From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261243AbUBZUmm (ORCPT ); Thu, 26 Feb 2004 15:42:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261256AbUBZUmm (ORCPT ); Thu, 26 Feb 2004 15:42:42 -0500 Received: from e4.ny.us.ibm.com ([32.97.182.104]:54915 "EHLO e4.ny.us.ibm.com") by vger.kernel.org with ESMTP id S261243AbUBZUmk (ORCPT ); Thu, 26 Feb 2004 15:42:40 -0500 Message-ID: <403E5A31.5020900@watson.ibm.com> Date: Thu, 26 Feb 2004 15:42:25 -0500 From: Shailabh Nagar User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.5b) Gecko/20030829 Thunderbird/0.2 X-Accept-Language: en-us, en MIME-Version: 1.0 To: Mike Fedyk CC: Peter Williams , Timothy Miller , linux-kernel@vger.kernel.org Subject: Re: [RFC][PATCH] O(1) Entitlement Based Scheduler References: <403D3E47.4080501@techsource.com> <403D576A.6030900@aurema.com> <403D5D32.4010007@matchmail.com> <403D71AB.9060609@aurema.com> <403D73B4.4060600@matchmail.com> <403E47C4.4080104@watson.ibm.com> <403E4D1B.9060503@matchmail.com> In-Reply-To: <403E4D1B.9060503@matchmail.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Mike Fedyk wrote: > Shailabh Nagar wrote: > >>>> Mike Fedyk wrote: >>>> >>>>> Better would be to have the kernel tell the daemon whenever a >>>>> process in exec-ed, and you have simplicity in the kernel, and >>>>> policy in user space. >>>> >> >> >> >> As it turns out, one can still use a fairly simple in-kernel module >> which provides a *mechanism* for effectively changing a process' >> entitlement while retaining the policy component in userland. > > > How much code could be removed if CKRM triggered a userspace process > to perform the operations required? In CKRM, the code to perform classification is an optional kernel module. So size isn't really an issue in terms of impact to core kernel code. Our prototype version of the classification engine, RBCE, is about 2700 lines without any effort being put into reducing its size etc. If that were to be completely pared down to only provide events to userspace, it would come down by quite a bit (can't say exactly how much but atleast 50% is a safe bet). I think the more important question is performance impact - what do you give up in terms of efficiency and granularity of control by going to userspace vs what you gain in reduced kernel pathlength. Empirically, we found RBCE was quite efficient but no quantitative analysis was done. -- Shailabh