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| author | Florian Zumbiehl <florz@florz.de> | 2007-08-01 00:47:57 +0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2007-08-01 00:47:57 +0400 |
| commit | f1543f8b8316f49b318ac6cd8c78a7fd18509311 (patch) | |
| tree | 50506ab3d7057e9de2e65bf726ad48043cfbfc45 /drivers/net/pppoe.c | |
| parent | 48b8d78315bf2aef4b6b4fb41c2c94e0b6600234 (diff) | |
| download | linux-f1543f8b8316f49b318ac6cd8c78a7fd18509311.tar.xz | |
[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>
Diffstat (limited to 'drivers/net/pppoe.c')
| -rw-r--r-- | drivers/net/pppoe.c | 25 |
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) (memcmp(a->remote,addr,ETH_ALEN) == 0)); } -static int hash_item(unsigned long sid, unsigned char *addr) +#if 8%PPPOE_HASH_BITS +#error 8 must be a multiple of PPPOE_HASH_BITS +#endif + +static int hash_item(unsigned int sid, unsigned char *addr) { - char hash = 0; - int i, j; + unsigned char hash = 0; + unsigned int i; - for (i = 0; i < ETH_ALEN ; ++i) { - for (j = 0; j < 8/PPPOE_HASH_BITS ; ++j) { - hash ^= addr[i] >> ( j * PPPOE_HASH_BITS ); - } + for (i = 0 ; i < ETH_ALEN ; i++) { + hash ^= addr[i]; + } + for (i = 0 ; i < sizeof(sid_t)*8 ; i += 8 ){ + hash ^= sid>>i; + } + for (i = 8 ; (i>>=1) >= PPPOE_HASH_BITS ; ) { + hash ^= hash>>i; } - - for (i = 0; i < (sizeof(unsigned long)*8) / PPPOE_HASH_BITS ; ++i) - hash ^= sid >> (i*PPPOE_HASH_BITS); return hash & ( PPPOE_HASH_SIZE - 1 ); } |