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Commit 0a2cf20c authored by Soheil Hassas Yeganeh's avatar Soheil Hassas Yeganeh Committed by David S. Miller
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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: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Suggested-by: default avatarWillem de Bruijn <willemb@google.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 863c1fd9

include/linux/skbuff.h

+1 −5
Original line number Diff line number Diff line
@@ -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)



/*

net/ipv4/tcp.c

+3 −2
Original line number Diff line number Diff line
@@ -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);

	}

}

net/ipv4/tcp_input.c

+1 −2
Original line number Diff line number Diff line
@@ -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);

}

net/ipv4/tcp_output.c

+11 −6
Original line number Diff line number Diff line
@@ -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;

net/socket.c

+0 −3
Original line number Diff line number Diff line
@@ -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);