Garrett D'Amore writes:
> James Carlson wrote:
> > Fishing for +1s ... has anyone read this?
> >
> >
> I'll reply later today. I need to check your materials for one thing --
> I'm a bit surprised you intend to disable crossbow polling mode. The
> rest of your proposal (without looking at the detailed changes) looked
> good to me.
This was discussed with Nicolas Droux and Venugopal Iyer at length.
The issue is that the hooks I have in the mac layer in order to
intercept packets at a low level for bridging purposes are in a place
where only interrupt-based packets are processed.
I investigated adding hooks for the polled mode, and got a handle on
what might be required, but the Crossbow folks suggested that I just
disable polling for these ports. The reasons are several:
- The data paths used for polling mode are diverse, complicated, and
very performance sensitive. Adding hooks there would likely lower
performance for the most critical high-end features, and would be
complex as many of the functions involved have doppelgaengers.
- Polling mode is used only for high-speed high-performance
interfaces, and enabling bridging forces us turn on promiscuous
mode (as a basic requirement of doing bridging), which in turn
substantially impacts performance in many ways (not just the extra
data, but also by causing performance features to be disabled as a
side-effect). In other words, there's a fundamental conflict
between these two goals: if you want to sling packets fast, you
don't want bridging, and if you want bridging, you have to be
willing to give up the upper end (>1Gbps) of performance.
- The whole issue goes away when the Crossbow team redesigns the
classifier components so that they're able to handle the
functionality required for bridging. (We don't currently have an
ETA on that, though it's not expected to be immanent, which is why
the bridging project is going forward with the existing design.)
--
James Carlson, Solaris Networking <james.d.carlson at sun.com>
Sun Microsystems / 35 Network Drive 71.232W Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677
