[ovs-dev] [PATCH] ofproto: Avoid user->kernel->user round-trip for many controller actions.
blp at nicira.com
Thu Aug 5 18:05:15 UTC 2010
On Thu, Aug 05, 2010 at 01:41:24PM -0400, Jesse Gross wrote:
> On Wed, Aug 4, 2010 at 2:09 PM, Ben Pfaff <blp at nicira.com> wrote:
> > + copy = ofpbuf_new(DPIF_RECV_MSG_PADDING + sizeof(struct odp_msg)
> > + + packet->size);
> > + ofpbuf_reserve(copy, DPIF_RECV_MSG_PADDING);
> > + msg = ofpbuf_put_uninit(copy, sizeof *msg);
> > + msg->type = _ODPL_ACTION_NR;
> > + msg->length = sizeof(struct odp_msg) + packet->size;
> > + msg->port = in_port;
> > + msg->reserved = 0;
> > + msg->arg = actions.controller.arg;
> > + ofpbuf_put(copy, packet->data, packet->size);
> How common is it that sending to the controller is the only action? It
> seems like that might be a fairly common scenario here. If so, it would be
> ideal if we could avoid copying the packet an additional time here. I don't
> know if it is worth it though seeing as this is already a fairly narrow use
> case (first packet to the controller).
I was looking at that as a possibly fairly risky micro-optimization on
top of what seems to be a valuable optimization that avoids multiple
user<->kernel trips and trips through the main loop. It is worth
considering, I guess.
If you think it's valuable, then I'll make a followup patch that adds
that optimization too.
Did you see any problems with this one?
More information about the dev