diff options
| author | Soheil Hassas Yeganeh <soheil@google.com> | 2016-04-02 23:08:08 -0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2016-04-04 15:50:29 -0400 |
| commit | 6b084928baac562ed61866f540a96120e9c9ddb7 (patch) | |
| tree | 775a973c0dc77e0c42c7fde2e128843d18bf95d9 /net/ipv4 | |
| parent | 6db8b963a7a31047573f229492ff6fc0f51cc377 (diff) | |
| download | linux-rt-6b084928baac562ed61866f540a96120e9c9ddb7.tar.gz | |
tcp: use one bit in TCP_SKB_CB to mark ACK timestamps
Currently, to avoid a cache line miss for accessing skb_shinfo,
tcp_ack_tstamp skips socket that do not have
SOF_TIMESTAMPING_TX_ACK bit set in sk_tsflags. This is
implemented based on an implicit assumption that the
SOF_TIMESTAMPING_TX_ACK is set via socket options for the
duration that ACK timestamps are needed.
To implement per-write timestamps, this check should be
removed and replaced with a per-packet alternative that
quickly skips packets missing ACK timestamps marks without
a cache-line miss.
To enable per-packet marking without a cache line miss, use
one bit in TCP_SKB_CB to mark a whether a SKB might need a
ack tx timestamp or not. Further checks in tcp_ack_tstamp are not
modified and work as before.
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/ipv4')
| -rw-r--r-- | net/ipv4/tcp.c | 2 | ||||
| -rw-r--r-- | net/ipv4/tcp_input.c | 2 |
2 files changed, 3 insertions, 1 deletions
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 08b8b960a8ed..ce3c9eb901a0 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -432,10 +432,12 @@ static void tcp_tx_timestamp(struct sock *sk, struct sk_buff *skb) { if (sk->sk_tsflags) { struct skb_shared_info *shinfo = skb_shinfo(skb); + struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); sock_tx_timestamp(sk, &shinfo->tx_flags); if (shinfo->tx_flags & SKBTX_ANY_TSTAMP) shinfo->tskey = TCP_SKB_CB(skb)->seq + skb->len - 1; + tcb->txstamp_ack = !!(shinfo->tx_flags & SKBTX_ACK_TSTAMP); } } diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index f87b84a75691..a26e2d262358 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3082,7 +3082,7 @@ static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb, const struct skb_shared_info *shinfo; /* Avoid cache line misses to get skb_shinfo() and shinfo->tx_flags */ - if (likely(!(sk->sk_tsflags & SOF_TIMESTAMPING_TX_ACK))) + if (likely(!TCP_SKB_CB(skb)->txstamp_ack)) return; shinfo = skb_shinfo(skb); |