Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752220AbcJJLIb (ORCPT ); Mon, 10 Oct 2016 07:08:31 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:41566 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751688AbcJJLIa (ORCPT ); Mon, 10 Oct 2016 07:08:30 -0400 Date: Mon, 10 Oct 2016 13:08:18 +0200 From: Peter Zijlstra To: Luca Abeni Cc: linux-kernel@vger.kernel.org, Tommaso Cucinotta , Juri Lelli , Thomas Gleixner , Andrea Parri Subject: Re: About group scheduling for SCHED_DEADLINE Message-ID: <20161010110818.GA11311@worktop.programming.kicks-ass.net> References: <20161009213938.3cec05ea@utopia> <20161010101558.GL3568@worktop.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161010101558.GL3568@worktop.programming.kicks-ass.net> 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 Content-Length: 856 Lines: 17 On Mon, Oct 10, 2016 at 12:15:58PM +0200, Peter Zijlstra wrote: > However, I think there's a third alternative. I have memories of a paper > from UNC (I'd have to dig through the site to see if I can still find > it) where they argue that for a hierarchical (G-)FIFO you should use > minimal concurrency, that is run the minimal number of (v)cpu servers. > > This would mean we give a single CBS parameter and carve out the minimal > number (of max CBS) (v)cpu that fit in that. > > I'm just not sure how the random affinity crap works out for that, if we > have the (v)cpu servers migratable in the G-EDF and migrate to whatever > is demanded by the task at runtime it might work, but who knows.. > Analysis would be needed I think. Hurm,.. thinking slightly more on this, this ends up being a DL task with random affinity, which is problematic IIRC.