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

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Message-ID: <CANn89iKRU6QDfmRa=YikyGHjC=v-8RepTWHtHPMQivAqP=gt2Q@mail.gmail.com>
Date:   Mon, 27 Jun 2022 21:46:41 +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 <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 9:41 PM Cong Wang <xiyou.wangcong@...il.com> wrote:
>
> On Mon, Jun 27, 2022 at 12:33 PM Eric Dumazet <edumazet@...gle.com> wrote:
> >
> > 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 :
>
> Already did:
> https://lore.kernel.org/all/CAM_iQpV3Qm_GTfCX1E_OC0PXu+diT9QHtPt4OYcJdyGRcA37Sw@mail.gmail.com/
>
> >
> > 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
>
> You are changing this topic, no one here in this thread cares about non-skb
> addresses.
>

I will not ack a revert.

Unless you get ACK from Linus Torvalds maybe.

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