From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 47821ECAAD4 for ; Mon, 29 Aug 2022 23:35:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229740AbiH2XfW (ORCPT ); Mon, 29 Aug 2022 19:35:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229684AbiH2XfT (ORCPT ); Mon, 29 Aug 2022 19:35:19 -0400 Received: from smtp-fw-6001.amazon.com (smtp-fw-6001.amazon.com [52.95.48.154]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 385F51CFC0 for ; Mon, 29 Aug 2022 16:35:17 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.com; i=@amazon.com; q=dns/txt; s=amazon201209; t=1661816117; x=1693352117; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=Q05xUxZuHumk+Su3QipY8VUPVliLI1XBsiMwMZ0tC9w=; b=bYPXbh6PMvQwRMmWxQOWA+BvqbIzImRsoJ0pKSjiuWIUJN3k6x9K8NQS 0dNQtW2K1ifO8dZFnU0kPcvt+/z0XCKJHcp05Z5wa4PGGdcUINFWvQDFT bu+/bEVSVtpQ4FEXR8TZ3hq/ejGRdmpyDK7R4IBHFhZiwa5q1sDZpqSCK Q=; Received: from iad12-co-svc-p1-lb1-vlan2.amazon.com (HELO email-inbound-relay-iad-1d-35b1f9a2.us-east-1.amazon.com) ([10.43.8.2]) by smtp-border-fw-6001.iad6.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 29 Aug 2022 23:35:05 +0000 Received: from EX13MTAUWB001.ant.amazon.com (iad12-ws-svc-p26-lb9-vlan2.iad.amazon.com [10.40.163.34]) by email-inbound-relay-iad-1d-35b1f9a2.us-east-1.amazon.com (Postfix) with ESMTPS id ACA0B2014FF; Mon, 29 Aug 2022 23:35:03 +0000 (UTC) Received: from EX19D004ANA001.ant.amazon.com (10.37.240.138) by EX13MTAUWB001.ant.amazon.com (10.43.161.249) with Microsoft SMTP Server (TLS) id 15.0.1497.38; Mon, 29 Aug 2022 23:35:02 +0000 Received: from 88665a182662.ant.amazon.com (10.43.162.52) by EX19D004ANA001.ant.amazon.com (10.37.240.138) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1118.12; Mon, 29 Aug 2022 23:35:00 +0000 From: Kuniyuki Iwashima To: CC: , , , , , Subject: Re: [PATCH v2 net-next 4/5] tcp: Save unnecessary inet_twsk_purge() calls. Date: Mon, 29 Aug 2022 16:34:53 -0700 Message-ID: <20220829233453.20921-1-kuniyu@amazon.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-Originating-IP: [10.43.162.52] X-ClientProxiedBy: EX13D13UWA001.ant.amazon.com (10.43.160.136) To EX19D004ANA001.ant.amazon.com (10.37.240.138) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Dumazet Date: Mon, 29 Aug 2022 16:11:57 -0700 > On Mon, Aug 29, 2022 at 9:21 AM Kuniyuki Iwashima wrote: > > > > While destroying netns, we call inet_twsk_purge() in tcp_sk_exit_batch() > > and tcpv6_net_exit_batch() for AF_INET and AF_INET6. These commands > > trigger the kernel to walk through the potentially big ehash twice even > > though the netns has no TIME_WAIT sockets. > > > > # ip netns add test > > # ip netns del test > > > > AF_INET6 uses module_init() to be loaded after AF_INET which uses > > fs_initcall(), so tcpv6_net_ops is always registered after tcp_sk_ops. > > Also, we clean up netns in the reverse order, so tcpv6_net_exit_batch() > > is always called before tcp_sk_exit_batch(). > > > > The characteristic enables us to save such unneeded iterations. This > > change eliminates the tax by the additional unshare() described in the > > next patch to guarantee the per-netns ehash size. > > Patch seems wrong to me, or not complete at least... > > It seems you missed an existing check in inet_twsk_purge(): > > if ((tw->tw_family != family) || > refcount_read(&twsk_net(tw)->ns.count)) > continue; > > To get rid of both IPv6 and IPv6 tw sockets, we currently need to call > inet_twsk_purge() twice, > with AF_INET and AF_INET6. For the first call of AF_INET6, if tw_refcount is 1, the count is what is set by tcp_sk_init() and there is no tw socket at least in the netns. And same for the AF_INET, if tw_refcount is 0 and death_row is NULL, there is no tw socket in the netns. If all netns in net_exit_list satify the condition, we need not call inet_twsk_purge(). However, one of netns in the list doesn't satisfy it, we have to call inet_twsk_purge() twice. Then we need to check the ns.count because another netns in the list may be freed in tcp_sk_exit(). So, the optimisation works only when all netns in the batch list do not have tw sockets. > > > > Signed-off-by: Kuniyuki Iwashima > > --- > > include/net/tcp.h | 1 + > > net/ipv4/tcp_ipv4.c | 6 ++++-- > > net/ipv4/tcp_minisocks.c | 24 ++++++++++++++++++++++++ > > net/ipv6/tcp_ipv6.c | 2 +- > > 4 files changed, 30 insertions(+), 3 deletions(-) > > > > diff --git a/include/net/tcp.h b/include/net/tcp.h > > index d10962b9f0d0..f60996c1d7b3 100644 > > --- a/include/net/tcp.h > > +++ b/include/net/tcp.h > > @@ -346,6 +346,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb); > > void tcp_rcv_space_adjust(struct sock *sk); > > int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp); > > void tcp_twsk_destructor(struct sock *sk); > > +void tcp_twsk_purge(struct list_head *net_exit_list, int family); > > ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos, > > struct pipe_inode_info *pipe, size_t len, > > unsigned int flags); > > diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c > > index b07930643b11..f4a502d57d45 100644 > > --- a/net/ipv4/tcp_ipv4.c > > +++ b/net/ipv4/tcp_ipv4.c > > @@ -3109,8 +3109,10 @@ static void __net_exit tcp_sk_exit(struct net *net) > > if (net->ipv4.tcp_congestion_control) > > bpf_module_put(net->ipv4.tcp_congestion_control, > > net->ipv4.tcp_congestion_control->owner); > > - if (refcount_dec_and_test(&tcp_death_row->tw_refcount)) > > + if (refcount_dec_and_test(&tcp_death_row->tw_refcount)) { > > kfree(tcp_death_row); > > + net->ipv4.tcp_death_row = NULL; > > + } > > } > > > > static int __net_init tcp_sk_init(struct net *net) > > @@ -3210,7 +3212,7 @@ static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list) > > { > > struct net *net; > > > > - inet_twsk_purge(&tcp_hashinfo, AF_INET); > > + tcp_twsk_purge(net_exit_list, AF_INET); > > > > list_for_each_entry(net, net_exit_list, exit_list) > > tcp_fastopen_ctx_destroy(net); > > diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c > > index 361aad67c6d6..9168c5a33344 100644 > > --- a/net/ipv4/tcp_minisocks.c > > +++ b/net/ipv4/tcp_minisocks.c > > @@ -347,6 +347,30 @@ void tcp_twsk_destructor(struct sock *sk) > > } > > EXPORT_SYMBOL_GPL(tcp_twsk_destructor); > > > > +void tcp_twsk_purge(struct list_head *net_exit_list, int family) > > +{ > > + struct net *net; > > + > > + list_for_each_entry(net, net_exit_list, exit_list) { > > + if (!net->ipv4.tcp_death_row) > > + continue; > > + > > + /* AF_INET6 using module_init() is always registered after > > + * AF_INET using fs_initcall() and cleaned up in the reverse > > + * order. > > + * > > + * The last refcount is decremented later in tcp_sk_exit(). > > + */ > > + if (IS_ENABLED(CONFIG_IPV6) && family == AF_INET6 && > > + refcount_read(&net->ipv4.tcp_death_row->tw_refcount) == 1) > > + continue; > > + > > + inet_twsk_purge(&tcp_hashinfo, family); > > + break; > > + } > > +} > > +EXPORT_SYMBOL_GPL(tcp_twsk_purge); > > + > > /* Warning : This function is called without sk_listener being locked. > > * Be sure to read socket fields once, as their value could change under us. > > */ > > diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c > > index 27b2fd98a2c4..9cbc7f0d7149 100644 > > --- a/net/ipv6/tcp_ipv6.c > > +++ b/net/ipv6/tcp_ipv6.c > > @@ -2229,7 +2229,7 @@ static void __net_exit tcpv6_net_exit(struct net *net) > > > > static void __net_exit tcpv6_net_exit_batch(struct list_head *net_exit_list) > > { > > - inet_twsk_purge(&tcp_hashinfo, AF_INET6); > > + tcp_twsk_purge(net_exit_list, AF_INET6); > > } > > > > static struct pernet_operations tcpv6_net_ops = { > > -- > > 2.30.2 > >