Re: PATCH: Fix broken PIO with libata

[Jeff Garzik]

Kevin Radloff wrote:
> On 5/16/06, Alan Cox <alan@xxxxxxxxxxxxxxxxxxx> 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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