Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932405AbWEMMak (ORCPT ); Sat, 13 May 2006 08:30:40 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932407AbWEMMaj (ORCPT ); Sat, 13 May 2006 08:30:39 -0400 Received: from smtp.osdl.org ([65.172.181.4]:1444 "EHLO smtp.osdl.org") by vger.kernel.org with ESMTP id S932405AbWEMMaj (ORCPT ); Sat, 13 May 2006 08:30:39 -0400 Date: Sat, 13 May 2006 05:27:30 -0700 From: Andrew Morton To: "Chen, Kenneth W" Cc: kernel@kolivas.org, tim.c.chen@linux.intel.com, linux-kernel@vger.kernel.org, mingo@elte.hu Subject: Re: Regression seen for patch "sched:dont decrease idle sleep avg" Message-Id: <20060513052730.389ea002.akpm@osdl.org> In-Reply-To: <4sur0l$12a3ma@fmsmga001.fm.intel.com> References: <4sur0l$12a3ma@fmsmga001.fm.intel.com> X-Mailer: Sylpheed version 1.0.4 (GTK+ 1.2.10; i386-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1983 Lines: 42 (Catching up on lkml) On Thu, 11 May 2006 17:04:11 -0700 "Chen, Kenneth W" wrote: > Tim Chen writes: > > See patch: > > http://www.kernel.org/git/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=e72ff0bb2c163eb13014ba113701bd42dab382fe > > Con Kolivas wrote on Monday, May 08, 2006 5:43 PM > > This patch corrects a bug in the original code which unintentionally dropped > > the priority of tasks that were idle but were already high priority on other > > merits. It doesn't further increase the priority. > > > This got me to take a non-casual look at that particular git commit. The > first portion of the change log description says perfectly about the intent, > but after studying the code, I have to say that the actual code does not > implement what people say it will do. In recalc_task_prio(), if a task's > sleep_time is more than INTERACTIVE_SLEEP, it will bump up p->sleep_avg all > the way to near maximum (at MAX_SLEEP_AVG - DEF_TIMESLICE), which according > to my calculation, it will have a priority bonus of 4 (out of max 5). > > IOW, for a prolonged sleep, a task will immediately get near maximum priority > boost. Is that what the real intent is? Seems to be on the contrary to what > the source code comments as well. > > I think in the if (sleep_time > INTERACTIVE_SLEEP) block, p->sleep_avg should > be treated similarly like what the "else" block is doing: scale it proportionally > with past sleep time, perhaps not the immediate previously prolonged sleep > because that would for sure bump up priority too fast. A better method might > be p->sleep_avg *= 2 or something like that. > That seems to be a pretty significant discovery. Is anything happening with it? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/