From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759770AbYCCJYs (ORCPT ); Mon, 3 Mar 2008 04:24:48 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754155AbYCCJYk (ORCPT ); Mon, 3 Mar 2008 04:24:40 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:59029 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753840AbYCCJYk (ORCPT ); Mon, 3 Mar 2008 04:24:40 -0500 Date: Mon, 3 Mar 2008 10:24:22 +0100 From: Ingo Molnar To: Michael Kerrisk Cc: Arnd Bergmann , Christoph Hellwig , cbe-oss-dev@ozlabs.org, Jeremy Kerr , linux-kernel@vger.kernel.org Subject: Re: SCHED_IDLE documentation Message-ID: <20080303092422.GA18281@elte.hu> References: <1203376368.275756.252634247263.1.gpush@pokey> <200803030612.28039.arnd@arndb.de> <20080303051719.GA26102@lst.de> <200803030721.52869.arnd@arndb.de> <20080303073311.GB5934@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Michael Kerrisk wrote: > On Mon, Mar 3, 2008 at 8:33 AM, Ingo Molnar wrote: > > > > * Arnd Bergmann wrote: > > > > > If we don't have any man page, what is the actual definition of > > > SCHED_IDLE anyway? > > > > it's rather simple: "it's a priority level even lower priority than nice > > +19". > > Some other questions whose answers may be worth including in the man page: > > * When was SCHED_IDLE added? (Actually, who added it?) "git-blame include/linux/sched.h" gives you that information, it was added by me as part of CFS: commit 0e6aca43e08a62a48d6770e9a159dbec167bf4c6 Author: Ingo Molnar Date: Mon Jul 9 18:51:57 2007 +0200 sched: add SCHED_IDLE policy > * Why was it added? (What are the particular benefits of the new > sceuling class as opposed to using a very low nice value for > SCHED_OTHER?) because some people wanted even lower priorities than what nice +19 gave, and extending nice levels wasnt possible for ABI reasons. > * What's the difference between SCHED_IDLE and SCHED_BATCH? SCHED_BATCH can still have nice levels from -20 to +19, it is a modified SCHED_OTHER/SCHED_NORMAL for "throughput oriented" workloads. SCHED_IDLE overrides the nice settings and it means a "super idle" workload. Ingo