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

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Message-Id: <20170530.110933.385314582905902944.davem@davemloft.net>
Date:   Tue, 30 May 2017 11:09:33 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     andrew@...n.ch
Cc:     vivien.didelot@...oirfairelinux.com, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel@...oirfairelinux.com,
        f.fainelli@...il.com
Subject: Re: [PATCH net-next 2/7] net: dsa: remove useless rcv copy in DSA
 tree

From: Andrew Lunn <andrew@...n.ch>
Date: Tue, 30 May 2017 17:05:31 +0200

> 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.

Agreed.