Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933469AbaDIPes (ORCPT ); Wed, 9 Apr 2014 11:34:48 -0400 Received: from mail-ob0-f182.google.com ([209.85.214.182]:55589 "EHLO mail-ob0-f182.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932786AbaDIPeq (ORCPT ); Wed, 9 Apr 2014 11:34:46 -0400 MIME-Version: 1.0 In-Reply-To: <20140409113143.6174143f@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> Date: Wed, 9 Apr 2014 21:04:46 +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 21:01, Steven Rostedt wrote: >> Do we? This is only called by tick_check_oneshot_change() which has the >> following: >> >> int tick_check_oneshot_change(int allow_nohz) >> { >> struct tick_sched *ts = &__get_cpu_var(tick_cpu_sched); >> >> if (!test_and_clear_bit(0, &ts->check_clocks)) >> return 0; >> >> if (ts->nohz_mode != NOHZ_MODE_INACTIVE) >> return 0; >> >> if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available()) >> return 0; >> >> if (!allow_nohz) >> return 1; >> >> tick_nohz_switch_to_nohz(); >> return 0; >> } >> >> How often does it make it to that last check? Probably we will reach here only once per boot per cpu. > Hmm, looking at the code, I see it probably should still do the check. But still we need it for that one time. :) -- 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/