Re: Horrible drive performance under concurrent i/o jobs (dlh problem?)

[Torben Frey <kernel@mailsammler.de>]

Hi Andrew, hi Con,

> Here's a diff against base 2.4.20.  It may be a little out of date
> wrt Andrea's latest but it should tell us if we're looking in the
> right place.
Ok, I did not run the complete 2.4.20aa1 kernel yet since I am not sure 
if it is intended to be used, but I applied your patch, Andrew (thanks 
for mailing it). It still does not fix the problem. One job doing much 
I/O starts with about 80% CPU but then drops down to about 30% in the 
first 40 seconds. Load goes from 0.00 to 2.4 within that time.

And I can see bdflush and my process marked with "D" in the process list.

Catting the device to /dev/null only made it worse :-(

Creating a 1GB file using dd takes about 1 minute compared to 16 seconds 
without other jobs running.

Do you think it could be a ReiserFS problem on a RAID? Do you know of 
anything else I could try? Sorry, but my knowledge doesn't reach that far.

TIA,
Torben