Re: How to make apps play nice?
On Sun, Dec 18, 2005 at 11:35:09PM +0900, Craig Hagerman wrote:
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> $ hdparm /dev/hda
>
> /dev/hda:
> multcount = 16 (on)
> IO_support = 0 (default 16-bit)
> unmaskirq = 0 (off)
> using_dma = 0 (off)
^^^^^^^^^^^^^^^^^^^^^^^^^^
[skip]
> (NOTE- sda and sdb are joined up via LVM2 into one big volume)
> So what does all of this mean? Seems that dma is not activated for
> /dev/hda. Does the above mean that is IS active for /dev/sda and
> /dev/sdb?
Are sda and sdb real SCSI HDDs or SATA? If they are SATA DMA is
turning regarding to their read speeds you showed below.
>
> the -tT flag gives this:
>
> $ hdparm -tT /dev/hda
>
> /dev/hda:
> Timing cached reads: 2652 MB in 2.00 seconds = 1325.92 MB/sec
> Timing buffered disk reads: 12 MB in 3.14 seconds = 3.82 MB/sec
^^^^^^^^^^^
The performance is very poor (missing of DMA explains it), modern HDD
should give at least 30 MB/sec.
[skip]
> Meanwhile the -d activating option fails:
>
> $ hdparm -d1 /dev/hda
>
> /dev/hda:
> setting using_dma to 1 (on)
> HDIO_SET_DMA failed: Operation not permitted
> using_dma = 0 (off)
>
>
> Any advice concerning this? How does one get dma activated?
> (Thanks again.)
It seems that driver you are using for now doesn't support DMA
transfers on your chipset. You have to load kernel module that supports
your IDE chipset. You can determine your IDE chipset by reading output
of
$ lspci
Then find appropriate module and load it instead of ide_generic.
>
> Craig
>
>
--
With best regards, Oleg Gritsinevich
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