From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Lameter Subject: Re: AIM9 regression Date: Mon, 29 Sep 2008 09:54:11 -0500 Message-ID: <48E0EC13.3060907@linux-foundation.org> References: <20080924051237.GA6173@gondor.apana.org.au> <20080923.221831.126801015.davem@davemloft.net> <20080924081603.08a5f808@extreme> <20080924.123657.217162945.davem@davemloft.net> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: David Miller , shemminger@vyatta.com, herbert@gondor.apana.org.au, netdev@vger.kernel.org To: =?ISO-8859-1?Q?Ilpo_J=E4rvinen?= Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:50912 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751411AbYI2OzF (ORCPT ); Mon, 29 Sep 2008 10:55:05 -0400 In-Reply-To: Sender: netdev-owner@vger.kernel.org List-ID: Ilpo J=E4rvinen wrote: > ...I was thinking earlier to answer "time?", but now once been there,= it=20 > seems that more time is more appropriate... So far I haven't been abl= e to=20 > find a way to create a reproducable serie of result numbers with aim9= =20 > tcp_test... it seems that the results vary within that (at least) 20%= =20 > margin. Can Christoph actually get stable numbers out of it with 27-r= cs > (I haven't extensively tested .22 yet with long test durations but it= =20 > seems that same problem occurs with it as well if short tests were us= ed)? Results fluctuate between 10 - 25%. The problem occurs with the short durations as well. If this is due to the additional code complexity in = later kernels as we suspect then it may be an issue with cpu cache effectiven= ess. Going to 64 bit binaries also yields a significant hit (as high as 30%)= which also indicates caching issues. Both 64 bit kernels and later kernels cause the variability of results = to increase. 64 bit has double the effect than a 2.6.27 kernel. All indica= tions of cpu caching issues. The L1 cache may become ineffective due to the increased cache footprint.