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Date: Tue, 17 Apr 2018 00:03:32 +0800 From: Yafang Shao <laoar.shao@...il.com> To: Eric Dumazet <eric.dumazet@...il.com> Cc: David Miller <davem@...emloft.net>, Alexey Kuznetsov <kuznet@....inr.ac.ru>, yoshfuji@...ux-ipv6.org, Song Liu <songliubraving@...com>, netdev@...r.kernel.org, LKML <linux-kernel@...r.kernel.org> Subject: Re: [PATCH net-next] net: introduce a new tracepoint for tcp_rcv_space_adjust On Mon, Apr 16, 2018 at 11:43 PM, Eric Dumazet <eric.dumazet@...il.com> wrote: > > > 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 ) > > Thanks for your explanation. Will have a try. Thanks Yafang
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