From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756755AbYJXRrg (ORCPT ); Fri, 24 Oct 2008 13:47:36 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752351AbYJXRr3 (ORCPT ); Fri, 24 Oct 2008 13:47:29 -0400 Received: from zrtps0kp.nortel.com ([47.140.192.56]:46184 "EHLO zrtps0kp.nortel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751574AbYJXRr2 (ORCPT ); Fri, 24 Oct 2008 13:47:28 -0400 Message-ID: <49020A2A.5070809@nortel.com> Date: Fri, 24 Oct 2008 11:47:22 -0600 From: "Chris Friesen" User-Agent: Thunderbird 2.0.0.17 (X11/20080914) MIME-Version: 1.0 To: Peter Zijlstra CC: linux-kernel@vger.kernel.org, mingo@elte.hu, efault@gmx.de, vatsa@in.ibm.com Subject: Re: [PATCH 7/8] sched: non-zero lag renice References: <20081024090611.936552213@chello.nl> <20081024091109.912152294@chello.nl> In-Reply-To: <20081024091109.912152294@chello.nl> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-OriginalArrivalTime: 24 Oct 2008 17:47:24.0150 (UTC) FILETIME=[92704160:01C93600] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Peter Zijlstra wrote: > Then renicing, esp when lowering nice value (getting heavier), its possible > to get into a starvation scenario. If you got too much runtime as a very > light task, you get shot way far too the right, which means you'll have to > wait for a long time in order to run again. > > If during that wait you get reniced down, fairness would suggest you get run > earlier, because you deserve more time. > > This can be solved by scaling the vruntime so that we keep the real-time > lag invariant. If we've already been shot way out to the right, presumably that would give us a large real-time lag. If we renice to a lower nice level, wouldn't we want to reduce the real-time lag rather than make it constant? Chris