netdev - Re: [PATCH v2 net-next 2/6] net: add add indirect call wrapper in skb_release_head

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Message-ID: <CANn89i+PnwtgiM4G9Kbrj7kjjpJ5rU07rCyRTpPJpdYHUGhBvg@mail.gmail.com>
Date: Wed, 15 Oct 2025 05:16:05 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Alexander Lobakin <aleksander.lobakin@...el.com>
Cc: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>, Simon Horman <horms@...nel.org>, 
	Jamal Hadi Salim <jhs@...atatu.com>, Cong Wang <xiyou.wangcong@...il.com>, 
	Jiri Pirko <jiri@...nulli.us>, Kuniyuki Iwashima <kuniyu@...gle.com>, 
	Willem de Bruijn <willemb@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com
Subject: Re: [PATCH v2 net-next 2/6] net: add add indirect call wrapper in skb_release_head_state()

On Wed, Oct 15, 2025 at 5:02 AM Alexander Lobakin
<aleksander.lobakin@...el.com> wrote:
>
> From: Eric Dumazet <edumazet@...gle.com>
> Date: Tue, 14 Oct 2025 17:19:03 +0000
>
> > While stress testing UDP senders on a host with expensive indirect
> > calls, I found cpus processing TX completions where showing
> > a very high cost (20%) in sock_wfree() due to
> > CONFIG_MITIGATION_RETPOLINE=y.
> >
> > Take care of TCP and UDP TX destructors and use INDIRECT_CALL_3() macro.
> >
> > Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> > ---
> >  net/core/skbuff.c | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/core/skbuff.c b/net/core/skbuff.c
> > index bc12790017b0..692e3a70e75e 100644
> > --- a/net/core/skbuff.c
> > +++ b/net/core/skbuff.c
> > @@ -1136,7 +1136,16 @@ void skb_release_head_state(struct sk_buff *skb)
> >       skb_dst_drop(skb);
> >       if (skb->destructor) {
> >               DEBUG_NET_WARN_ON_ONCE(in_hardirq());
> > -             skb->destructor(skb);
> > +#ifdef CONFIG_INET
> > +             INDIRECT_CALL_3(skb->destructor,
> > +                             tcp_wfree, __sock_wfree, sock_wfree,
> > +                             skb);
> > +#else
> > +             INDIRECT_CALL_1(skb->destructor,
> > +                             sock_wfree,
> > +                             skb);
> > +
> > +#endif
>
> Is it just me or seems like you ignored the suggestion/discussion under
> v1 of this patch...
>

I did not. Please send a patch when you can demonstrate the difference.

We are not going to add all the possible destructors unless there is evidence.