Re: [patch] do not readlock all buckets in /proc/net/tcp

[YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@xxxxxxxxxxxxxx>]

In article <20040705120610.GA5728@xxxxxxxxxxxxxxxxxxx> (at Mon, 5 Jul 2004 
22:06:10 +1000), Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx> says:

> On Mon, Jul 05, 2004 at 01:35:55PM +0200, Marcus Meissner wrote:
> > 
> > Oh, and NETLINK+TCP_DIAG seems to have the same readlock contention problem,
> > see tcpdiag_dump().
> 
> Then you wouldn't mind adding this optimisation for tcp_diag as well,
> right? :)

here it is. :-)

Signed-off-by: Hideaki YOSHIFUJI <yoshfuji@xxxxxxxxxxxxxx>

===== net/ipv4/tcp_diag.c 1.15 vs edited =====
--- 1.15/net/ipv4/tcp_diag.c    2004-06-08 07:27:58 +09:00
+++ edited/net/ipv4/tcp_diag.c  2004-07-05 21:18:17 +09:00
@@ -522,9 +522,13 @@
                if (i > s_i)
                        s_num = 0;
 
-               read_lock_bh(&head->lock);
-
                num = 0;
+
+               if (hlist_empty(&head->chain) &&
+                   (!(r->tcpdiag_states&TCPF_TIME_WAIT) || 
hlist_empty(&head->chain)))
+                       continue;
+
+               read_lock_bh(&head->lock);
                sk_for_each(sk, node, &head->chain) {
                        struct inet_opt *inet = inet_sk(sk);
 

-- 
Hideaki YOSHIFUJI @ USAGI Project <yoshfuji@xxxxxxxxxxxxxx>
GPG FP: 9022 65EB 1ECF 3AD1 0BDF  80D8 4807 F894 E062 0EEA