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authorFlorian Zumbiehl <florz@florz.de>2007-07-31 16:47:57 -0400
committerDavid S. Miller <davem@davemloft.net>2007-07-31 16:47:57 -0400
commitf1543f8b8316f49b318ac6cd8c78a7fd18509311 (patch)
tree50506ab3d7057e9de2e65bf726ad48043cfbfc45
parent48b8d78315bf2aef4b6b4fb41c2c94e0b6600234 (diff)
[PPPOE]: Improve hashing function in hash_item().
The new code produces the same results as the old version and is ~ 3 to 6 times faster for 4-bit hashes on the CPUs I tested. Signed-off-by: Florian Zumbiehl <florz@florz.de> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/pppoe.c25
1 files changed, 15 insertions, 10 deletions
diff --git a/drivers/net/pppoe.c b/drivers/net/pppoe.c
index 35a7385ccb2a..68631a5721ac 100644
--- a/drivers/net/pppoe.c
+++ b/drivers/net/pppoe.c
@@ -108,19 +108,24 @@ static inline int cmp_addr(struct pppoe_addr *a, unsigned long sid, char *addr)
108 (memcmp(a->remote,addr,ETH_ALEN) == 0)); 108 (memcmp(a->remote,addr,ETH_ALEN) == 0));
109} 109}
110 110
111static int hash_item(unsigned long sid, unsigned char *addr) 111#if 8%PPPOE_HASH_BITS
112#error 8 must be a multiple of PPPOE_HASH_BITS
113#endif
114
115static int hash_item(unsigned int sid, unsigned char *addr)
112{ 116{
113 char hash = 0; 117 unsigned char hash = 0;
114 int i, j; 118 unsigned int i;
115 119
116 for (i = 0; i < ETH_ALEN ; ++i) { 120 for (i = 0 ; i < ETH_ALEN ; i++) {
117 for (j = 0; j < 8/PPPOE_HASH_BITS ; ++j) { 121 hash ^= addr[i];
118 hash ^= addr[i] >> ( j * PPPOE_HASH_BITS ); 122 }
119 } 123 for (i = 0 ; i < sizeof(sid_t)*8 ; i += 8 ){
124 hash ^= sid>>i;
125 }
126 for (i = 8 ; (i>>=1) >= PPPOE_HASH_BITS ; ) {
127 hash ^= hash>>i;
120 } 128 }
121
122 for (i = 0; i < (sizeof(unsigned long)*8) / PPPOE_HASH_BITS ; ++i)
123 hash ^= sid >> (i*PPPOE_HASH_BITS);
124 129
125 return hash & ( PPPOE_HASH_SIZE - 1 ); 130 return hash & ( PPPOE_HASH_SIZE - 1 );
126} 131}