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

[Chris Leech]

Local traffic (loopback) is generally in cache anyway, and the overhead
cost of offloading the copy is worse than just doing it with the CPU.

Signed-off-by: Chris Leech <christopher.leech@xxxxxxxxx>
---

 net/ipv4/tcp.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 36f6b64..7971e73 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1107,6 +1107,7 @@ int tcp_recvmsg(struct kiocb *iocb, stru
 	int copied_early = 0;
 	int available = 0;
 	struct sk_buff *skb;
+	struct dst_entry *dst;
 
 	lock_sock(sk);
 
@@ -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)) &&
 	    (len > sysctl_tcp_dma_copybreak) && !(flags & MSG_PEEK) &&
 	    !sysctl_tcp_low_latency && __get_cpu_var(softnet_data).net_dma) {
 		preempt_enable_no_resched();

-
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