[ovs-dev] [PATCH] ofproto: Avoid user->kernel->user round-trip for many controller actions.

[Jesse Gross]

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[0].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).
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