[Techtalk] Turning on DMA

[Carlo Hamalainen]

Hi everyone,

I've missed most of this thread apart from these two lines:

> > 2.  What config files would have to be changed to allow dma to be on by
> > default?

Since turning on DMA isn't a terribly urgent thing, I just modified
/etc/rc.d/rc.local to call hdparm.

This reminds me of a seemingly unrelated issue: a slow PPP dialup
connection. It turned out that since my harddisk had PIO turned on. Then,
roughly speaking, the CPU got too busy handling harddisk interrupts, and
missed the occasional packet from the modem. Then, connections had to be
restarted, etc, and caused transfer rates of a few bytes/second (painful).

More disturbingly, this started happening without me changing things on my
system, nor the ISP. No idea why.

The fix is to run "/sbin/hdparm -u1 /dev/hda" to allow interrupts to be
unmasked (and has warnings of harddisk corruption on certain hardware).
The -d1 option may be enough most of the time anyway.

Anyway, very mysterious, but easily fixed.

-- Carlo