lkml.org 
[lkml]   [2002]   [Jul]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: How many copies to get from NIC RX to user read()?
From
   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/

\
 
 \ /
  Last update: 2005-03-22 13:27    [W:0.065 / U:0.408 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site