Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754364AbYJaJkf (ORCPT ); Fri, 31 Oct 2008 05:40:35 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752822AbYJaJkV (ORCPT ); Fri, 31 Oct 2008 05:40:21 -0400 Received: from courier.cs.helsinki.fi ([128.214.9.1]:35253 "EHLO mail.cs.helsinki.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752004AbYJaJkT (ORCPT ); Fri, 31 Oct 2008 05:40:19 -0400 Date: Fri, 31 Oct 2008 11:40:16 +0200 (EET) From: "=?ISO-8859-1?Q?Ilpo_J=E4rvinen?=" X-X-Sender: ijjarvin@wrl-59.cs.helsinki.fi To: David Miller cc: shemminger@vyatta.com, zbr@ioremap.net, rjw@sisk.pl, mingo@elte.hu, s0mbre@tservice.net.ru, a.p.zijlstra@chello.nl, LKML , Netdev , efault@gmx.de, Andrew Morton Subject: Re: [tbench regression fixes]: digging out smelly deadmen. In-Reply-To: <20081031.005219.141937694.davem@davemloft.net> Message-ID: References: <20081026122300.GA30905@ioremap.net> <20081030111526.7d9bb0f8@extreme> <20081031.005219.141937694.davem@davemloft.net> MIME-Version: 1.0 Content-Type: MULTIPART/MIXED; BOUNDARY="-696208474-739433781-1225446016=:7072" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2710 Lines: 60 This message is in MIME format. The first part should be readable text, while the remaining parts are likely unreadable without MIME-aware tools. ---696208474-739433781-1225446016=:7072 Content-Type: TEXT/PLAIN; charset=iso-8859-1 Content-Transfer-Encoding: 8BIT On Fri, 31 Oct 2008, David Miller wrote: > From: "Ilpo J?rvinen" > Date: Thu, 30 Oct 2008 21:01:19 +0200 (EET) > > > On Thu, 30 Oct 2008, Stephen Hemminger wrote: > > > > > Has anyone looked into the impact of port randomization on this benchmark. > > > If it is generating lots of sockets quickly there could be an impact: > > > * port randomization causes available port space to get filled non-uniformly > > > and what was once a linear scan may have to walk over existing ports. > > > (This could be improved by a hint bitmap) > > > > > > * port randomization adds at least one modulus operation per socket > > > creation. This could be optimized by using a loop instead. > > > > I did something with AIM9's tcp_test recently (1-2 days ago depending on > > how one calculates that so didn't yet have time summarize the details in > > the AIM9 thread) by deterministicly binding in userspace and got much more > > sensible numbers than with randomized ports (2-4%/5-7% vs 25% variation > > some difference in variation in different kernel versions even with > > deterministic binding). Also, I'm still to actually oprofile and bisect > > the remaining ~4% regression (around 20% was reported by Christoph). For > > oprofiling I might have to change aim9 to do predefined number of loops > > instead of a deadline to get more consistent view on changes in per func > > runtime. > > Yes, it looks like port selection cache and locking effects are > a very real issue. > > Good find. Let me remind that it is just a single process, so no ping-pong & other lock related cache effects should play any significant role here, no? (I'm no expert though :-)). One thing I didn't mention earlier, is that I also turned on tcp_tw_recycle to get the binding to work without giving -ESOMETHING very early (also did some, possibly meaningless things, like drop_caches before each test run, might be significant only because of the test harness cause minor variantions). I intend to try w/o binding of the client end but I guess I might again get more variation between different test runs. -- i. ---696208474-739433781-1225446016=:7072-- -- 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/