af_unix: speedup /proc/net/unix

/proc/net/unix has quadratic behavior, and can hold unix_table_lock for
a while if high number of unix sockets are alive. (90 ms for 200k
sockets...)

We already have a hash table, so its quite easy to use it.

Problem is unbound sockets are still hashed in a single hash slot
(unix_socket_table[UNIX_HASH_TABLE])

This patch also spreads unbound sockets to 256 hash slots, to speedup
both /proc/net/unix and unix_diag.

Time to read /proc/net/unix with 200k unix sockets :
(time dd if=/proc/net/unix of=/dev/null bs=4k)

before : 520 secs
after : 2 secs

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 2 deletions

diff --git a/net/unix/diag.c b/net/unix/diag.c
index 47d3002737f5..7e8a24bff34a 100644
--- a/net/unix/diag.c
+++ b/net/unix/diag.c
@@ -195,7 +195,9 @@ static int unix_diag_dump(struct sk_buff *skb, struct netlink_callback *cb)
         num = s_num = cb->args[1];
 
         spin_lock(&unix_table_lock);
-        for (slot = s_slot; slot <= UNIX_HASH_SIZE; s_num = 0, slot++) {
+        for (slot = s_slot;
+             slot < ARRAY_SIZE(unix_socket_table);
+             s_num = 0, slot++) {
                 struct sock *sk;
                 struct hlist_node *node;
 
@@ -228,7 +230,7 @@ static struct sock *unix_lookup_by_ino(int ino)
         struct sock *sk;
 
         spin_lock(&unix_table_lock);
-        for (i = 0; i <= UNIX_HASH_SIZE; i++) {
+        for (i = 0; i < ARRAY_SIZE(unix_socket_table); i++) {
                 struct hlist_node *node;
 
                 sk_for_each(sk, node, &unix_socket_table[i])