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Message-ID: <20220907005534.72876-3-kuniyu@amazon.com>
Date: Tue, 6 Sep 2022 17:55:30 -0700
From: Kuniyuki Iwashima <kuniyu@...zon.com>
To: "David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
CC: Kuniyuki Iwashima <kuniyu@...zon.com>,
Kuniyuki Iwashima <kuni1840@...il.com>,
<netdev@...r.kernel.org>
Subject: [PATCH v5 net-next 2/6] tcp: Don't allocate tcp_death_row outside of struct netns_ipv4.
We will soon introduce an optional per-netns ehash and access hash
tables via net->ipv4.tcp_death_row->hashinfo instead of &tcp_hashinfo
in most places.
It could harm the fast path because dereferences of two fields in net
and tcp_death_row might incur two extra cache line misses. To save one
dereference, let's place tcp_death_row back in netns_ipv4 and fetch
hashinfo via net->ipv4.tcp_death_row"."hashinfo.
Note tcp_death_row was initially placed in netns_ipv4, and commit
fbb8295248e1 ("tcp: allocate tcp_death_row outside of struct netns_ipv4")
changed it to a pointer so that we can fire TIME_WAIT timers after freeing
net. However, we don't do so after commit 04c494e68a13 ("Revert "tcp/dccp:
get rid of inet_twsk_purge()""), so we need not define tcp_death_row as a
pointer.
Also, we move refcount_dec_and_test(&tw_refcount) from tcp_sk_exit() to
tcp_sk_exit_batch() as a debug check.
Signed-off-by: Kuniyuki Iwashima <kuniyu@...zon.com>
---
include/net/netns/ipv4.h | 3 ++-
net/ipv4/inet_timewait_sock.c | 4 +---
net/ipv4/proc.c | 2 +-
net/ipv4/sysctl_net_ipv4.c | 8 ++------
net/ipv4/tcp_ipv4.c | 19 +++++++------------
net/ipv4/tcp_minisocks.c | 2 +-
net/ipv6/tcp_ipv6.c | 2 +-
7 files changed, 15 insertions(+), 25 deletions(-)
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index 6320a76cefdc..2c7df93e3403 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -34,6 +34,7 @@ struct inet_hashinfo;
struct inet_timewait_death_row {
refcount_t tw_refcount;
+ /* Padding to avoid false sharing, tw_refcount can be often written */
struct inet_hashinfo *hashinfo ____cacheline_aligned_in_smp;
int sysctl_max_tw_buckets;
};
@@ -41,7 +42,7 @@ struct inet_timewait_death_row {
struct tcp_fastopen_context;
struct netns_ipv4 {
- struct inet_timewait_death_row *tcp_death_row;
+ struct inet_timewait_death_row tcp_death_row;
#ifdef CONFIG_SYSCTL
struct ctl_table_header *forw_hdr;
diff --git a/net/ipv4/inet_timewait_sock.c b/net/ipv4/inet_timewait_sock.c
index 47ccc343c9fb..71d3bb0abf6c 100644
--- a/net/ipv4/inet_timewait_sock.c
+++ b/net/ipv4/inet_timewait_sock.c
@@ -59,9 +59,7 @@ static void inet_twsk_kill(struct inet_timewait_sock *tw)
inet_twsk_bind_unhash(tw, hashinfo);
spin_unlock(&bhead->lock);
- if (refcount_dec_and_test(&tw->tw_dr->tw_refcount))
- kfree(tw->tw_dr);
-
+ refcount_dec(&tw->tw_dr->tw_refcount);
inet_twsk_put(tw);
}
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 0088a4c64d77..5386f460bd20 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -59,7 +59,7 @@ static int sockstat_seq_show(struct seq_file *seq, void *v)
socket_seq_show(seq);
seq_printf(seq, "TCP: inuse %d orphan %d tw %d alloc %d mem %ld\n",
sock_prot_inuse_get(net, &tcp_prot), orphans,
- refcount_read(&net->ipv4.tcp_death_row->tw_refcount) - 1,
+ refcount_read(&net->ipv4.tcp_death_row.tw_refcount) - 1,
sockets, proto_memory_allocated(&tcp_prot));
seq_printf(seq, "UDP: inuse %d mem %ld\n",
sock_prot_inuse_get(net, &udp_prot),
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 5490c285668b..4d7c110c772f 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -530,10 +530,9 @@ static struct ctl_table ipv4_table[] = {
};
static struct ctl_table ipv4_net_table[] = {
- /* tcp_max_tw_buckets must be first in this table. */
{
.procname = "tcp_max_tw_buckets",
-/* .data = &init_net.ipv4.tcp_death_row.sysctl_max_tw_buckets, */
+ .data = &init_net.ipv4.tcp_death_row.sysctl_max_tw_buckets,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = proc_dointvec
@@ -1361,8 +1360,7 @@ static __net_init int ipv4_sysctl_init_net(struct net *net)
if (!table)
goto err_alloc;
- /* skip first entry (sysctl_max_tw_buckets) */
- for (i = 1; i < ARRAY_SIZE(ipv4_net_table) - 1; i++) {
+ for (i = 0; i < ARRAY_SIZE(ipv4_net_table) - 1; i++) {
if (table[i].data) {
/* Update the variables to point into
* the current struct net
@@ -1377,8 +1375,6 @@ static __net_init int ipv4_sysctl_init_net(struct net *net)
}
}
- table[0].data = &net->ipv4.tcp_death_row->sysctl_max_tw_buckets;
-
net->ipv4.ipv4_hdr = register_net_sysctl(net, "net/ipv4", table);
if (!net->ipv4.ipv4_hdr)
goto err_reg;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index a07243f66d4c..3930b6a1e0d6 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -292,7 +292,7 @@ int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
* complete initialization after this.
*/
tcp_set_state(sk, TCP_SYN_SENT);
- tcp_death_row = net->ipv4.tcp_death_row;
+ tcp_death_row = &net->ipv4.tcp_death_row;
err = inet_hash_connect(tcp_death_row, sk);
if (err)
goto failure;
@@ -3091,13 +3091,9 @@ EXPORT_SYMBOL(tcp_prot);
static void __net_exit tcp_sk_exit(struct net *net)
{
- struct inet_timewait_death_row *tcp_death_row = net->ipv4.tcp_death_row;
-
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))
- kfree(tcp_death_row);
}
static int __net_init tcp_sk_init(struct net *net)
@@ -3129,13 +3125,10 @@ static int __net_init tcp_sk_init(struct net *net)
net->ipv4.sysctl_tcp_tw_reuse = 2;
net->ipv4.sysctl_tcp_no_ssthresh_metrics_save = 1;
- net->ipv4.tcp_death_row = kzalloc(sizeof(struct inet_timewait_death_row), GFP_KERNEL);
- if (!net->ipv4.tcp_death_row)
- return -ENOMEM;
- refcount_set(&net->ipv4.tcp_death_row->tw_refcount, 1);
+ refcount_set(&net->ipv4.tcp_death_row.tw_refcount, 1);
cnt = tcp_hashinfo.ehash_mask + 1;
- net->ipv4.tcp_death_row->sysctl_max_tw_buckets = cnt / 2;
- net->ipv4.tcp_death_row->hashinfo = &tcp_hashinfo;
+ net->ipv4.tcp_death_row.sysctl_max_tw_buckets = cnt / 2;
+ net->ipv4.tcp_death_row.hashinfo = &tcp_hashinfo;
net->ipv4.sysctl_max_syn_backlog = max(128, cnt / 128);
net->ipv4.sysctl_tcp_sack = 1;
@@ -3201,8 +3194,10 @@ static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list)
inet_twsk_purge(&tcp_hashinfo, AF_INET);
- list_for_each_entry(net, net_exit_list, exit_list)
+ list_for_each_entry(net, net_exit_list, exit_list) {
+ WARN_ON_ONCE(!refcount_dec_and_test(&net->ipv4.tcp_death_row.tw_refcount));
tcp_fastopen_ctx_destroy(net);
+ }
}
static struct pernet_operations __net_initdata tcp_sk_ops = {
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 80ce27f8f77e..8bddb2a78b21 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -250,7 +250,7 @@ void tcp_time_wait(struct sock *sk, int state, int timeo)
struct net *net = sock_net(sk);
struct inet_timewait_sock *tw;
- tw = inet_twsk_alloc(sk, net->ipv4.tcp_death_row, state);
+ tw = inet_twsk_alloc(sk, &net->ipv4.tcp_death_row, state);
if (tw) {
struct tcp_timewait_sock *tcptw = tcp_twsk((struct sock *)tw);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 5c562d69fddf..eb1da7a63fbb 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -325,7 +325,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
inet->inet_dport = usin->sin6_port;
tcp_set_state(sk, TCP_SYN_SENT);
- tcp_death_row = net->ipv4.tcp_death_row;
+ tcp_death_row = &net->ipv4.tcp_death_row;
err = inet6_hash_connect(tcp_death_row, sk);
if (err)
goto late_failure;
--
2.30.2
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