From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Miller Subject: Re: [tbench regression fixes]: digging out smelly deadmen. Date: Fri, 31 Oct 2008 16:51:44 -0700 (PDT) Message-ID: <20081031.165144.86556444.davem@davemloft.net> References: <20081031125713.6c6923de@extreme> <20081031201016.GA4748@ioremap.net> <490B7284.2010003@cosmosbay.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: zbr@ioremap.net, shemminger@vyatta.com, ilpo.jarvinen@helsinki.fi, rjw@sisk.pl, mingo@elte.hu, s0mbre@tservice.net.ru, a.p.zijlstra@chello.nl, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, efault@gmx.de, akpm@linux-foundation.org To: dada1@cosmosbay.com Return-path: Received: from 74-93-104-97-Washington.hfc.comcastbusiness.net ([74.93.104.97]:52779 "EHLO sunset.davemloft.net" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1750965AbYJaXwK convert rfc822-to-8bit (ORCPT ); Fri, 31 Oct 2008 19:52:10 -0400 In-Reply-To: <490B7284.2010003@cosmosbay.com> Sender: netdev-owner@vger.kernel.org List-ID: =46rom: Eric Dumazet Date: Fri, 31 Oct 2008 22:03:00 +0100 > Evgeniy Polyakov a =E9crit : > > On Fri, Oct 31, 2008 at 12:57:13PM -0700, Stephen Hemminger (shemmi= nger@vyatta.com) wrote: > >> Why bother with last_rx at all on loopback. I have been thinking > >> we should figure out a way to get rid of last_rx all together. It = only > >> seems to be used by bonding, and the bonding driver could do the c= alculation > >> in its receive handling. > > Not related to the regression: bug will be just papered out by this > > changes. Having bonding on loopback is somewhat strange idea, but s= till > > this kind of changes is an attempt to make a good play in the bad g= ame: > > this loopback-only optimization does not fix the problem. >=20 > Just to be clear, this change was not meant to be committed. > It already was rejected by David some years ago (2005, and 2006) >=20 > http://www.mail-archive.com/netdev@vger.kernel.org/msg07382.html However, I do like Stephen's suggestion that maybe we can get rid of this ->last_rx thing by encapsulating the logic completely in the bonding driver. > If you read my mail, I was *only* saying that tbench results can be s= ensible to > cache line ping pongs. tbench is a crazy benchmark, and only is a cra= zy benchmark. >=20 > Optimizing linux for tbench sake would be .... crazy ? Unlike dbench I think tbench is worth cranking up as much as possible. It doesn't have a huge memory working set, it just writes mostly small messages over a TCP socket back and forth, and does a lot of blocking And I think we'd like all of those operating to run as fast as possible= =2E When Tridge first wrote tbench I would see the expected things at the top of the profiles. Things like tcp_ack(), copy to/from user, and perhaps SLAB. Things have changed considerably.