David Miller a écrit :
> From: Patrick McHardy <kaber@xxxxxxxxx>
> Date: Tue, 24 Mar 2009 15:03:16 +0100 (MET)
>
>> +/*
>> + * Unfortunatly, _b and _mask are not aligned to an int (or long int)
>> + * Some arches dont care, unrolling the loop is a win on them.
>> + */
>> +static unsigned long ifname_compare(const char *_a, const char *_b, const char *_mask)
>> +{
>> +#ifdef CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS
>> + const unsigned long *a = (const unsigned long *)_a;
>> + const unsigned long *b = (const unsigned long *)_b;
>
> I think we can at least give some help for the platforms which
> require alignment.
>
> We can, for example, assume 16-bit alignment and thus loop
> over u16's
Right. How about this incremental patch ?
Thanks
[PATCH] arp_tables: ifname_compare() can assume 16bit alignment
Arches without efficient unaligned access can still perform a loop
assuming 16bit alignment in ifname_compare()
Signed-off-by: Eric Dumazet <dada1@xxxxxxxxxxxxx>
diff --git a/net/ipv4/netfilter/arp_tables.c b/net/ipv4/netfilter/arp_tables.c
index 64a7c6c..84b9c17 100644
--- a/net/ipv4/netfilter/arp_tables.c
+++ b/net/ipv4/netfilter/arp_tables.c
@@ -76,6 +76,7 @@ static inline int arp_devaddr_compare(const struct arpt_devaddr_info *ap,
/*
* Unfortunatly, _b and _mask are not aligned to an int (or long int)
* Some arches dont care, unrolling the loop is a win on them.
+ * For other arches, we only have a 16bit alignement.
*/
static unsigned long ifname_compare(const char *_a, const char *_b, const char *_mask)
{
@@ -95,10 +96,13 @@ static unsigned long ifname_compare(const char *_a, const char *_b, const char *
BUILD_BUG_ON(IFNAMSIZ > 4 * sizeof(unsigned long));
#else
unsigned long ret = 0;
+ const u16 *a = (const u16 *)_a;
+ const u16 *b = (const u16 *)_b;
+ const u16 *mask = (const u16 *)_mask;
int i;
- for (i = 0; i < IFNAMSIZ; i++)
- ret |= (_a[i] ^ _b[i]) & _mask[i];
+ for (i = 0; i < IFNAMSIZ/sizeof(u16); i++)
+ ret |= (a[i] ^ b[i]) & mask[i];
#endif
return ret;
}
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