From owner-freebsd-current@FreeBSD.ORG Wed Oct 27 20:15:40 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 087D916A554 for ; Wed, 27 Oct 2004 20:15:40 +0000 (GMT) Received: from mail1.speakeasy.net (mail1.speakeasy.net [216.254.0.201]) by mx1.FreeBSD.org (Postfix) with ESMTP id D0AA443D2D for ; Wed, 27 Oct 2004 20:15:39 +0000 (GMT) (envelope-from jhb@FreeBSD.org) Received: (qmail 21443 invoked from network); 27 Oct 2004 20:15:39 -0000 Received: from dsl027-160-063.atl1.dsl.speakeasy.net (HELO server.baldwin.cx) ([216.27.160.63]) (envelope-sender ) encrypted SMTP for ; 27 Oct 2004 20:15:15 -0000 Received: from [10.50.40.221] (gw1.twc.weather.com [216.133.140.1]) (authenticated bits=0) by server.baldwin.cx (8.12.11/8.12.11) with ESMTP id i9RKF2iO022438; Wed, 27 Oct 2004 16:15:10 -0400 (EDT) (envelope-from jhb@FreeBSD.org) From: John Baldwin To: Mike Tancsa Date: Wed, 27 Oct 2004 15:09:57 -0400 User-Agent: KMail/1.6.2 References: <6.1.2.0.0.20041022113405.08fe2c48@64.7.153.2> <200410271400.31895.jhb@FreeBSD.org> <6.1.2.0.0.20041027144023.0952bfb8@64.7.153.2> In-Reply-To: <6.1.2.0.0.20041027144023.0952bfb8@64.7.153.2> MIME-Version: 1.0 Content-Disposition: inline Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <200410271509.57177.jhb@FreeBSD.org> X-Spam-Checker-Version: SpamAssassin 2.63 (2004-01-11) on server.baldwin.cx cc: freebsd-current@FreeBSD.org Subject: Re: device apic on a single processor machine X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 27 Oct 2004 20:15:40 -0000 On Wednesday 27 October 2004 02:47 pm, Mike Tancsa wrote: > At 02:00 PM 27/10/2004, John Baldwin wrote: > >On Friday 22 October 2004 11:40 am, Mike Tancsa wrote: > > > When moving from RELENG_4 to RELENG_5, I noticed that in GENERIC, the > > > options > > > > > > options SMP # Symmetric MultiProcessor Kernel > > > device apic # I/O APIC > > > > > > are enabled by default. Going forward, is this the best thing to leave > > > in my default kernel on a uniprocessor machine ? I am not using the > > > ULE scheduler either and have hyperthreading disabled in the BIOS. > > > > > > I did a search on google, and in 2003 it was said not to having either > > > on a single processor machine but its not clear if this is no longer > > > the case. > > > >You do want to drop SMP. As far as 'apic', that is less clear. If you > > have lots of PCI devices that share interrupts for the !apic case and you > > do lots of interrupt intensive tasks, then 'device apic' might help. > > There may also be cases where it hurts. There have been reports that > > access to the apic registers for things like masking sources takes longer > > than on the 8259As. > > Thanks for the feedback. I guess my question is, what constitutes "lots" ? > Typically, I strip down boxes to their bare min hardware wise so in most > cases, I dont have anything sharing interrupts (I usually turn off USB > which is the most gratuitous). But I do have a POS app that needs USB as > well as 2 PCI serial cards. In this case, I do have a lot of shared > interrupts. However, it almost never is CPU bound or has an interrupt rate > higher than 10-20%. In this case, stability is more important to me. I > have run into a number of cases where there are interrupt storms (e.g > http://lists.freebsd.org/pipermail/freebsd-current/2004-September/036967.ht >ml) > > ... So if it provides a cleaner / more stable way to talk to the devices, I > will certainly run with it. I would try it both ways and see if one works better than the other. -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org