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authorSoheil Hassas Yeganeh <soheil@google.com>2016-04-02 23:08:08 -0400
committerDavid S. Miller <davem@davemloft.net>2016-04-04 15:50:29 -0400
commit6b084928baac562ed61866f540a96120e9c9ddb7 (patch)
tree775a973c0dc77e0c42c7fde2e128843d18bf95d9 /net/ipv4/tcp.c
parenttcp: accept SOF_TIMESTAMPING_OPT_ID for passive TFO (diff)
downloadlinux-dev-6b084928baac562ed61866f540a96120e9c9ddb7.tar.xz
linux-dev-6b084928baac562ed61866f540a96120e9c9ddb7.zip
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/tcp.c')
-rw-r--r--net/ipv4/tcp.c2
1 files changed, 2 insertions, 0 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);
}
}