From: Qingfang Deng Date: Wed, 29 Apr 2026 02:38:46 +0000 (+0800) Subject: pppoe: optimize hash with word access X-Git-Url: http://git.ipfire.org/gitweb/index.cgi?a=commitdiff_plain;h=ff393252f99f261ba885f05fbfdfe89807c7ffd3;p=thirdparty%2Fkernel%2Flinux.git pppoe: optimize hash with word access 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 Link: https://patch.msgid.link/20260429023848.153425-1-qingfang.deng@linux.dev Signed-off-by: Jakub Kicinski --- diff --git a/drivers/net/ppp/pppoe.c b/drivers/net/ppp/pppoe.c index bdd61c504a1c..ad5bb98c1579 100644 --- a/drivers/net/ppp/pppoe.c +++ b/drivers/net/ppp/pppoe.c @@ -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;