From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1031405AbWK3UbH (ORCPT ); Thu, 30 Nov 2006 15:31:07 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1031406AbWK3UbG (ORCPT ); Thu, 30 Nov 2006 15:31:06 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:47007 "EHLO mx2.mail.elte.hu") by vger.kernel.org with ESMTP id S1031402AbWK3UbD (ORCPT ); Thu, 30 Nov 2006 15:31:03 -0500 Date: Thu, 30 Nov 2006 21:30:26 +0100 From: Ingo Molnar To: David Miller Cc: johnpol@2ka.mipt.ru, nickpiggin@yahoo.com.au, wenji@fnal.gov, akpm@osdl.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [patch 1/4] - Potential performance bottleneck for Linxu TCP Message-ID: <20061130203026.GD14696@elte.hu> References: <456EAD6E.6040709@yahoo.com.au> <20061130102205.GA20654@2ka.mipt.ru> <20061130103240.GA25733@elte.hu> <20061130.122258.68041055.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20061130.122258.68041055.davem@davemloft.net> User-Agent: Mutt/1.4.2.2i X-ELTE-VirusStatus: clean X-ELTE-SpamScore: 0.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=0.0 required=5.9 tests=none autolearn=no SpamAssassin version=3.0.3 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * David Miller wrote: > I want to point out something which is slightly misleading about this > kind of analysis. > > Your disk I/O speed doesn't go down by a factor of 10 just because 9 > other non disk I/O tasks are running, yet for TCP that's seemingly OK > :-) disk I/O is typically not CPU bound, and i believe these TCP tests /are/ CPU-bound. Otherwise there would be no expiry of the timeslice to begin with and the TCP receiver task would always be boosted to 'interactive' status by the scheduler and would happily chug along at 500 mbits ... (and i grant you, if a disk IO test is 20% CPU bound in process context and system load is 10, then the scheduler will throttle that task quite effectively.) Ingo