On Fri, 2016-11-18 at 17:18 -0800, Eric Dumazet wrote:
> From: Eric Dumazet <eduma...@google.com>
>
> UDP_SKB_CB(skb)->partial_cov is located at offset 66 in skb,
> requesting a cold cache line being read in cpu cache.
>
> We can avoid this cache line miss for UDP sockets,
> as partial_cov has a meaning only for UDPLite.
>
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> ---
> net/ipv4/udp.c | 3 ++-
> net/ipv6/udp.c | 3 ++-
> 2 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index
> e1fc0116e8d59d8185670c6e55d1219bde55610d..b949770fdc08398a10f3974505a50b2b4f4b2cf3
> 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1389,7 +1389,8 @@ int udp_recvmsg(struct sock *sk, struct msghdr *msg,
> size_t len, int noblock,
> * coverage checksum (UDP-Lite), do it before the copy.
> */
>
> - if (copied < ulen || UDP_SKB_CB(skb)->partial_cov || peeking) {
> + if (copied < ulen || peeking ||
> + (is_udplite && UDP_SKB_CB(skb)->partial_cov)) {
> checksum_valid = !udp_lib_checksum_complete(skb);
> if (!checksum_valid)
> goto csum_copy_err;
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index
> 4f99417d9b401f2a65c7828e7d6b86d1d6161794..8fd4d89380b86c8630f7fd27ce4e9958497a2b89
> 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -363,7 +363,8 @@ int udpv6_recvmsg(struct sock *sk, struct msghdr *msg,
> size_t len,
> * coverage checksum (UDP-Lite), do it before the copy.
> */
>
> - if (copied < ulen || UDP_SKB_CB(skb)->partial_cov || peeking) {
> + if (copied < ulen || peeking ||
> + (is_udplite && UDP_SKB_CB(skb)->partial_cov)) {
> checksum_valid = !udp_lib_checksum_complete(skb);
> if (!checksum_valid)
> goto csum_copy_err;
>
>
Nice catch, thank you Eric!
This gives up to 8% speed-up in my performance test (wire speed udp flood
with small packets)
Tested-by: Paolo Abeni <pab...@redhat.com>
