Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S964789AbVLSQF6 (ORCPT ); Mon, 19 Dec 2005 11:05:58 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S964795AbVLSQF6 (ORCPT ); Mon, 19 Dec 2005 11:05:58 -0500 Received: from omx2-ext.sgi.com ([192.48.171.19]:10439 "EHLO omx2.sgi.com") by vger.kernel.org with ESMTP id S964789AbVLSQF5 (ORCPT ); Mon, 19 Dec 2005 11:05:57 -0500 Date: Mon, 19 Dec 2005 08:04:01 -0800 From: Paul Jackson To: Paul Jackson Cc: paulmck@us.ibm.com, akpm@osdl.org, dada1@cosmosbay.com, linux-kernel@vger.kernel.org, nickpiggin@yahoo.com.au, Simon.Derr@bull.net, ak@suse.de, Greg Edwards , clameter@sgi.com Subject: CONFIG_DEBUG_PREEMPT (was: [PATCH 04/04] Cpuset: skip rcu check ...) Message-Id: <20051219080401.861acca2.pj@sgi.com> In-Reply-To: <20051219064810.0ec403ee.pj@sgi.com> References: <20051214084031.21054.13829.sendpatchset@jackhammer.engr.sgi.com> <20051214084049.21054.34108.sendpatchset@jackhammer.engr.sgi.com> <20051216175201.GA24876@us.ibm.com> <20051216120651.cb57ad2e.pj@sgi.com> <20051217164723.GA28255@us.ibm.com> <20051219064810.0ec403ee.pj@sgi.com> Organization: SGI X-Mailer: Sylpheed version 2.1.7 (GTK+ 2.4.9; i686-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1685 Lines: 39 pj wrote: > instead consider removing CONFIG_DEBUG_PREEMPT from at least sn2 Ah - perhaps not so. Adding my SGI colleague Greg Edwards to the cc list. My email archives suggest that he enabled CONFIG_DEBUG_PREEMPT in ia64 sn2_defconfig a few months ago, and I presume did so intentionally. The change enabling CONFIG_DEBUG_PREEMPT was: user: Greg Edwards date: Tue Aug 16 23:38:16 2005 +0011 summary: [IA64] Refresh arch/ia64/configs/sn2_defconfig. Greg - CONFIG_DEBUG_PREEMPT adds a couple of pages of assembly code due to various BUG checks beneath rcu_read_lock() on some hot code paths (which is where rcu is most popular). See the two calls add_preempt_count() and sub_preempt_count() in kernel/sched.c. Was this intentional to enable CONFIG_DEBUG_PREEMPT in sn2_defconfig? Other evidence opposing this DEBUG opttion: Most other DEBUG options are turned off in the defconfigs. Other evidence supporting setting this DEBUG option: We're not the only arch enabling CONFIG_DEBUG_PREEMPT. See also: collie simpad s390 se7705 lpd7a400 bigsur dreamcast sh03 lpd7a404 microdev systemh mx1ads -- I won't rest till it's the best ... Programmer, Linux Scalability Paul Jackson 1.925.600.0401 - 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/