On Jan 12, 2004, at 11:22, audin@okb-1.org wrote:
Is DMA turned on and interrupt unmasking enabled on Ursula?
DMA is on. Interrupt unmasking, no.
`/sbin/hdparm /dev/hda` (or whatever device it is) will show the current configuration.
# /sbin/hdparm /dev/hda
/dev/hda: multcount = 16 (on) IO_support = 0 (default 16-bit) unmaskirq = 0 (off) using_dma = 1 (on) keepsettings = 0 (off) readonly = 0 (off) readahead = 8 (on) geometry = 7476/255/63, sectors = 120103200, start = 0
/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.
Well, went ahead and turned on interrupt unmasking and 32-bit io. The numbers in vmstat don't look too much different yet, but we'll see.
-- brion vibber (brion @ pobox.com)