netdev - Re: [PATCH net-next v2] net: Print hashed skb addresses for all net and qdisc events

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Date:   Fri, 8 Jul 2022 16:18:28 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     "Subash Abhinov Kasiviswanathan (KS)" <quic_subashab@...cinc.com>,
        David Miller <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        quic_jzenner@...cinc.com, "Cong Wang ." <cong.wang@...edance.com>,
        Qitao Xu <qitao.xu@...edance.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Sean Tranchetti <quic_stranche@...cinc.com>
Subject: Re: [PATCH net-next v2] net: Print hashed skb addresses for all net
 and qdisc events

On Sat, 2 Jul 2022 21:36:19 -0700
Cong Wang <xiyou.wangcong@...il.com> wrote:

> > Matching skbs addresses (in a particular format) helps to track the
> > packet traversal timings / delays in processing.  
> 
> So... how didn't you notice the duplicated addresses with hashed ones?
> It is 100% reproducible to see duplicates with hashed ones.

Yes the hashes are reproducible giving the same address for this exact
purpose (to match like addresses).

I'm not sure if your last sentence was a question or a statement (it did
not end with a question mark).

But I agree with this patch that the trace events that reference the same
address should be consistent in its use of %p and %px, where it uses one or
the other and not mix and match. Because the value itself may not be
important to a trace, but knowing that the value is consistent throughout
the trace with different tracepoints is.

-- Steve