linux-kernel - Re: [PATCH net-next 2/7] net: dsa: remove useless rcv copy in DSA tree

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Message-ID: <20170530150531.GD22758@lunn.ch>
Date:   Tue, 30 May 2017 17:05:31 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Vivien Didelot <vivien.didelot@...oirfairelinux.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel@...oirfairelinux.com,
        "David S. Miller" <davem@...emloft.net>,
        Florian Fainelli <f.fainelli@...il.com>
Subject: Re: [PATCH net-next 2/7] net: dsa: remove useless rcv copy in DSA
 tree

On Tue, May 30, 2017 at 10:21:26AM -0400, Vivien Didelot wrote:
> The dsa_switch_tree holds a copy of the rcv member of the dsa_device_ops
> structure. dst->rcv is always assigned to dst->tag_ops->rcv. Remove this
> useless copy.
> 
> Signed-off-by: Vivien Didelot <vivien.didelot@...oirfairelinux.com>
> ---
>  include/net/dsa.h | 4 ----
>  net/dsa/dsa.c     | 4 ++--
>  net/dsa/dsa2.c    | 2 --
>  net/dsa/legacy.c  | 2 --
>  4 files changed, 2 insertions(+), 10 deletions(-)
> 
> diff --git a/include/net/dsa.h b/include/net/dsa.h
> index cb5d668b265d..4b82766715e9 100644
> --- a/include/net/dsa.h
> +++ b/include/net/dsa.h
> @@ -126,10 +126,6 @@ struct dsa_switch_tree {
>  	 * protocol to use.
>  	 */
>  	struct net_device	*master_netdev;
> -	struct sk_buff *	(*rcv)(struct sk_buff *skb,
> -				       struct net_device *dev,
> -				       struct packet_type *pt,
> -				       struct net_device *orig_dev);
>  
>  	/*
>  	 * Original copy of the master netdev ethtool_ops
> diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
> index 7a8a0358299b..861dc0e5020d 100644
> --- a/net/dsa/dsa.c
> +++ b/net/dsa/dsa.c
> @@ -29,7 +29,7 @@
>  
>  bool dsa_uses_tagged_protocol(struct dsa_switch_tree *dst)
>  {
> -	return !!dst->rcv;
> +	return dst->tag_ops && dst->tag_ops->rcv;

This makes the hot path more expensive. The copy is probably worth it
in terms of performance.

   Andrew