net: Batch inet_twsk_purge

This function walks the whole hashtable so there is no point in
passing it a network namespace.  Instead I purge all timewait
sockets from dead network namespaces that I find.  If the namespace
is one of the once I am trying to purge I am guaranteed no new timewait
sockets can be formed so this will get them all.  If the namespace
is one I am not acting for it might form a few more but I will
call inet_twsk_purge again and  shortly to get rid of them.  In
any even if the network namespace is dead timewait sockets are
useless.

Move the calls of inet_twsk_purge into batch_exit routines so
that if I am killing a bunch of namespaces at once I will just
call inet_twsk_purge once and save a lot of redundant unnecessary
work.

My simple 4k network namespace exit test the cleanup time dropped from
roughly 8.2s to 1.6s.  While the time spent running inet_twsk_purge fell
to about 2ms.  1ms for ipv4 and 1ms for ipv6.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 3 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 59c911f3889d..fee9aabd5aa1 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2529,12 +2529,17 @@ static int __net_init tcp_sk_init(struct net *net)
 static void __net_exit tcp_sk_exit(struct net *net)
 {
         inet_ctl_sock_destroy(net->ipv4.tcp_sock);
-        inet_twsk_purge(net, &tcp_hashinfo, &tcp_death_row, AF_INET);
+}
+
+static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list)
+{
+        inet_twsk_purge(&tcp_hashinfo, &tcp_death_row, AF_INET);
 }
 
 static struct pernet_operations __net_initdata tcp_sk_ops = {
-       .init = tcp_sk_init,
-       .exit = tcp_sk_exit,
+       .init       = tcp_sk_init,
+       .exit       = tcp_sk_exit,
+       .exit_batch = tcp_sk_exit_batch,
 };
 
 void __init tcp_v4_init(void)