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ipv4: add net_hash_mix() dispersion to fib_info_laddrhash keys

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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@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Eric Dumazet 2022-01-19 02:04:13 -08:00 committed by Jakub Kicinski
parent d07418afea
commit 79eb15da3c
1 changed files with 15 additions and 14 deletions
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29
net/ipv4/fib_semantics.c
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@ -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 @@ link_it:
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 @@ nla_put_failure:
*/
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)