Nicolas Droux writes:
> James Carlson wrote:
> > OK ... so I'll look into how to disable polling and force interrupt
> > mode for everything. It looks like that should be possible to do, but
> > it's somewhat unclear in the code.
>
> We can provide you the functions to enable/disable polling that you can
> call from the bridging code. Someone on our team will look into the best
> approach (either calling existing code or provide a new API) and
> follow-up separately.
OK; thanks. That'll help a good bit, as I'm likely to get hurt in
there. If you want, you're welcome to look at and contribute directly
to the rbridges-on gate. (That way, you can deliver the feature along
with an actual consumer, rather than trying to deliver to ON with no
consumer.)
My sense of it now is that it's important to get right, but likely not
a gating item in practice. The reason is that:
(a) The polling feature gets invoked in and is intended for
situations where we're compute-bound due to network traffic on
very high speed interfaces, and we need that incremental savings
gained by avoiding interrupts. Those are situations where the
user is very performance sensitive and is trying to run right to
the edge of what the hardware can do. Those are exactly the
users who will not want to use bridging, at least because of the
cost of having all interfaces forced into promiscuous mode all
of the time. You do this on e1000g, but not nxge.
(b) The failure mode that occurs effectively just results in packet
loss when we're driven into polling mode. Packet loss under
very high utilization is unfortunate, but at some point, it's
completely unavoidable. This problem just makes it happen a
little earlier in the performance curve. (And it's unclear how
much earlier, and whether with reasonable configurations it
happens at all.)
It might not actually be a blocker.
--
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
