Messages in this thread | | | Date | Tue, 16 May 2006 14:13:31 -0400 | From | "Kevin Radloff" <> | Subject | Re: PATCH: Fix broken PIO with libata |
| |
On 5/16/06, Tejun Heo <htejun@gmail.com> wrote: > Jeff Garzik wrote: > > 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. > > Yeap, in addition, if doing real PIO (unbuffered by the HBA), the time > it takes is soley determined by what PIO mode is in use. It doesn't > matter how fast the CPU is. Faster CPUs only end up wasting more > cycles. :-(
(oops, hit 'reply', but given the incredible importance of my response... ;P)
Ah, well then never mind. ;) I just have a dim memory of it being different a long time ago. At least it works now. :D
-- Kevin 'radsaq' Radloff radsaq@gmail.com http://thesaq.com/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |