Re: [PATCH] tcp: Support tcp socket allocated counter in namespace.

[David Miller <davem@davemloft.net>]

From: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Date: Mon, 12 Feb 2018 18:44:00 -0800

> Sometimes, we want to know how many tcp sockets are in use
> different _net_ namespaces. It's a key resource metric. With
> this patch, we can get it via /proc/net/sockstat.
> 
> The 'alloc' show in /proc/net/sockstat is the total tcp
> sockets in the kernel. This patch moves it to namespace,
> via adding a counter because the previous counter is used
> in proto(e.g tcp, udp and sctp) memory management.
> 
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
 ...
> @@ -453,6 +453,8 @@ void tcp_init_sock(struct sock *sk)
>  	sk->sk_rcvbuf = sock_net(sk)->ipv4.sysctl_tcp_rmem[1];
>  
>  	sk_sockets_allocated_inc(sk);
> +	if (likely(sk->sk_net_refcnt))
> +		tcp_sock_allocated_add(sock_net(sk), 1);
>  }
>  EXPORT_SYMBOL(tcp_init_sock);
>  
 ...
> @@ -1928,6 +1928,8 @@ void tcp_v4_destroy_sock(struct sock *sk)
>  	tcp_saved_syn_free(tp);
>  
>  	sk_sockets_allocated_dec(sk);
> +	if (likely(sk->sk_net_refcnt))
> +		tcp_sock_allocated_add(sock_net(sk), -1);
>  }
>  EXPORT_SYMBOL(tcp_v4_destroy_sock);
>  
 ...
> @@ -559,6 +559,9 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
>  		newtp->rack.reo_wnd_persist = 0;
>  		newtp->rack.dsack_seen = 0;
>  
> +		if (likely(newsk->sk_net_refcnt))
> +			tcp_sock_allocated_add(sock_net(newsk), 1);
> +
>  		__TCP_INC_STATS(sock_net(sk), TCP_MIB_PASSIVEOPENS);

The amount of new conditional tests in these fast paths are not
justified for this new counter which is of debatable usefullness.

I'm not applying this, sorry.