From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan-Philip gehrcke Subject: Read sent/received bytes -- without opening a file in /sys or /proc Date: Thu, 17 Feb 2011 11:57:29 +0100 Message-ID: <4D5CFF19.6050400@googlemail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit To: netdev@vger.kernel.org Return-path: Received: from mail-fx0-f46.google.com ([209.85.161.46]:65115 "EHLO mail-fx0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752020Ab1BQK5c (ORCPT ); Thu, 17 Feb 2011 05:57:32 -0500 Received: by fxm20 with SMTP id 20so2449033fxm.19 for ; Thu, 17 Feb 2011 02:57:31 -0800 (PST) Sender: netdev-owner@vger.kernel.org List-ID: Dear list, I'm about to write a small C program for measurements of the bandwidth on some network interface of my home router (uname -a: Linux fritz.fonwlan.box 2.6.19.2 #2 Thu Nov 18 16:35:17 CET 2010 mips GNU/Linux). I would like to accomplish very *precise* results, while keeping the absolute measurement time low. In general, this problem requires the knowledge of time and byte differences. Therefore, two time measurements and two byte counter measurements for each, received and sent bytes, are required. Currently, I am measuring time via clock_gettime(CLOCK_MONOTONIC, ...) and reading the byte counters by reading files in sysfs, e.g. /sys/class/net/${interface}/statistics/rx_bytes. This is very easy and works well, but reading these files four times takes some (varying) time* on my device, which introduces an error to my calculation. Hence, I am wondering, if there is a way to receive this kind of data directly and much faster, via "kernel API". My question is related to this unanswered one from 2005: http://linux.derkeiler.com/Mailing-Lists/RedHat/2005-02/0557.html *On my device, reading such a file and interpreting the result as integer takes 1-10 ms, measured via: clock_gettime(CLOCK_MONOTONIC, &t_start); rx_bytes = read_int_from_file("/sys/class/net/wan/statistics/rx_bytes"); clock_gettime(CLOCK_MONOTONIC, &t_end); read_int_from_file() basically consists of fopen(), fgets(), and sscanf(). Please note that I don't have kernel/driver programming experience so far. Thank you for help and any suggestions! Jan-Philip Gehrcke -- http://gehrcke.de