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authorEric Dumazet <dada1@cosmosbay.com>2007-02-08 14:16:46 -0800
committerDavid S. Miller <davem@davemloft.net>2007-02-08 14:16:46 -0800
commitdbca9b2750e3b1ee6f56a616160ccfc12e8b161f (patch)
treebf84c0acb5495fc95bc616d32b8af946f2e3bca9 /net/ipv4
parenteac3731bd04c7131478722a3c148b78774553116 (diff)
[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>
Diffstat (limited to 'net/ipv4')
-rw-r--r--net/ipv4/inet_diag.c2
-rw-r--r--net/ipv4/inet_hashtables.c2
-rw-r--r--net/ipv4/inet_timewait_sock.c4
-rw-r--r--net/ipv4/tcp.c7
-rw-r--r--net/ipv4/tcp_ipv4.c4
5 files changed, 10 insertions, 9 deletions
diff --git a/net/ipv4/inet_diag.c b/net/ipv4/inet_diag.c
index 9cd53addb78..8aa7d51e688 100644
--- a/net/ipv4/inet_diag.c
+++ b/net/ipv4/inet_diag.c
@@ -778,7 +778,7 @@ next_normal:
struct inet_timewait_sock *tw;
inet_twsk_for_each(tw, node,
- &hashinfo->ehash[i + hashinfo->ehash_size].chain) {
+ &head->twchain) {
if (num < s_num)
goto next_dying;
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index 8c79c8a4ea5..150ace18dc7 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -212,7 +212,7 @@ static int __inet_check_established(struct inet_timewait_death_row *death_row,
write_lock(&head->lock);
/* Check TIME-WAIT sockets first. */
- sk_for_each(sk2, node, &(head + hinfo->ehash_size)->chain) {
+ sk_for_each(sk2, node, &head->twchain) {
tw = inet_twsk(sk2);
if (INET_TW_MATCH(sk2, hash, acookie, saddr, daddr, ports, dif)) {
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 9f414e35c48..a73cf93cee3 100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -78,8 +78,8 @@ void __inet_twsk_hashdance(struct inet_timewait_sock *tw, struct sock *sk,
if (__sk_del_node_init(sk))
sock_prot_dec_use(sk->sk_prot);
- /* Step 3: Hash TW into TIMEWAIT half of established hash table. */
- inet_twsk_add_node(tw, &(ehead + hashinfo->ehash_size)->chain);
+ /* Step 3: Hash TW into TIMEWAIT chain. */
+ inet_twsk_add_node(tw, &ehead->twchain);
atomic_inc(&tw->tw_refcnt);
write_unlock(&ehead->lock);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b67e0dd743b..5bd43d7294f 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2415,10 +2415,11 @@ void __init tcp_init(void)
&tcp_hashinfo.ehash_size,
NULL,
0);
- tcp_hashinfo.ehash_size = (1 << tcp_hashinfo.ehash_size) >> 1;
- for (i = 0; i < (tcp_hashinfo.ehash_size << 1); i++) {
+ tcp_hashinfo.ehash_size = 1 << tcp_hashinfo.ehash_size;
+ for (i = 0; i < tcp_hashinfo.ehash_size; i++) {
rwlock_init(&tcp_hashinfo.ehash[i].lock);
INIT_HLIST_HEAD(&tcp_hashinfo.ehash[i].chain);
+ INIT_HLIST_HEAD(&tcp_hashinfo.ehash[i].twchain);
}
tcp_hashinfo.bhash =
@@ -2475,7 +2476,7 @@ void __init tcp_init(void)
printk(KERN_INFO "TCP: Hash tables configured "
"(established %d bind %d)\n",
- tcp_hashinfo.ehash_size << 1, tcp_hashinfo.bhash_size);
+ tcp_hashinfo.ehash_size, tcp_hashinfo.bhash_size);
tcp_register_congestion_control(&tcp_reno);
}
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 383e4b52dbd..f51d6404c61 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2051,7 +2051,7 @@ static void *established_get_first(struct seq_file *seq)
}
st->state = TCP_SEQ_STATE_TIME_WAIT;
inet_twsk_for_each(tw, node,
- &tcp_hashinfo.ehash[st->bucket + tcp_hashinfo.ehash_size].chain) {
+ &tcp_hashinfo.ehash[st->bucket].twchain) {
if (tw->tw_family != st->family) {
continue;
}
@@ -2107,7 +2107,7 @@ get_tw:
}
st->state = TCP_SEQ_STATE_TIME_WAIT;
- tw = tw_head(&tcp_hashinfo.ehash[st->bucket + tcp_hashinfo.ehash_size].chain);
+ tw = tw_head(&tcp_hashinfo.ehash[st->bucket].twchain);
goto get_tw;
found:
cur = sk;