netdev - Re: [PATCH net-next] net: Make gro complete function to return void

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Date: Tue, 30 May 2023 17:48:22 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: David Ahern <dsahern@...nel.org>
Cc: Parav Pandit <parav@...dia.com>, davem@...emloft.net, kuba@...nel.org, 
	pabeni@...hat.com, netdev@...r.kernel.org
Subject: Re: [PATCH net-next] net: Make gro complete function to return void

On Tue, May 30, 2023 at 5:25 PM David Ahern <dsahern@...nel.org> wrote:
>
> On 5/29/23 7:44 AM, Parav Pandit wrote:
> > diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
> > index 45dda7889387..88f9b0081ee7 100644
> > --- a/net/ipv4/tcp_offload.c
> > +++ b/net/ipv4/tcp_offload.c
> > @@ -296,7 +296,7 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb)
> >       return pp;
> >  }
> >
> > -int tcp_gro_complete(struct sk_buff *skb)
> > +void tcp_gro_complete(struct sk_buff *skb)
> >  {
> >       struct tcphdr *th = tcp_hdr(skb);
> >
> > @@ -311,8 +311,6 @@ int tcp_gro_complete(struct sk_buff *skb)
> >
> >       if (skb->encapsulation)
> >               skb->inner_transport_header = skb->transport_header;
> > -
> > -     return 0;
> >  }
> >  EXPORT_SYMBOL(tcp_gro_complete);
>
> tcp_gro_complete seems fairly trivial. Any reason not to make it an
> inline and avoid another function call in the datapath?

Probably, although it is a regular function call, not an indirect one.

In the grand total of driver rx napi + GRO cost, saving a few cycles
per GRO completed packet is quite small.