Re: [PATCH net-next 01/15] tcp: use tp->tcp_mstamp in output path

[Soheil Hassas Yeganeh]

On Tue, May 16, 2017 at 5:00 PM, Eric Dumazet  wrote:
> Idea is to later convert tp->tcp_mstamp to a full u64 counter
> using usec resolution, so that we can later have fine
> grained TCP TS clock (RFC 7323), regardless of HZ value.
>
> We try to refresh tp->tcp_mstamp only when necessary.
>
> Signed-off-by: Eric Dumazet 

Acked-by: Soheil Hassas Yeganeh 

> ---
>  net/ipv4/tcp_ipv4.c |  1 +
>  net/ipv4/tcp_output.c   | 21 +++--
>  net/ipv4/tcp_recovery.c |  1 -
>  net/ipv4/tcp_timer.c|  3 ++-
>  4 files changed, 14 insertions(+), 12 deletions(-)
>
> diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
> index 
> 5ab2aac5ca191075383fc75214da816873bb222c..d8fe25db79f223e3fde85882effd2ac6ec15f8ca
>  100644
> --- a/net/ipv4/tcp_ipv4.c
> +++ b/net/ipv4/tcp_ipv4.c
> @@ -483,6 +483,7 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
> skb = tcp_write_queue_head(sk);
> BUG_ON(!skb);
>
> +   skb_mstamp_get(>tcp_mstamp);
> remaining = icsk->icsk_rto -
> min(icsk->icsk_rto,
> tcp_time_stamp - tcp_skb_timestamp(skb));
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 
> a32172d69a03cbe76b45ec3094222f6c3a73e27d..4c8a6eaba6b39a2aea061dd6857ed8df954c5ca2
>  100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -997,8 +997,8 @@ static int tcp_transmit_skb(struct sock *sk, struct 
> sk_buff *skb, int clone_it,
> BUG_ON(!skb || !tcp_skb_pcount(skb));
> tp = tcp_sk(sk);
>
> +   skb->skb_mstamp = tp->tcp_mstamp;
> if (clone_it) {
> -   skb_mstamp_get(>skb_mstamp);
> TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
> - tp->snd_una;
> tcp_rate_skb_sent(sk, skb);
> @@ -1906,7 +1906,6 @@ static bool tcp_tso_should_defer(struct sock *sk, 
> struct sk_buff *skb,
> const struct inet_connection_sock *icsk = inet_csk(sk);
> u32 age, send_win, cong_win, limit, in_flight;
> struct tcp_sock *tp = tcp_sk(sk);
> -   struct skb_mstamp now;
> struct sk_buff *head;
> int win_divisor;
>
> @@ -1962,8 +1961,8 @@ static bool tcp_tso_should_defer(struct sock *sk, 
> struct sk_buff *skb,
> }
>
> head = tcp_write_queue_head(sk);
> -   skb_mstamp_get();
> -   age = skb_mstamp_us_delta(, >skb_mstamp);
> +
> +   age = skb_mstamp_us_delta(>tcp_mstamp, >skb_mstamp);
> /* If next ACK is likely to come too late (half srtt), do not defer */
> if (age < (tp->srtt_us >> 4))
> goto send_now;
> @@ -2280,6 +2279,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned 
> int mss_now, int nonagle,
> }
>
> max_segs = tcp_tso_segs(sk, mss_now);
> +   skb_mstamp_get(>tcp_mstamp);
> while ((skb = tcp_send_head(sk))) {
> unsigned int limit;
>
> @@ -2291,7 +2291,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned 
> int mss_now, int nonagle,
>
> if (unlikely(tp->repair) && tp->repair_queue == 
> TCP_SEND_QUEUE) {
> /* "skb_mstamp" is used as a start point for the 
> retransmit timer */
> -   skb_mstamp_get(>skb_mstamp);
> +   skb->skb_mstamp = tp->tcp_mstamp;
> goto repair; /* Skip network transmission */
> }
>
> @@ -2879,7 +2879,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct 
> sk_buff *skb, int segs)
>  skb_headroom(skb) >= 0x)) {
> struct sk_buff *nskb;
>
> -   skb_mstamp_get(>skb_mstamp);
> +   skb->skb_mstamp = tp->tcp_mstamp;
> nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
> err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
>  -ENOBUFS;
> @@ -3095,7 +3095,7 @@ void tcp_send_active_reset(struct sock *sk, gfp_t 
> priority)
> skb_reserve(skb, MAX_TCP_HEADER);
> tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
>  TCPHDR_ACK | TCPHDR_RST);
> -   skb_mstamp_get(>skb_mstamp);
> +   skb_mstamp_get(_sk(sk)->tcp_mstamp);
> /* Send it off. */
> if (tcp_transmit_skb(sk, skb, 0, priority))
> NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
> @@ -3453,7 +3453,8 @@ int tcp_connect(struct sock *sk)
> return -ENOBUFS;
>
> tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
> -   tp->retrans_stamp = tcp_time_stamp;
> +   skb_mstamp_get(>tcp_mstamp);
> +   tp->retrans_stamp = tp->tcp_mstamp.stamp_jiffies;
> tcp_connect_queue_skb(sk, buff);
> tcp_ecn_send_syn(sk, buff);
>
> @@ -3572,7 +3573,6 @@ void tcp_send_ack(struct sock *sk)
> skb_set_tcp_pure_ack(buff);
>
>   

[PATCH net-next 01/15] tcp: use tp->tcp_mstamp in output path

[Eric Dumazet]

Idea is to later convert tp->tcp_mstamp to a full u64 counter
using usec resolution, so that we can later have fine
grained TCP TS clock (RFC 7323), regardless of HZ value.

We try to refresh tp->tcp_mstamp only when necessary.

Signed-off-by: Eric Dumazet 
---
 net/ipv4/tcp_ipv4.c |  1 +
 net/ipv4/tcp_output.c   | 21 +++--
 net/ipv4/tcp_recovery.c |  1 -
 net/ipv4/tcp_timer.c|  3 ++-
 4 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 
5ab2aac5ca191075383fc75214da816873bb222c..d8fe25db79f223e3fde85882effd2ac6ec15f8ca
 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -483,6 +483,7 @@ void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
skb = tcp_write_queue_head(sk);
BUG_ON(!skb);
 
+   skb_mstamp_get(>tcp_mstamp);
remaining = icsk->icsk_rto -
min(icsk->icsk_rto,
tcp_time_stamp - tcp_skb_timestamp(skb));
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 
a32172d69a03cbe76b45ec3094222f6c3a73e27d..4c8a6eaba6b39a2aea061dd6857ed8df954c5ca2
 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -997,8 +997,8 @@ static int tcp_transmit_skb(struct sock *sk, struct sk_buff 
*skb, int clone_it,
BUG_ON(!skb || !tcp_skb_pcount(skb));
tp = tcp_sk(sk);
 
+   skb->skb_mstamp = tp->tcp_mstamp;
if (clone_it) {
-   skb_mstamp_get(>skb_mstamp);
TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq
- tp->snd_una;
tcp_rate_skb_sent(sk, skb);
@@ -1906,7 +1906,6 @@ static bool tcp_tso_should_defer(struct sock *sk, struct 
sk_buff *skb,
const struct inet_connection_sock *icsk = inet_csk(sk);
u32 age, send_win, cong_win, limit, in_flight;
struct tcp_sock *tp = tcp_sk(sk);
-   struct skb_mstamp now;
struct sk_buff *head;
int win_divisor;
 
@@ -1962,8 +1961,8 @@ static bool tcp_tso_should_defer(struct sock *sk, struct 
sk_buff *skb,
}
 
head = tcp_write_queue_head(sk);
-   skb_mstamp_get();
-   age = skb_mstamp_us_delta(, >skb_mstamp);
+
+   age = skb_mstamp_us_delta(>tcp_mstamp, >skb_mstamp);
/* If next ACK is likely to come too late (half srtt), do not defer */
if (age < (tp->srtt_us >> 4))
goto send_now;
@@ -2280,6 +2279,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int 
mss_now, int nonagle,
}
 
max_segs = tcp_tso_segs(sk, mss_now);
+   skb_mstamp_get(>tcp_mstamp);
while ((skb = tcp_send_head(sk))) {
unsigned int limit;
 
@@ -2291,7 +2291,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int 
mss_now, int nonagle,
 
if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) 
{
/* "skb_mstamp" is used as a start point for the 
retransmit timer */
-   skb_mstamp_get(>skb_mstamp);
+   skb->skb_mstamp = tp->tcp_mstamp;
goto repair; /* Skip network transmission */
}
 
@@ -2879,7 +2879,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff 
*skb, int segs)
 skb_headroom(skb) >= 0x)) {
struct sk_buff *nskb;
 
-   skb_mstamp_get(>skb_mstamp);
+   skb->skb_mstamp = tp->tcp_mstamp;
nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC);
err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) :
 -ENOBUFS;
@@ -3095,7 +3095,7 @@ void tcp_send_active_reset(struct sock *sk, gfp_t 
priority)
skb_reserve(skb, MAX_TCP_HEADER);
tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk),
 TCPHDR_ACK | TCPHDR_RST);
-   skb_mstamp_get(>skb_mstamp);
+   skb_mstamp_get(_sk(sk)->tcp_mstamp);
/* Send it off. */
if (tcp_transmit_skb(sk, skb, 0, priority))
NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED);
@@ -3453,7 +3453,8 @@ int tcp_connect(struct sock *sk)
return -ENOBUFS;
 
tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN);
-   tp->retrans_stamp = tcp_time_stamp;
+   skb_mstamp_get(>tcp_mstamp);
+   tp->retrans_stamp = tp->tcp_mstamp.stamp_jiffies;
tcp_connect_queue_skb(sk, buff);
tcp_ecn_send_syn(sk, buff);
 
@@ -3572,7 +3573,6 @@ void tcp_send_ack(struct sock *sk)
skb_set_tcp_pure_ack(buff);
 
/* Send it off, this clears delayed acks for us. */
-   skb_mstamp_get(>skb_mstamp);
tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0);
 }
 EXPORT_SYMBOL_GPL(tcp_send_ack);
@@ -3606,15 +3606,16 @@ static int tcp_xmit_probe_skb(struct sock *sk, int 
urgent, int mib)
 * send it.
 */
tcp_init_nondata_skb(skb,