netdev - Re: [PATCH net-next] udp: Add tracepoint for udp

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Message-ID: <0f67e414-d39a-4b71-9c9e-7dc027cc4ac3@redhat.com>
Date: Thu, 17 Apr 2025 15:17:05 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Breno Leitao <leitao@...ian.org>
Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 "David S. Miller" <davem@...emloft.net>, David Ahern <dsahern@...nel.org>,
 Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Simon Horman <horms@...nel.org>, kuniyu@...zon.com, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
 yonghong.song@...ux.dev, song@...nel.org, kernel-team@...a.com
Subject: Re: [PATCH net-next] udp: Add tracepoint for udp_sendmsg()

On 4/17/25 1:34 PM, Breno Leitao wrote:
> On Thu, Apr 17, 2025 at 08:57:24AM +0200, Paolo Abeni wrote:
>> On 4/16/25 9:23 PM, Breno Leitao wrote:
>>> Add a lightweight tracepoint to monitor UDP send message operations,
>>> similar to the recently introduced tcp_sendmsg_locked() trace event in
>>> commit 0f08335ade712 ("trace: tcp: Add tracepoint for
>>> tcp_sendmsg_locked()")
>>
>> Why is it needed? what would add on top of a plain perf probe, which
>> will be always available for such function with such argument, as the
>> function can't be inlined?
> 
> Why this function can't be inlined? 

Because the kernel need to be able find a pointer to it:

	.sendmsg		= udp_sendmsg,

I'll be really curious to learn how the compiler could inline that.

/P