From owner-freebsd-arm@FreeBSD.ORG Sat Mar 23 18:33:03 2013 Return-Path: Delivered-To: freebsd-arm@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 E2A98225F for ; Sat, 23 Mar 2013 18:33:03 +0000 (UTC) (envelope-from ian@FreeBSD.org) Received: from mho-01-ewr.mailhop.org (mho-03-ewr.mailhop.org [204.13.248.66]) by mx1.freebsd.org (Postfix) with ESMTP id BE9138D8 for ; Sat, 23 Mar 2013 18:33:03 +0000 (UTC) Received: from c-24-8-230-52.hsd1.co.comcast.net ([24.8.230.52] helo=damnhippie.dyndns.org) by mho-01-ewr.mailhop.org with esmtpsa (TLSv1:AES256-SHA:256) (Exim 4.72) (envelope-from ) id 1UJTFR-000PNg-Fy; Sat, 23 Mar 2013 18:32:57 +0000 Received: from [172.22.42.240] (revolution.hippie.lan [172.22.42.240]) by damnhippie.dyndns.org (8.14.3/8.14.3) with ESMTP id r2NIWtuQ007278; Sat, 23 Mar 2013 12:32:55 -0600 (MDT) (envelope-from ian@FreeBSD.org) X-Mail-Handler: Dyn Standard SMTP by Dyn X-Originating-IP: 24.8.230.52 X-Report-Abuse-To: abuse@dyndns.com (see http://www.dyndns.com/services/sendlabs/outbound_abuse.html for abuse reporting information) X-MHO-User: U2FsdGVkX19VkKZX/cHJF5jvzcPJRrE8 Subject: Re: Preemption on MV78100 (ARMv5TE)? From: Ian Lepore To: MagnusNilsson In-Reply-To: <1364062508310-5798411.post@n5.nabble.com> References: <1364062508310-5798411.post@n5.nabble.com> Content-Type: text/plain; charset="us-ascii" Date: Sat, 23 Mar 2013 12:32:55 -0600 Message-ID: <1364063575.1157.155.camel@revolution.hippie.lan> Mime-Version: 1.0 X-Mailer: Evolution 2.32.1 FreeBSD GNOME Team Port Content-Transfer-Encoding: 7bit Cc: freebsd-arm@FreeBSD.org X-BeenThere: freebsd-arm@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Porting FreeBSD to the StrongARM Processor List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 23 Mar 2013 18:33:03 -0000 On Sat, 2013-03-23 at 11:15 -0700, MagnusNilsson wrote: > I am looking for information about FreeBSD 8.2 on Marvell MV78100 (Discovery > SOC) - an ARMv5TE - with preemption enabled. > My kernel is stable, but if I enable preemption it promptly crashes - during > or within minutes of boot. > > My configuration is similar to: > http://svn.freebsd.org/base/head/sys/arm/conf/DB-78XXX > I notice that this configuration does not have the PREEMPTION option - not > even commented - whereas many other configurations in: > http://svn.freebsd.org/base/head/sys/arm/conf/ > do have it. > > I am interested to hear if anyone has been able to run MV78100 (or similar) > with preemption enabled - and in that case what your configuration and > FreeBSD version is - or if anyone can confirm that preemption is not > implemented for this processor. > > Thank you. Can you provide any information about the crashes? In my experience with 8.2 on arm (extensive, we use it at work, but with a variety of fixes pulled in from 9 and 10), the main source of problems has been busdma cache coherency problems. A variety of such problems have been fixed since 8.2, but I'm not sure all the fixes have been merged back to the 8-stable branch. I've never tried enabling PREEMPTION, I'll give that a try. I'm not sure why you're enabling it, but something to try that may give you most of the same benefits would be to compile with HZ=1000 or even higher, to shorten the scheduling quantum. Most of our ARM configs have HZ=100, but I've successfully run with HZ=4000 even on a low-end at91 chip running at 180mhz (just to see if I could, we don't normally do that on our products at work). -- Ian