Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760936AbZJNB7P (ORCPT ); Tue, 13 Oct 2009 21:59:15 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1760840AbZJNB7P (ORCPT ); Tue, 13 Oct 2009 21:59:15 -0400 Received: from hera.kernel.org ([140.211.167.34]:47199 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1760077AbZJNB7O (ORCPT ); Tue, 13 Oct 2009 21:59:14 -0400 Message-ID: <4AD53022.2050309@kernel.org> Date: Wed, 14 Oct 2009 10:57:54 +0900 From: Tejun Heo User-Agent: Thunderbird 2.0.0.23 (X11/20090817) MIME-Version: 1.0 To: Christoph Lameter 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 References: <20091007211024.442168959@gentwo.org> <20091007211052.614790286@gentwo.org> <4AD302A8.4010409@kernel.org> <4AD3E23B.8020103@kernel.org> <4AD4950A.6050201@kernel.org> In-Reply-To: X-Enigmail-Version: 0.95.7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Wed, 14 Oct 2009 01:57:58 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1661 Lines: 44 Hello, Christoph. Christoph Lameter 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. Right. > __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. That doesn't make much sense. __ for this_cpu_ptr() means "bypass sanity check, we're knowingly violating the required conditions" not "we know sanity checks will pass here". > 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. Yeah, we need to clean it up. The naming is too confusing. Thanks. -- tejun -- 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/