> I have written a data acquistion application using an rtlinux module,
> and, while everything works well when I am not saving data to disk, during disk
> writes I get pauses in the display. This is, as far as I understand it, a
> result of disk write buffering, and I'm wondering if there is anything I can do
> about it.
Interrupts are probably not being used by your hard disk driver. You can
enable them with:
hdparm -u1 /dev/hda
Repeat the above command for each drive in your system. You can examine
the drive configuration with:
[root@wayne wwright]# hdparm /dev/hda
/dev/hda:
multcount = 32 (on)
I/O support = 1 (32-bit)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
nowerr = 0 (off)
readonly = 0 (off)
readahead = 8 (on)
geometry = 16383/16/63, sectors = 16514064, start = 0
[root@wayne wwright]#
The man page on hdparm has all kinds of warnings about enabling interrupts
and dma, but I've yet to have a really bad experience with it yet. It is
the only way I've found to get expected performance from the hard drives.
It appears the Linux generally will configure hard drives for the lowest
performance ie. no interrupts and no dma. The man page has good
explainations on each possible option.
-Wayne
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