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Date:      Mon, 11 Aug 2014 20:33:44 +0200
From:      Luigi Rizzo <rizzo@iet.unipi.it>
To:        Adrian Chadd <adrian@freebsd.org>
Cc:        Victor Balada Diaz <victor@bsdes.net>, Sushanth Rai <sushanth_rai@yahoo.com>, "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org>
Subject:   Re: Support for zero copy sockets
Message-ID:  <CA%2BhQ2%2Bjcd%2BVsnVucch00O5SwRAQWdDvCqmR=z=NaPiUkmvEPTA@mail.gmail.com>
In-Reply-To: <CAJ-VmonTYPz7qJ3WG52ADp69FdYQkKQ6D_DOM1piEybGwgOmWA@mail.gmail.com>
References:  <1407171616.44440.YahooMailBasic@web181702.mail.ne1.yahoo.com> <20140811082610.GF7828@equilibrium.bsdes.net> <CAJ-VmonTYPz7qJ3WG52ADp69FdYQkKQ6D_DOM1piEybGwgOmWA@mail.gmail.com>

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On Monday, August 11, 2014, Adrian Chadd <adrian@freebsd.org> wrote:

> On 11 August 2014 01:26, Victor Balada Diaz <victor@bsdes.net
> <javascript:;>> wrote:
> > On Mon, Aug 04, 2014 at 10:00:16AM -0700, Sushanth Rai via
> freebsd-hackers wrote:
> >> Hello,
> >>
> >> FreeBSD 10 release sources doesn't seem to have zero copy socket code
> anymore. What's is alternative to do zero_copy ?
> >>
> >> Thanks,
> >> Sushanth
> >
> > You need to use sendfile(2). In the man page is stated that the
> implementation in FreeBSD
> > is zero copy.
> >
> > You can also check:
> >
> > http://svnweb.freebsd.org/base?view=revision&revision=255608
> >
>
> I'd like to reintroduce a zero copy socket IO method for at least
> write that doesn't rely on sendfile.
>
> The zero-copy socket page flipping thing was interesting because IIRC
> tried to work for both sending and receiving socket data. Doing that
> via an API would be nicer.
>
> So, if people have an idea for how it could be done / what the API
> looks like then I'm all ears.
>
>
What concerns me is how expensive it is to do the page flipping and tlb
invalidation. Not saying that it cannot work, but isn't there a large set
of constraints to make it worthwhile ?

Cheers
Luigi


>
>
> -a
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> <javascript:;>"
>


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 Prof. Luigi RIZZO, rizzo@iet.unipi.it  . Dip. di Ing. dell'Informazione
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