From owner-freebsd-net@FreeBSD.ORG Wed Jan 9 14:14:45 2013 Return-Path: Delivered-To: freebsd-net@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by hub.freebsd.org (Postfix) with ESMTP id 1D4F1148 for ; Wed, 9 Jan 2013 14:14:45 +0000 (UTC) (envelope-from erichsfreebsdlist@alogt.com) Received: from alogt.com (alogt.com [69.36.191.58]) by mx1.freebsd.org (Postfix) with ESMTP id CF7FA1B3 for ; Wed, 9 Jan 2013 14:14:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=alogt.com; s=default; h=Content-Transfer-Encoding:Content-Type:Mime-Version:References:In-Reply-To:Message-ID:Subject:Cc:To:From:Date; bh=d+OeePXNtDXfS5m/jnfYMUkKJyGZjc2Z7Z83kK3FoG4=; b=kIamPsXJlS3ZCP2pBX/O51lwIeyyDllnicCjSCKy8A4R/sCNmHQQEWsVBRxDy9iwlh14JXf8kCsWjl+M1NPIaStvXMFEpJ6l5B3AAor3KqHBAa2eYb93ld6JSRtNldW0; Received: from [122.129.203.50] (port=15739 helo=X220.ovitrap.com) by sl-508-2.slc.westdc.net with esmtpsa (SSLv3:DHE-RSA-AES128-SHA:128) (Exim 4.80) (envelope-from ) id 1TswQV-002Fuu-Bu; Wed, 09 Jan 2013 07:14:43 -0700 Date: Wed, 9 Jan 2013 21:14:39 +0700 From: Erich Dollansky To: Barney Cordoba Subject: Re: To SMP or not to SMP Message-ID: <20130109211439.5b590bf5@X220.ovitrap.com> In-Reply-To: <1357738813.28186.YahooMailClassic@web121601.mail.ne1.yahoo.com> References: <20130109130133.0399a6cc@X220.ovitrap.com> <1357738813.28186.YahooMailClassic@web121601.mail.ne1.yahoo.com> X-Mailer: Claws Mail 3.9.0 (GTK+ 2.24.6; amd64-portbld-freebsd10.0) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - sl-508-2.slc.westdc.net X-AntiAbuse: Original Domain - freebsd.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - alogt.com X-Get-Message-Sender-Via: sl-508-2.slc.westdc.net: authenticated_id: erichsfreebsdlist@alogt.com X-Source: X-Source-Args: X-Source-Dir: Cc: freebsd-net@freebsd.org, jack.vogel@gmail.com, Mark Atkinson X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 09 Jan 2013 14:14:45 -0000 Hi, On Wed, 9 Jan 2013 05:40:13 -0800 (PST) Barney Cordoba wrote: > --- On Wed, 1/9/13, Erich Dollansky > wrote: > > From: Erich Dollansky > > Subject: Re: To SMP or not to SMP > > To: "Mark Atkinson" > > Cc: freebsd-net@freebsd.org > > Date: Wednesday, January 9, 2013, 1:01 AM > > Hi, > > > > On Tue, 08 Jan 2013 08:29:51 -0800 > > Mark Atkinson > > wrote: > > > > > -----BEGIN PGP SIGNED MESSAGE----- > > > Hash: SHA1 > > > > > > On 01/07/2013 18:25, Barney Cordoba wrote: > > > > I have a situation where I have to run 9.1 on an > > old single core > > > > box. Does anyone have a handle on whether it's > > better to build a > > > > non SMP kernel or to just use a standard SMP build > > with just the > > > > one core? Thanks. > > > > > > You can build a SMP kernel, but you'll get better > > performance (in my > > > experience) with SCHED_4BSD on single cpu than with > > ULE. > > > > > I would not say so. The machine behaves different with the > > two > > schedulers. It depends mostly what you want to do with the > > machine. I > > forgot which scheduler I finally left in the single CPU > > kernel. > > > > Erich > > 4BSD runs pretty well with an SMP kernel. I can test ULE and compare > easily. A no SMP kernel is problematic as the igb driver doesn't seem > to work and my onboard NICs are, sadly, igb. > this is bad luck. I know of the kernels as I have had SMP and single CPU machines since 4.x times. > Rather than say "depends what you want to do", perhaps an explanation > of which cases you might choose one or the other would be helpful. > > So can anyone in the know confirm that the kernel really isn't smart > enough to know there there's only 1 core so that most of the SMP The kernel does not think like this. It is a fixed program flow. > "overhead" is avoided? It seems to me that SMP scheduling should only > be enabled if there is more than 1 core as part of the scheduler > initialization. Its arrogant indeed to assume that just because SMP > support is compiled in that there are multiple cores. I compile my own kernels and set the parameters as needed. Erich