On Mon, Jan 12, 2004 at 11:11:28AM -0800, Brion Vibber wrote:
Ursula's sitting around with a 90% idle CPU, but everything's blocked on disk I/O to the point it's got a load average of about 16. At any given time from 8-20 processes are blocked and waiting. Operations that hit a lot of rows like history and watchlist are particularly badly hit since they don't play as well with caching.
I mentioned this before, but it may have gotten lost as the server fell over completely right afterwords...
Is DMA turned on and interrupt unmasking enabled on Ursula?
`/sbin/hdparm /dev/hda` (or whatever device it is) will show the current configuration.
/sbin/hdparm -u1 -c3 -d1 /dev/hda` will turn on DMA, turn off interrupt masking, and enable 32bit i/o support. Interrupt masking itself can have a huge impact on the amount of cpu time spent waiting for the disk...and it is almost always set conservatively (ie: wrong) on an untweaked linux installation.