PCI interrupts passing DMA

[Peter Jeremy]

On Wed, Sep 17, 2003 at 06:12:44PM -0400, Andrew Gallatin wrote:
>My question is: What the heck could the SMP kernel be doing which
>causes the DMA to "complete" faster?   

My guess is that this is a coherency issue rather than a timing issue.
The SMP kernels are far more careful about ensuring consistency
between CPUs and this could be fixing/masking the problem

That said, any decent disk controller uses DMA and if the UP kernel
really did have PCI-bus coherency problems (or massive delays), a
significant part of the user-base would be screaming.

The other possibility: Is your PCI card doing something wierd?  Are
you bending one of the PCI specs a bit far?

Peter