generic: net: tcp: backport tcp tx performance patches

[openwrt/staging/mkresin.git] / target / linux / generic / backport-4.9 / 024-5-tcp-tsq-add-a-shortcut-in-tcp_small_queue_check.patch

diff --git a/target/linux/generic/backport-4.9/024-5-tcp-tsq-add-a-shortcut-in-tcp_small_queue_check.patch b/target/linux/generic/backport-4.9/024-5-tcp-tsq-add-a-shortcut-in-tcp_small_queue_check.patch
new file mode 100644 (file)
index 0000000..dd1a37e
--- /dev/null
+++ b/target/linux/generic/backport-4.9/024-5-tcp-tsq-add-a-shortcut-in-tcp_small_queue_check.patch
@@ -0,0 +1,37 @@
+From 75eefc6c59fd2c5f1ab95a3a113c217237d12a31 Mon Sep 17 00:00:00 2001
+From: Eric Dumazet <edumazet@google.com>
+Date: Sat, 3 Dec 2016 11:14:54 -0800
+Subject: [PATCH 05/10] tcp: tsq: add a shortcut in tcp_small_queue_check()
+
+Always allow the two first skbs in write queue to be sent,
+regardless of sk_wmem_alloc/sk_pacing_rate values.
+
+This helps a lot in situations where TX completions are delayed either
+because of driver latencies or softirq latencies.
+
+Test is done with no cache line misses.
+
+Signed-off-by: Eric Dumazet <edumazet@google.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+---
+ net/ipv4/tcp_output.c | 9 +++++++++
+ 1 file changed, 9 insertions(+)
+
+--- a/net/ipv4/tcp_output.c
++++ b/net/ipv4/tcp_output.c
+@@ -2084,6 +2084,15 @@ static bool tcp_small_queue_check(struct
+       limit <<= factor;
+ 
+       if (atomic_read(&sk->sk_wmem_alloc) > limit) {
++              /* Always send the 1st or 2nd skb in write queue.
++               * No need to wait for TX completion to call us back,
++               * after softirq/tasklet schedule.
++               * This helps when TX completions are delayed too much.
++               */
++              if (skb == sk->sk_write_queue.next ||
++                  skb->prev == sk->sk_write_queue.next)
++                      return false;
++
+               set_bit(TSQ_THROTTLED, &tcp_sk(sk)->tsq_flags);
+               /* It is possible TX completion already happened
+                * before we set TSQ_THROTTLED, so we must