From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: lk@tantalophile.demon.co.uk (Jamie Lokier)
Cc: alan@lxorguk.ukuu.org.uk (Alan Cox), dank@kegel.com (Dan Kegel),
linux-kernel@vger.kernel.org (linux-kernel@vger.kernel.org),
zab@zabbo.net (Zach Brown)
Subject: Re: is CONFIG_PACKET_MMAP always a win?
Date: Fri, 22 Feb 2002 19:57:33 +0000 (GMT) [thread overview]
Message-ID: <E16eLoz-0002vD-00@the-village.bc.nu> (raw)
In-Reply-To: <20020222190431.A16926@kushida.apsleyroad.org> from "Jamie Lokier" at Feb 22, 2002 07:04:31 PM
> > You can process them in the ring buffer. If you can't keep up then you
> > are screwed any way you look at it 8)
>
> That still doesn't avoid copying: af_packet copies the whole packet (if
> you want the whole packet) from the original skbuff to the ring buffer.
I'd make a handwaved claim that the first copy of the packet from a DMA
receiving source is free. Its certainly pretty close to free because the
overhead of sucking it into L1 cache will dominate and you need to do that
anyway.
Zero copy is sometimes a false friend.
next prev parent reply other threads:[~2002-02-22 19:43 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-02-22 1:51 Dan Kegel
2002-02-22 2:33 ` Alan Cox
2002-02-22 5:59 ` David S. Miller
2002-02-22 6:45 ` Ben Greear
2002-02-22 7:04 ` Dan Kegel
2002-02-22 14:04 ` Maciej W. Rozycki
2002-02-22 8:37 ` Gianni Tedesco
2002-02-22 18:09 ` Jamie Lokier
2002-02-22 18:40 ` Alan Cox
2002-02-22 19:04 ` Jamie Lokier
2002-02-22 19:57 ` Alan Cox [this message]
2002-02-22 21:44 ` Mike Fedyk
2002-02-23 0:24 ` Alan Cox
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