Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760270AbZJMP2n (ORCPT ); Tue, 13 Oct 2009 11:28:43 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1759958AbZJMP2n (ORCPT ); Tue, 13 Oct 2009 11:28:43 -0400 Received: from smtp2.ultrahosting.com ([74.213.174.253]:43085 "EHLO smtp.ultrahosting.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753247AbZJMP2m (ORCPT ); Tue, 13 Oct 2009 11:28:42 -0400 Date: Tue, 13 Oct 2009 11:20:57 -0400 (EDT) From: Christoph Lameter X-X-Sender: cl@gentwo.org To: Tejun Heo cc: linux-kernel@vger.kernel.org, Pekka Enberg , Mel Gorman , Mathieu Desnoyers Subject: Re: [this_cpu_xx V6 3/7] Use this_cpu operations in slub In-Reply-To: <4AD4950A.6050201@kernel.org> Message-ID: References: <20091007211024.442168959@gentwo.org> <20091007211052.614790286@gentwo.org> <4AD302A8.4010409@kernel.org> <4AD3E23B.8020103@kernel.org> <4AD4950A.6050201@kernel.org> User-Agent: Alpine 1.10 (DEB 962 2008-03-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1355 Lines: 31 On Tue, 13 Oct 2009, Tejun Heo wrote: > Yeah, widespread use of underscored versions isn't very desirable. > The underscored versions should notify certain specific exceptional > conditions instead of being used as general optimization (which > doesn't make much sense after all as the optimization is only > meaningful with debug option turned on). Are you interested in doing > a sweeping patch to drop underscores from __this_cpu_*() conversions? Nope. __this_cpu_add/dec cannot be converted. __this_cpu_ptr could be converted to this_cpu_ptr but I think the __ are useful there too to show that we are in a preempt section. The calls to raw_smp_processor_id and smp_processor_id() are only useful in the fallback case. There is no need for those if the arch has a way to provide the current percpu offset. So we in effect have two meanings of __ right now. 1. We do not care about the preempt state (thus we call raw_smp_processor_id so that the preempt state does not trigger) 2. We do not need to disable preempt before the operation. __this_cpu_ptr only implies 1. __this_cpu_add uses 1 and 2. -- 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/