linux-kernel - Re: [RFC PATCH net-next] tcp: add a tracepoint for tcp_listen_queue

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Message-ID: <20230711193612.22c9bc04@kernel.org>
Date:   Tue, 11 Jul 2023 19:36:12 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Ivan Babrou <ivan@...udflare.com>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...udflare.com, Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        David Ahern <dsahern@...nel.org>
Subject: Re: [RFC PATCH net-next] tcp: add a tracepoint for
 tcp_listen_queue_drop

On Mon, 10 Jul 2023 21:34:52 -0700 Ivan Babrou wrote:
> There's already a way to count the overall numbers of queue overflows:
> 
>     $ sudo netstat -s | grep 'listen queue'
>     4 times the listen queue of a socket overflowed
> 
> However, it's too coarse for monitoring and alerting when a user wants to
> track errors per socket and route alerts to people responsible for those
> sockets directly. For UDP there's udp_fail_queue_rcv_skb, which fills
> a similar need for UDP sockets. This patch adds a TCP equivalent.

Makes me want to revert your recent UDP tracepoint to be honest :(
We can play whack a mole like this. You said that kfree_skb fires
too often, why is that? Maybe it's an issue of someone using
kfree_skb() when they should be using consume_skb() ?