Re: 2.6.15-rc5-mm1

Jeff Garzik
2005-12-09T01:52:57Z

Alexander E. Patrakov wrote:
> Andrew Morton wrote:
>
>> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.15-rc5/2.6.15-rc5-mm1/
>>
>
>
> I just noticed (maybe too late) that this kernel has the "pata_via"
> driver and decided to try it. It works here, but has one drawback: it is
> slower than the old "via82cxxx" IDE driver.
>
> My configuration with the via82cxxx driver:
>
> /dev/hda = disk, QUANTUM FIREBALLlct20
> Drive conforms to: ATA/ATAPI-5 T13 1321D revision 1
>
> /dev/hdb = SAMSUNG CD-ROM SC-148F
> Drive is old, supports only mdma2
>
> There are also /dev/hdc and /dev/hdd, irrelevant here.
>
> With the via82cxxx driver, I can get speed around 20 MB/s from /dev/hda.
> The pata_via driver downgrades this to 7 MB/s because it needlessly
> drops the disk to MWDMA2 mode.

That's expected, as libata currently limits all drives on a bus to the
maximum speed of the slowest drive. That's needed by some controllers,
but not all.

I'm pretty sure Alan plans to fix that (at least ISTR him mentioning it).

Jeff