ways to check dma?

nakkaya · 02-17-2003, 11:08 PM

is there way to check if dma support is activated in my system or not?

born4linux · 02-17-2003, 11:35 PM

if u are referring to your disk drives, use hdparm:

for example:

hdparm /dev/hdc

you'd be able to see the DMA flag there if it is set or not. 1 means it is set. 0 is not set.

carlywarly · 02-18-2003, 01:48 AM

To see what effect it has, run hdparm -tT /dev/hda It will do 2 timed reads, one from the cache and one direct from the drive.

Here's mine -
/dev/hda:
Timing buffer-cache reads: 128 MB in 0.63 seconds =203.17 MB/sec
Timing buffered disk reads: 64 MB in 1.60 seconds = 40.00 MB/sec
[root@1600 carlie]#

nakkaya · 02-18-2003, 03:03 AM

my second result is 23 mb so i dont have dma support right and what do i have to do enable it?

Silent Bob · 02-18-2003, 03:19 AM

use hdparm -i /dev/hdX for LOADS of information about your drive, including what DMA modes it can support.

To find out whether it is on or not, do what born4linux suggested: hdparm /dev/hdX

To turn DMA on use hdparm -d1 -X<modenumber> /dev/hdX

You work out <modenumber> by adding 64 to the DMA mode you want to use, e.g. mode 2 you would use -X66, mode 5 -X69

whansard · 02-18-2003, 03:57 AM

your bios probably sets your dma mode to the max
the drive can handle, but its just not getting enabled
by linux
hdparm -d1 /dev/hda
probably

if that doesn't cause any trouble, add it to one of your init
scripts.

nakkaya · 02-18-2003, 05:44 AM

dma support is on i checked it with hdparm /dev/hda but why is the data transfer is so slow my hardware is inspiron 2650 with ibm harddrive bu not sure btw it is a lop top

whansard · 02-18-2003, 07:06 AM

did you try
hdparm -t /dev/hda
with and without dma enabled?
you can disable it with
hdparm -d0 /dev/hda

maybe it's something else thats making you
think the hard drive is slow.

23 megs a second is normal for a slower hard
drive running dma. if dma was off, it would
probably be around 3 megs a second.

Bert · 02-18-2003, 07:36 AM

cat /proc/dma

will do it - it'll tell you which IRQ is routed to deal with DMA requests. If it doesn't work, you don't have it.