Re: Memory mapped IO vs Port IO

[Jesse Barnes]

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
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/