netdev - [PATCH] tcp: adjust rcvbuff according copied rate of user space

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Date:   Tue,  9 Aug 2022 16:47:46 +0800
From:   Yonglong Li <liyonglong@...natelecom.cn>
To:     netdev@...r.kernel.org
Cc:     davem@...emloft.net, edumazet@...gle.com, dsahern@...nel.org,
        kuba@...nel.org, pabeni@...hat.com, liyonglong@...natelecom.cn
Subject: [PATCH] tcp: adjust rcvbuff according copied rate of user space

it is more reasonable to adjust rcvbuff by copied rate instead
of copied buff len.

Signed-off-by: Yonglong Li <liyonglong@...natelecom.cn>
---
 include/linux/tcp.h  |  1 +
 net/ipv4/tcp_input.c | 16 +++++++++++++---
 2 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index a9fbe22..18e091c 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -410,6 +410,7 @@ struct tcp_sock {
 		u32	space;
 		u32	seq;
 		u64	time;
+		u32	prior_rate;
 	} rcvq_space;
 
 /* TCP-specific MTU probe information. */
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index ab5f0ea..2bdf2a5 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -544,6 +544,7 @@ static void tcp_init_buffer_space(struct sock *sk)
 	tcp_mstamp_refresh(tp);
 	tp->rcvq_space.time = tp->tcp_mstamp;
 	tp->rcvq_space.seq = tp->copied_seq;
+	tp->rcvq_space.prior_rate = 0;
 
 	maxwin = tcp_full_space(sk);
 
@@ -701,6 +702,7 @@ static inline void tcp_rcv_rtt_measure_ts(struct sock *sk,
 void tcp_rcv_space_adjust(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
+	u64 pre_copied_rate, copied_rate;
 	u32 copied;
 	int time;
 
@@ -713,7 +715,14 @@ void tcp_rcv_space_adjust(struct sock *sk)
 
 	/* Number of bytes copied to user in last RTT */
 	copied = tp->copied_seq - tp->rcvq_space.seq;
-	if (copied <= tp->rcvq_space.space)
+	copied_rate = copied * USEC_PER_SEC;
+	do_div(copied_rate, time);
+	pre_copied_rate = tp->rcvq_space.prior_rate;
+	if (!tp->rcvq_space.prior_rate) {
+		pre_copied_rate = tp->rcvq_space.space * USEC_PER_SEC;
+		do_div(pre_copied_rate, time);
+	}
+	if (copied_rate <= pre_copied_rate || !pre_copied_rate)
 		goto new_measure;
 
 	/* A bit of theory :
@@ -736,8 +745,8 @@ void tcp_rcv_space_adjust(struct sock *sk)
 		rcvwin = ((u64)copied << 1) + 16 * tp->advmss;
 
 		/* Accommodate for sender rate increase (eg. slow start) */
-		grow = rcvwin * (copied - tp->rcvq_space.space);
-		do_div(grow, tp->rcvq_space.space);
+		grow = rcvwin * (copied_rate - pre_copied_rate);
+		do_div(grow, pre_copied_rate);
 		rcvwin += (grow << 1);
 
 		rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER);
@@ -755,6 +764,7 @@ void tcp_rcv_space_adjust(struct sock *sk)
 		}
 	}
 	tp->rcvq_space.space = copied;
+	tp->rcvq_space.prior_rate = pre_copied_rate;
 
 new_measure:
 	tp->rcvq_space.seq = tp->copied_seq;
-- 
1.8.3.1