Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752872AbdLSQFR (ORCPT ); Tue, 19 Dec 2017 11:05:17 -0500 Received: from merlin.infradead.org ([205.233.59.134]:57710 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751713AbdLSQFL (ORCPT ); Tue, 19 Dec 2017 11:05:11 -0500 Date: Tue, 19 Dec 2017 17:04:57 +0100 From: Peter Zijlstra To: Christopher Lameter Cc: Frederic Weisbecker , LKML , Chris Metcalf , Thomas Gleixner , Luiz Capitulino , "Paul E . McKenney" , Ingo Molnar , Wanpeng Li , Mike Galbraith , Rik van Riel Subject: Re: [PATCH 4/5] sched/isolation: Residual 1Hz scheduler tick offload Message-ID: <20171219160457.rp4rkc75yruezepm@hirez.programming.kicks-ass.net> References: <1513653838-31314-1-git-send-email-frederic@kernel.org> <1513653838-31314-5-git-send-email-frederic@kernel.org> <20171219091911.tg2k4w7mgv2bcmeb@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170609 (1.8.3) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 721 Lines: 16 On Tue, Dec 19, 2017 at 10:01:46AM -0600, Christopher Lameter wrote: > On Tue, 19 Dec 2017, Peter Zijlstra wrote: > > > On Tue, Dec 19, 2017 at 04:23:57AM +0100, Frederic Weisbecker wrote: > > > When a CPU runs in full dynticks mode, a 1Hz tick remains in order to > > > keep the scheduler stats alive. However this residual tick is a burden > > > for Real-Time tasks that can't stand no interruption at all. > > > > I'm not sure that is accurate. RT doesn't necessarily have anything much > > to so with this. The tick is per definition very deterministic and thus > > should not be a problem. > > Depends what one means by RT. Real Time computing as per the literature. Any other definition is wrong and confusing.