From owner-freebsd-stable@FreeBSD.ORG Sun Nov 28 02:18:28 2004 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id D30F016A4CE for ; Sun, 28 Nov 2004 02:18:28 +0000 (GMT) Received: from auk2.snu.ac.kr (auk2.snu.ac.kr [147.46.100.32]) by mx1.FreeBSD.org (Postfix) with ESMTP id 73C9B43D1F for ; Sun, 28 Nov 2004 02:18:28 +0000 (GMT) (envelope-from spamrefuse@yahoo.com) Received: from [147.46.44.181] (spamrefuse@yahoo.com) by auk2.snu.ac.kr (Terrace Internet Messaging Server) with ESMTP id 2004112811:18:15:870737.21758.2860604336 for ; Sun, 28 Nov 2004 11:18:15 +0900 (KST) Message-ID: <41A93570.6050607@yahoo.com> Date: Sun, 28 Nov 2004 11:18:24 +0900 From: Rob User-Agent: Mozilla/5.0 (X11; U; FreeBSD i386; en-US; rv:1.7.3) Gecko/20041113 X-Accept-Language: en-us, en MIME-Version: 1.0 To: freebsd-stable@freebsd.org References: <41A91E7E.8050409@yahoo.com> In-Reply-To: Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit X-TERRACE-SPAMMARK: YES-__TRSYS_LV__3 (SR:-1.27) (SRN:SPAMROBOT) ----------------- Subject: Re: make -j$n buildworld : use of -j investigated X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sun, 28 Nov 2004 02:18:29 -0000 David Schwartz wrote: >>According to my formula: >> >> time(minutes) = 1e5 / ( speed(MHz) * nproc ) >> >>and taking nproc = 1, this results in >> >> time = 1e5 / 2798.66 = 36 minutes >> >>Quite accurate for your system as well. At least this formula gives a >>resonable estimate about the compile time. >> >>Apparently HT does not help much, since with SMP kernel, times do not >>get any close to 36/2 = 18 minutes. However, there is a slight improvement >>from -j1 to -j2 with SMP. > > > You're saying that HT does not help because it doesn't double the speed? > That makes no sense. HT helps if it brings the time down. If it brings it > down to 34 minutes, it helps a little. If it brings it down to 24 minutes, > it helps quite a bit. It's unrealistic to even imagine that HT will bring > anything close to the benefit of a second physical CPU. OK, sorry for me rushing into conclusions. All I tried to say was that in cases when 'nproc' plays are role, then nproc=2 with a second CPU, but it is somewhere between 1 and 2 for HT systems; possibly closer to 1 than to 2 (but indeed still larger than 1 !) Rob.