Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757562Ab3ETQEV (ORCPT ); Mon, 20 May 2013 12:04:21 -0400 Received: from mail-wg0-f42.google.com ([74.125.82.42]:42578 "EHLO mail-wg0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756808Ab3ETQCF (ORCPT ); Mon, 20 May 2013 12:02:05 -0400 From: Frederic Weisbecker To: LKML Cc: Steven Rostedt , "Paul E. McKenney" , Ingo Molnar , Andrew Morton , Thomas Gleixner , "H. Peter Anvin" , Peter Zijlstra , Frederic Weisbecker Subject: [PATCH 1/8] nohz: Warn if the machine can not perform nohz_full Date: Mon, 20 May 2013 18:01:49 +0200 Message-Id: <1369065716-22801-2-git-send-email-fweisbec@gmail.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1369065716-22801-1-git-send-email-fweisbec@gmail.com> References: <1369065716-22801-1-git-send-email-fweisbec@gmail.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1552 Lines: 45 From: Steven Rostedt If the user configures NO_HZ_FULL and defines nohz_full=XXX on the kernel command line, or enables NO_HZ_FULL_ALL, but nohz fails due to the machine having a unstable clock, warn about it. We do not want users thinking that they are getting the benefit of nohz when their machine can not support it. Signed-off-by: Steven Rostedt Cc: Paul E. McKenney Cc: Ingo Molnar Cc: Andrew Morton Cc: Thomas Gleixner Cc: H. Peter Anvin Cc: Peter Zijlstra Signed-off-by: Frederic Weisbecker --- kernel/time/tick-sched.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-) diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c index bc67d42..cfc798b 100644 --- a/kernel/time/tick-sched.c +++ b/kernel/time/tick-sched.c @@ -178,6 +178,11 @@ static bool can_stop_full_tick(void) */ if (!sched_clock_stable) { trace_tick_stop(0, "unstable sched clock\n"); + /* + * Don't allow the user to think they can get + * full NO_HZ with this machine. + */ + WARN_ONCE(1, "NO_HZ FULL will not work with unstable sched clock"); return false; } #endif -- 1.7.5.4 -- 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/