From owner-freebsd-arch@FreeBSD.ORG Thu Mar 3 14:37:20 2005 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 4452A16A4CE; Thu, 3 Mar 2005 14:37:20 +0000 (GMT) Received: from freefall.freebsd.org (freefall.freebsd.org [216.136.204.21]) by mx1.FreeBSD.org (Postfix) with ESMTP id 26CED43D1F; Thu, 3 Mar 2005 14:37:20 +0000 (GMT) (envelope-from davidxu@freebsd.org) Received: from [127.0.0.1] (davidxu@localhost [127.0.0.1]) by freefall.freebsd.org (8.13.1/8.13.1) with ESMTP id j23EbHJ7091654; Thu, 3 Mar 2005 14:37:19 GMT (envelope-from davidxu@freebsd.org) Message-ID: <4227211F.5070505@freebsd.org> Date: Thu, 03 Mar 2005 22:37:19 +0800 From: David Xu User-Agent: Mozilla/5.0 (X11; U; FreeBSD amd64; en-US; rv:1.7.2) Gecko/20041004 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Ryan Sommers References: <20050303074242.GA14699@VARK.MIT.EDU> <42271B6A.4070802@gamersimpact.com> In-Reply-To: <42271B6A.4070802@gamersimpact.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit cc: arch@freebsd.org cc: David Schultz Subject: Re: Removing kernel thread stack swapping X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 03 Mar 2005 14:37:20 -0000 Ryan Sommers wrote: > David Schultz wrote: > >> Any objections to the idea of removing the feature of swapping out >> kernel stacks? Unlike disabling UAREA swapping, this has the >> small downside that it wastes 16K (give or take a power of 2) of >> wired memory per kernel thread that we would otherwise have >> swapped out. However, this disadvantage is probably negligible by >> today's standards, and there are several advantages: > > > I like the idea of fixing a lot of possible panics. However, I don't > know if we should nix it completely. Wasting this little memory won't > hurt anyone on a contemporary computer. However, our embedded systems > folks don't look at memory in the same light, and 16K here or there > can begin to really add up in a memory tight architecture. Of course > it could be argued that embedded systems probably don't have many > threads, many threads that can be swapped, or even swap space in the > first place. > > I guess it's a judgment call that one of our embedded systems > engineers could better answer. > Does your embedded system has swap device ? I have joined some embedded projects in the company, and there is no swap devices at all, no HDD etcs, just a CF card or flash memory card and swap is totally turned off. David Xu