netdev - Re: [External] Re: [PATCH v5] sock: add tracepoint for send recv length

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Date:   Wed, 11 Jan 2023 11:53:24 +0800
From:   运辉崔 <cuiyunhui@...edance.com>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Eric Dumazet <edumazet@...gle.com>, mhiramat@...nel.org,
        davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
        kuniyu@...zon.com, xiyou.wangcong@...il.com,
        duanxiongchun@...edance.com, linux-kernel@...r.kernel.org,
        linux-trace-kernel@...r.kernel.org, netdev@...r.kernel.org,
        dust.li@...ux.alibaba.com
Subject: Re: [External] Re: [PATCH v5] sock: add tracepoint for send recv length

On Tue, Jan 10, 2023 at 11:44 PM Steven Rostedt <rostedt@...dmis.org> wrote:
>
>
>         TP_printk("sk address = %p, family = %s protocol = %s, length = %d, error = %d, flags = 0x%x",
>                   __entry->sk, show_family_name(__entry->family),
>                   show_inet_protocol_name(__entry->protocol),
>                   __entry->ret > 0 ? ret : 0, __entry->ret < 0 ? ret : 0,
>                   __entry->flags)
> );
>
> DEFINE_EVENT(sock_msg_length, sock_send_length,
>         TP_PROTO(struct sock *sk, int ret, int flags),
>
>         TP_ARGS(sk, ret, flags)
> );
>
> DEFINE_EVENT_PRINT(sock_msg_length, sock_recv_length,
>         TP_PROTO(struct sock *sk, int ret, int flags),
>
>         TP_ARGS(sk, ret, flags)
>
>         TP_printk("sk address = %p, family = %s protocol = %s, length = %d, error = %d, flags = 0x%x",
>                   __entry->sk, show_family_name(__entry->family),
>                   show_inet_protocol_name(__entry->protocol),
>                   !(__entry->flags & MSG_PEEK) ? __entry->ret : __entry->ret > 0 ? ret : 0,
>                   __entry->ret < 0 ? ret : 0,
>                   __entry->flags)
> );
> #endif /* _TRACE_SOCK_H */
>
> As DEFINE_EVENT_PRINT() uses the class template, but overrides the
> TP_printk() portion (still saving memory).
>

Hi Steve, Based on your suggestion, can we use the following code
instead of using DEFINE_EVENT_PRINT ？

DECLARE_EVENT_CLASS(sock_msg_length,

        TP_PROTO(struct sock *sk, int ret, int flags),

        TP_ARGS(sk, ret, flags),

        TP_STRUCT__entry(
                __field(void *, sk)
                __field(__u16, family)
                __field(__u16, protocol)
                __field(int, ret)
                __field(int, flags)
        ),

        TP_fast_assign(
                __entry->sk = sk;
                __entry->family = sk->sk_family;
                __entry->protocol = sk->sk_protocol;
                __entry->ret = ret;
                __entry->flags = flags;
        ),

        TP_printk("sk address = %p, family = %s protocol = %s, length
= %d, error = %d, flags = 0x%x",
                  __entry->sk, show_family_name(__entry->family),
                  show_inet_protocol_name(__entry->protocol),
                  !(__entry->flags & MSG_PEEK) ?
                  (__entry->ret > 0 ? __entry->ret : 0) : 0,
                  __entry->ret < 0 ? __entry->ret : 0,
                  __entry->flags)
);

DEFINE_EVENT(sock_msg_length, sock_send_length,
        TP_PROTO(struct sock *sk, int ret, int flags),

        TP_ARGS(sk, ret, flags)
);

DEFINE_EVENT(sock_msg_length, sock_recv_length,
        TP_PROTO(struct sock *sk, int ret, int flags),

        TP_ARGS(sk, ret, flags)
);


> And then both calls can just do:
>
>         trace_sock_send_length(sk, ret, 0);
>
>         trace_sock_recv_length(sock->sk, ret, flags);
>
> And I bet that will also solve all the gcc being smart waste.
>
> -- Steve
>

Btw,  we still need noinline helpers, right?
Otherwise the following code would be inlined into sock_recvmsg:
mov    0x18(%r13),%rsi
mov    %gs:0x7e832d87(%rip),%eax        # 0x2e68c <pcpu_hot+12>
mov    %eax,%eax
bt     %rax,0xdca591(%rip)        # 0xffffffff825c5ea0 <__cpu_online_mask>


Thanks,
Yunhui