netdev - Re: [PATCH net-next] udp: introduce and use indirect call wrapper for data ready()

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Message-ID: <c835b29be1c86d765e9691b1f9772577fa3f560c.camel@redhat.com>
Date: Mon, 17 Jul 2023 16:13:11 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>, 
	netdev@...r.kernel.org
Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>,  Jakub Kicinski <kuba@...nel.org>, David Ahern
 <dsahern@...nel.org>
Subject: Re: [PATCH net-next] udp: introduce and use indirect call wrapper
 for data ready()

On Mon, 2023-07-17 at 09:44 -0400, Willem de Bruijn wrote:
> Paolo Abeni wrote:
> > In most cases UDP sockets use the default data ready callback.
> > This patch Introduces and uses a specific indirect call wrapper for
> > such callback to avoid an indirect call in fastpath.
> > 
> > The above gives small but measurable performance gain under UDP flood.
> 
> Interesting. I recently wrote a patch to add indirect call wrappers
> around getfrag (ip_generic_getfrag), expecting that to improve  UDP
> senders. Since it's an indirect call on each send call. Not sent,
> because I did not see measurable gains, at least with a udp_rr bench.
> 
> > Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> > ---
> > Note that this helper could be used for TCP, too. I did not send such
> > patch right away because in my tests the perf delta there is below the
> > noise level even in RR scenarios and the patch would be a little more
> > invasive - there are more sk_data_ready() invocation places.
> > ---
> >  include/net/sock.h | 4 ++++
> >  net/ipv4/udp.c     | 2 +-
> >  2 files changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/net/sock.h b/include/net/sock.h
> > index 2eb916d1ff64..1b26dbecdcca 100644
> > --- a/include/net/sock.h
> > +++ b/include/net/sock.h
> > @@ -2947,6 +2947,10 @@ static inline bool sk_dev_equal_l3scope(struct sock *sk, int dif)
> >  }
> >  
> >  void sock_def_readable(struct sock *sk);
> > +static inline void sk_data_ready(struct sock *sk)
> > +{
> > +	INDIRECT_CALL_1(sk->sk_data_ready, sock_def_readable, sk);
> > +}
> > 
> 
> Why introduce a static inline in the header for this?
> 
> To reuse it in other protocols later?

I originally thought about re-using it even for TCP, but showed no gain
there. I think/hope there could be other users, and I found the code
nicer this way ;)

Cheers,

Paolo