On Wed, 2014-12-03 at 07:05 +0000, Hayes Wang wrote: > Eric Dumazet [mailto:eric.dumazet@xxxxxxxxx] > > Sent: Wednesday, December 03, 2014 2:08 PM > [...] > > Better performance for what workload exactly ? > > I test it by using Chariot with 4 Tx and 4 Rx. > It has about 4% improvement. > Have you tried using more concurrent RX flows, in a possibly lossy environment (so that TCP is forced to queue packets in out of order queue) ? > > cloning in rx path has many drawbacks, with skb->truesize > > being usually wrong. > > Excuse me. I find the skb_clone() would copy the > truesize from original skb. Do you mean the value > may not be suitable for the cloned skb? With cloning, (skb->len / skb->truesize) will eventually be very very small, forcing TCP stack to perform collapses (copies !!!) under pressure. > > Could other method do the same thing? Or, do you > think keeping the original one is better? skb cloning prevents GRO and TCP coalescing from working. netfilter might also be forced to copy whole frame in case a mangle is needed (eg with NAT ...) I would rather try to implement GRO, and/or using fragments instead of pure linear skbs. (skb->head would be around 128 or 256 bytes, and you attach to skb the frame as a page fragment) -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
