kernel-ark/include/net/inet_hashtables.h
Eric Dumazet dbca9b2750 [NET]: change layout of ehash table
ehash table layout is currently this one :

First half of this table is used by sockets not in TIME_WAIT state
Second half of it is used by sockets in TIME_WAIT state.

This is non optimal because of for a given hash or socket, the two chain heads 
are located in separate cache lines.
Moreover the locks of the second half are never used.

If instead of this halving, we use two list heads in inet_ehash_bucket instead 
of only one, we probably can avoid one cache miss, and reduce ram usage, 
particularly if sizeof(rwlock_t) is big (various CONFIG_DEBUG_SPINLOCK, 
CONFIG_DEBUG_LOCK_ALLOC settings). So we still halves the table but we keep 
together related chains to speedup lookups and socket state change.

In this patch I did not try to align struct inet_ehash_bucket, but a future 
patch could try to make this structure have a convenient size (a power of two 
or a multiple of L1_CACHE_SIZE).
I guess rwlock will just vanish as soon as RCU is plugged into ehash :) , so 
maybe we dont need to scratch our heads to align the bucket...

Note : In case struct inet_ehash_bucket is not a power of two, we could 
probably change alloc_large_system_hash() (in case it use __get_free_pages()) 
to free the unused space. It currently allocates a big zone, but the last 
quarter of it could be freed. Again, this should be a temporary 'problem'.

Patch tested on ipv4 tcp only, but should be OK for IPV6 and DCCP.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2007-02-08 14:16:46 -08:00

423 lines
14 KiB
C

/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* Authors: Lotsa people, from code originally in tcp
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*/
#ifndef _INET_HASHTABLES_H
#define _INET_HASHTABLES_H
#include <linux/interrupt.h>
#include <linux/ipv6.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/socket.h>
#include <linux/spinlock.h>
#include <linux/types.h>
#include <linux/wait.h>
#include <net/inet_connection_sock.h>
#include <net/inet_sock.h>
#include <net/route.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <asm/atomic.h>
#include <asm/byteorder.h>
/* This is for all connections with a full identity, no wildcards.
* One chain is dedicated to TIME_WAIT sockets.
* I'll experiment with dynamic table growth later.
*/
struct inet_ehash_bucket {
rwlock_t lock;
struct hlist_head chain;
struct hlist_head twchain;
};
/* There are a few simple rules, which allow for local port reuse by
* an application. In essence:
*
* 1) Sockets bound to different interfaces may share a local port.
* Failing that, goto test 2.
* 2) If all sockets have sk->sk_reuse set, and none of them are in
* TCP_LISTEN state, the port may be shared.
* Failing that, goto test 3.
* 3) If all sockets are bound to a specific inet_sk(sk)->rcv_saddr local
* address, and none of them are the same, the port may be
* shared.
* Failing this, the port cannot be shared.
*
* The interesting point, is test #2. This is what an FTP server does
* all day. To optimize this case we use a specific flag bit defined
* below. As we add sockets to a bind bucket list, we perform a
* check of: (newsk->sk_reuse && (newsk->sk_state != TCP_LISTEN))
* As long as all sockets added to a bind bucket pass this test,
* the flag bit will be set.
* The resulting situation is that tcp_v[46]_verify_bind() can just check
* for this flag bit, if it is set and the socket trying to bind has
* sk->sk_reuse set, we don't even have to walk the owners list at all,
* we return that it is ok to bind this socket to the requested local port.
*
* Sounds like a lot of work, but it is worth it. In a more naive
* implementation (ie. current FreeBSD etc.) the entire list of ports
* must be walked for each data port opened by an ftp server. Needless
* to say, this does not scale at all. With a couple thousand FTP
* users logged onto your box, isn't it nice to know that new data
* ports are created in O(1) time? I thought so. ;-) -DaveM
*/
struct inet_bind_bucket {
unsigned short port;
signed short fastreuse;
struct hlist_node node;
struct hlist_head owners;
};
#define inet_bind_bucket_for_each(tb, node, head) \
hlist_for_each_entry(tb, node, head, node)
struct inet_bind_hashbucket {
spinlock_t lock;
struct hlist_head chain;
};
/* This is for listening sockets, thus all sockets which possess wildcards. */
#define INET_LHTABLE_SIZE 32 /* Yes, really, this is all you need. */
struct inet_hashinfo {
/* This is for sockets with full identity only. Sockets here will
* always be without wildcards and will have the following invariant:
*
* TCP_ESTABLISHED <= sk->sk_state < TCP_CLOSE
*
* TIME_WAIT sockets use a separate chain (twchain).
*/
struct inet_ehash_bucket *ehash;
/* Ok, let's try this, I give up, we do need a local binding
* TCP hash as well as the others for fast bind/connect.
*/
struct inet_bind_hashbucket *bhash;
int bhash_size;
unsigned int ehash_size;
/* All sockets in TCP_LISTEN state will be in here. This is the only
* table where wildcard'd TCP sockets can exist. Hash function here
* is just local port number.
*/
struct hlist_head listening_hash[INET_LHTABLE_SIZE];
/* All the above members are written once at bootup and
* never written again _or_ are predominantly read-access.
*
* Now align to a new cache line as all the following members
* are often dirty.
*/
rwlock_t lhash_lock ____cacheline_aligned;
atomic_t lhash_users;
wait_queue_head_t lhash_wait;
struct kmem_cache *bind_bucket_cachep;
};
static inline struct inet_ehash_bucket *inet_ehash_bucket(
struct inet_hashinfo *hashinfo,
unsigned int hash)
{
return &hashinfo->ehash[hash & (hashinfo->ehash_size - 1)];
}
extern struct inet_bind_bucket *
inet_bind_bucket_create(struct kmem_cache *cachep,
struct inet_bind_hashbucket *head,
const unsigned short snum);
extern void inet_bind_bucket_destroy(struct kmem_cache *cachep,
struct inet_bind_bucket *tb);
static inline int inet_bhashfn(const __u16 lport, const int bhash_size)
{
return lport & (bhash_size - 1);
}
extern void inet_bind_hash(struct sock *sk, struct inet_bind_bucket *tb,
const unsigned short snum);
/* These can have wildcards, don't try too hard. */
static inline int inet_lhashfn(const unsigned short num)
{
return num & (INET_LHTABLE_SIZE - 1);
}
static inline int inet_sk_listen_hashfn(const struct sock *sk)
{
return inet_lhashfn(inet_sk(sk)->num);
}
/* Caller must disable local BH processing. */
static inline void __inet_inherit_port(struct inet_hashinfo *table,
struct sock *sk, struct sock *child)
{
const int bhash = inet_bhashfn(inet_sk(child)->num, table->bhash_size);
struct inet_bind_hashbucket *head = &table->bhash[bhash];
struct inet_bind_bucket *tb;
spin_lock(&head->lock);
tb = inet_csk(sk)->icsk_bind_hash;
sk_add_bind_node(child, &tb->owners);
inet_csk(child)->icsk_bind_hash = tb;
spin_unlock(&head->lock);
}
static inline void inet_inherit_port(struct inet_hashinfo *table,
struct sock *sk, struct sock *child)
{
local_bh_disable();
__inet_inherit_port(table, sk, child);
local_bh_enable();
}
extern void inet_put_port(struct inet_hashinfo *table, struct sock *sk);
extern void inet_listen_wlock(struct inet_hashinfo *hashinfo);
/*
* - We may sleep inside this lock.
* - If sleeping is not required (or called from BH),
* use plain read_(un)lock(&inet_hashinfo.lhash_lock).
*/
static inline void inet_listen_lock(struct inet_hashinfo *hashinfo)
{
/* read_lock synchronizes to candidates to writers */
read_lock(&hashinfo->lhash_lock);
atomic_inc(&hashinfo->lhash_users);
read_unlock(&hashinfo->lhash_lock);
}
static inline void inet_listen_unlock(struct inet_hashinfo *hashinfo)
{
if (atomic_dec_and_test(&hashinfo->lhash_users))
wake_up(&hashinfo->lhash_wait);
}
static inline void __inet_hash(struct inet_hashinfo *hashinfo,
struct sock *sk, const int listen_possible)
{
struct hlist_head *list;
rwlock_t *lock;
BUG_TRAP(sk_unhashed(sk));
if (listen_possible && sk->sk_state == TCP_LISTEN) {
list = &hashinfo->listening_hash[inet_sk_listen_hashfn(sk)];
lock = &hashinfo->lhash_lock;
inet_listen_wlock(hashinfo);
} else {
struct inet_ehash_bucket *head;
sk->sk_hash = inet_sk_ehashfn(sk);
head = inet_ehash_bucket(hashinfo, sk->sk_hash);
list = &head->chain;
lock = &head->lock;
write_lock(lock);
}
__sk_add_node(sk, list);
sock_prot_inc_use(sk->sk_prot);
write_unlock(lock);
if (listen_possible && sk->sk_state == TCP_LISTEN)
wake_up(&hashinfo->lhash_wait);
}
static inline void inet_hash(struct inet_hashinfo *hashinfo, struct sock *sk)
{
if (sk->sk_state != TCP_CLOSE) {
local_bh_disable();
__inet_hash(hashinfo, sk, 1);
local_bh_enable();
}
}
static inline void inet_unhash(struct inet_hashinfo *hashinfo, struct sock *sk)
{
rwlock_t *lock;
if (sk_unhashed(sk))
goto out;
if (sk->sk_state == TCP_LISTEN) {
local_bh_disable();
inet_listen_wlock(hashinfo);
lock = &hashinfo->lhash_lock;
} else {
lock = &inet_ehash_bucket(hashinfo, sk->sk_hash)->lock;
write_lock_bh(lock);
}
if (__sk_del_node_init(sk))
sock_prot_dec_use(sk->sk_prot);
write_unlock_bh(lock);
out:
if (sk->sk_state == TCP_LISTEN)
wake_up(&hashinfo->lhash_wait);
}
static inline int inet_iif(const struct sk_buff *skb)
{
return ((struct rtable *)skb->dst)->rt_iif;
}
extern struct sock *__inet_lookup_listener(struct inet_hashinfo *hashinfo,
const __be32 daddr,
const unsigned short hnum,
const int dif);
static inline struct sock *inet_lookup_listener(struct inet_hashinfo *hashinfo,
__be32 daddr, __be16 dport, int dif)
{
return __inet_lookup_listener(hashinfo, daddr, ntohs(dport), dif);
}
/* Socket demux engine toys. */
/* What happens here is ugly; there's a pair of adjacent fields in
struct inet_sock; __be16 dport followed by __u16 num. We want to
search by pair, so we combine the keys into a single 32bit value
and compare with 32bit value read from &...->dport. Let's at least
make sure that it's not mixed with anything else...
On 64bit targets we combine comparisons with pair of adjacent __be32
fields in the same way.
*/
typedef __u32 __bitwise __portpair;
#ifdef __BIG_ENDIAN
#define INET_COMBINED_PORTS(__sport, __dport) \
((__force __portpair)(((__force __u32)(__be16)(__sport) << 16) | (__u32)(__dport)))
#else /* __LITTLE_ENDIAN */
#define INET_COMBINED_PORTS(__sport, __dport) \
((__force __portpair)(((__u32)(__dport) << 16) | (__force __u32)(__be16)(__sport)))
#endif
#if (BITS_PER_LONG == 64)
typedef __u64 __bitwise __addrpair;
#ifdef __BIG_ENDIAN
#define INET_ADDR_COOKIE(__name, __saddr, __daddr) \
const __addrpair __name = (__force __addrpair) ( \
(((__force __u64)(__be32)(__saddr)) << 32) | \
((__force __u64)(__be32)(__daddr)));
#else /* __LITTLE_ENDIAN */
#define INET_ADDR_COOKIE(__name, __saddr, __daddr) \
const __addrpair __name = (__force __addrpair) ( \
(((__force __u64)(__be32)(__daddr)) << 32) | \
((__force __u64)(__be32)(__saddr)));
#endif /* __BIG_ENDIAN */
#define INET_MATCH(__sk, __hash, __cookie, __saddr, __daddr, __ports, __dif)\
(((__sk)->sk_hash == (__hash)) && \
((*((__addrpair *)&(inet_sk(__sk)->daddr))) == (__cookie)) && \
((*((__portpair *)&(inet_sk(__sk)->dport))) == (__ports)) && \
(!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
#define INET_TW_MATCH(__sk, __hash, __cookie, __saddr, __daddr, __ports, __dif)\
(((__sk)->sk_hash == (__hash)) && \
((*((__addrpair *)&(inet_twsk(__sk)->tw_daddr))) == (__cookie)) && \
((*((__portpair *)&(inet_twsk(__sk)->tw_dport))) == (__ports)) && \
(!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
#else /* 32-bit arch */
#define INET_ADDR_COOKIE(__name, __saddr, __daddr)
#define INET_MATCH(__sk, __hash, __cookie, __saddr, __daddr, __ports, __dif) \
(((__sk)->sk_hash == (__hash)) && \
(inet_sk(__sk)->daddr == (__saddr)) && \
(inet_sk(__sk)->rcv_saddr == (__daddr)) && \
((*((__portpair *)&(inet_sk(__sk)->dport))) == (__ports)) && \
(!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
#define INET_TW_MATCH(__sk, __hash,__cookie, __saddr, __daddr, __ports, __dif) \
(((__sk)->sk_hash == (__hash)) && \
(inet_twsk(__sk)->tw_daddr == (__saddr)) && \
(inet_twsk(__sk)->tw_rcv_saddr == (__daddr)) && \
((*((__portpair *)&(inet_twsk(__sk)->tw_dport))) == (__ports)) && \
(!((__sk)->sk_bound_dev_if) || ((__sk)->sk_bound_dev_if == (__dif))))
#endif /* 64-bit arch */
/*
* Sockets in TCP_CLOSE state are _always_ taken out of the hash, so we need
* not check it for lookups anymore, thanks Alexey. -DaveM
*
* Local BH must be disabled here.
*/
static inline struct sock *
__inet_lookup_established(struct inet_hashinfo *hashinfo,
const __be32 saddr, const __be16 sport,
const __be32 daddr, const u16 hnum,
const int dif)
{
INET_ADDR_COOKIE(acookie, saddr, daddr)
const __portpair ports = INET_COMBINED_PORTS(sport, hnum);
struct sock *sk;
const struct hlist_node *node;
/* Optimize here for direct hit, only listening connections can
* have wildcards anyways.
*/
unsigned int hash = inet_ehashfn(daddr, hnum, saddr, sport);
struct inet_ehash_bucket *head = inet_ehash_bucket(hashinfo, hash);
prefetch(head->chain.first);
read_lock(&head->lock);
sk_for_each(sk, node, &head->chain) {
if (INET_MATCH(sk, hash, acookie, saddr, daddr, ports, dif))
goto hit; /* You sunk my battleship! */
}
/* Must check for a TIME_WAIT'er before going to listener hash. */
sk_for_each(sk, node, &head->twchain) {
if (INET_TW_MATCH(sk, hash, acookie, saddr, daddr, ports, dif))
goto hit;
}
sk = NULL;
out:
read_unlock(&head->lock);
return sk;
hit:
sock_hold(sk);
goto out;
}
static inline struct sock *
inet_lookup_established(struct inet_hashinfo *hashinfo,
const __be32 saddr, const __be16 sport,
const __be32 daddr, const __be16 dport,
const int dif)
{
return __inet_lookup_established(hashinfo, saddr, sport, daddr,
ntohs(dport), dif);
}
static inline struct sock *__inet_lookup(struct inet_hashinfo *hashinfo,
const __be32 saddr, const __be16 sport,
const __be32 daddr, const __be16 dport,
const int dif)
{
u16 hnum = ntohs(dport);
struct sock *sk = __inet_lookup_established(hashinfo, saddr, sport, daddr,
hnum, dif);
return sk ? : __inet_lookup_listener(hashinfo, daddr, hnum, dif);
}
static inline struct sock *inet_lookup(struct inet_hashinfo *hashinfo,
const __be32 saddr, const __be16 sport,
const __be32 daddr, const __be16 dport,
const int dif)
{
struct sock *sk;
local_bh_disable();
sk = __inet_lookup(hashinfo, saddr, sport, daddr, dport, dif);
local_bh_enable();
return sk;
}
extern int inet_hash_connect(struct inet_timewait_death_row *death_row,
struct sock *sk);
#endif /* _INET_HASHTABLES_H */