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SubjectRe: PATCH: Fix broken PIO with libata
Kevin Radloff wrote:
> On 5/16/06, Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
>> On Maw, 2006-05-16 at 11:33 -0400, Kevin Radloff wrote:
>> > However, I still have a problem with pata_pcmcia (that I actually
>> > experienced also with the ide-cs driver) where sustained reading or
>> > writing to the CF card spikes the CPU with nearly 100% system time.
>>
>> That is normal. The PCMCIA devices don't support DMA. As a result of
>> this the processor has to fetch each byte itself over the ISA speed
>> PCMCIA bus link.
>
> Hrm, as I recall that only started happening with ide-cs sometime in
> the single digits of 2.6.x.. And note that it's only maxing out at
> about 1.5MB/s. Should that saturate my laptop's 1.1GHz Pentium M
> processor?

Doing data xfer using PIO rather than DMA definitely eats tons of CPU
cycles.

Jeff



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