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net: listening_hash get a spinlock per bucket

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This patch prepares RCU migration of listening_hash table for
TCP/DCCP protocols.

listening_hash table being small (32 slots per protocol), we add
a spinlock for each slot, instead of a single rwlock for whole table.

This should reduce hold time of readers, and writers concurrency.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2008-11-20 00:40:07 -08:00
committed by David S. Miller
parent d8b83c57a7
commit 5caea4ea70
6 changed files with 79 additions and 119 deletions
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45
include/net/inet_hashtables.h
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@@ -99,6 +99,11 @@ struct inet_bind_hashbucket {
struct hlist_head chain;
};
struct inet_listen_hashbucket {
spinlock_t lock;
struct hlist_head head;
};
/* This is for listening sockets, thus all sockets which possess wildcards. */
#define INET_LHTABLE_SIZE 32 /* Yes, really, this is all you need. */
@@ -123,22 +128,21 @@ struct inet_hashinfo {
unsigned int bhash_size;
/* Note : 4 bytes padding on 64 bit arches */
/* 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];
struct kmem_cache *bind_bucket_cachep;
/* 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.
* might be often dirty.
*/
rwlock_t lhash_lock ____cacheline_aligned;
atomic_t lhash_users;
wait_queue_head_t lhash_wait;
struct kmem_cache *bind_bucket_cachep;
/* 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 inet_listen_hashbucket listening_hash[INET_LHTABLE_SIZE]
____cacheline_aligned_in_smp;
};
static inline struct inet_ehash_bucket *inet_ehash_bucket(
@@ -236,26 +240,7 @@ extern void __inet_inherit_port(struct sock *sk, struct sock *child);
extern void inet_put_port(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);
}
void inet_hashinfo_init(struct inet_hashinfo *h);
extern void __inet_hash_nolisten(struct sock *sk);
extern void inet_hash(struct sock *sk);