Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752483AbbELBsF (ORCPT ); Mon, 11 May 2015 21:48:05 -0400 Received: from mail-wi0-f171.google.com ([209.85.212.171]:35231 "EHLO mail-wi0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752345AbbELBsA (ORCPT ); Mon, 11 May 2015 21:48:00 -0400 Message-ID: <1431395275.3195.19.camel@gmail.com> Subject: Re: [PATCH 0/6] support "dataplane" mode for nohz_full From: Mike Galbraith To: Chris Metcalf Cc: Frederic Weisbecker , Steven Rostedt , Ingo Molnar , Andrew Morton , Gilad Ben Yossef , Ingo Molnar , Peter Zijlstra , Rik van Riel , Tejun Heo , Thomas Gleixner , "Paul E. McKenney" , Christoph Lameter , "Srivatsa S. Bhat" , linux-doc@vger.kernel.org, linux-api@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 12 May 2015 03:47:55 +0200 In-Reply-To: <55510218.9090104@ezchip.com> References: <1431107927-13998-1-git-send-email-cmetcalf@ezchip.com> <20150508141824.797eb0d89d514e39fd30fffe@linux-foundation.org> <20150508172210.559830a9@gandalf.local.home> <554D428E.6020702@ezchip.com> <20150508161909.308d60e21f6b83b897174276@linux-foundation.org> <20150509070538.GA9413@gmail.com> <20150511085759.71deeb64@gandalf.local.home> <20150511153602.GA32512@lerouge> <1431371974.3195.126.camel@gmail.com> <55510218.9090104@ezchip.com> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.12.11 Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1435 Lines: 30 On Mon, 2015-05-11 at 15:25 -0400, Chris Metcalf wrote: > On 05/11/2015 03:19 PM, Mike Galbraith wrote: > > I really shouldn't have acked nohz_full -> isolcpus. Beside the fact > > that old static isolcpus was_supposed_ to crawl off and die, I know > > beyond doubt that having isolated a cpu as well as you can definitely > > does NOT imply that said cpu should become tickless. > > True, at a high level, I agree that it would be better to have a > top-level concept like Frederic's proposed ISOLATION that includes > isolcpus and nohz_cpu (and other stuff as needed). > > That said, what you wrote above is wrong; even with the patch you > acked, setting isolcpus does not automatically turn on nohz_full for > a given cpu. The patch made it true the other way around: when > you say nohz_full, you automatically get isolcpus on that cpu too. > That does, at least, make sense for the semantics of nohz_full. I didn't write that, I wrote nohz_full implies (spelled '->') isolcpus. Yes, with nohz_full currently being static, the old allegedly dying but also static isolcpus scheduler off switch is a convenient thing to wire the nohz_full CPU SET (<- hint;) property to. -Mike -- 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/