From 6b084928baac562ed61866f540a96120e9c9ddb7 Mon Sep 17 00:00:00 2001 From: Soheil Hassas Yeganeh Date: Sat, 2 Apr 2016 23:08:08 -0400 Subject: 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 Acked-by: Willem de Bruijn Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/tcp.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include/net') diff --git a/include/net/tcp.h b/include/net/tcp.h index f8bb4a4ed3d1..a23282996ca9 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -754,7 +754,8 @@ struct tcp_skb_cb { TCPCB_REPAIRED) __u8 ip_dsfield; /* IPv4 tos or IPv6 dsfield */ - /* 1 byte hole */ + __u8 txstamp_ack:1, /* Record TX timestamp for ack? */ + unused:7; __u32 ack_seq; /* Sequence number ACK'd */ union { struct inet_skb_parm h4; -- cgit