Commit 06044751 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
Browse files

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: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 06fcb3b6

include/net/sock.h

+2 −20
Original line number Diff line number Diff line
@@ -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)

{

include/net/tcp.h

+2 −1
Original line number Diff line number Diff line
@@ -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)

{

include/uapi/linux/snmp.h

+1 −0
Original line number Diff line number Diff line
@@ -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 */

net/core/sock.c

+20 −0
Original line number Diff line number Diff line
@@ -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)

net/decnet/af_decnet.c

+1 −1
Original line number Diff line number Diff line
@@ -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)

{

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