Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933994AbaDIP44 (ORCPT ); Wed, 9 Apr 2014 11:56:56 -0400 Received: from mail-oa0-f48.google.com ([209.85.219.48]:52763 "EHLO mail-oa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933869AbaDIP4w (ORCPT ); Wed, 9 Apr 2014 11:56:52 -0400 MIME-Version: 1.0 In-Reply-To: <20140409113923.7dcaf183@gandalf.local.home> References: <20131113113927.GA13875@mwhitehe.csb> <20131113102153.5f10e6b5@gandalf.local.home> <20131113103134.5b8cf02f@gandalf.local.home> <20131113105737.3f7a0b1b@gandalf.local.home> <20131113111257.482c2955@gandalf.local.home> <20131113161829.GE4138@linux.vnet.ibm.com> <20131113112338.7d303c0f@gandalf.local.home> <20131113163552.GF4138@linux.vnet.ibm.com> <20140409103138.29be16b9@gandalf.local.home> <20140409112950.7be9f8ac@gandalf.local.home> <20140409113143.6174143f@gandalf.local.home> <20140409113923.7dcaf183@gandalf.local.home> Date: Wed, 9 Apr 2014 21:26:51 +0530 Message-ID: Subject: Re: nohz problem with idle time on old hardware From: Viresh Kumar To: Steven Rostedt Cc: Thomas Gleixner , "Paul E. McKenney" , Matthew Whitehead , John Stultz , "linux-kernel@vger.kernel.org" , mwhitehe@redhat.com, Frederic Weisbecker Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9 April 2014 21:09, Steven Rostedt wrote: > Reading even more of the code, now I'm totally confused :-) :) > When tick_setup_sched_timer() is called, if tick_nohz_enabled is set, > then we set tick_nohz_active. correct. > This gets called by hrtimer_switch_to_hres(), and before that is > called, the tick_check_oneshot_changed() will never get to the > tick_nohz_switch_to_nohz() call. If hrtimer_switch_to_hres() is called or HRES is enabled, we will never ever call tick_nohz_switch_to_nohz(). > Looks to me, the real answer is to nuke both the if statement *and* the > setting of the tick_nohz_active in that function. Both looks a bit > redundant to me. When HRES isn't enabled and NOHZ isn't enabled as well, in that case we should stick to the periodic code from tick-common.c and the oneshot options of tick_nohz_switch_to_nohz() or hrtimer_switch_to_hres() shouldn't be used. And so, we still need those checks, as per my understanding. :) Lets see what others have for this discussion :) -- 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/