Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752958Ab2BVHx4 (ORCPT ); Wed, 22 Feb 2012 02:53:56 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:39107 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751159Ab2BVHxz (ORCPT ); Wed, 22 Feb 2012 02:53:55 -0500 Date: Wed, 22 Feb 2012 08:53:34 +0100 From: Ingo Molnar To: Steven Rostedt Cc: Jason Baron , "H. Peter Anvin" , a.p.zijlstra@chello.nl, mathieu.desnoyers@efficios.com, davem@davemloft.net, ddaney.cavm@gmail.com, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: [PATCH 00/10] jump label: introduce very_[un]likely + cleanups + docs Message-ID: <20120222075334.GA25053@elte.hu> References: <4F43F9F0.4000605@zytor.com> <20120221202019.GB2381@redhat.com> <1329856745.25686.72.camel@gandalf.stny.rr.com> <20120222073251.GB17291@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120222073251.GB17291@elte.hu> User-Agent: Mutt/1.5.21 (2010-09-15) X-ELTE-SpamScore: -2.0 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-2.0 required=5.9 tests=AWL,BAYES_00 autolearn=no SpamAssassin version=3.3.1 -2.0 BAYES_00 BODY: Bayes spam probability is 0 to 1% [score: 0.0000] 0.0 AWL AWL: From: address is in the auto white-list Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1087 Lines: 42 * Ingo Molnar wrote: > But it is fundamentally mixing execution and *data type* and > it is not conveying the build time bias properly. > > So the best high level naming would be something like: > > struct static_condition static_flag = STATIC_COND_FALSE; > > > if (very_unlikely(&static_flag)) { > ... > } > > ... > > static_cond_inc(&static_flag); > ... > static_cond_dec(&static_flag); Btw., I think the modification path could also carry the high cost of modification (stopping all cpus, modifying code, etc.). This could be done via: static_cond_slow_inc(&static_flag); ... static_cond_slow_dec(&static_flag); And if a developer does not notice that 'slow' implies a performance cost, then he probably would have doubly missed this aspect of jump_label_inc()/jump_label_dec(). Thanks, Ingo -- 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/