From: Yafang Shao <laoar.s...@gmail.com> Date: Fri, 20 Apr 2018 23:18:26 +0800
> 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. > > 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. > With these two tracepoints, we could figure out whether the user program > processes this packet immediately or there's latency. > > Hence in the printk message, sk_cookie is printed as a key to relate > tcp_rcv_space_adjust with tcp_probe. > > Maybe we could export sockfd in this new tracepoint as well, then we > could relate this new tracepoint with epoll/read/recv* tracepoints, and > finally that could show us the whole lifespan of this packet. But we > could also implement that with pid as these functions are executed in > process context. > > Signed-off-by: Yafang Shao <laoar.s...@gmail.com> > > --- > v2 -> v3: use sock_gen_cookie in tcp_event_sk as well. > Maybe we could init sk_cookie in the stack then in other code > path we just read it other than set it. If that is needed I > will do it in another new patch. > v1 -> v2: use sk_cookie as a key suggested by Eric. Applied, thank you.
