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Date: Wed, 19 Jan 2022 02:04:13 -0800 From: Eric Dumazet <eric.dumazet@...il.com> To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org> Cc: David Ahern <dsahern@...nel.org>, netdev <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>, Eric Dumazet <eric.dumazet@...il.com> Subject: [PATCH v2 net 2/2] ipv4: add net_hash_mix() dispersion to fib_info_laddrhash keys From: Eric Dumazet <edumazet@...gle.com> net/ipv4/fib_semantics.c uses a hash table (fib_info_laddrhash) in which fib_sync_down_addr() can locate fib_info based on IPv4 local address. This hash table is resized based on total number of hashed fib_info, but the hash function is only using the local address. For hosts having many active network namespaces, all fib_info for loopback devices (IPv4 address 127.0.0.1) are hashed into a single bucket, making netns dismantles very slow. Signed-off-by: Eric Dumazet <edumazet@...gle.com> --- net/ipv4/fib_semantics.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c index 9813949da10493de36b9db797b6a5d94fd9bd3b1..b4589861b84c6bc4daa7149e078ad63749c7622f 100644 --- a/net/ipv4/fib_semantics.c +++ b/net/ipv4/fib_semantics.c @@ -52,6 +52,7 @@ static DEFINE_SPINLOCK(fib_info_lock); static struct hlist_head *fib_info_hash; static struct hlist_head *fib_info_laddrhash; static unsigned int fib_info_hash_size; +static unsigned int fib_info_hash_bits; static unsigned int fib_info_cnt; #define DEVINDEX_HASHBITS 8 @@ -1247,13 +1248,13 @@ int fib_check_nh(struct net *net, struct fib_nh *nh, u32 table, u8 scope, return err; } -static inline unsigned int fib_laddr_hashfn(__be32 val) +static struct hlist_head * +fib_info_laddrhash_bucket(const struct net *net, __be32 val) { - unsigned int mask = (fib_info_hash_size - 1); + u32 slot = hash_32(net_hash_mix(net) ^ (__force u32)val, + fib_info_hash_bits); - return ((__force u32)val ^ - ((__force u32)val >> 7) ^ - ((__force u32)val >> 14)) & mask; + return &fib_info_laddrhash[slot]; } static struct hlist_head *fib_info_hash_alloc(int bytes) @@ -1289,6 +1290,7 @@ static void fib_info_hash_move(struct hlist_head *new_info_hash, old_info_hash = fib_info_hash; old_laddrhash = fib_info_laddrhash; fib_info_hash_size = new_size; + fib_info_hash_bits = ilog2(new_size); for (i = 0; i < old_size; i++) { struct hlist_head *head = &fib_info_hash[i]; @@ -1306,21 +1308,20 @@ static void fib_info_hash_move(struct hlist_head *new_info_hash, } fib_info_hash = new_info_hash; + fib_info_laddrhash = new_laddrhash; for (i = 0; i < old_size; i++) { - struct hlist_head *lhead = &fib_info_laddrhash[i]; + struct hlist_head *lhead = &old_laddrhash[i]; struct hlist_node *n; struct fib_info *fi; hlist_for_each_entry_safe(fi, n, lhead, fib_lhash) { struct hlist_head *ldest; - unsigned int new_hash; - new_hash = fib_laddr_hashfn(fi->fib_prefsrc); - ldest = &new_laddrhash[new_hash]; + ldest = fib_info_laddrhash_bucket(fi->fib_net, + fi->fib_prefsrc); hlist_add_head(&fi->fib_lhash, ldest); } } - fib_info_laddrhash = new_laddrhash; spin_unlock_bh(&fib_info_lock); @@ -1605,7 +1606,7 @@ struct fib_info *fib_create_info(struct fib_config *cfg, if (fi->fib_prefsrc) { struct hlist_head *head; - head = &fib_info_laddrhash[fib_laddr_hashfn(fi->fib_prefsrc)]; + head = fib_info_laddrhash_bucket(net, fi->fib_prefsrc); hlist_add_head(&fi->fib_lhash, head); } if (fi->nh) { @@ -1877,16 +1878,16 @@ int fib_dump_info(struct sk_buff *skb, u32 portid, u32 seq, int event, */ int fib_sync_down_addr(struct net_device *dev, __be32 local) { - int ret = 0; - unsigned int hash = fib_laddr_hashfn(local); - struct hlist_head *head = &fib_info_laddrhash[hash]; int tb_id = l3mdev_fib_table(dev) ? : RT_TABLE_MAIN; struct net *net = dev_net(dev); + struct hlist_head *head; struct fib_info *fi; + int ret = 0; if (!fib_info_laddrhash || local == 0) return 0; + head = fib_info_laddrhash_bucket(net, local); hlist_for_each_entry(fi, head, fib_lhash) { if (!net_eq(fi->fib_net, net) || fi->fib_tb_id != tb_id) -- 2.34.1.703.g22d0c6ccf7-goog
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