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

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Message-ID: <CANn89i+X4+w91MwZNW7qsb9dK3W0s72iehh5Kkb077ApTis_Vg@mail.gmail.com>
Date:   Mon, 27 Jun 2022 21:33:34 +0200
From:   Eric Dumazet <edumazet@...gle.com>
To:     Cong Wang <xiyou.wangcong@...il.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 Mon, Jun 27, 2022 at 9:25 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> 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.
>

Make sure to include lkml for this discussion :

Vast majority (100%) of TP_printk() using %p use %p, not %px

$ git grep -n TP_printk|grep %p|wc -l
425
$ git grep -n TP_printk|grep %px|wc -l
0


> Thanks.