netdev - Re: [PATCH net-next] net: introduce SO_INCOMING

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Date:	Mon, 10 Nov 2014 15:51:21 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org, ycai@...gle.com, willemb@...gle.com,
	ncardwell@...gle.com
Subject: Re: [PATCH net-next] net: introduce SO_INCOMING_CPU

On Mon, 2014-11-10 at 15:08 -0500, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@...il.com>
> Date: Fri, 07 Nov 2014 12:51:12 -0800
> 
> > @@ -1455,6 +1455,7 @@ process:
> >  		goto discard_and_relse;
> >  
> >  	sk_mark_napi_id(sk, skb);
> > +	sk_incoming_cpu_update(sk);
> 
> Just make sk_mark_napi_id() call sk_incoming_cpu_update().
> 
> You've matched up the calls precisely in this patch, and I can't think
> of any situation where we'd add a sk_mark_napi_call() not not want to
> do an sk_incoming_cpu_update().

I believe this was a coincidence.

In fact some sk_mark_napi_id() calls are not at the right place.
It makes little sense to change sk->sk_napi_id for a listener socket.

sk_mark_napi_id() should better be done [1] at the same time we call
sock_rps_save_rxhash

But we need to store cpu before prequeue or backlog (as I did in my
patch)


[1]

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 9c7d7621466b1241f404a5ca11de809dcff2d02a..f10438ac9c0a4013a8a812b64d94e1cf6dfbd83e 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1429,6 +1429,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 		struct dst_entry *dst = sk->sk_rx_dst;
 
 		sock_rps_save_rxhash(sk, skb);
+		sk_mark_napi_id(sk, skb);
 		if (dst) {
 			if (inet_sk(sk)->rx_dst_ifindex != skb->skb_iif ||
 			    dst->ops->check(dst, 0) == NULL) {
@@ -1450,6 +1451,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 
 		if (nsk != sk) {
 			sock_rps_save_rxhash(nsk, skb);
+			sk_mark_napi_id(nsk, skb);
 			if (tcp_child_process(sk, nsk, skb)) {
 				rsk = nsk;
 				goto reset;
@@ -1661,7 +1663,6 @@ process:
 	if (sk_filter(sk, skb))
 		goto discard_and_relse;
 
-	sk_mark_napi_id(sk, skb);
 	skb->dev = NULL;
 
 	bh_lock_sock_nested(sk);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index ace29b60813cf8a1d7182ad2262cbcbd21810fa7..a83eaff0d936677ef71e8f9f9cd0509cb023b45d 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1293,6 +1293,7 @@ static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
 		struct dst_entry *dst = sk->sk_rx_dst;
 
 		sock_rps_save_rxhash(sk, skb);
+		sk_mark_napi_id(sk, skb);
 		if (dst) {
 			if (inet_sk(sk)->rx_dst_ifindex != skb->skb_iif ||
 			    dst->ops->check(dst, np->rx_dst_cookie) == NULL) {
@@ -1322,6 +1323,7 @@ static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
 		 */
 		if (nsk != sk) {
 			sock_rps_save_rxhash(nsk, skb);
+			sk_mark_napi_id(nsk, skb);
 			if (tcp_child_process(sk, nsk, skb))
 				goto reset;
 			if (opt_skb)
@@ -1454,7 +1456,6 @@ process:
 	if (sk_filter(sk, skb))
 		goto discard_and_relse;
 
-	sk_mark_napi_id(sk, skb);
 	skb->dev = NULL;
 
 	bh_lock_sock_nested(sk);



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