diff options
| author | Patrick McHardy <kaber@trash.net> | 2007-12-17 22:45:52 -0800 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2008-01-28 14:59:11 -0800 |
| commit | 34498825cb9062192b77fa02dae672a4fe6eec70 (patch) | |
| tree | 7f856aff21ae3ab1328ab9bcf3549bca8e13df35 /net/netfilter/nf_conntrack_expect.c | |
| parent | 7b21e09d1c17ef0296ec5a6df231a6c5c87b2fd7 (diff) | |
[NETFILTER]: non-power-of-two jhash optimizations
Apply Eric Dumazet's jhash optimizations where applicable. Quoting Eric:
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: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/netfilter/nf_conntrack_expect.c')
| -rw-r--r-- | net/netfilter/nf_conntrack_expect.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/net/netfilter/nf_conntrack_expect.c b/net/netfilter/nf_conntrack_expect.c index 0efbf343eac8..e0cd9d00aa61 100644 --- a/net/netfilter/nf_conntrack_expect.c +++ b/net/netfilter/nf_conntrack_expect.c @@ -73,15 +73,17 @@ static void nf_ct_expectation_timed_out(unsigned long ul_expect) static unsigned int nf_ct_expect_dst_hash(const struct nf_conntrack_tuple *tuple) { + unsigned int hash; + if (unlikely(!nf_ct_expect_hash_rnd_initted)) { get_random_bytes(&nf_ct_expect_hash_rnd, 4); nf_ct_expect_hash_rnd_initted = 1; } - return jhash2(tuple->dst.u3.all, ARRAY_SIZE(tuple->dst.u3.all), + hash = jhash2(tuple->dst.u3.all, ARRAY_SIZE(tuple->dst.u3.all), (((tuple->dst.protonum ^ tuple->src.l3num) << 16) | - (__force __u16)tuple->dst.u.all) ^ nf_ct_expect_hash_rnd) % - nf_ct_expect_hsize; + (__force __u16)tuple->dst.u.all) ^ nf_ct_expect_hash_rnd); + return ((u64)hash * nf_ct_expect_hsize) >> 32; } struct nf_conntrack_expect * |