Re: 2.6.x Scheduler, preemption and responsiveness - puzzlement

[Alistair John Strachan <s0348365@sms.ed.ac.uk>]

On Sunday 11 July 2004 23:55, Sid Boyce wrote:
[snip]
>
> I've been wondering why this is, I can't remember what the BIOS says
> about the hard drives, from memory it looked OK, I think it was set to
> AUTO, haven't tried LBA.
> # hdparm -d1 /dev/hda
>
> /dev/hda:
>  setting using_dma to 1 (on)
>  HDIO_SET_DMA failed: Operation not permitted
>  using_dma    =  0 (off)
> # hdparm -d1 /dev/hdc
>
> /dev/hdc:
>  setting using_dma to 1 (on)
>  HDIO_SET_DMA failed: Operation not permitted
>  using_dma    =  0 (off)
>

Your BIOS geometry settings are irrelevant. You've just forgotten to enable 
the correct busmaster DMA driver in your kernel. It looks as though this is 
an nForce 2 system, so you need to enable "Generic PCI bus-master DMA 
support", then further down "AMD and nVidia IDE support", in menuconfig. 
You'll then be able to set DMA on, and this will likely resolve the 
performance issue.

In .config, the relevant options are

CONFIG_BLK_DEV_IDEDMA_PCI=y
CONFIG_BLK_DEV_AMD74XX=y

Hope this helps!

-- 
Cheers,
Alistair.

personal:   alistair()devzero!co!uk
university: s0348365()sms!ed!ac!uk
student:    CS/AI Undergraduate
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