From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net-next] net: introduce a new tracepoint for tcp_rcv_space_adjust Date: Mon, 16 Apr 2018 08:43:31 -0700 Message-ID: References: <1523892818-12820-1-git-send-email-laoar.shao@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: kuznet@ms2.inr.ac.ru, yoshfuji@linux-ipv6.org, songliubraving@fb.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Yafang Shao , davem@davemloft.net Return-path: In-Reply-To: <1523892818-12820-1-git-send-email-laoar.shao@gmail.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On 04/16/2018 08:33 AM, Yafang Shao wrote: > tcp_rcv_space_adjust is called every time data is copied to user space, > introducing a tcp tracepoint for which could show us when the packet is > copied to user. > This could help us figure out whether there's latency in user process. > > When a tcp packet arrives, tcp_rcv_established() will be called and with > the existed tracepoint tcp_probe we could get the time when this packet > arrives. > Then this packet will be copied to user, and tcp_rcv_space_adjust will > be called and with this new introduced tracepoint we could get the time > when this packet is copied to user. > > arrives time : user process time => latency caused by user > tcp_probe tcp_rcv_space_adjust > > Hence in the prink message, sk is printed as a key to connect these two > tracepoints. > socket pointer is not a key. TCP sockets can be reused pretty fast after free. I suggest you go for cookie instead, this is an unique 64bit identifier. ( sock_gen_cookie() for details )