From: Kuniyuki Iwashima <kuniyu@google.com>
To: Josh Don <joshdon@google.com>
Cc: Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
"David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@kernel.org>,
Jakub Kicinski <kuba@kernel.org>,
Paolo Abeni <pabeni@redhat.com>, Simon Horman <horms@kernel.org>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] udp: Add noinline_for_tracing annotation for udp{,_v6}_send_skb()
Date: Tue, 20 Oct 2026 04:28:10 +0000 [thread overview]
Message-ID: <atbsxDZecXYSDBqH@google.com> (raw)
In-Reply-To: <20261019230758.2960779-1-joshdon@google.com>
On Mon, 19 Oct 2026 23:07:58 +0000, Josh Don wrote:
> We hook udp_send_skb() and udp_v6_send_skb() using BPF fentry programs
> to monitor UDP transmits. Both functions are static and have two
> callers: udp{,v6}_sendmsg() and udp{,_v6}_push_pending_frames().
>
> After an FDO profile update, udp_v6_send_skb() is now inlined into
> udpv6_sendmsg(), while an out-of-line copy remains for
> udp_v6_push_pending_frames(). The fentry program still attaches
> successfully, but it is silently bypassed for all uncorked sends.
>
> To address this, make both functions noinline explicitly for tracing,
> as was done for tcp_drop_reason() in commit dbd5e2e79ed8 ("net: tcp:
> Add noinline_for_tracing annotation for tcp_drop_reason()").
Unlike tcp_drop_reason(), udp_send_skb() is a hot function as
inlined by FDO.
Did you see how this change affects to udp_rr performance ?
Also, net-next is closed.
https://lore.kernel.org/netdev/7a0446eb-8539-4300-ae0b-a3d66a692cbc@redhat.com/
>
> Assisted-by: LLM
> Signed-off-by: Josh Don <joshdon@google.com>
> ---
> net/ipv4/udp.c | 4 ++--
> net/ipv6/udp.c | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
> index b090bd1f59e86..487c8cc8ab206 100644
> --- a/net/ipv4/udp.c
> +++ b/net/ipv4/udp.c
> @@ -1110,8 +1110,8 @@ void udp_set_csum(bool nocheck, struct sk_buff *skb,
> }
> EXPORT_SYMBOL(udp_set_csum);
>
> -static int udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4,
> - struct inet_cork *cork)
> +noinline_for_tracing static int
> +udp_send_skb(struct sk_buff *skb, struct flowi4 *fl4, struct inet_cork *cork)
> {
> struct sock *sk = skb->sk;
> int offset, len, datalen;
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index 93478d1ad5769..fe92538835176 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -1366,8 +1366,8 @@ static void udp6_hwcsum_outgoing(struct sock *sk, struct sk_buff *skb,
> * Sending
> */
>
> -static int udp_v6_send_skb(struct sk_buff *skb, struct flowi6 *fl6,
> - struct inet_cork *cork)
> +noinline_for_tracing static int
> +udp_v6_send_skb(struct sk_buff *skb, struct flowi6 *fl6, struct inet_cork *cork)
> {
> struct sock *sk = skb->sk;
> int offset, len, datalen;
> --
> 2.56.0.212.g129ede20d9-goog
>
prev parent reply other threads:[~2026-10-20 4:28 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-19 23:07 Josh Don
2026-10-19 23:39 ` Willem de Bruijn
2026-10-20 4:28 ` Kuniyuki Iwashima [this message]
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