On Wed, 20 Jan 2016 15:27:38 -0800 Tom Herbert <[email protected]> wrote:
> eth_type_trans touches headers
True, the eth_type_trans() call in the driver is a major bottleneck,
because it touch the packet header and happens very early in the driver.
In my experiments, where I extract several packet before calling
napi_gro_receive(), and I also delay calling eth_type_trans(). Most of
my speedup comes from this trick, as the prefetch() now that enough
time.
while ((skb = __skb_dequeue(&rx_skb_list)) != NULL) {
skb->protocol = eth_type_trans(skb, rq->netdev);
napi_gro_receive(cq->napi, skb);
}
What is the HW could provide the info we need in the descriptor?!?
eth_type_trans() does two things:
1) determine skb->protocol
2) setup skb->pkt_type = PACKET_{BROADCAST,MULTICAST,OTHERHOST}
Could the HW descriptor deliver the "proto", or perhaps just some bits
on the most common proto's?
The skb->pkt_type don't need many bits. And I bet the HW already have
the information. The BROADCAST and MULTICAST indication are easy. The
PACKET_OTHERHOST, can be turned around, by instead set a PACKET_HOST
indication, if the eth->h_dest match the devices dev->dev_addr (else a
SW compare is required).
Is that doable in hardware?
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
Author of http://www.iptv-analyzer.org
LinkedIn: http://www.linkedin.com/in/brouer
