From owner-freebsd-current@FreeBSD.ORG Wed Oct 27 18:40:41 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 BFD3516A4CE; Wed, 27 Oct 2004 18:40:41 +0000 (GMT) Received: from avscan2.sentex.ca (avscan2.sentex.ca [199.212.134.19]) by mx1.FreeBSD.org (Postfix) with ESMTP id 56EBF43D39; Wed, 27 Oct 2004 18:40:41 +0000 (GMT) (envelope-from mike@sentex.net) Received: from localhost (localhost.sentex.ca [127.0.0.1]) by avscan2.sentex.ca (8.12.11/8.12.11) with ESMTP id i9RIefRd023092; Wed, 27 Oct 2004 14:40:41 -0400 (EDT) (envelope-from mike@sentex.net) Received: from avscan2.sentex.ca ([127.0.0.1]) by localhost (avscan2.sentex.ca [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 22805-04; Wed, 27 Oct 2004 14:40:41 -0400 (EDT) Received: from lava.sentex.ca (pyroxene.sentex.ca [199.212.134.18]) by avscan2.sentex.ca (8.12.11/8.12.11) with ESMTP id i9RIefB2023071; Wed, 27 Oct 2004 14:40:41 -0400 (EDT) (envelope-from mike@sentex.net) Received: from simian.sentex.net (simeon.sentex.ca [192.168.43.27]) by lava.sentex.ca (8.12.11/8.12.11) with ESMTP id i9RIeXsj000447; Wed, 27 Oct 2004 14:40:34 -0400 (EDT) (envelope-from mike@sentex.net) Message-Id: <6.1.2.0.0.20041027144023.0952bfb8@64.7.153.2> X-Sender: mdtpop@64.7.153.2 (Unverified) X-Mailer: QUALCOMM Windows Eudora Version 6.1.2.0 Date: Wed, 27 Oct 2004 14:47:32 -0400 To: John Baldwin , freebsd-current@FreeBSD.org From: Mike Tancsa In-Reply-To: <200410271400.31895.jhb@FreeBSD.org> References: <6.1.2.0.0.20041022113405.08fe2c48@64.7.153.2> <200410271400.31895.jhb@FreeBSD.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii"; format=flowed X-Virus-Scanned: by amavisd-new X-Virus-Scanned: by amavisd-new at avscan2b 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 18:40:41 -0000 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.html) ... So if it provides a cleaner / more stable way to talk to the devices, I will certainly run with it. ---Mike