Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752362AbbGRNgJ (ORCPT ); Sat, 18 Jul 2015 09:36:09 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:34869 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751344AbbGRNgH (ORCPT ); Sat, 18 Jul 2015 09:36:07 -0400 Date: Sat, 18 Jul 2015 15:36:03 +0200 From: Frederic Weisbecker To: Mike Galbraith Cc: Tejun Heo , Daniel Bristot de Oliveira , LKML , Lai Jiangshan , Rik van Riel , "Luis Claudio R. Goncalves" Subject: Re: [RFC] workqueue: avoiding unbounded wq on isolated CPUs by default Message-ID: <20150718133602.GA3041@lerouge> References: <9e53de7c91c885ee255e16ee25f401d9eedf08d9.1437067317.git.bristot@redhat.com> <20150716192448.GY15934@mtj.duckdns.org> <1437107190.3438.23.camel@gmail.com> <20150717152720.GD15934@mtj.duckdns.org> <1437153348.5860.32.camel@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1437153348.5860.32.camel@gmail.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1254 Lines: 26 On Fri, Jul 17, 2015 at 07:15:48PM +0200, Mike Galbraith wrote: > On Fri, 2015-07-17 at 11:27 -0400, Tejun Heo wrote: > > > I'm just curious whether there was any specific reason we didn't do > > this before (ISTR people discussing it back then too). > > I'm dead set against all this auto-presume nonsense fwtw Allocating a > pool of no_hz_full _capable_ CPUs should not entice the kernel to make > any rash assumptions. Let users do the button poking, they know what > they want, and when they want it. We need to make a choice then. Either we do all the affinity tuning from userspace with a common tool, which is what I had wished before everybody asked for pre-settings. Or we do it in the kernel, now we should define some kind of CONFIG_ISOLATION to make that proper and rule the various kinds of isolation people are interested in. But we can't leave it half-way like it is currently with everything preset on top of nohz: rcu nocb mask, watchdog mask, cpu_isolation_map and exclude workqueue. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/