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/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index fc0a4e5895e..aadd7cef73b 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -2184,12 +2184,17 @@ static int tcpv6_net_init(struct net *net)
 static void tcpv6_net_exit(struct net *net)
 {
 	inet_ctl_sock_destroy(net->ipv6.tcp_sk);
-	inet_twsk_purge(net, &tcp_hashinfo, &tcp_death_row, AF_INET6);
+}
+
+static void tcpv6_net_exit_batch(struct list_head *net_exit_list)
+{
+	inet_twsk_purge(&tcp_hashinfo, &tcp_death_row, AF_INET6);
 }
 
 static struct pernet_operations tcpv6_net_ops = {
-	.init = tcpv6_net_init,
-	.exit = tcpv6_net_exit,
+	.init	    = tcpv6_net_init,
+	.exit	    = tcpv6_net_exit,
+	.exit_batch = tcpv6_net_exit_batch,
 };
 
 int __init tcpv6_init(void)