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pppoe: optimize hash with word access

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Currently, hash_item() processes the 6-byte Ethernet address and the
2-byte session ID byte-wise to compute a hash.

Optimize this by using 16-bit word operations: XOR three 16-bit words
from the Ethernet address and the 16-bit session ID, then fold the
result. This reduces the total number of loads and XORs. The Ethernet
addresses in a skb and struct pppoe_addr are both 2-byte aligned, so the
u16 pointer cast is safe.

Signed-off-by: Qingfang Deng <qingfang.deng@linux.dev>
Link: https://patch.msgid.link/20260429023848.153425-1-qingfang.deng@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Qingfang Deng
2026-04-29 10:38:46 +08:00
committed by Jakub Kicinski
parent 286efd34d1
commit ff393252f9
1 changed files with 6 additions and 6 deletions
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12
drivers/net/ppp/pppoe.c
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@@ -136,15 +136,15 @@ static inline int cmp_addr(struct pppoe_addr *a, __be16 sid, char *addr)
#error 8 must be a multiple of PPPOE_HASH_BITS
#endif
static int hash_item(__be16 sid, unsigned char *addr)
static u8 hash_item(__be16 sid, const u8 addr[ETH_ALEN])
{
unsigned char hash = 0;
const u16 *addr16 = (const u16 *)addr;
unsigned int i;
u16 hash16;
u8 hash;
for (i = 0; i < ETH_ALEN; i++)
hash ^= addr[i];
for (i = 0; i < sizeof(sid_t) * 8; i += 8)
hash ^= (__force __u32)sid >> i;
hash16 = addr16[0] ^ addr16[1] ^ addr16[2] ^ (__force u16)sid;
hash = (hash16 >> 8) ^ hash16;
for (i = 8; (i >>= 1) >= PPPOE_HASH_BITS;)
hash ^= hash >> i;