Messages in this thread | | | Date | Wed, 10 Jul 2002 19:12:12 -0700 (PDT) | Subject | Re: How many copies to get from NIC RX to user read()? | From | "David S. Miller" <> |
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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). - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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