From 34498825cb9062192b77fa02dae672a4fe6eec70 Mon Sep 17 00:00:00 2001 From: Patrick McHardy Date: Mon, 17 Dec 2007 22:45:52 -0800 Subject: [PATCH] [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 Signed-off-by: David S. Miller --- net/ipv4/netfilter/ipt_CLUSTERIP.c | 2 +- net/ipv4/netfilter/nf_nat_core.c | 10 +++++++--- net/netfilter/nf_conntrack_core.c | 2 +- net/netfilter/nf_conntrack_expect.c | 8 +++++--- 4 files changed, 14 insertions(+), 8 deletions(-) diff --git a/net/ipv4/netfilter/ipt_CLUSTERIP.c b/net/ipv4/netfilter/ipt_CLUSTERIP.c index a48e26449fd5..df39ca07fb12 100644 --- a/net/ipv4/netfilter/ipt_CLUSTERIP.c +++ b/net/ipv4/netfilter/ipt_CLUSTERIP.c @@ -273,7 +273,7 @@ clusterip_hashfn(const struct sk_buff *skb, } /* node numbers are 1..n, not 0..n */ - return (hashval % config->num_total_nodes) + 1; + return (((u64)hashval * config->num_total_nodes) >> 32) + 1; } static inline int diff --git a/net/ipv4/netfilter/nf_nat_core.c b/net/ipv4/netfilter/nf_nat_core.c index aec157d0ad93..e53ae1ef8f5e 100644 --- a/net/ipv4/netfilter/nf_nat_core.c +++ b/net/ipv4/netfilter/nf_nat_core.c @@ -77,10 +77,13 @@ EXPORT_SYMBOL_GPL(nf_nat_proto_put); static inline unsigned int hash_by_src(const struct nf_conntrack_tuple *tuple) { + unsigned int hash; + /* Original src, to ensure we map it consistently if poss. */ - return jhash_3words((__force u32)tuple->src.u3.ip, + hash = jhash_3words((__force u32)tuple->src.u3.ip, (__force u32)tuple->src.u.all, - tuple->dst.protonum, 0) % nf_nat_htable_size; + tuple->dst.protonum, 0); + return ((u64)hash * nf_nat_htable_size) >> 32; } /* Is this tuple already taken? (not by us) */ @@ -211,7 +214,8 @@ find_best_ips_proto(struct nf_conntrack_tuple *tuple, maxip = ntohl(range->max_ip); j = jhash_2words((__force u32)tuple->src.u3.ip, (__force u32)tuple->dst.u3.ip, 0); - *var_ipp = htonl(minip + j % (maxip - minip + 1)); + j = ((u64)j * (maxip - minip + 1)) >> 32; + *var_ipp = htonl(minip + j); } /* Manipulate the tuple into the range given. For NF_INET_POST_ROUTING, diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 5920f953f782..25564073ee23 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -81,7 +81,7 @@ static u_int32_t __hash_conntrack(const struct nf_conntrack_tuple *tuple, ((__force __u16)tuple->src.u.all << 16) | (__force __u16)tuple->dst.u.all); - return jhash_2words(a, b, rnd) % size; + return ((u64)jhash_2words(a, b, rnd) * size) >> 32; } static inline u_int32_t hash_conntrack(const struct nf_conntrack_tuple *tuple) 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 * -- 2.39.5