Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753798Ab0LUXjp (ORCPT ); Tue, 21 Dec 2010 18:39:45 -0500 Received: from palinux.external.hp.com ([192.25.206.14]:55159 "EHLO mail.parisc-linux.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751799Ab0LUXjo (ORCPT ); Tue, 21 Dec 2010 18:39:44 -0500 Date: Tue, 21 Dec 2010 16:39:43 -0700 From: Matthew Wilcox To: Thomas Gleixner Cc: Arjan van de Ven , linux-kernel@vger.kernel.org Subject: [PATCH] Prevent users from disabling tickless Message-ID: <20101221233942.GL1263@parisc-linux.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1216 Lines: 36 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 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" -- Matthew Wilcox Intel Open Source Technology Centre "Bill, look, we understand that you're interested in selling us this operating system, but compare it to ours. We can't possibly take such a retrograde step." -- 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/