From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1767275AbXCIN3X (ORCPT ); Fri, 9 Mar 2007 08:29:23 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1767278AbXCIN3X (ORCPT ); Fri, 9 Mar 2007 08:29:23 -0500 Received: from MAIL.13thfloor.at ([213.145.232.33]:50769 "EHLO MAIL.13thfloor.at" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1767275AbXCIN3X (ORCPT ); Fri, 9 Mar 2007 08:29:23 -0500 Date: Fri, 9 Mar 2007 14:29:22 +0100 From: Herbert Poetzl To: Kirill Korotaev Cc: Paul Menage , pj@sgi.com, "Eric W. Biederman" , winget@google.com, containers@lists.osdl.org, akpm@linux-foundation.org, ckrm-tech@lists.sourceforge.net, linux-kernel@vger.kernel.org, xemul@sw.ru Subject: Re: [PATCH 1/2] rcfs core patch Message-ID: <20070309132922.GB14907@MAIL.13thfloor.at> Mail-Followup-To: Kirill Korotaev , Paul Menage , pj@sgi.com, "Eric W. Biederman" , winget@google.com, containers@lists.osdl.org, akpm@linux-foundation.org, ckrm-tech@lists.sourceforge.net, linux-kernel@vger.kernel.org, xemul@sw.ru References: <20070301133543.GK15509@in.ibm.com> <20070301134528.GL15509@in.ibm.com> <6599ad830703080110j15aa961anc39954928cbc3851@mail.gmail.com> <20070309003819.GA4506@MAIL.13thfloor.at> <45F123CF.2000902@sw.ru> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <45F123CF.2000902@sw.ru> User-Agent: Mutt/1.5.11 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Mar 09, 2007 at 12:07:27PM +0300, Kirill Korotaev wrote: >> nobody actually cares about a precise accounting and >> calculating shares or partitions of whatever resource, >> all that matters is that you have a way to prevent a >> potential hostile environment from sucking up all your >> resources (or even a single one) resulting in a DoS > This is not true. People care. Reasons: > - resource planning > - fairness > - guarantees let me make that a little more clear ... _nobody_ cares wether a shared memory page is accounted as full page or as fraction of a page (depending on the number of guests sharing it) as long as the accounted amount is substracted correctly when the page is disposed so there _is_ a difference between _false_ accounting (which seems what you are referring to in the next paragraph) and imprecise, but consistant accounting (which is what I was talking about) best, Herbert > What you talk is about security only. Not the above issues. > So good precision is required. If there is no precision at all, > security sucks as well and can be exploited, e.g. for CPU > schedulers doing an accounting based on jiffies accounting in > scheduler_tick() it is easy to build an application consuming > 90% of CPU, but ~0% from scheduler POV. > Kirill