From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261767AbVAIUfP (ORCPT ); Sun, 9 Jan 2005 15:35:15 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261762AbVAIUfO (ORCPT ); Sun, 9 Jan 2005 15:35:14 -0500 Received: from fw.osdl.org ([65.172.181.6]:19855 "EHLO mail.osdl.org") by vger.kernel.org with ESMTP id S261755AbVAIUem (ORCPT ); Sun, 9 Jan 2005 15:34:42 -0500 Date: Sun, 9 Jan 2005 12:34:41 -0800 From: Chris Wright To: Arjan van de Ven Cc: utz lehmann , LKML , Chris Wright Subject: Re: [PATCH] scheduling priorities with rlimit Message-ID: <20050109123441.O469@build.pdx.osdl.net> References: <1105290936.24812.29.camel@segv.aura.of.mankind> <1105297598.4173.52.camel@laptopd505.fenrus.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.2.5i In-Reply-To: <1105297598.4173.52.camel@laptopd505.fenrus.org>; from arjan@infradead.org on Sun, Jan 09, 2005 at 08:06:37PM +0100 Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org * Arjan van de Ven (arjan@infradead.org) wrote: > On Sun, 2005-01-09 at 18:15 +0100, utz lehmann wrote: > > Hi > > > > I really like the idea of controlling the maximum settable scheduling > > priorities via rlimit. See the Realtime LSM thread. I want to give users > > the right to raise the priority of previously niced jobs. > > > > I have modified Chris Wright's patch (against 2.6.10): > > (http://marc.theaimsgroup.com/?l=linux-kernel&m=110513793228776&w=2) > > > > - allow always to increase nice levels (lower priority). > > - set the default for RLIMIT_PRIO to 0. > > - add the other architectures. > > > > With this the default is compatible with the old behavior. > > > > With RLIMIT_PRIO > 0 a user is able to raise the priority up to the > > value. 0-39 for nice levels 19 .. -20, 40-139 for realtime priorities > > (0 .. 99). > > this is a bit of an awkward interface don't you think? Yes it is. But I didn't think of a better one. > I much rather have the rlimit match the exact nice values we communicate > to userspace elsewhere, both to be consistent and to not expose > scheduler internals to userpsace. The problem is the numbers are inconsistent between user interfaces already. RT priorities are [0, 99], nice vaules are [-20, 19]. Perhaps it'd be simpler to break it down to just three values for the rlimit. 0: Same as now, raise nice value only. 1: Can lower nice value. 2: Can set RT policy (this includes any priority [1, 99], or optionally max out at something lower than 99, reserving full CAP_SYS_NICE to 99). Each level inherits the permissions of the lower level, and none of them allow the CAP_SYS_NICE ability to affect processes other than your own. > Also I like the idea of allowing sysadmins to make certain users/groups > nice levels 5 and higher (think a university machine that makes all > students nice 5 and higher only, while giving staff 0 and higher, and > the sysadmin -5 and higher ;) This is a separate issue. It's about setting the default during login which can be done with setpriority (still could be done via pam). thanks, -chris -- Linux Security Modules http://lsm.immunix.org http://lsm.bkbits.net