From owner-freebsd-arch@FreeBSD.ORG Wed Mar 23 11:54:52 2011 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 23D0B1065670; Wed, 23 Mar 2011 11:54:52 +0000 (UTC) (envelope-from jhb@freebsd.org) Received: from cyrus.watson.org (cyrus.watson.org [65.122.17.42]) by mx1.freebsd.org (Postfix) with ESMTP id 96BB68FC19; Wed, 23 Mar 2011 11:54:51 +0000 (UTC) Received: from bigwig.baldwin.cx (66.111.2.69.static.nyinternet.net [66.111.2.69]) by cyrus.watson.org (Postfix) with ESMTPSA id 3638346B09; Wed, 23 Mar 2011 07:54:51 -0400 (EDT) Received: from jhbbsd.localnet (unknown [209.249.190.124]) by bigwig.baldwin.cx (Postfix) with ESMTPSA id C347E8A02A; Wed, 23 Mar 2011 07:54:50 -0400 (EDT) From: John Baldwin To: Ed Maste Date: Wed, 23 Mar 2011 07:51:56 -0400 User-Agent: KMail/1.13.5 (FreeBSD/7.4-CBSD-20110107; KDE/4.4.5; amd64; ; ) References: <201103221551.14289.jhb@freebsd.org> <20110322224554.GA67925@sandvine.com> In-Reply-To: <20110322224554.GA67925@sandvine.com> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201103230751.56647.jhb@freebsd.org> X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.2.6 (bigwig.baldwin.cx); Wed, 23 Mar 2011 07:54:50 -0400 (EDT) Cc: "Bjoern A. Zeeb" , freebsd-arch@freebsd.org Subject: Re: kernel memory checks on boot vs. boot time X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 23 Mar 2011 11:54:52 -0000 On Tuesday, March 22, 2011 6:45:54 pm Ed Maste wrote: > On Tue, Mar 22, 2011 at 03:51:13PM -0400, John Baldwin wrote: > > > Do other platforms bother with these sorts of memory tests? If not I'd vote > > to just drop it. I think this mattered more when you didn't have things like > > SMAP (so you had to guess at where memory ended sometimes). Also, modern > > server class x86 machines generally support ECC RAM which will trigger a > > machine check if there is a problem. I doubt that the early checks are > > catching anything even for the non-ECC case. > > In the common case at work we want this off to reduce boot time. The > desire for a tunable though that can add extended memory tests is to be > able to use the FreeBSD startup code as a replacement for memtest86+, > for a couple of reasons: > > - FreeBSD's serial console output is more easily parsed by automated > tools > - Memtest86+ appears to be limited to 64GB of RAM at the moment > - Memtest86+ lacks support for the Tylersburg architecture last I looked The existing memory check is nowhere near the level of what memtest86+ does and relying on that to give you the same testing strength as memtest86+ seems very dubious to me. If you want a real memory tester, I'd be tempted to just write a custom kernel for that, probably still using BIOS routines for I/O similar to the boot loader, etc. You'd also want to install a MC handler before kicking off the test, but you would want to minimize the amount of RAM you used so you could test as much of the RAM as possible. -- John Baldwin