Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751286AbdH1NXM (ORCPT ); Mon, 28 Aug 2017 09:23:12 -0400 Received: from mail-wr0-f196.google.com ([209.85.128.196]:38335 "EHLO mail-wr0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751184AbdH1NXL (ORCPT ); Mon, 28 Aug 2017 09:23:11 -0400 Date: Mon, 28 Aug 2017 15:23:06 +0200 From: Frederic Weisbecker To: Peter Zijlstra Cc: LKML , Chris Metcalf , Thomas Gleixner , Luiz Capitulino , Christoph Lameter , "Paul E . McKenney" , Ingo Molnar , Mike Galbraith , Rik van Riel , Wanpeng Li Subject: Re: [RFC PATCH 12/12] housekeeping: Reimplement isolcpus on housekeeping Message-ID: <20170828132302.GA32618@lerouge> References: <1503453071-952-1-git-send-email-fweisbec@gmail.com> <1503453071-952-13-git-send-email-fweisbec@gmail.com> <20170828100957.jcjhh77ylxvsyisy@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170828100957.jcjhh77ylxvsyisy@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1044 Lines: 20 On Mon, Aug 28, 2017 at 12:09:57PM +0200, Peter Zijlstra wrote: > On Wed, Aug 23, 2017 at 03:51:11AM +0200, Frederic Weisbecker wrote: > > We want to centralize the isolation features on the housekeeping > > subsystem and scheduler isolation is a significant part of it. > > > > While at it, this is a proposition for a reimplementation of isolcpus= > > that doesn't involve scheduler domain isolation. Therefore this > > brings a behaviour change: all user tasks inherit init/1 affinity which > > avoid the isolcpus= range. But if a task later overrides its affinity > > which turns out to intersect an isolated CPU, load balancing may occur > > on it. > > > > OTOH such a reimplementation that doesn't shortcut scheduler internals > > makes a better candidate for an interface extension to cpuset. > > Not sure we can do this. It'll break users that rely on the no > scheduling thing, that's a well documented part of isolcpus. That was my worry :-s That NULL domain was probably a design mistake and I fear we now have to maintain it.