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From: Eric Dumazet <edumazet@google.com>
To: Paolo Abeni <pabeni@redhat.com>
Cc: Jon Maloy <jmaloy@redhat.com>,
	kuba@kernel.org, passt-dev@passt.top, sbrivio@redhat.com,
	lvivier@redhat.com, dgibson@redhat.com, netdev@vger.kernel.org,
	davem@davemloft.net
Subject: Re: [PATCH v3] tcp: add support for SO_PEEK_OFF
Date: Thu, 15 Feb 2024 18:46:18 +0100	[thread overview]
Message-ID: <CANn89iKXOZdT7_ww_Jytm4wMoXAe0=pqX+M_iVpNGaHqe_9o4Q@mail.gmail.com> (raw)
In-Reply-To: <178b9f2dbb3c56fcfef46a97ea395bdd13ebfb59.camel@redhat.com>

On Thu, Feb 15, 2024 at 6:41 PM Paolo Abeni <pabeni@redhat.com> wrote:
>
> Note: please send text-only email to netdev.
>
> On Thu, 2024-02-15 at 10:11 -0500, Jon Maloy wrote:
> > I wonder if the following could be acceptable:
> >
> >  if (flags & MSG_PEEK)
> >         sk_peek_offset_fwd(sk, used);
> >  else if (peek_offset > 0)
> >        sk_peek_offset_bwd(sk, used);
> >
> >  peek_offset is already present in the data cache, and if it has the value
> >  zero it means either that that sk->sk_peek_off is unused (-1) or actually is zero.
> >  Either way, no rewind is needed in that case.
>
> I agree the above should avoid touching cold cachelines in the
> fastpath, and looks functionally correct to me.
>
> The last word is up to Eric :)
>

An actual patch seems needed.

In the current form, local variable peek_offset is 0 when !MSG_PEEK.

So the "else if (peek_offset > 0)" would always be false.

  reply	other threads:[~2024-02-15 17:46 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-02-09 22:12 [PATCH v3] tcp: add support for SO_PEEK_OFF jmaloy
2024-02-11 23:17 ` Stefano Brivio
2024-02-13 10:49 ` Paolo Abeni
2024-02-13 12:24   ` Eric Dumazet
2024-02-13 13:02     ` Paolo Abeni
2024-02-13 13:34       ` Eric Dumazet
2024-02-13 15:28         ` Paolo Abeni
2024-02-13 15:49           ` Eric Dumazet
2024-02-13 18:39             ` Paolo Abeni
2024-02-13 19:31               ` Eric Dumazet
     [not found]                 ` <20687849-ec5c-9ce5-0a18-cc80f5b64816@redhat.com>
2024-02-15 17:41                   ` Paolo Abeni
2024-02-15 17:46                     ` Eric Dumazet [this message]
2024-02-15 22:24                       ` Jon Maloy
2024-02-16  9:14                         ` Paolo Abeni
2024-02-16  9:21                           ` Eric Dumazet
     [not found]                             ` <6a9f5dec-eb0c-51ef-0911-7345f50e08f0@redhat.com>
2024-02-16 10:55                               ` Eric Dumazet
2024-02-19  2:02                               ` David Gibson
2024-02-13 23:34             ` David Gibson
2024-02-14  3:41               ` Eric Dumazet
2024-02-15  3:16                 ` David Gibson
2024-02-15  3:21               ` David Gibson
2024-02-15  9:15                 ` Eric Dumazet

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