netdev - [PATCH 05/14] ipv6: don't zero cork's flowi after use

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Message-Id: <e2cbbc9e6d55253fa4e254f746dfb8f91b6b0fe7.1641863490.git.asml.silence@gmail.com>
Date:   Tue, 11 Jan 2022 01:21:37 +0000
From:   Pavel Begunkov <asml.silence@...il.com>
To:     netdev@...r.kernel.org, "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        linux-kernel@...r.kernel.org,
        Pavel Begunkov <asml.silence@...il.com>
Subject: [PATCH 05/14] ipv6: don't zero cork's flowi after use

It doesn't appear there is any reason to zero cork->fl after use, i.e.
in ip6_cork_release(), especially when cork struct is on-stack. Not
only the memset accounts to 0.3-0.5% of total cycles (perf profiling),
but also prevents other optimisations implemented in further patches.
Also, now we can remove a relatively expensive flow copy in
udp_v6_push_pending_frames().

Signed-off-by: Pavel Begunkov <asml.silence@...il.com>
---
 net/ipv6/ip6_output.c |  1 -
 net/ipv6/udp.c        | 10 ++--------
 2 files changed, 2 insertions(+), 9 deletions(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 88349e49717a..b8fdda9ac797 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1831,7 +1831,6 @@ static void ip6_cork_release(struct inet_cork_full *cork,
 		cork->base.dst = NULL;
 		cork->base.flags &= ~IPCORK_ALLFRAG;
 	}
-	memset(&cork->fl, 0, sizeof(cork->fl));
 }
 
 struct sk_buff *__ip6_make_skb(struct sock *sk,
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 0c10ee0124b5..9a91b51d8e3f 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1266,23 +1266,17 @@ static int udp_v6_push_pending_frames(struct sock *sk)
 {
 	struct sk_buff *skb;
 	struct udp_sock  *up = udp_sk(sk);
-	struct flowi6 fl6;
 	int err = 0;
 
 	if (up->pending == AF_INET)
 		return udp_push_pending_frames(sk);
 
-	/* ip6_finish_skb will release the cork, so make a copy of
-	 * fl6 here.
-	 */
-	fl6 = inet_sk(sk)->cork.fl.u.ip6;
-
 	skb = ip6_finish_skb(sk);
 	if (!skb)
 		goto out;
 
-	err = udp_v6_send_skb(skb, &fl6, &inet_sk(sk)->cork.base);
-
+	err = udp_v6_send_skb(skb, &inet_sk(sk)->cork.fl.u.ip6,
+			      &inet_sk(sk)->cork.base);
 out:
 	up->len = 0;
 	up->pending = 0;
-- 
2.34.1