From owner-freebsd-questions@FreeBSD.ORG Tue Feb 24 18:47:37 2015 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 7C20B6B9 for ; Tue, 24 Feb 2015 18:47:37 +0000 (UTC) Received: from mail-qa0-x22a.google.com (mail-qa0-x22a.google.com [IPv6:2607:f8b0:400d:c00::22a]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 2E2193F0 for ; Tue, 24 Feb 2015 18:47:37 +0000 (UTC) Received: by mail-qa0-f42.google.com with SMTP id w8so28453735qac.1 for ; Tue, 24 Feb 2015 10:47:36 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=message-id:date:from:user-agent:mime-version:to:subject:references :in-reply-to:content-type:content-transfer-encoding; bh=ftRIndMqLlzmxIr68qInQ+N3OuXhFNjvoXzGuoiANpA=; b=CAeVhnQoFQEaFinZcG7IHfHgvuxW1fdsJn3LesnYhtMwmh4Pzg9Z8+d/KaY+f2WQE7 fCSLFQwyRetNzJKgMnO9Ug5KHgTTOjXSbO2CLJ/YQtoE2+Aiit10mtlJTZ8b3eBzaFYG KrmwcIF1L0znlhnRbpXTqdpPqv5GlnMrvjJlt4u6GNgwjnYn/zBnmoC09SPUPnbIEdNQ w+zPaS0lZ1Ra3Ez694mMKytSu4C1GkwB/VRnGyBfa4D/dIVerJZkWbOGY9BYGu3GAY2I SgimPy6tYnIg+sjVj4cwqTNoSAPKQv3oP0yUp3e8Z9smz3GUwN0aclKcgGFX8alENFau 2QWQ== X-Received: by 10.140.202.144 with SMTP id x138mr39483064qha.14.1424803656332; Tue, 24 Feb 2015 10:47:36 -0800 (PST) Received: from localhost.localdomain ([209.181.150.218]) by mx.google.com with ESMTPSA id h6sm29988733qgh.32.2015.02.24.10.47.34 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 24 Feb 2015 10:47:35 -0800 (PST) Message-ID: <54ECC745.9040303@gmail.com> Date: Tue, 24 Feb 2015 11:47:33 -0700 From: jd1008 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 MIME-Version: 1.0 To: freebsd-questions@freebsd.org Subject: Re: why would I get a segmentation fault on one system but not the other? References: <20150221224006.GA5501@home.parts-unknown.org> <09da5ec0816e098badc49432c802dc18@sdf.org> <20150222041421.GA36213@home.parts-unknown.org> <20150224024309.GA8251@neutralgood.org> In-Reply-To: <20150224024309.GA8251@neutralgood.org> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.18-1 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 24 Feb 2015 18:47:37 -0000 On 02/23/2015 07:43 PM, kpneal@pobox.com wrote: > On Sat, Feb 21, 2015 at 08:14:21PM -0800, David Benfell wrote: >> The system experiencing the segfaults is new--and from a vendor that >> has previously shipped me a system with bad memory. > >> I haven't stopped the memory test yet. But it has been running for an >> hour and completed one pass without error. From what I can see on >> line, that's a pretty good sign. > Memory testers reporting bad memory means you know you have bad memory. > > Memory testers _not_ reporting bad memory tells you nothing. > > Don't rely on memory testers to diagnose bad memory. In the past 20 years > I've seen a number of really weird cases where machines had problems but > only under certain workloads. Right. When running the standalone mem86 tester, the CPU and memory might not be getting clocked at high clock rates. Sometimes when the system load gets high and clocking is upped either by the chipset (I had a system that did that), or by the kernel issuing directives to the hardware to up the clock, the it is possible for the hardware to muck up the data read from the RAM (especially when the data happens to be addresses of user or kernel data).