From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964825AbWDGR0h (ORCPT ); Fri, 7 Apr 2006 13:26:37 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964826AbWDGR0h (ORCPT ); Fri, 7 Apr 2006 13:26:37 -0400 Received: from fmr18.intel.com ([134.134.136.17]:54220 "EHLO orsfmr003.jf.intel.com") by vger.kernel.org with ESMTP id S964825AbWDGR0g (ORCPT ); Fri, 7 Apr 2006 13:26:36 -0400 Subject: [PATCH] Kconfig.debug: Set DEBUG_MUTEX to off by default From: Tim Chen Reply-To: tim.c.chen@linux.intel.com To: linux-kernel@vger.kernel.org Content-Type: text/plain Organization: Intel Date: Fri, 07 Apr 2006 09:56:48 -0700 Message-Id: <1144429008.25886.17.camel@localhost.localdomain> Mime-Version: 1.0 X-Mailer: Evolution 2.0.2 (2.0.2-8) Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Hi, DEBUG_MUTEX flag is on by default in current kernel configuration. During performance testing, we saw mutex debug functions like mutex_debug_check_no_locks_freed (called by kfree()) is expensive as it goes through a global list of memory areas with mutex lock and do the checking. For benchmarks such as Volanomark and Hackbench, we have seen more than 40% drop in performance on some platforms. We suggest to set DEBUG_MUTEX off by default. Or at least do that later when we feel that the mutex changes in the current code have stabilized. Tim Chen Signed-off-by: Tim Chen diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug --- a/lib/Kconfig.debug +++ b/lib/Kconfig.debug @@ -101,7 +101,7 @@ config DEBUG_PREEMPT config DEBUG_MUTEXES bool "Mutex debugging, deadlock detection" - default y + default n depends on DEBUG_KERNEL help This allows mutex semantics violations and mutex related deadlocks