From: "David S. Miller" <davem@redhat.com>
To: matti.aarnio@zmailer.org
Cc: hurwitz@lanl.gov, linux-kernel@vger.kernel.org
Subject: Re: How many copies to get from NIC RX to user read()?
Date: Wed, 10 Jul 2002 19:12:12 -0700 (PDT) [thread overview]
Message-ID: <20020710.191212.08323174.davem@redhat.com> (raw)
In-Reply-To: <20020710112916.R28720@mea-ext.zmailer.org>
From: Matti Aarnio <matti.aarnio@zmailer.org>
Date: Wed, 10 Jul 2002 11:29:16 +0300
I suspect that in many cases there is third copy right in the network
card driver to realign data so that TCP frame begins at a 32-bit boundary.
Perhaps that is only for RISC CPU systems (e.g. Alpha, primarily.)
Can the GigE cards do ethernet-frame reception pre-alignment so that
after the 14 byte ethernet header, the TCP frame begins at 32-bit
boundary ?
All gigabit chips allow to start the receive DMA buffer on a 2-byte
aligned boundary. The exception is the ns83820. Andi Kleen had some
ideas of how to deal with even the ns83820 type chips without copying
anything more than the headers (ie. not the data portion).
next prev parent reply other threads:[~2002-07-11 2:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-09 22:29 Hurwitz Justin W.
2002-07-09 23:11 ` Alan Cox
2002-07-10 8:29 ` Matti Aarnio
2002-07-11 2:12 ` David S. Miller [this message]
2002-07-10 15:52 niv
2002-07-10 21:15 ` Hurwitz Justin W.
2002-07-10 21:27 ` Nivedita Singhvi
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