From 0a2cf20c3fb62ad4717276b5303bf831f7b29d54 Mon Sep 17 00:00:00 2001 From: Soheil Hassas Yeganeh Date: Wed, 27 Apr 2016 23:39:01 -0400 Subject: [PATCH] tcp: remove SKBTX_ACK_TSTAMP since it is redundant The SKBTX_ACK_TSTAMP flag is set in skb_shinfo->tx_flags when the timestamp of the TCP acknowledgement should be reported on error queue. Since accessing skb_shinfo is likely to incur a cache-line miss at the time of receiving the ack, the txstamp_ack bit was added in tcp_skb_cb, which is set iff the SKBTX_ACK_TSTAMP flag is set for an skb. This makes SKBTX_ACK_TSTAMP flag redundant. Remove the SKBTX_ACK_TSTAMP and instead use the txstamp_ack bit everywhere. Note that this frees one bit in shinfo->tx_flags. Signed-off-by: Soheil Hassas Yeganeh Acked-by: Martin KaFai Lau Suggested-by: Willem de Bruijn Acked-by: Eric Dumazet Signed-off-by: David S. Miller --- include/linux/skbuff.h | 6 +----- net/ipv4/tcp.c | 5 +++-- net/ipv4/tcp_input.c | 3 +-- net/ipv4/tcp_output.c | 17 +++++++++++------ net/socket.c | 3 --- 5 files changed, 16 insertions(+), 18 deletions(-) diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h index a1ce639..c84a5a1 100644 --- a/include/linux/skbuff.h +++ b/include/linux/skbuff.h @@ -382,14 +382,10 @@ enum { /* generate software time stamp when entering packet scheduling */ SKBTX_SCHED_TSTAMP = 1 << 6, - - /* generate software timestamp on peer data acknowledgment */ - SKBTX_ACK_TSTAMP = 1 << 7, }; #define SKBTX_ANY_SW_TSTAMP (SKBTX_SW_TSTAMP | \ - SKBTX_SCHED_TSTAMP | \ - SKBTX_ACK_TSTAMP) + SKBTX_SCHED_TSTAMP) #define SKBTX_ANY_TSTAMP (SKBTX_HW_TSTAMP | SKBTX_ANY_SW_TSTAMP) /* diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 53890a7..9199378 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -435,9 +435,10 @@ static void tcp_tx_timestamp(struct sock *sk, u16 tsflags, struct sk_buff *skb) struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); sock_tx_timestamp(sk, tsflags, &shinfo->tx_flags); - if (shinfo->tx_flags & SKBTX_ANY_TSTAMP) + if (tsflags & SOF_TIMESTAMPING_TX_ACK) + tcb->txstamp_ack = 1; + if (tsflags & SOF_TIMESTAMPING_TX_RECORD_MASK) 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 0d5239c..70c370b 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3087,8 +3087,7 @@ static void tcp_ack_tstamp(struct sock *sk, struct sk_buff *skb, return; shinfo = skb_shinfo(skb); - if ((shinfo->tx_flags & SKBTX_ACK_TSTAMP) && - !before(shinfo->tskey, prior_snd_una) && + if (!before(shinfo->tskey, prior_snd_una) && before(shinfo->tskey, tcp_sk(sk)->snd_una)) __skb_tstamp_tx(skb, NULL, sk, SCM_TSTAMP_ACK); } diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index b1b2045..b3a31b4 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1111,11 +1111,17 @@ static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int de tcp_verify_left_out(tp); } +static bool tcp_has_tx_tstamp(const struct sk_buff *skb) +{ + return TCP_SKB_CB(skb)->txstamp_ack || + (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP); +} + static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2) { struct skb_shared_info *shinfo = skb_shinfo(skb); - if (unlikely(shinfo->tx_flags & SKBTX_ANY_TSTAMP) && + if (unlikely(tcp_has_tx_tstamp(skb)) && !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) { struct skb_shared_info *shinfo2 = skb_shinfo(skb2); u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP; @@ -2446,13 +2452,12 @@ u32 __tcp_select_window(struct sock *sk) void tcp_skb_collapse_tstamp(struct sk_buff *skb, const struct sk_buff *next_skb) { - const struct skb_shared_info *next_shinfo = skb_shinfo(next_skb); - u8 tsflags = next_shinfo->tx_flags & SKBTX_ANY_TSTAMP; - - if (unlikely(tsflags)) { + if (unlikely(tcp_has_tx_tstamp(next_skb))) { + const struct skb_shared_info *next_shinfo = + skb_shinfo(next_skb); struct skb_shared_info *shinfo = skb_shinfo(skb); - shinfo->tx_flags |= tsflags; + shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP; shinfo->tskey = next_shinfo->tskey; TCP_SKB_CB(skb)->txstamp_ack |= TCP_SKB_CB(next_skb)->txstamp_ack; diff --git a/net/socket.c b/net/socket.c index 5dbb0bb..7789d79 100644 --- a/net/socket.c +++ b/net/socket.c @@ -600,9 +600,6 @@ void __sock_tx_timestamp(__u16 tsflags, __u8 *tx_flags) if (tsflags & SOF_TIMESTAMPING_TX_SCHED) flags |= SKBTX_SCHED_TSTAMP; - if (tsflags & SOF_TIMESTAMPING_TX_ACK) - flags |= SKBTX_ACK_TSTAMP; - *tx_flags = flags; } EXPORT_SYMBOL(__sock_tx_timestamp); -- 2.7.4