From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756009AbcAOIl5 (ORCPT ); Fri, 15 Jan 2016 03:41:57 -0500 Received: from casper.infradead.org ([85.118.1.10]:55098 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750890AbcAOIl4 (ORCPT ); Fri, 15 Jan 2016 03:41:56 -0500 Date: Fri, 15 Jan 2016 09:41:50 +0100 From: Peter Zijlstra To: Luca Abeni Cc: linux-kernel@vger.kernel.org, Ingo Molnar , Juri Lelli Subject: Re: [RFC 7/8] Make GRUB a task's flag Message-ID: <20160115084150.GD3421@worktop> References: <1452785094-3086-1-git-send-email-luca.abeni@unitn.it> <1452785094-3086-8-git-send-email-luca.abeni@unitn.it> <20160114195651.GG6357@twins.programming.kicks-ass.net> <5698AAAB.9040606@unitn.it> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5698AAAB.9040606@unitn.it> User-Agent: Mutt/1.5.22.1 (2013-10-16) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jan 15, 2016 at 09:15:39AM +0100, Luca Abeni wrote: > On 01/14/2016 08:56 PM, Peter Zijlstra wrote: > >Something with an average runtime/budget that also puts limits on the > >max (say 2*avg) would be far more amenable to be exposed to unpriv > >tasks, except since that would directly result in an average tardiness > >bound this might be non-trivial to combine with tasks not opting for > >this. > I'll try to think about this... The advantage of GRUB is that a theoretically > sound algorithm already existed; here, we would need to design the algorithm > so that it does not break the SCHED_DEADLINE guarantees. Anyway, this is an > interesting challenge, I'll work on it :) Didn't Baruah and Jim do the whole theory on statistical EDF? Which shows that if you use a statistical budget the combined distribution transfers to the tardiness. With stdev=0 for the budgets this trivially collapses to the regular EDF, since then the combined distribution is also stdev=0 and you get 0 tardiness (on UP). But yes, combining the two into one scheduler is 'interesting'. I was thinking it would be possible with least-laxity-first, since you can assign the hard (stdev=0) tasks a tighter laxity bound. But LLF is horrendously painful to implement IIRC.