Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750858AbWELAEN (ORCPT ); Thu, 11 May 2006 20:04:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750860AbWELAEN (ORCPT ); Thu, 11 May 2006 20:04:13 -0400 Received: from mga01.intel.com ([192.55.52.88]:26971 "EHLO fmsmga101-1.fm.intel.com") by vger.kernel.org with ESMTP id S1750852AbWELAEM (ORCPT ); Thu, 11 May 2006 20:04:12 -0400 Message-Id: <4sur0l$12a3ma@fmsmga001.fm.intel.com> X-IronPort-AV: i="4.05,117,1146466800"; d="scan'208"; a="35983050:sNHT55328840" From: "Chen, Kenneth W" To: "'Con Kolivas'" , Cc: , Subject: RE: Regression seen for patch "sched:dont decrease idle sleep avg" Date: Thu, 11 May 2006 17:04:11 -0700 MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Mailer: Microsoft Office Outlook, Build 11.0.6353 Thread-Index: AcZzAatbAtx7xdtqR8K9xufWAU8wqwCUsv7A In-Reply-To: X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2900.2180 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1739 Lines: 34 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. - Ken - 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/