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From: Jamie Lokier <lk@tantalophile.demon.co.uk>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: dean gaudet <dean-list-linux-kernel@arctic.org>,
	alexander.eichhorn@rz.tu-ilmenau.de,
	linux-kernel@vger.kernel.org
Subject: Re: [Question] Explanation of zero-copy networking
Date: Tue, 8 May 2001 18:20:55 +0200	[thread overview]
Message-ID: <20010508182055.A19608@pcep-jamie.cern.ch> (raw)
In-Reply-To: <Pine.LNX.4.33.0105071106470.10009-100000@twinlark.arctic.org> <E14wt2p-00048d-00@the-village.bc.nu>
In-Reply-To: <E14wt2p-00048d-00@the-village.bc.nu>; from alan@lxorguk.ukuu.org.uk on Mon, May 07, 2001 at 10:59:52PM +0100

Alan Cox wrote:
> > so there's still single copy for write() of a mmap()ed page?
> 
> An mmap page will go direct to disk.

Looking at the 2.4.4 code, mmap() of file followed by write() to socket
will copy the data once.

I could be mistaken (only glanced at the code quickly) but I base that
on the only call to ->sendpage being through sendfile.

So yes, there's a single copy overhead for mmap()+write().

-- Jamie

      reply	other threads:[~2001-05-08 16:21 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2001-05-07 13:43 Alexander Eichhorn
2001-05-07 13:56 ` Alan Cox
2001-05-07 16:12   ` Richard B. Johnson
2001-05-07 17:53     ` Francois Romieu
2001-05-07 18:00       ` Blue Lang
2001-05-07 18:25     ` dean gaudet
2001-05-07 19:54       ` Richard B. Johnson
2001-05-07 20:23         ` dean gaudet
2001-05-08 11:09         ` Bjorn Wesen
2001-05-08 17:30         ` Alexander Eichhorn
2001-05-09  9:56           ` Reto Baettig
2001-05-07 18:30     ` Pekka Pietikainen
2001-05-07 19:00       ` Venkatesh Ramamurthy
2001-05-08  7:18     ` Jamie Lokier
2001-05-09 15:13       ` Eric W. Biederman
2001-05-07 18:21   ` dean gaudet
2001-05-07 21:59     ` Alan Cox
2001-05-08 16:20       ` Jamie Lokier [this message]

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