From: Soheil Hassas Yeganeh <soh...@google.com>
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 <soh...@google.com>
Acked-by: Martin KaFai Lau <ka...@fb.com>
Suggested-by: Willem de Bruijn <will...@google.com>
---
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 da0ace3..ae30555 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 3c542dc..8e05eb6 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 967520d..2f3fd92 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 9d3b4b3..ace183c 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);
--
2.8.0.rc3.226.g39d4020
