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authorWilly Tarreau <w@1wt.eu>2012-12-02 11:49:27 +0000
committerDavid S. Miller <davem@davemloft.net>2012-12-02 20:23:01 -0500
commit02275a2ee7c0ea475b6f4a6428f5df592bc9d30b (patch)
tree820c92949d326bcf394eca339453a0389a998300 /net
parent077b393d05915f04e2629bfc47c6fce95cae7d3f (diff)
tcp: don't abort splice() after small transfers
TCP coalescing added a regression in splice(socket->pipe) performance, for some workloads because of the way tcp_read_sock() is implemented. The reason for this is the break when (offset + 1 != skb->len). As we released the socket lock, this condition is possible if TCP stack added a fragment to the skb, which can happen with TCP coalescing. So let's go back to the beginning of the loop when this happens, to give a chance to splice more frags per system call. Doing so fixes the issue and makes GRO 10% faster than LRO on CPU-bound splice() workloads instead of the opposite. Signed-off-by: Willy Tarreau <w@1wt.eu> Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net')
-rw-r--r--net/ipv4/tcp.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 1aca02c9911..8fc5b3bd607 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -1494,15 +1494,19 @@ int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
copied += used;
offset += used;
}
- /*
- * If recv_actor drops the lock (e.g. TCP splice
+ /* If recv_actor drops the lock (e.g. TCP splice
* receive) the skb pointer might be invalid when
* getting here: tcp_collapse might have deleted it
* while aggregating skbs from the socket queue.
*/
- skb = tcp_recv_skb(sk, seq-1, &offset);
- if (!skb || (offset+1 != skb->len))
+ skb = tcp_recv_skb(sk, seq - 1, &offset);
+ if (!skb)
break;
+ /* TCP coalescing might have appended data to the skb.
+ * Try to splice more frags
+ */
+ if (offset + 1 != skb->len)
+ continue;
}
if (tcp_hdr(skb)->fin) {
sk_eat_skb(sk, skb, false);