这里记录了一些 sock 相关的总体性的数据. 我比较关注的是其中的 mem:

sockets: used 121
TCP: inuse 18 orphan 0 tw 64 alloc 20 mem 6
UDP: inuse 0 mem 0
UDPLITE: inuse 0
RAW: inuse 0
FRAG: inuse 0 memory 0

其中 mem 的单位很少有说清的地方, 我就自己看一一下 kernel 代码:

static int sockstat_seq_show(struct seq_file *seq, void *v)
{
        struct net *net = seq->private;
        unsigned int frag_mem;
        int orphans, sockets;

        local_bh_disable();
        orphans = percpu_counter_sum_positive(&tcp_orphan_count);
        sockets = proto_sockets_allocated_sum_positive(&tcp_prot);
        local_bh_enable();

        socket_seq_show(seq);
        seq_printf(seq, "TCP: inuse %d orphan %d tw %d alloc %d mem %ld\n",
                   sock_prot_inuse_get(net, &tcp_prot), orphans,
                   tcp_death_row.tw_count, sockets,
                   proto_memory_allocated(&tcp_prot));
        seq_printf(seq, "UDP: inuse %d mem %ld\n",
                   sock_prot_inuse_get(net, &udp_prot),
                   proto_memory_allocated(&udp_prot));
        seq_printf(seq, "UDPLITE: inuse %d\n",
                   sock_prot_inuse_get(net, &udplite_prot));
        seq_printf(seq, "RAW: inuse %d\n",
                   sock_prot_inuse_get(net, &raw_prot));
        frag_mem = ip_frag_mem(net);
        seq_printf(seq,  "FRAG: inuse %u memory %u\n", !!frag_mem, frag_mem);
        return 0;
}

static inline long
proto_memory_allocated(struct proto *prot)
{
        return atomic_long_read(prot->memory_allocated);
}

static inline long
sk_memory_allocated_add(struct sock *sk, int amt)
{
        return atomic_long_add_return(amt, sk->sk_prot->memory_allocated);
}

int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind)
{
        struct proto *prot = sk->sk_prot;
        long allocated = sk_memory_allocated_add(sk, amt);

        if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
            !mem_cgroup_charge_skmem(sk->sk_memcg, amt))
                goto suppress_allocation;


       ....
}

int __sk_mem_schedule(struct sock *sk, int size, int kind)
{
        int ret, amt = sk_mem_pages(size);

        sk->sk_forward_alloc += amt << SK_MEM_QUANTUM_SHIFT;
        ret = __sk_mem_raise_allocated(sk, size, amt, kind);
        if (!ret)
                sk->sk_forward_alloc -= amt << SK_MEM_QUANTUM_SHIFT;
        return ret;
}

以上是相关性的函数. 在 __sk_mem_schedule 中有一个 size 转成 amt 的过程, 这个过程是基于 page
进行计算的. 后面对于memory_allocated 的增加都是直接增加的 amt 这个变量. 所以这里认为其就是以 page
为单位的.