Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933300AbcKHQvl (ORCPT ); Tue, 8 Nov 2016 11:51:41 -0500 Received: from merlin.infradead.org ([205.233.59.134]:45838 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933255AbcKHQvg (ORCPT ); Tue, 8 Nov 2016 11:51:36 -0500 Date: Tue, 8 Nov 2016 17:51:33 +0100 From: Peter Zijlstra To: Steven Rostedt Cc: Daniel Bristot de Oliveira , Ingo Molnar , Christoph Lameter , linux-rt-users , LKML Subject: Re: [PATCH] sched/rt: RT_RUNTIME_GREED sched feature Message-ID: <20161108165133.GI3117@twins.programming.kicks-ass.net> References: <20161108115958.GO3142@twins.programming.kicks-ass.net> <20161108090740.4226ffc9@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20161108090740.4226ffc9@gandalf.local.home> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1281 Lines: 33 On Tue, Nov 08, 2016 at 09:07:40AM -0500, Steven Rostedt wrote: > On Tue, 8 Nov 2016 12:59:58 +0100 > Peter Zijlstra wrote: > > > No, none of this stands a chance of being accepted. > > > > This is making bad code worse. > > Peter, > > Instead of a flat out rejection, can you please provide some > constructive criticism to let those that are working on this know what > would be accepted? And what their next steps should be. > > There's obviously a problem with the current code, what steps do you > recommend to fix it? You really should already know this. As stands the current rt cgroup code (and all this throttling code) is a giant mess (as in, its not actually correct from a RT pov). We should not make it worse by adding random hacks to it. The right way to to about doing this is by replacing it with something better; like the proposed DL server for FIFO tasks -- which is entirely non-trivial as well, see existing discussion on that. I'm not entirely sure what this patch was supposed to fix, but it could be running CFS tasks with higher priority than RT for a window, instead of throttling RT tasks. This seems fairly ill specified, but something like that could easily done with an explicit or slack time DL server for CFS tasks.