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tcp: add TCPMemoryPressuresChrono counter

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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 <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet
2017-06-07 13:29:12 -07:00
committed by David S. Miller
parent 06fcb3b69f
commit 0604475119
10 changed files with 55 additions and 29 deletions
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22
include/net/sock.h
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@@ -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)
{