netdev - Re: [PATCH net-next] net: Print real skb addresses for all net events

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Message-ID: <YroEC3NV3d1yTnqi@pop-os.localdomain>
Date:   Mon, 27 Jun 2022 12:24:59 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Subash Abhinov Kasiviswanathan <quic_subashab@...cinc.com>,
        David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        netdev <netdev@...r.kernel.org>, quic_jzenner@...cinc.com,
        Cong Wang <cong.wang@...edance.com>, qitao.xu@...edance.com,
        Sean Tranchetti <quic_stranche@...cinc.com>
Subject: Re: [PATCH net-next] net: Print real skb addresses for all net events

On Fri, Jun 24, 2022 at 08:27:34AM +0200, Eric Dumazet wrote:
> On Fri, Jun 24, 2022 at 8:09 AM Subash Abhinov Kasiviswanathan
> <quic_subashab@...cinc.com> wrote:
> >
> > Commit 65875073eddd ("net: use %px to print skb address in trace_netif_receive_skb")
> > added support for printing the real addresses for the events using
> > net_dev_template.
> >
> 
> It is not clear why the 'real address' is needed in trace events.

Because hashed address is _further_ from being unique, we could even
observe same hashed addresses with a few manually injected packets.

Real address is much better. Although definitely it can't guarantee
uniqueness, it is already the cheapest way to identify the packets in
tracing. (Surely you can add an ID generator or something similiar, but
nothing is cheaper than just using the real address.)

> 
> I would rather do the opposite.
>

Strongly disagree. I will sent a revert.

Thanks.