Hi Dave: The Xen performance problem turned out to be something else altogether. It was an incorrect rcv mss estimate which leads to delayed acks. So it's not a bug in Linux yet :) However, since we need this for LRO as well, here's a patch for net-2.6.19.
[TCP]: Fix rcv mss estimate for LRO By passing a Linux-generated TSO packet straight back into Linux, Xen becomes our first LRO user :) Unfortunately, there is at least one spot in our stack that needs to be changed to cope with this. The receive MSS estimate is computed from the raw packet size. This is broken if the packet is GSO/LRO. Fortunately the real MSS can be found in gso_size so we simply need to use that if it is non-zero. Real LRO NICs should of course set the gso_size field in future. Signed-off-by: Herbert Xu <[EMAIL PROTECTED]> Cheers, -- Visit Openswan at http://www.openswan.org/ Email: Herbert Xu ~{PmV>HI~} <[EMAIL PROTECTED]> Home Page: http://gondor.apana.org.au/~herbert/ PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt -- diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 104af5d..1fa1536 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -127,7 +127,7 @@ static void tcp_measure_rcv_mss(struct s /* skb->len may jitter because of SACKs, even if peer * sends good full-sized frames. */ - len = skb->len; + len = skb_shinfo(skb)->gso_size ?: skb->len; if (len >= icsk->icsk_ack.rcv_mss) { icsk->icsk_ack.rcv_mss = len; } else { - To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
