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Message-Id: <20211014134126.3998932-1-eric.dumazet@gmail.com>
Date: Thu, 14 Oct 2021 06:41:26 -0700
From: Eric Dumazet <eric.dumazet@...il.com>
To: "David S . Miller" <davem@...emloft.net>,
Jakub Kicinski <kuba@...nel.org>
Cc: netdev <netdev@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
Eric Dumazet <eric.dumazet@...il.com>,
Stefan Bach <sfb@...gle.com>,
Neal Cardwell <ncardwell@...gle.com>
Subject: [PATCH v2 net-next] tcp: switch orphan_count to bare per-cpu counters
From: Eric Dumazet <edumazet@...gle.com>
Use of percpu_counter structure to track count of orphaned
sockets is causing problems on modern hosts with 256 cpus
or more.
Stefan Bach reported a serious spinlock contention in real workloads,
that I was able to reproduce with a netfilter rule dropping
incoming FIN packets.
53.56% server [kernel.kallsyms] [k] queued_spin_lock_slowpath
|
---queued_spin_lock_slowpath
|
--53.51%--_raw_spin_lock_irqsave
|
--53.51%--__percpu_counter_sum
tcp_check_oom
|
|--39.03%--__tcp_close
| tcp_close
| inet_release
| inet6_release
| sock_close
| __fput
| ____fput
| task_work_run
| exit_to_usermode_loop
| do_syscall_64
| entry_SYSCALL_64_after_hwframe
| __GI___libc_close
|
--14.48%--tcp_out_of_resources
tcp_write_timeout
tcp_retransmit_timer
tcp_write_timer_handler
tcp_write_timer
call_timer_fn
expire_timers
__run_timers
run_timer_softirq
__softirqentry_text_start
As explained in commit cf86a086a180 ("net/dst: use a smaller percpu_counter
batch for dst entries accounting"), default batch size is too big
for the default value of tcp_max_orphans (262144).
But even if we reduce batch sizes, there would still be cases
where the estimated count of orphans is beyond the limit,
and where tcp_too_many_orphans() has to call the expensive
percpu_counter_sum_positive().
One solution is to use plain per-cpu counters, and have
a timer to periodically refresh this cache.
Updating this cache every 100ms seems about right, tcp pressure
state is not radically changing over shorter periods.
percpu_counter was nice 15 years ago while hosts had less
than 16 cpus, not anymore by current standards.
v2: Fix the build issue for CONFIG_CRYPTO_DEV_CHELSIO_TLS=m,
reported by kernel test robot <lkp@...el.com>
Remove unused socket argument from tcp_too_many_orphans()
Fixes: dd24c00191d5 ("net: Use a percpu_counter for orphan_count")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Reported-by: Stefan Bach <sfb@...gle.com>
Cc: Neal Cardwell <ncardwell@...gle.com>
---
.../chelsio/inline_crypto/chtls/chtls_cm.c | 2 +-
.../chelsio/inline_crypto/chtls/chtls_cm.h | 2 +-
include/net/inet_connection_sock.h | 2 +-
include/net/sock.h | 2 +-
include/net/tcp.h | 17 ++-------
net/dccp/dccp.h | 2 +-
net/dccp/proto.c | 14 ++-----
net/ipv4/inet_connection_sock.c | 4 +-
net/ipv4/inet_hashtables.c | 2 +-
net/ipv4/proc.c | 2 +-
net/ipv4/tcp.c | 38 ++++++++++++++++---
11 files changed, 49 insertions(+), 38 deletions(-)
diff --git a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c
index bcad69c480740b85f9dec0401f8a92b78036dbc8..4af5561cbfc54cf82d92c5a3a667f2953ddbccce 100644
--- a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c
+++ b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.c
@@ -870,7 +870,7 @@ static void do_abort_syn_rcv(struct sock *child, struct sock *parent)
* created only after 3 way handshake is done.
*/
sock_orphan(child);
- percpu_counter_inc((child)->sk_prot->orphan_count);
+ INC_ORPHAN_COUNT(child);
chtls_release_resources(child);
chtls_conn_done(child);
} else {
diff --git a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h
index b1161bdeda4dc7ef349f353be316a964a54330bd..f61ca657601caeb3c0e5533e4fcf5819988cc3f7 100644
--- a/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h
+++ b/drivers/net/ethernet/chelsio/inline_crypto/chtls/chtls_cm.h
@@ -95,7 +95,7 @@ struct deferred_skb_cb {
#define WSCALE_OK(tp) ((tp)->rx_opt.wscale_ok)
#define TSTAMP_OK(tp) ((tp)->rx_opt.tstamp_ok)
#define SACK_OK(tp) ((tp)->rx_opt.sack_ok)
-#define INC_ORPHAN_COUNT(sk) percpu_counter_inc((sk)->sk_prot->orphan_count)
+#define INC_ORPHAN_COUNT(sk) this_cpu_inc(*(sk)->sk_prot->orphan_count)
/* TLS SKB */
#define skb_ulp_tls_inline(skb) (ULP_SKB_CB(skb)->ulp.tls.ofld)
diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index b06c2d02ec84e96c6222ac608473d7eaf71e5590..fa6a87246a7b85d3358b6ec66e6029445fe3b066 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -289,7 +289,7 @@ static inline void inet_csk_prepare_for_destroy_sock(struct sock *sk)
{
/* The below has to be done to allow calling inet_csk_destroy_sock */
sock_set_flag(sk, SOCK_DEAD);
- percpu_counter_inc(sk->sk_prot->orphan_count);
+ this_cpu_inc(*sk->sk_prot->orphan_count);
}
void inet_csk_destroy_sock(struct sock *sk);
diff --git a/include/net/sock.h b/include/net/sock.h
index d08ab55fa4a05f403d7591eff9752145ea73e008..596ba85611bc786affed2bf2b18e455b015f3774 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1235,7 +1235,7 @@ struct proto {
unsigned int useroffset; /* Usercopy region offset */
unsigned int usersize; /* Usercopy region size */
- struct percpu_counter *orphan_count;
+ unsigned int __percpu *orphan_count;
struct request_sock_ops *rsk_prot;
struct timewait_sock_ops *twsk_prot;
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4c2898ac65698a097ccaedcc59542041f15f4f70..af77e6453b1b461780df2d6e2fb94ab1baab688e 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -48,7 +48,9 @@
extern struct inet_hashinfo tcp_hashinfo;
-extern struct percpu_counter tcp_orphan_count;
+DECLARE_PER_CPU(unsigned int, tcp_orphan_count);
+int tcp_orphan_count_sum(void);
+
void tcp_time_wait(struct sock *sk, int state, int timeo);
#define MAX_TCP_HEADER L1_CACHE_ALIGN(128 + MAX_HEADER)
@@ -290,19 +292,6 @@ static inline bool tcp_out_of_memory(struct sock *sk)
void sk_forced_mem_schedule(struct sock *sk, int size);
-static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
-{
- struct percpu_counter *ocp = sk->sk_prot->orphan_count;
- int orphans = percpu_counter_read_positive(ocp);
-
- if (orphans << shift > sysctl_tcp_max_orphans) {
- orphans = percpu_counter_sum_positive(ocp);
- if (orphans << shift > sysctl_tcp_max_orphans)
- return true;
- }
- return false;
-}
-
bool tcp_check_oom(struct sock *sk, int shift);
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index c5c1d2b8045e8efd9bf32a2db1e679c13cbf1852..5183e627468d8901f4f80ed8d74a655aa2a6557f 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -48,7 +48,7 @@ extern bool dccp_debug;
extern struct inet_hashinfo dccp_hashinfo;
-extern struct percpu_counter dccp_orphan_count;
+DECLARE_PER_CPU(unsigned int, dccp_orphan_count);
void dccp_time_wait(struct sock *sk, int state, int timeo);
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index abb5c596a81763b3a571c48137e98d61d21207bf..fc44dadc778bbef72b2cade8b453f012831f592d 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -42,8 +42,8 @@ DEFINE_SNMP_STAT(struct dccp_mib, dccp_statistics) __read_mostly;
EXPORT_SYMBOL_GPL(dccp_statistics);
-struct percpu_counter dccp_orphan_count;
-EXPORT_SYMBOL_GPL(dccp_orphan_count);
+DEFINE_PER_CPU(unsigned int, dccp_orphan_count);
+EXPORT_PER_CPU_SYMBOL_GPL(dccp_orphan_count);
struct inet_hashinfo dccp_hashinfo;
EXPORT_SYMBOL_GPL(dccp_hashinfo);
@@ -1055,7 +1055,7 @@ void dccp_close(struct sock *sk, long timeout)
bh_lock_sock(sk);
WARN_ON(sock_owned_by_user(sk));
- percpu_counter_inc(sk->sk_prot->orphan_count);
+ this_cpu_inc(dccp_orphan_count);
/* Have we already been destroyed by a softirq or backlog? */
if (state != DCCP_CLOSED && sk->sk_state == DCCP_CLOSED)
@@ -1115,13 +1115,10 @@ static int __init dccp_init(void)
BUILD_BUG_ON(sizeof(struct dccp_skb_cb) >
sizeof_field(struct sk_buff, cb));
- rc = percpu_counter_init(&dccp_orphan_count, 0, GFP_KERNEL);
- if (rc)
- goto out_fail;
inet_hashinfo_init(&dccp_hashinfo);
rc = inet_hashinfo2_init_mod(&dccp_hashinfo);
if (rc)
- goto out_free_percpu;
+ goto out_fail;
rc = -ENOBUFS;
dccp_hashinfo.bind_bucket_cachep =
kmem_cache_create("dccp_bind_bucket",
@@ -1226,8 +1223,6 @@ static int __init dccp_init(void)
kmem_cache_destroy(dccp_hashinfo.bind_bucket_cachep);
out_free_hashinfo2:
inet_hashinfo2_free_mod(&dccp_hashinfo);
-out_free_percpu:
- percpu_counter_destroy(&dccp_orphan_count);
out_fail:
dccp_hashinfo.bhash = NULL;
dccp_hashinfo.ehash = NULL;
@@ -1250,7 +1245,6 @@ static void __exit dccp_fini(void)
dccp_ackvec_exit();
dccp_sysctl_exit();
inet_hashinfo2_free_mod(&dccp_hashinfo);
- percpu_counter_destroy(&dccp_orphan_count);
}
module_init(dccp_init);
diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index f25d02ad4a8af41790261a0c79188111ed408efc..f7fea3a7c5e64b92ca9c6b56293628923649e58c 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -1015,7 +1015,7 @@ void inet_csk_destroy_sock(struct sock *sk)
sk_refcnt_debug_release(sk);
- percpu_counter_dec(sk->sk_prot->orphan_count);
+ this_cpu_dec(*sk->sk_prot->orphan_count);
sock_put(sk);
}
@@ -1074,7 +1074,7 @@ static void inet_child_forget(struct sock *sk, struct request_sock *req,
sock_orphan(child);
- percpu_counter_inc(sk->sk_prot->orphan_count);
+ this_cpu_inc(*sk->sk_prot->orphan_count);
if (sk->sk_protocol == IPPROTO_TCP && tcp_rsk(req)->tfo_listener) {
BUG_ON(rcu_access_pointer(tcp_sk(child)->fastopen_rsk) != req);
diff --git a/net/ipv4/inet_hashtables.c b/net/ipv4/inet_hashtables.c
index bfb522e513461a92cbd19c0c2c14b2dda33bb4f7..75737267746f85a5be82fbe04bbfb429914334c1 100644
--- a/net/ipv4/inet_hashtables.c
+++ b/net/ipv4/inet_hashtables.c
@@ -598,7 +598,7 @@ bool inet_ehash_nolisten(struct sock *sk, struct sock *osk, bool *found_dup_sk)
if (ok) {
sock_prot_inuse_add(sock_net(sk), sk->sk_prot, 1);
} else {
- percpu_counter_inc(sk->sk_prot->orphan_count);
+ this_cpu_inc(*sk->sk_prot->orphan_count);
inet_sk_set_state(sk, TCP_CLOSE);
sock_set_flag(sk, SOCK_DEAD);
inet_csk_destroy_sock(sk);
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index b0d3a09dc84e7a1126bb45b0f8d4ff1d36131d25..f30273afb5399ddf0122e46e36da2ddae720a1c3 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -53,7 +53,7 @@ static int sockstat_seq_show(struct seq_file *seq, void *v)
struct net *net = seq->private;
int orphans, sockets;
- orphans = percpu_counter_sum_positive(&tcp_orphan_count);
+ orphans = tcp_orphan_count_sum();
sockets = proto_sockets_allocated_sum_positive(&tcp_prot);
socket_seq_show(seq);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 414c179c28e0dd5b91194456d34b46faf2b122e4..c2d9830136d298a27abc12a5633bf77d1224759c 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -287,8 +287,8 @@ enum {
TCP_CMSG_TS = 2
};
-struct percpu_counter tcp_orphan_count;
-EXPORT_SYMBOL_GPL(tcp_orphan_count);
+DEFINE_PER_CPU(unsigned int, tcp_orphan_count);
+EXPORT_PER_CPU_SYMBOL_GPL(tcp_orphan_count);
long sysctl_tcp_mem[3] __read_mostly;
EXPORT_SYMBOL(sysctl_tcp_mem);
@@ -2673,11 +2673,36 @@ void tcp_shutdown(struct sock *sk, int how)
}
EXPORT_SYMBOL(tcp_shutdown);
+int tcp_orphan_count_sum(void)
+{
+ int i, total = 0;
+
+ for_each_possible_cpu(i)
+ total += per_cpu(tcp_orphan_count, i);
+
+ return max(total, 0);
+}
+
+static int tcp_orphan_cache;
+static struct timer_list tcp_orphan_timer;
+#define TCP_ORPHAN_TIMER_PERIOD msecs_to_jiffies(100)
+
+static void tcp_orphan_update(struct timer_list *unused)
+{
+ WRITE_ONCE(tcp_orphan_cache, tcp_orphan_count_sum());
+ mod_timer(&tcp_orphan_timer, jiffies + TCP_ORPHAN_TIMER_PERIOD);
+}
+
+static bool tcp_too_many_orphans(int shift)
+{
+ return READ_ONCE(tcp_orphan_cache) << shift > sysctl_tcp_max_orphans;
+}
+
bool tcp_check_oom(struct sock *sk, int shift)
{
bool too_many_orphans, out_of_socket_memory;
- too_many_orphans = tcp_too_many_orphans(sk, shift);
+ too_many_orphans = tcp_too_many_orphans(shift);
out_of_socket_memory = tcp_out_of_memory(sk);
if (too_many_orphans)
@@ -2786,7 +2811,7 @@ void __tcp_close(struct sock *sk, long timeout)
/* remove backlog if any, without releasing ownership. */
__release_sock(sk);
- percpu_counter_inc(sk->sk_prot->orphan_count);
+ this_cpu_inc(tcp_orphan_count);
/* Have we already been destroyed by a softirq or backlog? */
if (state != TCP_CLOSE && sk->sk_state == TCP_CLOSE)
@@ -4479,7 +4504,10 @@ void __init tcp_init(void)
sizeof_field(struct sk_buff, cb));
percpu_counter_init(&tcp_sockets_allocated, 0, GFP_KERNEL);
- percpu_counter_init(&tcp_orphan_count, 0, GFP_KERNEL);
+
+ timer_setup(&tcp_orphan_timer, tcp_orphan_update, TIMER_DEFERRABLE);
+ mod_timer(&tcp_orphan_timer, jiffies + TCP_ORPHAN_TIMER_PERIOD);
+
inet_hashinfo_init(&tcp_hashinfo);
inet_hashinfo2_init(&tcp_hashinfo, "tcp_listen_portaddr_hash",
thash_entries, 21, /* one slot per 2 MB*/
--
2.33.0.882.g93a45727a2-goog
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