Re: Memory mapped IO vs Port IO

Jesse Barnes
2003-09-12T19:51:55Z

On Fri, Sep 12, 2003 at 11:58:07AM -0700, Martin J. Bligh wrote:
> >> Also - a perhaps more useful test is a write followed by a read.
> >
> > Well, someone else will have to run that test. On Altix, a read() is
> > freakishly expensive, and I'm not really interested in showing everyone
> > how bad it is ;)
>
> I find percentile comparisons useful for hiding the embarassement
> of occasional hardware realities ;-) (ie what's the speed *ratio*
> between the two types of read).

Well, in our case, read() and in() will be pretty close,
percentage-wise. The read() in itself is so bad that I think the
additional badness of in() will be mostly hidden.

Jesse