From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753906Ab0LUXrK (ORCPT ); Tue, 21 Dec 2010 18:47:10 -0500 Received: from ogre.sisk.pl ([217.79.144.158]:44348 "EHLO ogre.sisk.pl" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752684Ab0LUXrI (ORCPT ); Tue, 21 Dec 2010 18:47:08 -0500 From: "Rafael J. Wysocki" To: Matthew Wilcox Subject: Re: [PATCH] Prevent users from disabling tickless Date: Wed, 22 Dec 2010 00:46:23 +0100 User-Agent: KMail/1.13.5 (Linux/2.6.37-rc7+; KDE/4.4.4; x86_64; ; ) Cc: Thomas Gleixner , Arjan van de Ven , linux-kernel@vger.kernel.org References: <20101221233942.GL1263@parisc-linux.org> In-Reply-To: <20101221233942.GL1263@parisc-linux.org> MIME-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Message-Id: <201012220046.23759.rjw@sisk.pl> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wednesday, December 22, 2010, Matthew Wilcox wrote: > > Disabling NO_HZ has a serious negative effect on performance -- an extra > 70us per I/O. Prevent users from deselecting it. > > Signed-off-by: Matthew Wilcox OTOH, it causes some systems to not work at all still. Sadly. Thanks, Rafael > diff --git a/kernel/time/Kconfig b/kernel/time/Kconfig > index f06a8a3..55b9a04 100644 > --- a/kernel/time/Kconfig > +++ b/kernel/time/Kconfig > @@ -5,13 +5,9 @@ config TICK_ONESHOT > bool > > config NO_HZ > - bool "Tickless System (Dynamic Ticks)" > + def_bool y > depends on !ARCH_USES_GETTIMEOFFSET && GENERIC_CLOCKEVENTS > select TICK_ONESHOT > - help > - This option enables a tickless system: timer interrupts will > - only trigger on an as-needed basis both when the system is > - busy and when the system is idle. > > config HIGH_RES_TIMERS > bool "High Resolution Timer Support" > >