diff options
| author | Eric Dumazet <dada1@cosmosbay.com> | 2007-12-17 22:45:13 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2008-01-28 14:59:10 -0800 |
| commit | e2f82ac3fcffffca59751b65124544d11ed8be4a (patch) | |
| tree | 9eba528eb094b79da8c471c3980c6a6b90f371b4 /net/netfilter | |
| parent | 22c2d8bca212a655c120fd6617328ffa3480afad (diff) | |
| download | linux-e2f82ac3fcffffca59751b65124544d11ed8be4a.tar.bz2 | |
[NETFILTER]: xt_hashlimit: speedup hash_dst()
1) Using jhash2() instead of jhash() is a litle bit faster if applicable.
2) Thanks to jhash, hash value uses full 32 bits.
Instead of returning hash % size (implying a divide)
we return the high 32 bits of the (hash * size) that will
give results between [0 and size-1] and same hash distribution.
On most cpus, a multiply is less expensive than a divide, by an order
of magnitude.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netfilter')
| -rw-r--r-- | net/netfilter/xt_hashlimit.c | 11 |
1 files changed, 10 insertions, 1 deletions
diff --git a/net/netfilter/xt_hashlimit.c b/net/netfilter/xt_hashlimit.c index 951d4c829674..651c1d26564a 100644 --- a/net/netfilter/xt_hashlimit.c +++ b/net/netfilter/xt_hashlimit.c @@ -105,7 +105,16 @@ static inline bool dst_cmp(const struct dsthash_ent *ent, static u_int32_t hash_dst(const struct xt_hashlimit_htable *ht, const struct dsthash_dst *dst) { - return jhash(dst, sizeof(*dst), ht->rnd) % ht->cfg.size; + u_int32_t hash = jhash2((const u32 *)dst, + sizeof(*dst)/sizeof(u32), + ht->rnd); + /* + * Instead of returning hash % ht->cfg.size (implying a divide) + * we return the high 32 bits of the (hash * ht->cfg.size) that will + * give results between [0 and cfg.size-1] and same hash distribution, + * but using a multiply, less expensive than a divide + */ + return ((u64)hash * ht->cfg.size) >> 32; } static struct dsthash_ent * |