From owner-freebsd-stable@FreeBSD.ORG Mon Apr 12 09:49:16 2010 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 9B56B106566C for ; Mon, 12 Apr 2010 09:49:16 +0000 (UTC) (envelope-from bms@incunabulum.net) Received: from out2.smtp.messagingengine.com (out2.smtp.messagingengine.com [66.111.4.26]) by mx1.freebsd.org (Postfix) with ESMTP id 671268FC19 for ; Mon, 12 Apr 2010 09:49:16 +0000 (UTC) Received: from compute1.internal (compute1.internal [10.202.2.41]) by gateway1.messagingengine.com (Postfix) with ESMTP id CC960EAA79 for ; Mon, 12 Apr 2010 05:49:15 -0400 (EDT) Received: from heartbeat2.messagingengine.com ([10.202.2.161]) by compute1.internal (MEProxy); Mon, 12 Apr 2010 05:49:15 -0400 DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d=messagingengine.com; h=message-id:date:from:mime-version:to:subject:references:in-reply-to:content-type:content-transfer-encoding; s=smtpout; bh=WFW8/XVHK0Z8A/p0YKb+W7aEtEI=; b=Db6s+q9d8I6C/cQnmWtl0esNq/dK6uK29CTuGEIBD/LqrYzB7c2l2/b5l1Lte/NLwvhwuVolpLxxgfQdu0haXzQKao03QJrqH5P0NUpMxokXW1phRFyF53dFTAdb+JaJTbGaN/zIdyRcIh8/82vyc54zV1tWHF8+Q4g9A2KVJHY= X-Sasl-enc: E4tm6b3D6Cimi7D1HQqj37kJCf7Jj+LLl7P/YCTedBcU 1271065755 Received: from anglepoise.lon.incunabulum.net (cpc2-dals7-0-0-cust253.hari.cable.virginmedia.com [82.35.112.254]) by mail.messagingengine.com (Postfix) with ESMTPSA id 734AF2ECF for ; Mon, 12 Apr 2010 05:49:15 -0400 (EDT) Message-ID: <4BC2EC9A.2020207@incunabulum.net> Date: Mon, 12 Apr 2010 10:49:14 +0100 From: Bruce Simpson User-Agent: Mozilla/5.0 (X11; U; FreeBSD amd64; en-US; rv:1.9.1.9) Gecko/20100406 Thunderbird/3.0.4 MIME-Version: 1.0 To: freebsd-stable@freebsd.org References: <20100412.131213.4959786962516027.chat95@mac.com> In-Reply-To: <20100412.131213.4959786962516027.chat95@mac.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: Only 70% of theoretical peak performance on FreeBSD 8/amd64, Corei7 920 X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 12 Apr 2010 09:49:16 -0000 On 04/12/10 05:12, Maho NAKATA wrote: > *Abstract* > I compared the peak performance of FreeBSD 8.0/amd64 and Ubuntu 9.10 amd64 using dgemm > (a linear algebra routine, matrix-matrix multiplication). > I obtained only 70% of theoretical peak performance on FreeBSD 8/amd64 and > almost 95% on Ubuntu 9.10 /amd64. I'm really disappointed. > So, where's the profiling to discover why this is the case? Also I'm not clear on what constitutes 'theoretical peak performance' here or how it is being calculated. So figures like these come across as unscientific. I'm sure this is something which can be resolved if someone sits down, profiles the app, and makes the necessary adjustments (e.g. pthread_setaffinity_np()) to configure CPU affinity, if the lack of it is pessimizing your friend's app. The PMC framework is rapidly maturing, and you can use KCacheGrind with it to visualize context switch overhead. But I think it's expecting a bit much to post informal results to -stable, in an expectation of something other thaninformal suggestions of what may help someone's maths-intensive application. If there are performance issues, then reproducible results are needed, as well as some basic profiling effort of the system elements involved, before people could say anything either way, or offer further help. cheers, BMS