linux-kernel - Re: [PATCH 00/21] slight optimization of addr compare for some modules

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Message-ID: <1387787324.22671.57.camel@joe-AO722>
Date:	Mon, 23 Dec 2013 00:28:44 -0800
From:	Joe Perches <joe@...ches.com>
To:	Ding Tianhong <dingtianhong@...wei.com>
Cc:	Netdev <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 00/21] slight optimization of addr compare for some
 modules

On Mon, 2013-12-23 at 13:09 +0800, Ding Tianhong wrote:
> I use the recently added and possibly more efficient
> ether_addr_equal_unaligned to instead of memcmp for slight
> optimization.

Hi again.

These are the sorts of conversions that could be
either ether_addr_equal or ether_addr_equal_unaligned
depending on the existing alignment of the addresses
being compared.

For instance, in patch 21:
---
diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c
[]
@@ -131,12 +131,13 @@ static inline struct pppoe_net *pppoe_pernet(struct net *net)
 
 static inline int cmp_2_addr(struct pppoe_addr *a, struct pppoe_addr *b)
 {
-	return a->sid == b->sid && !memcmp(a->remote, b->remote, ETH_ALEN);
+	return a->sid == b->sid && ether_addr_equal_unaligned(a->remote,
+		ther					      b->remote);
---

This could be ether_addr_equal instead as remote is after a be16
and so remote is aligned to a u16.

include/uapi/linux/if_pppox.h:typedef __be16 sid_t;
[]
include/uapi/linux/if_pppox.h:struct pppoe_addr {
include/uapi/linux/if_pppox.h-  sid_t         sid;                    /* Session identifier */
include/uapi/linux/if_pppox.h-  unsigned char remote[ETH_ALEN];       /* Remote address */
include/uapi/linux/if_pppox.h-  char          dev[IFNAMSIZ];          /* Local device to use */
include/uapi/linux/if_pppox.h-}; 

It's of course possible to convert the appropriate
ether_addr_equal_unaligned uses to ether_addr_equal later.

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