On Wednesday August 17 2005 7:56 pm, Pupeno wrote:
> On Wednesday 17 August 2005 18:44, Mark Knecht wrote:
> > A quick test would be
> >
> > hdparm
>
> I got this:
> /dev/hda:
> Timing cached reads: 1344 MB in 2.00 seconds = 672.10 MB/sec
> Timing buffered disk reads: 8 MB in 3.51 seconds = 2.28 MB/sec
>
> > (or whatever drive you are concerned about.) Greater than 15MB/S is
> > almost certainly DMA but good DMA from newer drives should be
> > 25-50MB/S
>
> The second speed is evidently wrong.
>
> > You can look at the drives parameters using hdparm and reading through
> > the man page to understand what all the values mean.
>
> I tried to enable dma, but this happened:
> # hdparm -d1 /dev/hda
>
> /dev/hda:
> setting using_dma to 1 (on)
> HDIO_SET_DMA failed: Operation not permitted
> using_dma = 0 (off)
>
> What am I doing wrong ? some kernel option ?
>
> Thanks
If you want the kernel to set dma you need to enable it and the support for
your motherboard chipset. For a 2.6.12 kernel, you'll find this under
Block devices
ATA/ATAPI/MFM/RLL support
Enable
Generic PCI bus-master DMA support (BLK_DEV_IDEDMA_PCI)
Use PCI DMA by default when available (IDEDMA_PCI_AUTO)
And below that support for your MB chipset.
However, hdparm should have set this even without kernel support (I'm pretty
sure)...what say #hdparm /dev/hda
-jm
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