From owner-freebsd-arch@FreeBSD.ORG Thu Mar 3 14:12:51 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 3C64816A4CE for ; Thu, 3 Mar 2005 14:12:51 +0000 (GMT) Received: from node15.coopprint.com (node15.cooperativeprinting.com [208.4.77.15]) by mx1.FreeBSD.org (Postfix) with SMTP id 49A7043D48 for ; Thu, 3 Mar 2005 14:12:50 +0000 (GMT) (envelope-from ryans@gamersimpact.com) Received: (qmail 93022 invoked by uid 0); 3 Mar 2005 14:11:50 -0000 Received: from unknown (HELO ?192.168.0.5?) (63.231.157.250) by node15.coopprint.com with SMTP; 3 Mar 2005 14:11:50 -0000 Message-ID: <42271B6A.4070802@gamersimpact.com> Date: Thu, 03 Mar 2005 08:12:58 -0600 From: Ryan Sommers User-Agent: Mozilla Thunderbird 0.7.3 (Windows/20040803) X-Accept-Language: en-us, en MIME-Version: 1.0 To: David Schultz References: <20050303074242.GA14699@VARK.MIT.EDU> In-Reply-To: <20050303074242.GA14699@VARK.MIT.EDU> Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit cc: arch@FreeBSD.ORG 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 14:12:51 -0000 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. -- Ryan Sommers ryans@gamersimpact.com