-08-17 at 15:51 +0100, Richard wrote:
> 
> 
>>These programs run at 
>>nice level 20, taking the lowest level priority on the CPU. However, 
>>because they require lots of disk access, they make other programs that 
>>need to use the disk very unresponsive (eg starting bash, running su, 
>>opening files).
> 
> 
>>Given that the system is disk-bound rather than CPU-bound, what should I 
>>do about this? Google appears to have no advice.
> 
> 
> First thing I'd check is your hdparm settings.  Last time I had a
> problem like the one you describe, DMA and unmaskirq were disabled.
> 


Thank you very much. Actually, DMA is on, but I have just installed the
newest kernel, (upgraded from Mandriva 2005 to 2006 Beta). I know that
DMA usually defaults to on on this machine, but I forgot to test the
2005 configuration before I upgraded it. The performance is much better
now, anyway. [I can run updatedb, or rpm -Va, and still start a new root
shell in about 1 second].

So, I can't be sure whether the fix is due to some sort of
kernel-scheduler improvement in the last 6 months, or whether DMA was,
unusually, not enabled in Mdk 2005.

Umaskirq is off by default; I've turned it on, but it doesn't seem to
make much difference.  Should it? There is a dire warning in man hdparm
about -u  - is this warning obsolete?

Regards

Richard