From 0604475119de5f80dc051a5db055c6a2a75bd542 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Wed, 7 Jun 2017 13:29:12 -0700 Subject: [PATCH] tcp: add TCPMemoryPressuresChrono counter DRAM supply shortage and poor memory pressure tracking in TCP stack makes any change in SO_SNDBUF/SO_RCVBUF (or equivalent autotuning limits) and tcp_mem[] quite hazardous. TCPMemoryPressures SNMP counter is an indication of tcp_mem sysctl limits being hit, but only tracking number of transitions. If TCP stack behavior under stress was perfect : 1) It would maintain memory usage close to the limit. 2) Memory pressure state would be entered for short times. We certainly prefer 100 events lasting 10ms compared to one event lasting 200 seconds. This patch adds a new SNMP counter tracking cumulative duration of memory pressure events, given in ms units. $ cat /proc/sys/net/ipv4/tcp_mem 3088 4117 6176 $ grep TCP /proc/net/sockstat TCP: inuse 180 orphan 0 tw 2 alloc 234 mem 4140 $ nstat -n ; sleep 10 ; nstat |grep Pressure TcpExtTCPMemoryPressures 1700 TcpExtTCPMemoryPressuresChrono 5209 v2: Used EXPORT_SYMBOL_GPL() instead of EXPORT_SYMBOL() as David instructed. Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- include/net/sock.h | 22 ++-------------------- include/net/tcp.h | 3 ++- include/uapi/linux/snmp.h | 1 + net/core/sock.c | 20 ++++++++++++++++++++ net/decnet/af_decnet.c | 2 +- net/ipv4/proc.c | 1 + net/ipv4/tcp.c | 31 +++++++++++++++++++++++++------ net/ipv4/tcp_ipv4.c | 1 + net/ipv6/tcp_ipv6.c | 1 + net/sctp/socket.c | 2 +- 10 files changed, 55 insertions(+), 29 deletions(-) diff --git a/include/net/sock.h b/include/net/sock.h index 3467d9e89e7d..858891c36f94 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1080,6 +1080,7 @@ struct proto { bool (*stream_memory_free)(const struct sock *sk); /* Memory pressure */ void (*enter_memory_pressure)(struct sock *sk); + void (*leave_memory_pressure)(struct sock *sk); atomic_long_t *memory_allocated; /* Current allocated memory. */ struct percpu_counter *sockets_allocated; /* Current number of sockets. */ /* @@ -1088,7 +1089,7 @@ struct proto { * All the __sk_mem_schedule() is of this nature: accounting * is strict, actions are advisory and have some latency. */ - int *memory_pressure; + unsigned long *memory_pressure; long *sysctl_mem; int *sysctl_wmem; int *sysctl_rmem; @@ -1193,25 +1194,6 @@ static inline bool sk_under_memory_pressure(const struct sock *sk) return !!*sk->sk_prot->memory_pressure; } -static inline void sk_leave_memory_pressure(struct sock *sk) -{ - int *memory_pressure = sk->sk_prot->memory_pressure; - - if (!memory_pressure) - return; - - if (*memory_pressure) - *memory_pressure = 0; -} - -static inline void sk_enter_memory_pressure(struct sock *sk) -{ - if (!sk->sk_prot->enter_memory_pressure) - return; - - sk->sk_prot->enter_memory_pressure(sk); -} - static inline long sk_memory_allocated(const struct sock *sk) { diff --git a/include/net/tcp.h b/include/net/tcp.h index aec092560d9b..3ab677d11d02 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -276,7 +276,7 @@ extern int sysctl_tcp_pacing_ca_ratio; extern atomic_long_t tcp_memory_allocated; extern struct percpu_counter tcp_sockets_allocated; -extern int tcp_memory_pressure; +extern unsigned long tcp_memory_pressure; /* optimized version of sk_under_memory_pressure() for TCP sockets */ static inline bool tcp_under_memory_pressure(const struct sock *sk) @@ -1320,6 +1320,7 @@ extern void tcp_openreq_init_rwin(struct request_sock *req, const struct dst_entry *dst); void tcp_enter_memory_pressure(struct sock *sk); +void tcp_leave_memory_pressure(struct sock *sk); static inline int keepalive_intvl_when(const struct tcp_sock *tp) { diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h index 95cffcb21dfd..d85693295798 100644 --- a/include/uapi/linux/snmp.h +++ b/include/uapi/linux/snmp.h @@ -228,6 +228,7 @@ enum LINUX_MIB_TCPABORTONLINGER, /* TCPAbortOnLinger */ LINUX_MIB_TCPABORTFAILED, /* TCPAbortFailed */ LINUX_MIB_TCPMEMORYPRESSURES, /* TCPMemoryPressures */ + LINUX_MIB_TCPMEMORYPRESSURESCHRONO, /* TCPMemoryPressuresChrono */ LINUX_MIB_TCPSACKDISCARD, /* TCPSACKDiscard */ LINUX_MIB_TCPDSACKIGNOREDOLD, /* TCPSACKIgnoredOld */ LINUX_MIB_TCPDSACKIGNOREDNOUNDO, /* TCPSACKIgnoredNoUndo */ diff --git a/net/core/sock.c b/net/core/sock.c index bef844127e01..ad8a4bc84126 100644 --- a/net/core/sock.c +++ b/net/core/sock.c @@ -2076,6 +2076,26 @@ int sock_cmsg_send(struct sock *sk, struct msghdr *msg, } EXPORT_SYMBOL(sock_cmsg_send); +static void sk_enter_memory_pressure(struct sock *sk) +{ + if (!sk->sk_prot->enter_memory_pressure) + return; + + sk->sk_prot->enter_memory_pressure(sk); +} + +static void sk_leave_memory_pressure(struct sock *sk) +{ + if (sk->sk_prot->leave_memory_pressure) { + sk->sk_prot->leave_memory_pressure(sk); + } else { + unsigned long *memory_pressure = sk->sk_prot->memory_pressure; + + if (memory_pressure && *memory_pressure) + *memory_pressure = 0; + } +} + /* On 32bit arches, an skb frag is limited to 2^15 */ #define SKB_FRAG_PAGE_ORDER get_order(32768) diff --git a/net/decnet/af_decnet.c b/net/decnet/af_decnet.c index 405483a07efc..73a0399dc7a2 100644 --- a/net/decnet/af_decnet.c +++ b/net/decnet/af_decnet.c @@ -447,7 +447,7 @@ static void dn_destruct(struct sock *sk) dst_release(rcu_dereference_check(sk->sk_dst_cache, 1)); } -static int dn_memory_pressure; +static unsigned long dn_memory_pressure; static void dn_enter_memory_pressure(struct sock *sk) { diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c index fa44e752a9a3..43eb6567b3a0 100644 --- a/net/ipv4/proc.c +++ b/net/ipv4/proc.c @@ -250,6 +250,7 @@ static const struct snmp_mib snmp4_net_list[] = { SNMP_MIB_ITEM("TCPAbortOnLinger", LINUX_MIB_TCPABORTONLINGER), SNMP_MIB_ITEM("TCPAbortFailed", LINUX_MIB_TCPABORTFAILED), SNMP_MIB_ITEM("TCPMemoryPressures", LINUX_MIB_TCPMEMORYPRESSURES), + SNMP_MIB_ITEM("TCPMemoryPressuresChrono", LINUX_MIB_TCPMEMORYPRESSURESCHRONO), SNMP_MIB_ITEM("TCPSACKDiscard", LINUX_MIB_TCPSACKDISCARD), SNMP_MIB_ITEM("TCPDSACKIgnoredOld", LINUX_MIB_TCPDSACKIGNOREDOLD), SNMP_MIB_ITEM("TCPDSACKIgnoredNoUndo", LINUX_MIB_TCPDSACKIGNOREDNOUNDO), diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 87981fcdfcf2..cc8fd8b747a4 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -320,17 +320,36 @@ struct tcp_splice_state { * All the __sk_mem_schedule() is of this nature: accounting * is strict, actions are advisory and have some latency. */ -int tcp_memory_pressure __read_mostly; -EXPORT_SYMBOL(tcp_memory_pressure); +unsigned long tcp_memory_pressure __read_mostly; +EXPORT_SYMBOL_GPL(tcp_memory_pressure); void tcp_enter_memory_pressure(struct sock *sk) { - if (!tcp_memory_pressure) { + unsigned long val; + + if (tcp_memory_pressure) + return; + val = jiffies; + + if (!val) + val--; + if (!cmpxchg(&tcp_memory_pressure, 0, val)) NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMEMORYPRESSURES); - tcp_memory_pressure = 1; - } } -EXPORT_SYMBOL(tcp_enter_memory_pressure); +EXPORT_SYMBOL_GPL(tcp_enter_memory_pressure); + +void tcp_leave_memory_pressure(struct sock *sk) +{ + unsigned long val; + + if (!tcp_memory_pressure) + return; + val = xchg(&tcp_memory_pressure, 0); + if (val) + NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPMEMORYPRESSURESCHRONO, + jiffies_to_msecs(jiffies - val)); +} +EXPORT_SYMBOL_GPL(tcp_leave_memory_pressure); /* Convert seconds to retransmits based on initial and max timeout */ static u8 secs_to_retrans(int seconds, int timeout, int rto_max) diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c index 13c7ae7d4504..1dc8c449e16a 100644 --- a/net/ipv4/tcp_ipv4.c +++ b/net/ipv4/tcp_ipv4.c @@ -2387,6 +2387,7 @@ struct proto tcp_prot = { .unhash = inet_unhash, .get_port = inet_csk_get_port, .enter_memory_pressure = tcp_enter_memory_pressure, + .leave_memory_pressure = tcp_leave_memory_pressure, .stream_memory_free = tcp_stream_memory_free, .sockets_allocated = &tcp_sockets_allocated, .orphan_count = &tcp_orphan_count, diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c index 5a525426fe93..0840543fc245 100644 --- a/net/ipv6/tcp_ipv6.c +++ b/net/ipv6/tcp_ipv6.c @@ -1910,6 +1910,7 @@ struct proto tcpv6_prot = { .unhash = inet_unhash, .get_port = inet_csk_get_port, .enter_memory_pressure = tcp_enter_memory_pressure, + .leave_memory_pressure = tcp_leave_memory_pressure, .stream_memory_free = tcp_stream_memory_free, .sockets_allocated = &tcp_sockets_allocated, .memory_allocated = &tcp_memory_allocated, diff --git a/net/sctp/socket.c b/net/sctp/socket.c index 0822046e4f3f..5f58dd03e3ac 100644 --- a/net/sctp/socket.c +++ b/net/sctp/socket.c @@ -103,7 +103,7 @@ static int sctp_autobind(struct sock *sk); static void sctp_sock_migrate(struct sock *, struct sock *, struct sctp_association *, sctp_socket_type_t); -static int sctp_memory_pressure; +static unsigned long sctp_memory_pressure; static atomic_long_t sctp_memory_allocated; struct percpu_counter sctp_sockets_allocated; -- 2.20.1