Subject: Re: [PATCH 3/7] [I/OAT] Don't offload copies for loopback traffic

From: Andi Kleen <[email-masked]>
Date: Fri, 18 Aug 2006 20:17:18 +0200

> @@ -1136,7 +1137,8 @@ int tcp_recvmsg(struct kiocb *iocb, stru
>  	skb = skb_peek_tail(&sk->sk_receive_queue);
>  	if (skb)
>  		available = TCP_SKB_CB(skb)->seq + skb->len - (*seq);
> -	if ((available < target) &&
> +	dst = __sk_dst_get(sk);
> +	if ((available < target) && (!dst || (dst->dev != &loopback_dev)) &&

You just added another potential cache miss to a critical
path. A bit flag in the socket would be better.

But is it really worth this ugly special case?

-Andi