From owner-freebsd-stable@FreeBSD.ORG Thu Dec 4 22:11:48 2008 Return-Path: Delivered-To: freebsd-stable@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 0495B1065672 for ; Thu, 4 Dec 2008 22:11:48 +0000 (UTC) (envelope-from josh.carroll@gmail.com) Received: from rn-out-0910.google.com (rn-out-0910.google.com [64.233.170.188]) by mx1.freebsd.org (Postfix) with ESMTP id A95718FC29 for ; Thu, 4 Dec 2008 22:11:47 +0000 (UTC) (envelope-from josh.carroll@gmail.com) Received: by rn-out-0910.google.com with SMTP id j71so3971034rne.12 for ; Thu, 04 Dec 2008 14:11:46 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:reply-to :to:subject:cc:in-reply-to:mime-version:content-type :content-transfer-encoding:content-disposition:references; bh=VTgGECwKuluVbGO6mbzmVb0lpMy6Djfh2NAmVDYcoi4=; b=gVO/Z3+/6I98+2KB71E6MPu/57DffPe/0oZcO9ioovLysQlRb7bqtoxjp5oolqjoeX ZXGrIjdmvZEIjQZvcYePPlHF3uwI8l2366uUrrWTRJonaAz3YZysF2bIVwkSWAENX5lc jrHRaWtawvTVomMf0ajjArDSHD/PfCWOXO+SY= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:reply-to:to:subject:cc:in-reply-to :mime-version:content-type:content-transfer-encoding :content-disposition:references; b=AKnhCzptIRRknQpyyW/XjcDjJVQkhoFZRGD33oM8iuMSFHPXTd6GAkLbm8YZ+x1CO+ Yf0wN383Kj+xYU5JITVShv7ByRXE56NDPPfAqUiNVLC4GgGTmbDpNCWyfjH98zXxpt5O 2KGoRMLiqa4ufSiNiuwssnTNP4kJvg2wMSFRo= Received: by 10.151.110.14 with SMTP id n14mr335580ybm.141.1228428706872; Thu, 04 Dec 2008 14:11:46 -0800 (PST) Received: by 10.150.123.1 with HTTP; Thu, 4 Dec 2008 14:11:46 -0800 (PST) Message-ID: <8cb6106e0812041411t13ca9ffcjc4cc66a33ef43133@mail.gmail.com> Date: Thu, 4 Dec 2008 17:11:46 -0500 From: "Josh Carroll" To: "Steve Polyack" In-Reply-To: <49384863.9040807@comcast.net> MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Content-Disposition: inline References: <20081204204803.EB8D34500F@ptavv.es.net> <49384863.9040807@comcast.net> Cc: Alexandr Pakhomov , Mike Tancsa Subject: Re: repeatable crash on RELENG7 X-BeenThere: freebsd-stable@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list Reply-To: josh.carroll@gmail.com List-Id: Production branch of FreeBSD source code List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 04 Dec 2008 22:11:48 -0000 > It seems that the term "swap-backed" is misleading for some people. It does > NOT mean your md(4) device will be constantly swapping to disk (and the man > page does an alright job of relaying this). It simply means that generally > available memory will be used, and so will swap iff available memory happens > to drop low enough. > > The bottom line in my experience with md(4) devices greater than ~100MB is > that "swap-backed" is always reliable, while malloc'd md(4) devices will > cause unpredictable kernel panics. Using -t swap instead of -t malloc will prevent a panic, but creating an md greater than the size of the VM available and filling it will cause resource exhaustion and OOM will kick in and start killing processes, right? So while it won't panic the box, I still wouldn't consider it safe to use unless the size of the md is chosen carefully. Someone please correct me if I'm wrong, but I think that'd be the behavior if an md with -t swap is used, right? Regards, Josh