From mboxrd@z Thu Jan 1 00:00:00 1970 From: Evgeniy Polyakov Subject: Re: loaded router, excessive getnstimeofday in oprofile Date: Wed, 27 Aug 2008 00:51:58 +0400 Message-ID: <20080826205158.GA15266@2ka.mipt.ru> References: <200808220457.40892.denys@visp.net.lb> <20080826201406.GA24827@2ka.mipt.ru> <48B46B48.7030609@cosmosbay.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Denys Fedoryshchenko , netdev@vger.kernel.org, linux-kernel@vger.kernel.org To: Eric Dumazet Return-path: Received: from relay.2ka.mipt.ru ([194.85.80.65]:60274 "EHLO 2ka.mipt.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757130AbYHZUwV (ORCPT ); Tue, 26 Aug 2008 16:52:21 -0400 Content-Disposition: inline In-Reply-To: <48B46B48.7030609@cosmosbay.com> Sender: netdev-owner@vger.kernel.org List-ID: On Tue, Aug 26, 2008 at 10:44:56PM +0200, Eric Dumazet (dada1@cosmosbay.com) wrote: > >Do you have any packet sockets in this system? Like running dhcp daemon? > > > > Another way to see this problem can be to start a sniffer on the machine, > even with a restrictive pcap filter, to check if performance change or not. > (It should decrease) Or just check /proc/net/packet iirc. Anyway, having at least one packet socket ends up with timestamping of each packet, so you will get fair load of getnstimeofday() in that case. > For example, I believe that running "ping" could have the same effect > (increasing netstamp_needed variable : every incoming packet has to be > timestamped) > > So beware of pings, traceroute and other networking tools... Yup, this innocent toys can end up with this such behaviour on modern highly loaded machines. -- Evgeniy Polyakov